Carbohydrates, Fats, and Proteins

Macronutrients

1. carbohydrate

2. fat

3. protein

All three serve as a biologic fuel and are important in maintaining the structure and functional integrity of an organism.

Each will be addressed for structure, function, and source in specific foods in the diet.

An emphasis will be placed on the importance of these macronutrients in sustaining physiologic function during physical activity.

Carbohydrate -as the name implies, it is made of both carbon and water

a simple carbohydrate, or simple sugar is made of 3 -7 carbons w/ hydrogen and oxygen atoms attached singly

show figure of glucose molecule (C₆H₁₂O₆)

fructose and galactose are two other simple sugars which have the same chemical formula, but have different carbon- hydrogen-oxygen linkage

There are three basic types of carbohydrate:

1) monosaccharides

2) oligosaccharides

3) polysaccharides

 

Monosaccharides

- 200 found in nature

-glucose is the most prevalent ( second names are dextrose or blood sugar)

-can be ingested or formed

-formed by digestion or by gluconeogenesis in the liver

-fructose (from fruits and honey)

-is the sweetest of all monosaccharides

-is -- converted to glucose in the liver

-is slowly absorbed by the gut*

-galactose

-is created in mammary glands of lactating animals and is converted to glucose for energy metabolism

 

Oligosaccharides

-the major type of oligosaccharides are the disaccharides

-examples include: brown sugar, corn syrup, invert sugar, honey, and natural sweeteners

 

the three major disaccharides are:

 

1. Sucrose-- glucose + fructose

2. Lactose-- glucose + galactose

3. Maltose-- glucose + glucose

 

-Sucrose is the most common dietary disaccharide

-contributes up to 25% of the total quantity of ingested cals in U.S.

-occurs in : beet and cane sugar, brown sugar, sorghum, maple syrup and honey (honey is not nutritionally superior)

 

Lactose is only found in milk and is often called "milk sugar"

 

Maltose occurs in malt products and in germinating cereal (is negligible in an average person's diet)

 

Polysaccharides- are made of three or more simple sugars

From 300 to 26,000 monosaccharide molecules can be linked together to form a polysaccharide

Plant and Animal

Plant Polysaccharide

1. Starch

2. Fiber

-Starch -most familiar form of plant polysaccharide

-found in seeds, corn, and various grains

-grains make up bread, cereal, spaghetti, and pastries

-also found in peas, beans, potatoes and roots

-plant starch is the most important source of dietary carbohydrate in the American diet (50% of CHO)

 

-Fiber- cellulose and other nonstarch fibrous materials are generally resistant to the human digestive tract

-quite various and are found in: leaves, stems, roots, seeds, and fruit coverings

-have been linked to lower incidence of : obesity, diabetes, intestinal disorders, and heart disease

 

Dietary Fiber Intake

American Diet vs. Africa + India

 12 g/day vs. 40-150 g/day

 

Animal Polysaccharide

-glycogen is the polysaccharide synthesized from glucose in the process of gluconeogenesis and stored in the tissues of animals

-glycogen molecules are usually large and range in size from a few hundred to a few thousand molecules linked together

-approximately 375 to 475g of glycogen are stored in a well nourished person of average size -of this, approximately 325g are muscle glycogen, 90-110g are liver glycogen and 15-20g are present as blood-born glucose

-each gram of glycogen contains 4 calories of energy: therefore, the average person stores between 1,500 and 2,000 calories of energy (enough to power a 20-mile run)

-glycogen synthesis or breakdown is dependent on fasting or fed state and exercise vs. resting state

 

Recommended Intake of Carbohydrates

-Average U.S. citizen ingests 40-50% of their calories in carbohydrate

-For a sedentary 70 kg person, this is approximately 300 g of carbohydrate/ day

-For active people, the recommendation is to ingest approximately 60% of calories from CHO

-This should equate to approximately 400-600 g of CHO/ day

-About 50% of most CHO consumed by Americans is simple sugar, although this is not recommended

-Average American consumes about 60 lb. of table sugar and 46 lb. of corn syrup each year (in contrast to 4 lb./ year 100 years ago)

-The excess dietary sugar is related to tooth decay, diabetes, obesity, and coronary heart disease

 

Role of Carbohydrate in the Body

1. Energy Source

2. Protein Sparing

3. Metabolic Primer

4. Fuel for the Central Nervous System

Energy Source

-The main function of carbohydrate is to serve as an energy source for the body

-Energy liberated from the catabolism of glucose and glycogen is used to power muscle contraction and other biologic processes

-Once the capacity of the cell for glycogen storage is reached, the excess sugars are converted and stored as fat (even if your diet is low in fat)

Protein Sparing

-When CHO reserves are reduced, metabolic pathways exist for the synthesis of glucose from protein and the glycerol portion of a fat molecule

-Therefore, glycogen depletion which occurs in athletes quite often (especially aerobic athletes) can result in a loss of muscle mass and strength

-Through this mechanism, the kidneys can be damaged as they must handle an increased load of excretion of nitrogen-containing byproducts of protein breakdown

Metabolic Primer

-CHO acts as a primer for fat metabolism

-If insufficient carbohydrate metabolism exists, either through limitation in glucose transport into the cell (diabetes), or depletion of glycogen through improper diet or prolonged exercise, the body begins to mobilize fat to a greater extent than it can use

-This results in incomplete fat metabolism and the accumulation of acid by-products called ketone bodies

-This may result in a harmful increase in the acidity of body fluids, a condition called acidosis or more specifically with regard to fat breakdown- Ketosis

 

Fuel for the Central Nervous System

-Under normal conditions and in short-term starvation, the brain uses blood glucose almost exclusively as a fuel and essentially has no stored supply of this nutrient

-The symptoms of a modest reduction in blood glucose (hypoglycemia) include feelings of weakness, hunger, and dizziness

-This condition impairs exercise performance and may partially explain the fatigue associated with prolonged exercise

-Sustained and profound (hypoglycemia) can result in irreversible brain damage

 

Carbohydrate Balance in Exercise

The fuel used during an exercise bout depends on the intensity and duration of the exercise, as well as the fitness and nutritional status of the exerciser

" The biopsy technique permits the sampling of specific muscles with little interruption in exercise"

1. Intense Exercise

2. Moderate and Prolonged Exercise

Intense Exercise

-During the first few minutes of intense exercise, stored muscle glycogen and blood-borne glucose are the prime contributors of energy

-This is basically due to the fact that oxygen supply does not meet the demands for aerobic metabolism

 

Show Figure 1.3

 

During the initial stage of exercise, the uptake of circulating blood glucose by the muscles increases sharply and continues to increase as exercise progresses

-By the fourtieth minute of exercise, the glucose uptake has risen to between 7 and 20 times the uptake at rest (depending on intensity)

 

Moderate and Prolonged Exercise

1. Effect of Diet on Muscle Glycogen Stores

2. Administration of Oral Glucose Before and During Exercise

Transition from rest to submaximal exercise: almost all of the energy is supplied from glycogen stored in active muscles

During the next twenty minutes or so, liver and muscle glycogen provide about 40-50% of the energy requirement (rest from fat)

As glycogen stores decrease, a greater percentage of energy is supplied through fat metabolism

Eventually, gluconeogenesis by the liver can not keep pace with glucose removal by active muscle and blood glucose levels fall

Fatigue sets in when exercise is performed to the point at which the glycogen in the liver and specific muscles becomes severely lowered, even though sufficient oxygen is available to the muscles and the potential energy from stored fat remains almost unlimited

This type of fatigue is referred to as "hitting the wall"

1. Effect of Diet on Muscle Glycogen Stores

 

-Ingested CHO represents an energy nutrient that is readily available to exercising muscle

-Glycogen content in the quadriceps femoris muscle was determined by needle biopsy, and averaged:

 

2. Administration of Oral Glucose Before and During Exercise

-During exercise, ingestion of sugar-rich drinks benefit high intensity, long-term aerobic performance. (not low intensity)

 

-The benefits are two-fold:

-Helps spare glycogen levels

-Maintain blood glucose

-CHO feedings during exercise at 60-80% VO₂ max will prolong the development of fatigue by 15-30 minutes (very significant)

 

-If administered at about 30 minutes prior to anticipated fatigue, effect is similar to that seen if given earlier in exercise

 

Show Figure 1.5

 

-Interval feeding also increased time to exhaustion and decreased glycogen depletion

 

-What to Drink

-No sources of "sport drinks" have done better than glucose

-The drinks can be of weak concentration (5% solution) or concentrated (25-50%)

-When sugars are consumed during exercise, there is no overreaction in insulin response and resulting hypoglycemia

-Hormones of the sympathetic nervous system inhibit the release of insulin

-Exercise augments a muscle's ability to take up glucose (lessens need for insulin)

 

-Prior to Exercise, ingestion of strong sugary solutions can actually hinder one's performance

-A large rise in blood sugar causes a strong insulin response and eventual hypoglycemia by driving glucose into cells

-In addition, insulin inhibits the mobilization and utilization of fat

-This causes an overuse of muscle glycogen as a source of energy and premature glycogen depletion

 

-If more than 30 minutes is provided after initiation of pre-exercise glucose feedings, performance may not be impaired

Fructose feedings ?

1. Insulin response

2. Gastrointestinal distress

-Glucose Feedings and Water Uptake

-With increased osmolality, there is a decrease in water uptake in the gut

-This could compromise thermoregulation with exercise in the heat

-Glucose polymer solutions can be used

-Very considerable debate: Does a solution of certain concentration compromise fluid uptake in the intestines to the extent that thermoregulation and exercise performance is impaired?

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Fats - are very similar to carbohydrates in terms of constituents, but the ratio of hydrogen to oxygen is considerably higher:

Stearin - C₅₇H₁₁₀O₆

Kinds and Sources of Fats:

Fats can be placed into one of three main groups:

1. simple fats

2. compound fats

3. derived fats

Simple fats - are called neutral fats and consist primarily of triglycerides (95% of body fat is triglycerides)

made of one glycerol and three fatty acids

two major types of simple fats are saturated and unsaturated (unsaturated fatty acids have double bonds between carbon atoms)

a saturated fatty acid molecule is "saturated" because it holds as many hydrogens as is chemically possible

found in: beef, lamb, pork, chicken, egg yolk, cream, milk, butter, cheese, coconut oil, palm oil, vegetable shortening, hydrogenated margarine

each double bond in an unsaturated fatty acid reduces the number of hydrogen binding sites

1. monounsaturated

2. polyunsaturated

-unsaturated fats are more liquid, and can be made more saturated through hydrogenation

-saturated fats are highly correlated to coronary heart disease

it appears that total fat intake (saturated and unsaturated fats) are related to:

1. diabetes

2. heart disease

3. breast cancer

4. colon cancer

a general recommendation is to consume no more than 30% of total calories in the form of fat

of this fat, less than 30% should be saturated fat

linoleic acid- is particularly important because it is not synthesized in the body, and it is necessary for ensuring the integrity of the cell membranes, growth, reproduction, and skin maintenance

 

Compound Fats- are composed of a neutral fat in combination with other chemicals

Examples include:

1. Phospholipids

2. Glucolipids

3. Lipoproteins

-phospholipids consist of one or more fatty acids with phosphoric acid and a nitrogenous base

-they help with structure of cell, blood clotting, and myelin sheath

-glucolipids are fatty acids bound to carbohydrate and nitrogen

-lipoproteins are the union of either triglycerides, phospholipids or cholesterol with protein

-lipoproteins allow transport of fat in the blood

1. HDL- competes with LDL (removes chol ?)

2. LDL (VLDL)-deposits cholesterol which results in smooth muscle proliferation

Derived Fats- are substances derived from simple and compound fats

-the most widely known is cholesterol

-cholesterol is present in all cells and is either consumed or it is synthesized

-endogenous cholesterol is made at a faster rate when a diet is high in saturated fat

-a severe reduction in cholesterol intake is not a concern (except for in infants)

Functions of cholesterol:

1. building cell membranes

2. synthesis of Vitamin D

3. many hormones

cholesterol is in:

1. egg yolk

2. red meats

3. shellfish

4. dairy products

-cholesterol does not exist in plants

-American Heart Association suggest an intake of no more than 100mg/ 1000 cals consumed

 

Role of Fat in the Body:

1. Body's largest store of potential energy

2. Serves as a cushion for the protection of organs

3. Insulation from thermal stress of cold environment

4. Vitamin carrier and hunger depressor

ideal as a reserve fuel because it has large energy potential/ weight, transported and stored easily, readily converted to energy

 

When Triglyceride Formed vs. When Glycogen Formed

3 H₂O liberated vs. 2.7 H₂0 formed

(light) vs. (heavy)

-average male and female in the U.S. are 15% and 25% body fat respectively

-average American could run from New York City to Madison Wisconsin on stored fat

 

Fat Balance in Exercise

-FFA travel through the blood stream bound to albumin, and they are stored in muscle as triglyceride

-both contribute to energy requirements of exercise

-during brief moderate exercise, about 1/2 of the calories are from fat ; after about 1 hour, there is a gradual increase in the percent of calories from fat

-this percentage can reach 80% during prolonged endurance exercise

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Proteins

The Nature of Proteins

-from the Greek word meaning "of prime importance"

-contain carbon, hydrogen, oxygen, nitrogen (16%)

-polymerized from building blocks called amino acids

-20 amino acids:

-each has an amino radical and a radical called an organic acid

-it is the specific structure of the side chain that gives each amino acid its particular characteristics

-the combination of the 20 amino acids allows for an almost unlimited # of proteins

 

Kinds of Protein

-8 amino acids can not be synthesized in the body (these are the essential amino acids)

- isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine

-cystine and tyrosine are synthesized in the body from methionine and phenylalanine respectively

-protein nutrients that contain all of the essential amino acids in terms of quantity and in the correct ratio to maintain nitrogen balance and allow for tissue growth and repair known as complete proteins

-eggs, meat, fish, milk, and poultry are all sources of complete protein (eggs are judged to be the best)

-all of the essential amino acids can be obtained by consuming a variety of vegetable proteins

-lactovegetarian diets and ovolactovegetarian diets lessen the problem of inadequate protein intake

 

Recommended Intake of Proteins

-there is probably no benefit from eating excessive amounts of protein unless an athlete is training extremely intensely, and this training includes resistance training

-muscle mass is not increased by simply eating high-protein foods

-excessive protein may actually be harmful to the liver and kidney, both of which are effected by nitrogen wastes

-RDA suggests an intake of 0.8g/ kg body weight/ day (to determine your protein requirement, multiply your body weight in lbs by 0.37) for the average individual

-infants, and pregnant women require more

-stress, disease and injury cause a greater requirement

-simple amino acids prepared by companies for the purpose of consumption by athletes are a waste of money

-there is no need for predigested amino acid preparations as dietary proteins are absorbed rapidly in the intestines when they are in the di- and tripeptide forms

-amino acid supplementation in any form above the RDA has not been shown experimentally to improve:

1. strength

2. power

3. muscle mass

4. endurance

 

Role of Protein in the Body

-makes up 12-15% of body mass

-amino acids provide a major source for anabolism

-proteins are involved in an enormous variety of tissue and cellular functions

 

1. Nucleoproteins- transmit hereditary characteristics

2. Structural proteins- form hair and nails

3. Globular proteins- make up enzymes (2000)

 

-can act as a buffer in the blood for pH balance

-obviously needed for muscle proteins (actin, myosin, titin, vinculin, desmin, nebulin etc.)

 

Dynamics of Protein Metabolism

- catabolism contributes 2-5% of the energy requirement at rest

-during catabolism, nitrogen is stripped from an amino acid in the liver (deamination) and is excreted from the body in the form of urea

-the resulting carbon skeleton can be used as an energy source

-when intake of nitrogen equals nitrogen excretion, nitrogen balance exists

-protein from nervous and connective tissue is essentially fixed whereas muscle and liver protein can be altered and used for energy metabolism

-a loss of muscle mass with negative nitrogen balance is referred to as muscular atrophy

 

Protein Balance in Exercise and Training: Is the RDA Really Enough ?

-many studies provide evidence that the RDA provides a "margin of safety" for protein intake even with resistance training

-this is predicated on the basis that energy intake is adequate enough for the added needs of exercise

-if energy intake is too low during heavy training, even an augmented protein intake may be insufficient to maintain energy balance

-studies regarding protein breakdown with long term endurance exercise were complicated by only small increases in nitrogen content of urine

-much of the nitrogen waste is lost through sweat, especially when the diet is low on carbohydrate

 

The Alanine-Glucose Cycle

-amino acids in muscle are converted to glutamate and then to alanine

-the alanine released from the exercising muscle is transported to the liver where it is deaminated

-the remaining carbon skeleton is converted to glucose and then released to the working muscles

Show Figure 1-13 Alanine-Glucose Cycle

-energy derived from the alanine-glucose cycle may supply as much as 10-15% of the total exercise requirement

-Little is known with respect to protein requirements of individuals who train 4-6 hours/ day by resistance-type exercise

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Vitamins, Minerals and Water

 

Micronutrients- are small quantities of vitamins and minerals that play highly specific roles in energy transfer

Vitamins

The Nature of Vitamins

-knowledge of vitamins and their relevance in disease states (beriberi-thiamin; scurvy-vitamin C).

-with the exception of Vitamin D, vitamins can not be synthesized in the body

-plants manufacture vitamins during the process of photosynthesis and animals obtain their vitamins from the plants

-provitamins activate vitamins (A, D, niacin, and folacin) : the most well known provitamins are the carotenes

-carotenes are yellow and yellow-orange pigment precursors of vitamin A that give color to vegetables and fruits

Kinds of Vitamins

-13 vitamins classified as either fat soluble or water soluble

-fat soluble vitamins include vitamins A, D, E, K

 

Water Soluble Vitamins include:

 

1. Vitamin B6 (pyridoxine)

2. Thiamine (B1)

3. Riboflavin (B2)

4. Niacin (nicotinic acid)

5. Panthoenic acid

6. Biotin

7. Folacin (folic acid)

8. Cobalamin (B12)

9. Vitamin C (ascorbic acid)

Fat Soluble Vitamins

-dissolved and stored in the body

-can develop insufficient fat soluble vitamin stores over time, or can develop an over-supply (eg. hypervitaminosis A)

 

Water Soluble Vitamins

-vitamin B complex and vitamin C

-act as coenzymes which combine with large proteins to make an active enzyme

-transported easily in the body fluids and not stored to an appreciable extent

 

Role of Vitamins in the Body

-act to release energy during catabolism and help in tissue synthesis

-can be used repeatedly, so athletes do not need more than the general population

 

Vitamin Supplements: The Competitive Edge ?

-supplements can help relieve a deficiency

-synthesized vitamins are no worse than vitamins found in natural resources

 

Vitamins and Exercise Performance

-no controlled research has found positive results regarding the effect of extra doses of vitamin B, C, E

 

Megavitamins

-some megavitamins contain up to 1,000 times the recommended doses

-can cause complications such as excess vitamin C causing excess uric acid and eventually gout

-several other vitamins, when taken in excess doses, can cause an array of disease states

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Minerals

The Nature of Minerals

-22 mostly metallic elements which make up about 4% of the body weight

-most important are found in enzymes, hormones, and vitamins

-major minerals (large quantities; known effects)

-trace minerals (minute quantities; obscure effects)

 

Kinds and Sources of Minerals

-mineral supplements are generally not needed

-geographically specific (ex. near Great Lakes, low in iodine which makes thyroxine for metabolism)

-30-50% of women during child-bearing ages are iron deficient (can get from green vegetables, egg yolk, liver, kidney and heart)

 

Role of Minerals in The Body

1. structure - for bones and teeth

2. functional purpose - heart rhythm, muscle contraction, neural impulse

3. regulatory - cellular metabolism through enzymes and hormones

 

Calcium - calcium and phosphate together make up about 75% of the mineral deposit of the body

Osteoporosis - porous and brittle bones

1. can occur from lack of stress on bones

2. can occur from lack of estrogen in women

3. can occur form lack of calcium intake

4. usually occurs from all three

5. overtraining can induce osteoporosis (amenorrhea)

 

Phosphorous - joins with calcium to form bone, and is an essential component of adenosine triphosphate (ATP), and creatine phosphate (CP)

Magnesium - plays a crucial role in glucose metabolism by facilitating the formation of muscle and liver glycogen from blood-borne glucose (also nerve and muscle conduction)

Iron - 3-5 g in the entire body are responsible for hemoglobin in red blood cells

-increases oxygen carrying capacity of blood about 65 fold

-also contained in myoglobin (protein which facilitates oxygen transfer in muscle)

-also found in cytochromes of the ETS

-lack of iron in exercising women attributed to:

 

1. menstruation

2. pregnancy

3. poor iron diet

4. loss of iron in sweat

5. loss of hemoglobin in urine (from destruction of RBC with greater

temp, spleen activity, mechanical trauma)

 

Sodium, Potassium, Chlorine

- are all referred to as electrolytes because they all dissolve in the body as charged particles

-all are important in determining the cells electric potential

-it is possible to deplete these electrolytes through excessive sweating, but this does not usually occur ; the main focus is to replenish water for the body

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Water

Water in the Body

-40-60% of the body weight is water (70% of muscle and less than 25% of fat)

-exist in intracellular (62%) and extracellular compartments (38%)

 

water intake; about 2.5 liters from:

 

1. liquid (1.2 liters)

2. food (1.0 liters)

3. metabolism (350 ml)

 

water loss; about 2.5 liters from:

 

1. urine (1.5 liters)

2. feces (100 ml)

3. skin (600 ml)

4. lungs (350 ml)

-excessive sweating on a humid day causes a loss of body water, plasma volume; therefore, it directly effects the thermoregulatory mechanisms

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Optimal Nutrition for Exercise

-an optimal diet is defined as one in which the supply of required nutrients is adequate for tissue maintenance, repair, and growth without an excess energy intake

1. Age

2. Body size

3. Gender

4. Specificity of sport

5. Dietary Preferences

Nutrient Requirement

1. Coaches "feelings"

2. Athletes knowledge base

3. Top athletes eat similar to sedentary people

4. Total caloric intake

5. For endurance CHO is a special consideration

Recommended Nutrient Intake

1. Over-Generalized (Females 2100, Males 2700)

2. Depends heavily on Lean Body Mass

3. Protein- Athletes 2-5 times above recommendation

4. Fat- no more than 30% of total calories (70% of fat -unsaturated)

5. CHO- Very high percent for endurance athletes (Tarahumara Indians)

CHO Needs in Prolonged, Severe Training

1. Distance running, swimming, cross-country skiing, cycling

2. Recommend about 70% from CHO and up to 4,000 calories/day of CHO

3. Liver glycogen vs Muscle glycogen restoration

4. 2 days rest or light exercise to reach pre-exercise levels

 

Exercise and Food Intake

1. Adjustment of intake to match expenditure (unconscious)

2. The balance not maintained in sedentary people !!!

3. "Creeping obesity" in the U.S.

4. Original estimations (1936 Olympics)

5. More recent estimations (4,000 cals)

6. Only extremes above these levels

7. Huge variability

Eat More, Weigh Less

1. Those who run about 10 kilometers/day eat 40-60% more calories/day and weigh less than sedentary controls

2. Athletes take in disproportionately greater protein

 

The Pregame Meal

1. Main purpose: adequate CHO energy and hydration

2. Fasting, for any reason, is detrimental ("nerves")

3. Food preferences, "psychologic set", and digestability should all be considered

4. 3 hours before meal should be long enough

 

Protein or CHO

1. Steak and Eggs: Does anyone really eat this ?

2. Normal overnight fast, results in low CHO

3. CHO digested and absorbed more quickly

4. Amino acid breakdown requires water for excretion

5. Pre-event CHO drinks (timing)

Liquid Meals

1. Balanced nutritionally

2. Enough CHO

3. Liquid needs

4. Digested rapidly

5. Little time or interest for food in long day events

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Energy Value of Food

Measurement of Food Energy

Unit of Measurement, The Calorie

1. Definition- the amount of energy required to raise the temperature of 1 kg (1 liter) of water 1 degree Celsius

2. Often called kilogram calorie or "kcal"

3. International unit is joules: 1 kcal = 4.2 kJ

 

Gross Energy Value of Foods

1. The Bomb Calorimeter- Direct Calorimetry

2. Burning of food (oxidation)

3. Heat of combustion

4. Independent of Pathways for Combustion

Heat of Combustion: Fat

1. Varies depending on the type of fat

2. Average for all fat is 9.4 kcal/ g

Heat of Combustion: CHO

1. Glucose = 3.74 kcal/ g

2. Glycogen = 4.19 kcal/ g

3. Average value used = 4.2 kcal/g

Heat of Combustion: Protein

1. Depends on kind of protein

2. Average value used = 5.65 kcal/ g

Comparing the Energy Value of Nutrients

1. Energy content of fat = 65% more than protein

2. Energy content of fat = 120% more than CHO

 

Net Energy Value of Foods

1. Net energy available to the body not exactly the same as the gross energy from heat of combustion

2. From an applied standpoint, this is only of consequence for protein (net energy value is 4.6 kcal/ g)

 

Coefficient of Digestability

1. Definition- proportion of ingested food that is actually digested and absorbed to serve the metabolic needs of the body

2. CHO, Fat, and Protein are 97%, 95%, and 92% respectively

3. Large variability within each macronutrient

4. Protein from plants: difficult to digest

5. Due to digestability the net energy value is as follows:

 

CHO = 4 kcal/ g

Fat = 9 kcal/ g Atwater General

Protein = 4 kcal/ g Factors

Alcohol = 7 kcal/ g

 

Caloric Value of a Meal

1. Easy to Calculate

2. Look at Appendix B

3. Remember that Weight Gain or Loss is primarily the the result of total caloric consumption

 

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Introduction to Energy Transfer

Goal is to extract energy from food nutrients and transfer it to the contractile elements of skeletal muscle.

Energy, The Capacity for Work

1. Within this context, energy refers to the ability to perform work.

2. First Law of Thermodynamics:

 

Energy is neither created nor destroyed, but it is transformed from one form to another.

(Conservation of Energy)

 

3. Application to the Body

 

Potential and Kinetic Energy

1. Total E = potential E + kinetic E

2. When potential E is released, it is transformed into kinetic energy or energy of motion.

3. Chemical E transfer:

 

A. to mechanical energy

B. to increase potential E (biosynthesis)

 

Energy-Releasing and Energy-Conserving Processes

1. Exergonic- physical or chemical process that results in release of energy to its surroundings.

2. Endergonic- processes that store or absorb energy

3. Can be coupled to store energy

4. Liberated energy = difference in potential energy between reactant and product substances

5. Transfer of potential energy always decreases (Second Law of Thermodynamics)

6. Ultimately, all of the potential energy in a system is degraded to the nonusable form of kinetic energy or heat

 

Interconversions of Energy

Net entropy occurs even when isolated systems allow for potential energy to be harnessed for a useful purpose.

Entropy- is a measure of the continual process of energy change; all chemical and physical processes proceed in a direction where total randomness or disorder increases and the energy available to do work decreases.

Forms of Energy

1. Chemical

2. Mechanical

3. Heat

4. Light

5. Electric

6. Nuclear

Examples of Energy Conversions

The most fundamental examples are:

1. Photosynthesis

2. Respiration

Photosynthesis

1. Chlorophyll absorbs radiant energy from the sun and transforms it into chemical potential energy in the form of carbohydrates in plants

2. 686 kcal/ mole of glucose synthesized

Respiration

1. Basically the reverse of photosynthesis

2. Stored chemical E is extracted in presence of oxygen (release of 689 kcal/ mole glucose oxidized)

3. E released can be stored in other chemical compounds

4. Remaining E flows to the environment as heat

 

Biologic Work in Humans

1. Mechanical Work of Muscular Contraction

2. Chemical Work for Synthesis of Cellular Molecules

3. Transport Work that Concentrates Various Substances in the Intra- and Extracellular Fluids

 

Mechanical Work

Examples include:

 

1. Muscle contraction

2. Cilia in many cells

3. Other contracting filaments

 

Chemical Work

 

Cellular components are continually created as others are destroyed.

Transport Work

1. With diffusion, no work is needed

2. Movement of chemicals against a concentration gradient (active transport) requires E

3. Secretion and Reabsorption in the kidney tubules

4. Electrochemical gradients at cell membranes

Factors That Affect the Rate of Bioenergetics

"The rate at which chemical E in the food nutrients is extracted conserved, and transferred to the contractile filaments of skeletal muscle determines the intensity at which exercise can progress."

 

The Mass Action Effect

1. The effect of the [ ] of chemicals on the frequency of a particular reaction.

2. Certain chemicals play key roles in a whole chain of events.

3. Oxygen is often a limiting factor.

 

Enzymes: The Biologic Catalysts

1. Specific protein catalysts that accelerate the speed of a reaction

2. Substrates and Products

3. Turnover of Enzymes (relatively slow)

4. Specificity (19 in breakdown of glucose to CO₂ + H₂O)

Role of Coenzymes

1. definition- complex, nonprotein, organic substances that facilitate enzyme action by helping to bind the substrate with its specific enzyme

 

2. Less specific (can act in several different reactions)

A. Co-binder role

B. Temporary Carrier (NAD+)

 

3. Vitamins act a coenzymes

 

Measuring Energy Release in Humans

1. Direct Calorimetry (Lavoisier's Chamber)

2. Indirect Calorimetry

 

- Because the complete combustion of food is achieved at the expense of molecular oxygen, the heat generated in these exergonic reactions can be conveniently and accurately estimated by measuring oxygen consumption.

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Energy Transfer in the Body

Phosphate Bond Energy

1. ATP- provides the energy for all biologic work

ATPase causes the reaction of: ATP + H2O to ADP + Pi

It is a rxn that occurs without oxygen and is very rapid, but only 80-100g are stored in the body.

 

2. CrP - Considered an energy reservoir

Is stored at about 4-6 times the concentration of ATP.

Creatine Kinase causes the reaction of: CrP + ADP to ATP + Cr

---

Energy Transfer in Exercise

Immediate Energy: The ATP-CP System

-5 millimoles ATP/ kg muscle

-15 millimoles CP/ kg muscle

-20 kg muscle (all out exercise 5-6 secs)

-used for all immediate increases in energy expenditure

-NMR Nuclear Magnetic Resonance Spectroscopy:

 

Pi:CrP gives indication of mitochondrial respiration

 

Short Term Energy: The Lactic Acid System

-max power output is about 45% of ATP-CrP system

-forms lactic acid

- "buys time" through substrate level phosphorylation

-used when ATP-CP are exhausted during 400 m race etc.

-also used when athlete tries to sprint last 200 m of mile run

-highest lactate levels (60-180 secs all out)

-blood lactate See Figure 7.2

-NADH production exceeds hydrogen atom shuttling down the ETS (regardless of O2 supply)

-LDH type in different fiber types

-blood lactate threshold

-lactate producing capacities

Long Term Energy: The Aerobic System

-Oxygen uptake during exercise

-pulmonary oxygen uptake

-steady state exercise- lactate does not accumulate

-depends on individual

 

untrained vs. trained

 

-O₂ deficit - a lag in O₂ uptake with respect to energy expenditure

See Figure 7.3

 

-glycolysis contributes anaerobic energy during the early stages of vigorous exercise, even before the full utilization of the intramuscular high energy phosphates

-switch on-off vs. smooth blending

-VO₂ Max - capacity for aerobic resynthesis of ATP

Fast and Slow Twitch Muscle Fibers

-general types (metabolic aspects)

-% in average population

-% in elite athletes

The Energy Spectrum of Exercise

Show Figure 7.8

Relative Contributions of Aerobic and Anaerobic Work with Maximal Effort of Varying Durations

-improve energy transfer: improve athletic performance

Oxygen uptake during recovery: The so-called "oxygen debt"

-metabolic rate remains high during the recovery phase of exercise

-oxygen debt- increased oxygen uptake during the recovery phase

-fast component- 1/2 of recovery oxygen uptake is within 30 secs and complete recovery within 2-3 min

-slow component- associated with increased body temperature and change in hormonal balance; can last for several hours to a whole day

Metabolic Dynamics of Recovery Oxygen Uptake

-A.V. Hill -the lactic acid theory of oxygen debt

-revision to Alactacid debt and Lactacid debt which restored ATP and CrP, and glycogen repectively

-Controversy- excess post-exercise oxygen (EPOC) consumption occurs even without decreases in ATP-CrP and without resynthesis of glycogen from lactate

 

new concepts about EPOC:

 

1. some glycogen resynthesis and ATP-CrP

2. increased body temp increases metabolism

3. restore blood and body fluids with oxygen

4. increased O2 consumption by respiratory muscles

5. elevated metabolism due to hormone changes

6. tissue repair and redistribution of ions

 

Implications of EPOC for Exercise and Recovery

-active vs. passive recovery depends on intensity of bout of exercise

See Figure 7.11

 

Intermittent Exercise

-use interval training to increase intensity and increase rate of adaptation without becoming exhausted from the bout

-work/ rest intervals must be timed so as not to substantially elevate the blood lactate concentration

---

Muscle Structure and Levers

Types of Muscles

summary of the principle characteristics of muscle tissue:

• skeletal muscle tissue has voluntary nervous control, is located attached to bones and has a striated , multinucleated microscopic appearance
• cardiac muscle has involuntary nervous control, is located in the heart (myocardium), and has a striated uninucleated microscopic appearance; it also contains itercalated discs
• smooth muscle has involuntary nervous control, is located in the walls of hollow viscera and blood vessels, and has a non-striated, uninucleated microscopic appearance

 

* striated appearance is from existence of actin and myosin

 

** intercalated discs - transverse thickenings of the sarcolemma which separates each fiber within a network

 

Internal Structure of Muscle

1. epimysium (around muscle)

 

- extension of deep fascia

- fibrous connective tissue layer

- wraps around whole muscle

 

2. perimysium (around the bundles of fiber cells or fasciculi)

 

3. endomysium- invagination of the perimysium that penetrates fasciculi and separates into individual muscle cells

- muscle cell = muscle fiber = myofiber

- each cell has a bunch of myofibrils

- each myofibril has myofilaments (actin and myosin etc.) arranged in sarcomeres

 

Tendons

- attach to bone (periosteum)

- extensions of the perimysium and epimysium

Aponeurosis

- a tendon that extends into a broad flat layer

Tendon sheath

-synovial sheath which allow tendons to slide easily and prevent them from slipping out of place

 

Histology (the study of tissue) - skeletal muscle consists of :

1. Muscle fibers - elongated cells parallel to one another

2. Sarcolemma

- is just under the endomysium

- plasma membrane which envelops the muscle fiber including the sarcoplasm (cytoplasm)

- has many nuclei and mitochondria

3. Sarcoplasmic reticulum

-network of tubules within a myofiber which release and take up calcium to help regulate contraction

4. T-tubules

-transverse tubules that run from the outside of the muscle cells to the sarcoplasmic reticulum

5. Sarcomere

-the distance from z line to z line; the functional unit of muscle

 

H zone- zone where only myosin myofilaments exist; shortens during contraction

 

I band- area where only actin exists; shortens during contraction

 

A band- area including myosin and where the myosin and actin overlap; does not shorten during contraction

 

M line- a series of fine threads in the center of the H-zone: connects the middle parts of the adjacent thick filaments

 

6. Satellite cells- non-differentiated cells which lie between the basal lamina and the sarcolemma: can assist in some hyperplasia (increase in cell number) when the cell is damaged or possibly otherwise stimulated, therefore the tissue has some regenerative capacity

 

Two types of myofilaments

1. actin- the thin filament which joins with troponin and tropomyosin to form a "thin filament" complex

2. myosin- the thick filament which contains heads with enzymes (ATP-ase) to interact with actin

 

Muscles Classified by the Arrangement of their Fascicles

1. parallel - fibers run parallel to the line of pull and have greater range of motion

2. pennate - fibers attach at an angle allowing more fibers and thus greater strength, decreased range of motion

Muscles Classified by Action

1. prime mover - (agonist) causes the desired action

2. antagonist - opposes the desired action

3. synergist - helps to steady the movement

4. fixation - muscle contracts isometrically to stabilize the origin of the prime mover

Contractions - normally a muscle actively shortens and passively lengthens via contraction of an antagonist (not always the case)

 

Three types of contraction:

1. concentric - activation of the muscle accompanied by actual shortening resistance < muscular force

2. eccentric- activation of the muscle yet its length is increasing resistance > muscular force

3. isometric - activation of the muscle yet its length remains static resistance = muscular force

 

*Shortening of muscle occurs by shortening of the distance between the origin (the point where the muscle begins) and the insertion (the point where the muscle ends) - the bone that the muscle moves is the bone it inserts into. On rare occasion both the origin and insertion will move.

 

Levers:

1st class - fulcrum between muscle (effort) and weight (resistance) - most efficient for force production

 

2nd class - resistance between fulcrum (joint) and muscle (effort)

 

3rd class - the muscle (effort) is between the weight (resistance) and the fulcrum (joint) - least efficient for force production

 

Brief overview of nervous tissue---some terms which will definitely help you with the class !

 

1. Neuron - fundamental functional unit

2. Impulses - created by diffusion of charged atoms.

3. Dendrites - receive impulses

4. Axon - transmits impulses away

5. Axon coverings:

i. myelin - a phospholipid that insulates axons and speeds impulse.

ii. neurilemma - cell membrane of Shwann cells.

6. Nodes of Ranvier - periodic gaps between successive Shwann cells.

7. Afferent - towards the cell body, or towards the CNS

8. Efferent- away from the cell body, or away from the CNS

9. Parikaryon- the same as the cell body

10. Nissl substance- the rough endoplasmic reticulum of the nerve cell

11. Axoplasmic streaming- the delivery of protein and other substances made in the cell body to the axon or axon terminal

12. Axon Hillock- where the axon joins the cell body; the site where a new impulse may begin and travel down the axon

13. Acetylcholine- the neurotransmitter used to stimulate muscle cells at the motor end plate

14. Motor end plate- where an axon meets with a muscle fiber

15. Acetylcholinesterase- an enzyme which breaks down acetylcholine at the motor end plate

16. Synaptic cleft (synapse)- the space between an axon terminal and any other structure (i.e. muscle, neuron, gland, organ, etc.)

 

Length Tension Curve

• In original experiment
• In human

 

Excitation Contraction Coupling

-is the physiologic mechanism whereby an electrical discharge at the muscle initiates the chemical events at the cell surface that lead to the release of intracellular Ca++ and ultimately cause a muscle action. (Show Two Overheads)

 

Sequence of Events in Muscle Action

See Page 330

Muscle Fiber Type

Show Table 18-2

- species differences

- differences between athletic groups

- can fiber type be changed?

---

Neural Control of Human Movement

General outline in the book and this lecture

• Structural organization for motor control
• Neuromuscular transmission
• Motor unit function and activation
• Sensory input from muscle activity

 

Organization of the Neuromotor System

CNS = brain and spinal cord

PNS = nerves that transmit to and from the CNS

 

CNS The Brain- six main categories

• medulla oblongotta
• pons
• midbrain
• cerebellum
• diencephalon
• telencephalon Make up the Brainstem

 

There are also four lobes of the cerebral cortex and sensory areas.

• frontal lobe
• temporal lobe
• parietal lobe
• occipital lobe

 

Brain Stem = medulla + pons + midbrain

medulla - serves as a bridge between the two hemispheres of the cerebellum

midbrain -attached to the cerebellum; connection between pons and cerebral hemispheres

reticular formation - part of the midbrain; integrates incoming and outgoing messages

 

Cerebellum

- two lateral hemispheres and a central vermis

- very important in motor control coordination

- extremely large in birds

 

Functions of the cerebellum

1. postural adjustments

2. locomotion

3. maintenance of equilibrium

4. perceptions of speed and body movement

5. reflex motions

 

Diencephalon

Includes the:

 

1. hypothalamus - regulates from metabolism to degrees Celsius

2. thalamus - regulating center

3. epithalamus - regulates cyclic rythyms

4. subthalamus - ???

 

Telencephalon

Includes the:

 

1. two hemispheres of the cerebral cortex

2. corpus striatum

3. medulla

4. most of the limbic system

 

The cortical cells have specialized sensory and motor function.

Beneath each cerebral hemisphere = basal ganglia.

Basal ganglia in close connection with the thalamus and plays an important role in the control of human movements.

Limbic system is for emotional behavior.

 

CNS- The Spinal Cord

See Figure 19.3

• ventral and dorsal horns
• core made of interneurons, motoneurons, and sensory neurons
• motoneurons are efferent (vental exit; ventral horn)
• sensory neurons are afferent (dorsal entrance; dorsal horn)

 

Ascending Nerve Tracts

have three neurons:

 

1. in the dorsal root ganglion

2. in the spinal cord

3. in the thalamus

 

sensory receptors can sense the following:

 

1. temperature

2. pain

3. light conscious

4. sound

5. smell

6. taste

7. touch

8. barorecpetors subconscious

9. chemoreceptors

 

Descending Nerve Tracts

consist of:

 

1. pyramidal tracts - end in (µ) motoneurons (skeletal muscle); allow for discrete movements

2. extrapyramidal tracts - start at brain stem and provide continual background activity for posture etc.

 

reticular formation

• "arousal or wakefulness of the cortex"
• brainstem
• extrapyramidal tracts

 

The Peripheral Nervous System

Consists of 31 pairs of spinal nerves and 12 pairs of thoracic nerves.

8 cervical pairs

12 thoracic pairs

5 lumbar pairs

5 sacral pairs

1 coccygeal pair

Efferent spinal nerves are either:

1. somatic (motoneurons)

-always excitatory

-innervate skeletal muscle

 

2. autonomic

-excitatory or inhibitory

-innervate intestines, blood vessels, sweat and salivary glands, cardiac muscle and some endocrine glands

-divided into two parts

 

1. Sympathetic Nervous System (SNS)

2. Parasympathetic Nervous System (PNS)

 

Regions of the Medulla, Pons and Diencephalon control the Autonomic Nervous System (ANS):

 

SNS Fibers Leave Thorax and Upper Lumbar Region

PNS Fibers Leave Brainstem and Sacral Regions

 

The Reflex Arc Show Figure 19.5

Nerve Supply to Muscle

Motor unit = one motor neuron and all of the muscle fibers that it innervates

specific examples: muscle of the finger = 1:340

gastrocnemius = 1:2000

 

Show Figure 19.6 - anatomy of a motoneuron

1. Neuron - fundamental functional unit

2. Impulses - created by diffusion of charged atoms.

3. Dendrites - receive impulses

4. Axon - transmits impulses away

5. Axon coverings:

a. myelin - a phospholipid that insulates axons and speeds impulse.

b. neurilemma - cell membrane of Shwann cells.

6. Nodes of Ranvier - periodic gaps between successive Shwann cells.

7. Afferent - towards the cell body, or towards the CNS

8. Efferent- away from the cell body, or away from the CNS

9. Parikaryon- the same as the cell body

10. Nissl substance- the rough endoplasmic reticulum of the nerve cell

11. Axoplasmic streaming- the delivery of protein and other substances made in the cell body to the axon or axon terminal

12. Axon Hillock- where the axon joins the cell body; the site where a new impulse may begin and travel down the axon

13. Acetylcholine- the neurotransmitter used to stimulate muscle cells at the motor end plate

14. Motor end plate or Neuromuscular Junction - where an axon meets with a muscle fiber

15. Acetylcholinesterase- an enzyme which breaks down acetylcholine at the motor end plate within about 5 ms after the Ach is released

16. Synaptic cleft (synapse)- the space between an axon terminal and any other structure (i.e. muscle, neuron, gland, organ, etc.)

17. End Plate Potential- resulting change in the electrical properties of the postsynaptic membrane

 

Two types of motoneurons:

1. type A (alpha) motoneurons (8-20 um; very fast)

2. gamma efferent motoneurons (smaller and slow)

 

Facilitation (in neurons)

EPSP- Excitatory Postsynaptic Potential

Resting Membrane Potential (-70 mv)

Spatial vs. Temporal Summation

Contributions to Strength Gains Show Figure 19.8

 

Disinhibition

Decreased Motoneuron Sensitivity

Less Inhibitory Neurotransmitter Released

Can not occur at the NMJ because there are no inhibitory neurotransmitters here.

 

Inhibition

Inhibitory Postsynaptic Potentials (IPSP)

Neurotransmitter unknown (GABA)

 

Motor Unit Functional Characteristics

Classified by:

 

1. twitch characteristics

2. tension characteristics

3. fatigability

Show Table 19.1 and Figure 19.9

What is "all or none"?

 

Then how do we control a gradation of force?

 

1. # of motor units recruited (Henneman's Size principle)

 

Show Figure 19.10

 

synchronous vs. asynchronous firing

weightlifting vs. running

 

2. frequency of discharge

(20 - 100 Hz)

 

Neuromuscular Fatigue

1. CNS Could be related to blood glucose ?

2. PNS

3. NMJ Cause unknown ? (decreased EMG)

4. Muscle fiber function

 

Receptors in Muscles, Joints and Tendons: The Proprioceptors

can sense the following:

 

1. stretch

2. tension

3. pressure

 

Muscle Spindle Stretch Initiate Stronger Contraction

Nuclear bag fibers (2)

Nuclear chain fiber (4-5)

Have annulospiral nerves attached

Gamma motor efferents Have flower spray endings

Show Figure 19.12

Golgi Tendon Organs Show Figure 19.13

-sense tension not length

-reflex inhibition

 

"the ultimate function of the GTO is to protect the muscle and its connective tissue harness from injury due to an excessive load"

 

Pascinian Corpuscles

1. sense deep pressure

2. "fast-adapting"

---

The Endocrine System and Exercise

The Endocrine System Overview

Endocrine System Organization

Nature of Hormones

Hormone-Target Cell Specificity

Factors that Determine Hormone Levels

Resting and Exercise-Induced Endocrine Secretions*

Anterior Pituitary Hormones

Growth Hormone

Thyrotropin

Corticotropin*

Prolactin*

Gonadotropic Hormones*

Posterior Pituitary Hormones

Thyroid Hormones

Adrenal Hormones

Adrenal Medulla Hormones

Adrenocortical Hormones*

Gonadal Hormones

Pancreatic Hormones

Insulin

Glucagon

Other Glands and Hormones*

Exercise Training and Endocrine Function

Anterior Pituitary Hormones

Posterior Pituitary Hormones*

Thyroid Hormones

Adrenal Hormones

Pancreatic Hormones

Resistance Training and Endocrine Function

Opioid Peptides and Exercise

Exercise, Infectious Illness, Cancer, and Immune Response*

Upper Respiratory Tract Infections*

Exercise-Cancer Connection*

 

* No question on test #1 will come from these sections !

 

The Endocrine System Overview

Endocrine Glands

pituitary, thyroid, parathyroid, adrenal , pineal, thymus

 

Neuroendocrine Gland

hypothalamus

 

Endocrine System Organization

The endocrine system consists of a host organ (gland), minute quantities of chemical messengers (hormones), and a target or receptor organ.

 

Endocrine glands have no ducts and secrete directly into the extracellular spaces around the gland.

 

See Figure 20.2

 

Nature of Hormones

Hormones are chemical substances synthesized by a specific host gland, secreted in the blood, and carried throughout the body.

 

a. steroid hormones (cholesterol)

b. peptide hormones (proteins)

c. prostaglandins (arachidonic acid)

d. erythropoietin (glycoprotein)

 

Hormone-Target Cell Specificity

The major function of hormones is to alter the rates of specific cellular reactions of specific "target cells".

 

1. Altering the rate of intracellular protein synthesis

2. Changing the rate of enzyme activity

3. Modifying plasma membrane transport

4. Inducing secretory activity

 

• 10,000 receptors/ cell
• upregulation vs. downregulation
• cyclic AMP- response to many hormones
  • See Figure 20.3

 

Effects on Enzymes

1. stimulate increased production of the enzyme

2. allosteric modulation (increase or decrease)

3. activate inactive forms of the enzyme

Factors that Determine Hormone Levels

pulsatile release

hormonal stimulation

humoral stimulation

neural stimulation

 

Hormones Response to Exercise and Physical Training

Anterior Pituitary Hormones

widespread influence (master gland ?)

 

Growth Hormone (somatotropin)

 

1. protein synthesis

2. amino acid transport

3. RNA formation

4. activating cellular ribosomes

 

GH release proportional to intensity of exercise (pulse frequency and amplitude.

Endogenous opiates release somatostatin which inhibits GH release.

See Figure 20.5

 

Thyrotropin- also called thyroid stimulating hormone (TSH)

1. controls amount of hormone released from thyroid

2. growth and development of thyroid gland

3. increase metabolism of thyroid gland cells

4. TSH release increases with exercise

 

Posterior Pituitary Hormones

1. outgrowth of the hypothalamus

2. resembles neural tissue

3. stores antidiuretic hormone (ADH)

 

Thyroid Hormones

1. protein-iodine-bound hormones Thyroxine (T4) and Triiodothyronine (T3)

2. Has a very powerful effect on BMR

3. Can't be used to explain obesity

4. Low T4 Sluggishness

5. Exercise induces large increases (probably due to °C)

 

Adrenal Hormones

Are released from the adrenal glands (just above each kidney)

Medulla and Cortex

 

Adrenal Medulla Hormones

1. catecholamines (epinephrine and norepinephrine)

2. SNS releases norepinephrine lipolysis

3. adrenal medulla mostly secretes epinephrine

4. epinephrine is used for glycogenolysis

5. both important for blood flow distribution and cardiac contractility

6. release is based on relative intensity of exercise

 

Gonadal Hormones

1. Testosterone- raises in both males and females w/ exercise

2. Estrogens (estradiol and progesterone)

See Figure 20.10

 

Pancreatic Hormones

Come from the pancreas (14 cm and 60 grams)

 

The major function of insulin is regulation of glucose metabolism in all tissues except the brain. Without it, only trace amounts of glucose can be transported into cells.

 

Insulin

1. release of insulin determined by glucose in blood

2. decreased release with catecholamine release in exercise

 

Diabetes

1. type I

2. type II (NIDDM)

 

-exercise and insulin treatment

-exercise and prevention of NIDDM

-exercise benefits for NIDDM

 

1. glycemic control

2. decreased risk of cardiovascular disease

3. weight loss

4. psychological profile

5. NIDDM occurrence

 

Glucagon

1. Insulin's antagonist: promotes glycogenolysis and gluconeogenesis

2. Works through cAMP

3. Rises substantially late in exercise to combat hypoglycemia

 

Exercise Training and Endocrine Function

Generally, the magnitude of hormonal response to a standard exercise load declines with endurance training. (similar at the same relative intensity

 

Anterior Pituitary Hormones (Skip this)

Thyroid Hormones

Levels are changed somewhat with training, but it appears to be more related to body fat %. When % body fat is low, thyroid hormone tends to decrease and vice versa.

 

Adrenal Hormones

A trained individual exhibits a much weaker response to the same level of absolute work. (similar at the same relative intensity)

 

Pancreatic Hormones

Less insulin is needed for the same glucose uptake when a person is trained due to improved insulin sensitivity and less glucose is needed by the trained individual.

 

Resistance Training and Endocrine Function

Growth hormone, testosterone and the somatomedins seem to exhibit the hypertrophy effects more than any other factors.

 

Opioid Peptides and Exercise

ß-lipotrophin

ß-endorphin

dynorphin (most potent)

---

Pulmonary Structure and Function

Surface Area and Gas Exchange

Anatomy of Ventilation

• pulmonary ventilation - the exchange of gases at the lungs
• nose + mouth + trachea - filter, warm and humidify the air before it reaches the lungs
• bronchi - large tubes that serve as primary conduits to each lung
• bronchioles - tortuous and narrow route which ends in alveolar ducts
• alveoli - microscopic (many make up the alveolar duct)

 

The Lungs - major function is gas exchange

• move oxygen to the venous blood from the inspired air
• move carbon dioxide from the venous blood to the expired air
• 4-6 liter volume (air in a basketball)
• surface volume is enormous
• 50-100 square meters
• transit time changes with rest-exercise transition, but not so much that it can't be saturated with O2

 

The Alveoli

• 300 million of them (.3 mm in diameter)
• has the greatest blood supply of any tissue in the body
• pores of Kohn - allow gas exchange between adjacent alveoli
• 250 ml of O2 enter the blood stream each minute at rest
• 200 ml of CO2 diffuses in the opposite direction
• this can increase 25 fold during heavy exercise by an endurance athlete

 

Mechanics of Ventilation

See Figure 12.3

• conducting zones - also referred to as "dead space"
• respiratory zones

 

Fick's Law- the rate of gas transfer through a sheet of tissue is proportional to the tissue area, a diffusion constant, and the difference between the pressure of the gas on each side of the membrane and is inversely proportional to the thickness of the tissue

Inspiration and Expiration- depends on chest cavity and muscular action

 

Inspiration

1. Diaphragm - muscular dome (moves as much as 10 cm)

2. Intrapulmonic pressure - pressure within the lungs

3. Ribs and Sternum - scalene and external intercostals

 

Expiration

1. predominantly passive

2. heavy exercise - internal intercostals + abdominal muscles

 

Valsalva Maneuver

 

1. allows stabilization of the chest and abdomen during lifting

2. glottis closes (smallest portion of larynx)

3. increases intrathoracic pressure

4. enhances action of muscles attached to the chest

5. patients of heart disease should refrain from heavy lifting

 

Lung Volumes and Capacities

lung volumes vary with:

1. age

2. sex

3. body size

4. stature

 

Static Lung Volumes

Tidal volume - during exercise increases substantially

Forced Vital Capacity

1. up to 8.1 liters in tall athletes

2. not changed to any great degree with training

 

Residual lung volume

1. changes with age due to elasticity

2. can be measured through helium and O2 dilution methods

3. is affected by acute bout of short or long term exercise

due to:

a. closure of small peripheral airways

b. accumulation of pulmonary extravascular fluid

c. unknown ?

 

Dynamic Lung Volumes

depend on:

 

1. the vital capacity (max stroke volume)

2. the breathing rate

 

FEV/FVC ratio - forced expiratory volume/ forced vital capacity

1. measure of the % of FVC that can be expired in 1.0 second

2. indicates resistance to breathing

 

Maximum voluntary ventilation

1. breath rapidly and deeply for 15 seconds

2. extrapolate to one minute

3. 25% higher than during max exercise

4. 140-180 l/min for males; 80-120 l/min for females

5. #'s as high as 239 l/min in certain athletes

 

Lung Function, Training, and Exercise Performance

• Why don't all athletes adapt ?
• Swimming and Diving
• No relationship between lung capacities and VO₂ max.
• Although fatigue in strenuous exercise is frequently related to feeling "out of breath" or "winded", it appears that the normal capacity for pulmonary ventilation does not limit exercise performance.

Training-induced benefits for ventilatory endurance:

1. inspiratory muscle fatigue usually occurs with high intensity

2. training adaptation allows high level submax exercise

 

Exercise and Asthma

• Affects about 12 million Americans most of whom are children
• No immunity with exercise

 

Characterized by:

1. hyperirritability of the pulmonary airways

2. bronchial spasm

3. edema

4. mucus secretion

5. chest tightness, coughing, wheezing, shortness of breath

 

• Exercise is a potent stimulus for brochoconstriction
• Exercise-induced bronchospasm

 

Environment

1. humidity

2. temperature

3. swimming well tolerated by asthmatics

a. temperature is usually warm

b. humid air

c. high catecholamines with upper body exercise

4. also can use brochodilators or anti-inflammatory agents

 

Postexercise coughing

due to respiratory water loss (usually alleviated quickly)

 

Pulmonary Ventilation

Minute Ventilation

at rest :

 

12 breaths / minute

tidal volume of 500 ml (.5 liters) per breath

Minute ventilation (VE) = (12)*(.5) = 6 liters/ minute

 

normal young adults during strenuous exercise:

 

40 breaths/ minute

tidal volume of 2,500 ml (2.5 liters)

Minute ventilation (VE) = (40)*(2.5) = 100 liters/ minute

 

Well trained endurance athlete of large stature:

 

60-70 breaths/ minute

tidal volume of 3,000 ml (3 liters)

Minute ventilation (VE) = (65)*(3.0) = 195 liters/ minute

 

Alveolar Ventilation

• alveolar ventilation does not = minute ventilation because of the non-diffusable conducting passages (anatomic dead space)
• 500 ml enters alveoli from tidal volume
• 350 ml of this is fresh air

 

350 ml is about 15% of the total air volume of the alveoli : insures that alveolar air composition due not change drastically which insures consistency in arterial blood gases

 

Deep breathing provides more effective alveolar ventilation than a similar ventilation achieved only through an increase in breathing rate

 

Physiologic Dead Space

ventilation-perfusion ratio

• = alveolar ventilation / pulmonary blood flow (4.2 liters / 5.0 liters = .8)
• with exercise, ventilation-perfusion ratio can reach more than 5.0
• any portion of alveolar volume with poor ventilation-perfusion is physiologic dead space
• usually only substantial with disease states

 

Rate vs. Depth

• can increase both to obtain greater alveolar ventilation
• with moderate exercise, well trained individuals increase depth more than rate
• this is largely due to using more of the inspiratory reserve volume
• at about 60% of the total vital capacity alveolar ventilation is increased with breathing frequency
• key is to breath in a manner that seems most natural

 

---

Gas Exchange and Transport

 

Ambient Air

20.93 % oxygen

79.04 % nitrogen

.03 % carbon dioxide

 

• Air pressure vs. air %
• pressure is dependent upon the speed at which molecules move; thereby exhibiting pressure upon any surface they contact
• at sea level: pressure can raise a column of mercury 760 mm, therefore sea level pressure is 760 mmHg

 

Gas Exchange in the Lungs and Tissues

Concentrations and Partial Pressures of Respired Gases

 

partial pressure - the "part" of the whole ambient pressure that is applied from a particular gas

Partial pressure = % concentration x Total pressure of gas mixture

 

 

Ambient Air Partial Pressures

 

 

Tracheal Air

-water vapor accounts for 47 mmHg of the total 760 mmHg

-this leaves 713 mmHg for the other gases

-O₂ partial pressure drops to about 149 mmHg in the trachea

 

Alveolar Air

-alveolar air is dissipating O2 to the blood and absorbing CO2 from the blood

-represent pressure by gases on alveolar-capillary membrane

 

Movement of Gas in Air and Fluids

Henry's Law- states that two factors determine the amount of gas that dissolves in a fluid:

 

1. The Pressure Differential

2. The Solubility of the Gas in the Fluid

 

Pressure

- gases always move from high to low pressure

 

Solubility

- some gases dissolve in fluid much more readily than others

- the solubility of CO₂ is much greater (25x) than that of O₂

 

Gas Exchange in the Lungs and Tissues

-the exchange of gases between the lungs and the blood, as well as their movement at the tissue level, is due entirely to the passive process of diffusion

 

See Figure 13.2

Gas Exchange in the Lungs

- pressure gradient for O₂ at lungs is from 100 mmHg to 40 mmHg

- pressure gradient for CO₂ is much smaller at 6 mmHg, but the gas is much more soluble

- in .25 seconds, or 1/3 of the transit time, gases in the alveoli can reach an equilibrium with the capillaries

- therefore, arterial blood is at 100 mmHg and 40 mmHg

 

Gas Transfer in the Tissues

- just outside of a muscle cell, PO₂ is about 40 mmHg and PCO₂ is about 46 mmHg (at rest)

- during heavy exercise, PO₂ can reach 0 mmHg and PCO₂ can reach 90 mmHg

- pons and medullary centers of the brainstem sense the levels of PCO₂ and adjust breathing

 

Transport of Oxygen

Transport of Oxygen in the Blood

- two methods

 

1. in physical solution dissolved in the fluid portion of the blood

2. in loose combination with hemoglobin, the iron-protein compound in the RBC

 

Oxygen in Solution

- the small amount of oxygen found in the plasma plays an important role in loading hemoglobin at the lungs and subsequently releasing oxygen in the tissues

 

Oxygen Combined with Hemoglobin

- 280 million hemoglobin molecules are crowded into each of the bodies 25 trillion red blood cells

 

There are four iron atoms in a hemoglobin molecule:

Hb₄ + 4O₂ creates Hb₄O₈

The oxygenation of hemoglobin to oxyhemoglobin depends entirely on the partial pressure of oxygen in solution.

Men : 15-16 g Hb / 100 ml of blood

 

Women: 14 g Hb / 100 ml of blood

 

1.34 ml O2 / g Hb

 

(15g Hb / 100 ml) x (1.34 ml O2 / g Hb) = 20 ml O2 /100 ml blood

Anemia

 

PO₂ and Hemoglobin Saturation

-exhibits cooperativity

See Figure 13.4

 

PO₂ in the Lung

- is about 100 mmHg and hemoglobin leaving the lung is about 98% saturated

- little or no benefit to breathing 100 % O₂

See Figure 13.5

 

PO₂ in the Tissues

- arterio-venous Oxygen difference (a-v O₂ difference)

- 4-5 ml O₂ / 100 ml blood at rest

- during strenuous exercise can reach 15 ml O₂ / 100 ml blood

 

The Bohr Effect

- any increase in acidity, temperature, or concentration or carbon dioxide causes the dissociation curve to shift downward and to the right

 

Red Blood Cell 2,3 DPG

- 2,3 diphosphoglycerate is produced in RBC

- competes with hemoglobin for O₂

- helps deliver O₂ to cells at tissues

- may be increased with exercise

- higher in females and may compensate for lower hemoglobin

 

Myoglobin, The Muscle's Oxygen Store

- another globular protein: skeletal and cardiac muscle

- appears red in muscle

- probably increased with training, but not addressed in humans

Mb + O₂ creates MbO₂

 

Oxygen Released at Low Pressures

- when cellular PO₂ drops, Mb facilitates O₂ to mitochondria

- especially true when PO₂ drops to less than 5 mmHg

- no Bohr effect

 

Transport of Carbon Dioxide

Transport of Carbon Dioxide in the Blood

See Figure 13.6

- 5% of CO₂ formed during energy metabolism is in solution

- this small amount determines the PCO₂ in the blood

 

Carbon Dioxide Transport as Bicarbonate

CO₂ + H₂O creates H₂CO₃

 

In tissues:

CO₂ + H₂O creates H₂CO₃ which can create H+ + HCO₃-

- chloride shift - allows for bicarbonate ion to leave the RBC and be replaced with chloride; keeps the chloride content of venous blood above that of arterial blood

 

- 60-80% of CO₂ exists as plasma bicarbonate

 

In lungs:

H+ + HCO₃- creates H₂CO₃ which creates CO₂ + H₂O

 

Carbon Dioxide Transport as Carbamino Compounds

-at the tissues, CO2 reacts with amino acid portion of blood proteins to form carbamino compound (especially true of globin portion of hemoglobin)

CO₂ + HbNH creates HbNHCOOH

- high PO₂ at the lungs drives this reaction towards CO₂

 

- this is referred to as the Haldane Effect

---

The Cardiovascular System

oxygen transport coupled with the muscles ability to produce ATP (aerobically), determines the max level of work

 

Components of the Cardiovascular System

100,000 miles of blood vessels in our body

 

See Figure 15.1

 

60% of blood in small vessels

The Heart

at rest, pumps 1,400 gallons daily

myocardium - heart muscle, with all cells connected; therefore when one cell is stimulated they are all stimulated

See Figure 15.2

1. receives deoxygenated blood from the body

2. pumps blood to the lungs through pulmonary circulation

3. receives oxygenated blood from the lungs

4. pumps oxygenated blood to the body through systemic circulation

 

• interventricular septum - separates sides of the heart
• atrioventricular valve - on right side between atrium and ventricle
• mitral valve - on left side between atrium and ventricle

(atrioventricular and mitral valves are called tricuspid and bicuspid valves respectively)

 

isovolumetric contraction period - valves are closed on both sides of the ventricle, and myocardium is starting contraction

 

The Arterial System See Vessel Wall Figure

• high pressure vessels which conduct O2 to tissues
• elastic arteries (example: aorta)
• arterioles - control pressure and blood flow
• Windkessel effect and blood pressure

 

blood pressure = cardiac output x Total peripheral resistance

 

systole and diastole See Figure 15.4

systolic and diastolic blood pressure - estimate work of heart and peripheral resistance respectively

 

Mean arterial pressure = DBP + [ .333 (SBP - DBP)]

 

The Capillaries

• .01 mm in diameter and contain about 5% of total blood volume
• some allow only one blood cell at a time
• 2,000 - 3,000 capillaries / mm2 in skeletal muscle
• precapillary sphincter - allows control of blood flow

 

The Veins

• venules are small veins which collect the blood from the capillaries
• eventually feeding to the largest veins (inferior and superior vena cava)
• dissipation of blood pressure and thin walls of veins
• valves in veins - one way flow
• venous system contains 65% of all blood and therefore serves as a blood reservoir
• varicose veins - a loss of one way flow due to weakened valves
• phlebitis - severe varicose veins which become inflamed and may degenerate

 

Hypertension

• hardened arteries, nervous strain, or kidney malfunction can all contribute to high blood pressure
• 50 million Americans have blood pressures in the "borderline" hypertensive region
• can lead to heart failure, myocardial infarction, or stoke
• exercise and diet can modify blood pressure more efficiently than drug treatment (drug treatment side effects)

 

Effects of Regular Exercise

• exercise has a definite effect
• even a modest effect can alleviate disease states
• at least two actions may propagate this response:

1. reduced activity of sympathetic nervous system

2. altered renal function (removes excess sodium)

 

in one study, aerobically fit individuals with hypertension had 60% lower mortality rate than their unfit normotensive peers

 

Blood Pressure and Exercise

Static and Dynamic Resistance Exercise

-blood pressure rises steeply with concentric lifting due to increased peripheral resistance

proportional to intensity and muscle mass recruited

See Figure 15.8

 

Chronic Effects of Resistance Exercise

• some studies have shown lower resting blood pressure following resistance training regimes
• lowers blood pressure response to same absolute work
• not as effective as aerobic training

 

Steady-Rate Exercise

• rhythmic exercise allows for greater dilation of blood vessels and lower total peripheral resistance
• increased venous return through muscular pumps

Graded Exercise See Figure 15.9

 

Blood Pressure in Upper Body Exercise

• higher blood pressure with arm work at the same relative % of VO2 max
• smaller muscle mass and vasulature of the arms offer greater resistance to blood flow than the larger muscle mass and vasculature of the legs
• recommend large body exercise with therapy for cardiovascular disease
• avoid activities such as shoveling etc.

 

In Recovery

• the hypotensive response can last up to 12 hours into recovery from both low and moderate intensity exercise
• blood remains in the periphery rather than returning to central blood pool

 

Body Inversion

• beneficial effects have not been studied extensively
• harmful effect of increased blood pressure may counteract any possible benefit

 

The Heart's Blood Supply

• coronary circulation See Figure 15.10
• right and left coronary arteries branch from the aorta just above the aortic semilunar valve
• each branch subdivides and supplies the right and left sides of the heart respectively
• left venticular blood supply exits through the coronary sinus
• right ventricular blood supply exits through the anterior cardiac veins which empty into the right atrium

 

Myocardial Oxygen Utilization

• at rest, oxygen utilization of the myocardium is high with respect to its blood flow
• 200 - 250 ml / minute at rest (5% of total output)
• 70 -80 % of the oxygen is extracted
• therefore, increased myocardial demands are matched by increased myocardial blood flow

dilated coronary vessels by:

 

1. hypoxia

2. adenosine

3. hormones

 

• 2.5 x greater with diastole than during systole
• angina pectoris - chest pain due to lack of blood flow
• thrombus - blood clot
• myocardial infarction - death of cells due to ischemia

 

The Rate-Pressure Product: An Estimate of Myocardial Work

• calculated as the peak systolic BP of the brachial artery multiplied by the heart rate
• RPP = SBP x HR
• also referred to as the double product, and is directly related to oxygen consumption by the myocardium
• used extensively in exercise studies of heart disease patients

 

Myocardial Metabolism

• relies almost completely on aerobic mechanisms
• heart is a scavenger in terms of fuels which can be used

---

Cardiovascular Regulation and Integration

 

• vascular system has far greater capacity than volume of blood
• 5% to skin during rest: 20% to skin during exercise in hot humid environment

 

Intrinsic Regulation of Heart Rate

• autorhythmicity (70-90 bpm)
• S.A. node (spontaneous depolarization)
• otherwise known as the pacemaker See Conduction Figure

 

Heart's Electrical Activity

• S.A. node to A.V. node and across the Bundle of Bachmann to the left atria
• A.V. node to A.V. bundle (slowest portion of conduction system)
• A.V. Bundle is also called the Bundle of His
• Spreads to the Purkinje fibers which penetrate the left and right ventricles

 

ECG-Electrocardiogram

a graphic record of the heart's electrical activity

See Figure 16.2

• P wave - represents depolarization of the atria
• QRS wave- represents depolarization of the ventricles
• T wave- represents repolarization of the ventricles

rest period or refractory period - allows for the ventricles to fill during the filling phase of the cardiac cycle

 

Extrinsic Regulation of the Heart and Circulation

extrinsic controls include nerves to the heart and chemicals in the blood

 

can control rates of 25-30 beats/ min to over 200 beats/ min

See Figure 16.3

cardiovascular control center in the ventrolateral medulla (directions)

 

Sympathetic and Parsympathetic Neural Input

imposed on the inherent rhythm of the heart

 

Sympathetic Influence

• release of cardioaccelerators or catecholamines (epinephrine and norepinephrine)
• causes an accelerated heart rate called tachycardia and an increase in myocardial contractility

 

• myocardial contractility - increases the amount of blood ejected from the heart with each beat
• max sympathetic activity doubles the ventricular contraction
• epinephrine from the adrenal glands have the same response, but the action is much slower

  sympathetic stimulation effects blood supply throughout the body:

  1. norepinephrine is a general vasoconstrictor and is released from adrenergic nerve fibers

  2. acetylcholine is released from other sympathetic neurons called cholinergic fibers in heart and skeletal muscle; it is a general vasodilator

  vasomotor tone refers to the constant adrenergic stimulation of some of the vasculature

 

Parasympathetic Influence

• the parasympathetic neurons release acetylcholine which retards the rate of sinus discharge to slow the heart
• slowing of the heart is referred to as bradycardia (it is mediated through a pair of vagus nerves which originate in the cardioinhibitory region of the medulla)

 

Training Effects

• exercise training creates greater dominance by the parasympathetic depressor neurons
• may also cause a decrease in the inherent heart rate
• both cause resting bradycardia

 

Input From Higher Centers: A Central Command

• somatomotor centers in the brain which send messages to the active musculature, also send messages to the medulla
• this is referred to as "feed forward" or central command and is active during the "anticipatory period" and during the exercise bout
• central command is the greatest control over heart rate during exercise
• the anticipatory response is mediated by both the parasympathetic and sympathetic neural activity

 

Peripheral Input

• cardiovascular center influence from blood vessels, joints, and muscles
• when the reflex neural input is from the active muscle it is called the "exercise-pressor reflex"
• reflex responses from the blood vessels are from baroreceptors in the aorta and carotid sinus

 

Carotid Artery Palpation

• strong external pressure on the carotid artery in some individuals causes slowing of the heart rate
• this is due to direct stimulation of the baroreceptor
• because this method is often used to regulate intensity of exercise, it may cause problems with:

1. exercise training

2. rehabilitation of cardiac patients

 

Distribution of Blood

Physical Factors That Affect Blood Flow

physical laws are true only in a qualitative sense (not rigid cylindrical tubes and homogeneous fluid)

1. Volume of flow in any vessel is directly proportional to the pressure gradient between the two ends of the vessels and not to the absolute pressure within the vessel

 

2. Volume of flow in any vessel is inversely related to the resistance encountered to the flow

 

Poiseuille's Law

Flow = pressure gradient x vessel radius⁴ / vessel length x velocity

 

Effect of Exercise

large shift from venous distribution of blood to arterial side (particularly working musculature)

renal blood flow which is normally 20% of the cardiac output at rest can reduce itself to 1% of cardiac output during exercise

 

Local Factors

• at rest 1:30-40 capillaries open in muscle
• opening of dormant capillaries allows:

  1. increased muscle blood flow

  2. larger volume of blood w/ very little increase in velocity

  3. increased effective surface for exchange between blood and muscle fibers

   

  regional blood flow is controlled by:

1. decreased tissue O2 supply

2. temperature

3. carbon dioxide

4. acidity

5. adenosine

6. magnesium and potassium

7. nitric oxide (from vascular endothelium)

 

Integrated Response in Exercise

1. feed-forward central command early

2. regional blood flow changes with intensity

3. reflex feedback to the medulla from several mechanical and chemical receptors

4. local metabolic factors act directly for vasodilation

5. vasoconstriction at less active tissues

6. vasoconstriction at veins to increase venous return

 

Exercising After Cardiac Transplantation: A "Sluggish" Circulatory Response

• orthotopic transplantation = cardiac transplantation
• neural innervation of the myocardium is eliminated
• survival rate and complications not great
• severely lowered exercise capabilities
• heart rate increases are severely limited
• no pain response with coronary artery disease

---

Functional Capacity of the Cardiovascular System

 

Cardiac Output

• refers to the amount of blood pumped by the heart, usually during one minute
• Cardiac output = heart rate x stroke volume
• cardiac output is expressed as C.O. or Q in literature

 

Measuring Cardiac Output

three common methods assess cardiac output in humans:

 

1. direct Fick method

2. indicator dilution technique

3. CO2 rebreathing technique

 

Direct Fick Method

Fick equation:

Cardiac Output = O₂ Consumption/ a-vO₂ Difference x 100

average person at rest: = 250 ml O₂/ 5 ml O₂ x 100 = 5,000 ml blood

however this technique is not very practical:

1. sampling blood from artery can be traumatic

2. sampling blood from vein must be a major mixing vein or possibly the right atrium

3. invasive nature can change hemodynamics

See Figure 17.1

 

Indicator Dilution Method

a known quantity of indicator dye is injected into a vein

 

(indocyanine green is an example)

 

cardiac output = quantity of dye injected/ avg [ ] dye in blood x duration of curve/ duration of curve

 

CO₂ Rebreathing Method

• can use carbon dioxide substitution into Fick equation
• use open circuit spirometry
• noninvasive or bloodless
• requires breath by breath analysis of CO₂
• after venous and arterial carbon dioxide [ ]'s are estimated, cardiac output is calculated as:

 

Cardiac output = carbon dioxide production/ v-a CO₂ difference x 100

has many benefits:

1. no close medical supervision necessary

2. noninvasive

 

limited to steady-state exercise (difficult for max measurements)

 

Cardiac Output at Rest

a 5 liter cardiac output is the average for untrained and trained individuals at rest

 

untrained male: 5,000 ml = (70 beats/min) x (71 ml/beat)

 

untrained female: approximately 25% lower SV and CO

 

trained male: 5,000 ml = (50 beats/min) x (100 ml/beat)

 

trained female: much higher than untrained male, but lower than a trained male

 

Cardiac Output During Exercise

large rapid increase with exercise and then a slower rise until a plateau is reached

 

sedentary college-aged males can rise to 20-22 L / min

world class athletes have cardiac outputs of up to 35-40 L/ min

 

the endurance athlete achieves a large maximal cardiac output solely as the result of a large stroke volume

one cross country skier had a cardiac output of 210 ml/beat

 

Stroke Volume in Exercise: Training Effects

See Figure 17.2

1. heart of endurance athlete is larger

2. greatest increase in SV occurs in transition from rest to moderate exercise

3. max SV is reached at about 50% of VO2 max

4. untrained SV increases very little from rest to exercise so most of increase is from increased HR

5. trained person increases CO by increasing both HR and SV

 

Most differences in VO₂ max are explained by SV

 

Stroke Volume: Systolic Emptying vs. Diastolic Filling

Two mechanisms

 

1. intrinsic to the myocardium

2. neurohormonal influence

 

Enhanced diastolic filling (preload)

1. increased venous return

2. slowing of the heart

 

increased EDV causes greater SV

 

Frank-Starling's Mechanism or Starling's Law of the Heart

with greater stretch on the myocardium, there is a resulting greater force of contraction probably due to a more optimal arrangement of the sarcomere's myofilaments

 

is definitely affected by body position

 

Greater Systolic Emptying

• heart contains a functional residual volume which is used when the heart contracts more forcefully and lowers ESV
• this is probably mediated by catecholamines

 

Training Effects

• enlarged ventricular chamber
• more compliant left ventricle
• possible enhanced myocardial contractility

 

Heart Rate During Exercise: Training Effects

can lower 12-15 beats/ min at same submax exercise

 

See Figure 17.3

 

linear relationship, but the slopes are significantly different

 

with 2 months of training-- difference was reduced substantially

 

Distribution of Cardiac Output

demand from muscle can alter blood to kidneys, digestive organs, and skin

 

Blood Flow at Rest and During Exercise

See Figure 17.4

 

a substantial reduction in blood flow to digestive organs can be tolerated for over 1 hour

 

Blood Flow to the Heart and Brain

• some tissues cannot compromise their blood supply
• both the heart and brain increase their blood supply during exercise

 

Cardiac Output and Oxygen Transport at Rest and During Exercise

• 5 liters of blood / min at rest
• 200 ml O2/ liter of blood at rest; therefore:

 

• 1 liter of O2 is delivered each minute during rest
• only 250 ml O2 are used each minute at rest
• 750 ml O2 are reserve which can be released immediately upon demand of the tissues

 

• 16 liters of blood / min during heavy exercise
• 200 ml O2/ liter of blood during exercise; therefore
• 3.2 liters of oxygen are delivered each minute during heavy exercise (75-90% of it is used)

 

Close Association Between Maximum Cardiac Output and VO2 max

• 5-6 liters of blood = 1 liter of Oxygen uptake
• relationship remains the same over a wide range of exercises
• preadolescents and endurance athletes both have high levels of cardiac output and oxygen consumption
• females have a 5-10% greater cardiac output at any level of submaximal oxygen uptake due to 10% lower hemoglobin

 

Training and Submaximal Cardiac Output

submaximal cardiac output will decrease with training if the exercise is performed at the same level of VO2 as a result of:

 

See Figure 17.6

 

1. more effective distribution of cardiac output

2. enhanced ability of muscle to generate ATP from O₂

 

Extraction of Oxygen: The a-v O₂ Difference

 

can't rely on just increasing blood supply to increase O₂ uptake

 

two mechanisms:

1. increase cardiac output

2. expand the a-v O2 difference

 

Maximal O2 uptake = (max CO) x (max a-v O₂ difference)

 

a-v O₂ Difference at Rest and During Exercise

5 ml O₂ / 100 ml blood during rest

 

15 ml O₂ / 100 ml of blood for sedentary person during maximal exercise

 

17 ml O₂ / 100 ml of blood after 55 days training

 

• not any greater with years of training
• even with heart disease patients who cannot increase cardiac output substantially, increased a-v O₂ difference enables patients to exercise at higher levels
  • See Figure 17.7

 

Factors That Affect a-v O₂ Difference in Exercise

• redirection of central circulation is enhanced with training
• capillary to muscle fiber ratio increases with training
• enlarged mitochondria and increased mitochondrial density

 

Cardiovascular Adjustments to Upper Body Exercise

Maximal Oxygen Uptake

smaller muscle mass results in lower max O₂ uptake, heart rate and pulmonary ventilation

 

Submaximal Oxygen Uptake

greater oxygen uptake at the same power output with upper body exercise due to lower mechanical efficiency (additional cost of static muscle contractions)

 

See Figure 17.8

 

Physiological Response

at same submaximal VO₂ level, upper body exercise results in higher heart rate, pulmonary ventilation and perception of effort

 

due to greater feedforward and greater feedback

 

Cardiac Hypertrophy and the "Athlete's Heart"

• moderate increase in heart size with endurance training
• fundamental biological adaptation to increased workload
• 25% greater volume of the heart due to increase in heart chamber size
• difficult to separate genetic difference and change from endurance training
• book claims detraining effect causes decrease in heart weight
• different cardiac hypertrophy than is seen with CVD

 

Specific Nature of Training Hypertrophy

echocardiography uses sound waves to map dimensions of the myocardium itself and the size of its chambers

mass and volume dimensions differ considerably with specific types of training

 

1. endurance training - increased ventricular cavity w/ normal wall thickness

2. resistance training - increased ventricular mass and wall thickness

 

There is no compelling evidence that a normal heart can be harmed by specific forms of arduous exercise training.

 

Functional vs. Pathologic Hypertrophy

during exercise there is recuperative time unlike the sustained high workload of the heart with pathologic states

exercise-induced hypertrophy does not result in weakening of the left ventricle

 

Other Training Adaptations

1. increased coronary blood flow

2. increased vascularization of the myocardium

3. increased mitochondrial mass

4. increased concentration of respiratory enzymes

5. may provide protection to degenerative heart disease

---

Measurement of Human Energy Expenditure

 

Methods of Measuring the Body's Heat Production

several different methods classified as either direct or indirect calorimetry

 

Direct Calorimetry

human heat production can be determined by direct calorimetry similar to that used to determine the energy content of food

 

Atwater and Rosa (1890's) - related energy input to energy expenditure in the human body and demonstrated the conservation of energy

• subjects could live, eat, sleep and exercise on a bicycle ergometer: experiments lasted from several hours to 13 days
• exercise lasted for as long as 16 hours or an energy expenditure up to 10,000 cals
• airtight, thermally-insulated chamber (calorimeter) was staffed 24 hours / day
• heat absorbed by stream of cold water flowing at constant velocity through large copper coils
• change in temperature of water measured with microscope mounted on a thermometer

 

excellent study for proving theory, but not practical for studying most sport

 

Indirect Calorimetry

• all energy-releasing reactions in the body ultimately depend on the utilization of oxygen
• studies using the bomb calorimeter have shown that approximately 4.82 kcal is liberated when a blend of carbohydrate, lipid, and protein is burned in one liter of oxygen
• indirect calorimetry can be applied through closed circuit or open circuit

 

Closed-Circuit Spirometry

• is used in hospitals and other laboratory settings to estimate resting energy expenditure
• subject breathes from a prefilled container, or spirometer, of 100% oxygen
• called closed system because subject rebreathes only gas from the spirometer
• carbon dioxide is absorbed by soda lime
• inadequate for measures during exercise:

1. too much resistance in the circuit to large breathing volume

2. speed of CO2 removal by soda lime is inadequate

 

Open-Circuit Spirometry

• relatively simple
• no rebreathing from a closed circuit
• inhales ambient air with a constant composition
• exhaled air contains more carbon dioxide and less oxygen
• three common methods of indirect calorimetry are:

1. portable spirometry

2. bag technique

3. computerized instrumentation

 

Portable Spirometry

• originally used to estimate energy expenditure so as to allow equitable food rationing to people working industrial jobs in Germany during World War II
• unit weighs about 3 kg and is usually worn on the back
• through a two-way breathing valve, ambient air is inspired, and expired air passes through a gas meter that measures the total expired air volume and collects a small gas sample in a 100-ml butyl rubber bag
• bag is later analyzed for content
• advantage is the large degree of freedom of movement
• disadvantage is that the apparatus is cumbersome during vigorous activity

 

Bag Technique

• includes special headgear with a two-way, high velocity, low-resistance breathing valve
• ambient air is breathed in through one side of the valve while expired air is expelled out the other side
• air is collected in canvas bags, Douglas bags, or rubber meteorological balloons

 

Computerized Instrumentation

a computer is interfaced with at least three instruments:

 

1. a system to continually sample the subject's expired air

2. a flow meter or turbine device to record the volume of air breathed

3. oxygen and carbon dioxide analyzers to measure the fractional composition of the expired gas mixture

 

advanced systems allow automated measures of:

 

1. blood pressure

2. heart rate

3. temperature monitors

 

and computerized programs allow:

1. regulation of speed

2. duration

3. workload

 

• now have wireless telemetric transmission of data for "in vivo" data collection
• tremendous advantages in terms of operational ease and rapid data analysis
• tremendous disadvantages in terms of relatively high cost of equipment and system breakdowns
• even with high tech equipment, the accuracy is limited by the frequency and accuracy of calibration

 

Direct vs. Indirect Calorimetry

• the two methods have been proven to be extremely similar in data collected
• differences over the course of 40 days in three men summed to the equivalent of one life-saver (10 kcals)

 

The Respiratory Quotient (RQ)

• different amounts of oxygen are required to oxidize completely fat, carbohydrate, and protein
• respiratory quotient = CO2 produced / O2 consumed
• is useful in determining the mixture of fuel used for energy during rest and during exercise

 

RQ for Carbohydrate

when carbohydrate is completely oxidized, the same # of CO2 molecules are produced as are O2 molecules consumed

 

C₆H₁₂O₆ + 6 O₂ creates 6 CO₂ + 6 H₂O

 

RQ = 6 CO₂ / 6 O₂ = 1.00

 

RQ for Lipid

with a typical fatty acid such as palmitate, 16 carbon dioxide molecules are produced for each 23 molecules of O2 consumed

 

C₁₆H₃₂O₆ + 23 O₂ creates 16 CO₂ + 16 H₂O

 

RQ = 16 CO₂ / 23 O₂ = .696

 

RQ for Protein

an example protein for oxidation is albumin:

 

C₇₂H₁₁₂N₂O₂₂S + 77 O₂ creates 63 CO₂ + 38 H₂O + SO₃ + 9 CO (NH₂)₂

 

RQ = 63 CO₂ / 77 O₂ = .818

 

Nonprotein RQ

the gross metabolic RQ calculated without measures of urinary and other nitrogen introduces only minimal error because the contribution of protein to energy metabolism is relatively small

 

How Much Food Was Metabolized for Energy ?

 

See Table 8.1 last two columns

 

RQ for a Mixed Diet

respiratory quotient during rest and moderate exercise will almost always reflect a mixture of metabolic fuels being used

 

Respiratory Exchange Ratio

is calculated in the same manner as the RQ, but RQ assumes that the exchange of gases at the lungs reflects the actual gas exchange from nutrient catabolism at the cells

 

the RER or R will reflect excess carbon dioxide elimination:

 

1. during hyperventilation (breathing response is disproportionate to metabolic demands)

2. can also occur when excess lactate is buffered in the blood in cases such as this; RER can exceed 1.00

---

Human Energy Expenditure During Rest and Physical Activity

Total Daily Energy Expenditure (TDEE) is influenced by three factors:

See Figure 9.1

1. Resting metabolic rate (includes basal and sleeping conditions plus the added metabolic cost of arousal)

2. Thermogenic effect of food consumed

3. Energy expended during physical activity and recovery

 

Energy Expenditure at Rest

Basal Metabolic Rate

• the minimal level of energy required to sustain the body's vital functions in the waking state
• reflects the body's heat production and is determined indirectly by measuring oxygen consumption
• food is not eaten for 12 hours before testing
• physical activity is also restricted prior to testing
• ranges from 160-290 ml O2 / min and most heavily dependent on lean body mass

 

Resting Metabolic Rate

• is very similar to BMR, but is tested under less strict conditions
• measured 3-4 hours after a light meal
• for the typical person, RMR accounts for about 60-75% of the TDEE while the thermic effects of feeding account for about 10%
• physical activity accounts for about 15-30% of the average RMR
•  

Metabolism at Rest

• energy metabolism is often proportional to surface area of the body
• became common practice to express energy expenditure relative to surface area of the body
  • See Figure 9.2

body mass.75 = basal metabolic rate (watts)

 

many studies have shown that indexing the RMR to lean body mass (or FF body mass) provides the best method

 

• BMR is generally 5-10% lower in females than in males due to a slightly greater average body fat
• BMR decreases 2-3% / decade due to a loss of lean body mass
• in one study of older men and women, an 8% increase in resting metabolism was noted following a program of heavy resistance trainin
• regular endurance and resistance training can offset the decrease in resting metabolism usually seen with aging

 

Estimating Daily Resting Energy Expenditure

 

Fat-Free Body Mass

relatively easy and very accurate estimate of RDEE

 

See Table 9.1 RDEE = 370 + 21.6 (FFM, kg)

 

at rest, your brain and all of your skeletal muscle combined both consume about the same amount of energy

 

Factors That Affect Energy Expenditure

Important factors that affect a person's TDEE include:

 

1. physical activity

2. dietary-induced thermogenesis

3. climate

4. pregnancy and lactation

 

Physical Activity

• has the most profound effect on human energy expenditure
• elite athletes can double their daily expenditure with 3 or 4 hours of hard training
• during the sustained exercise, an athlete can maintain metabolic rates up to 10 times resting values

 

Dietary-Induced Thermogenesis

 

has two components:

 

1. obligatory thermogenesis- due to energy requiring processes of digesting, absorbing and assimilating food nutrients

2. facultative thermogenesis- due to activation of the sympathetic nervous system

 

• reaches a maximum about 1 hour after a meal
• can vary between 10 and 30% of the ingested food energy depending on the type of food eaten (protein is high)
• research indicates that individuals who have poor control of body mass often have a blunted response to eating, which can contribute to the accumulation of excess body fat
• very well trained individuals also have a lesser magnitude of dietary-induced thermogenesis

 

Calorigenic Effect of Food on Exercise Metabolism

a study:

 

• when exercise was performed following the ingestion of 1,000 or 3,000 kcals, energy expenditure was larger compared to exercise without prior food ingestion
• the calorigenic effect of food was nearly two times the effect at rest, therefore exercise augments dietary-induced thermogenesis
• it is reasonable to encourage moderate exercise following a meal to increase energy expenditure and control weight gain

 

Climate

 

• resting metabolisms of people in tropical climates are generally 5-20% higher than those of their counterparts living in more temperate areas
• in addition, exercise in the heat utilizes slightly more energy than exercise in the cold due to:

 

1. elevated core temperature

2. energy required for sweat gland activity

3. altered circulatory dynamics

 

• cold environments can increase resting energy expenditure if shivering is induced
• in some cases, shivering can increase resting energy expenditure by two or three fold

 

Pregnancy

See Table 9.3

• increased # of women involved in exercise, sports and occupations including those in the military and public safety
• increased heart rate and oxygen consumption with weight gain during pregnancy, whereas the #'s did not change during weight supported exercise such as bicycle ergometer
• other than weight gain, no other physiological impairments were noticed during pregnancy
• maternal hyperventilation is attributed to the direct stimulating effect of progesterone and increased sensitivity to CO₂

 

Effects of Exercise on Fetus

 

hypothetical risks had been proposed to jeopardize the health of the fetus:

 

1. reduced placental blood flow and fetal hypoxia

2. fetal hyperthermia

3. reduced fetal glucose supply

 

studies have shown that under normal conditions, vigorous maternal exercise is well tolerated by the fetus

 

Status of Current Opinion

• thirty to forty minutes of moderate aerobic exercise during uncomplicated pregnancy does not compromise mother or fetus ( paraphrase )
• exercise should be carried out in moderation, especially if the pregnancy is compromised to any degree
• late in pregnancy, there is some concern over hypoglycemia
• hyperthermia is of some concern as elevated core temperatures can cause neural tube defect within the first trimester
• in warm weather, pregnant women should exercise in the cool part of the day and for shorter intervals while maintaining regular fluid intake
• aquatic exercise serves as an ideal form or maternal exercise

 

Classification of Physical Activities by Energy Expenditure

• intensity and duration are two very important factors determining the difficulty of a particular task
• several classification systems have been used to rate difficulty of activity:

 

1. PAR (physical activity ratio)

a. light work (3 x resting requirement)

b. heavy work (6-8 x resting requirement)

c. maximal work (9 x resting requirement)

 

2. The Met - a multiple of the resting metabolic rate

 

See Table 9.4

 

Daily Rates of Average Energy Expenditure

• average man between 23-50 years of age in the U.S. expends about 2700-3000 kcals / day
• women of the same age expend between 2,000 and 2,100 kcals per day
• about 75% of average U.S. citizen's day is light expenditure

 

Effect of Body Mass

 

energy cost of a particular exercise is generally higher for heavier people, especially weight-bearing exercises

during weight-supported exercise such as cycling, the effect of body weight on caloric expenditure is very minimal (5%)

 

Use of Heart Rate to Estimate Energy Expenditure

• for each person, heart rate and oxygen uptake are very linear
• if a person is aware of their relationship, exercise heart rate can be used to estimate oxygen uptake

  • See Figure 9.6

• notice the slopes are different for each individual; therefore one relationship can not be used for several people
• relationships also change with various modes of exercise

 

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Energy Expenditure During Walking, Jogging, Running and Swimming

 

Gross and Net Energy Expenditure

net energy expenditure = gross energy expenditure - resting energy expenditure

 

Movement Economy and Mechanical Efficiency During Exercise

efficiency of human movement is a relation of the amount of energy required to perform a particular task to the actual work accomplished

 

Economy of Movement

• requires evaluating the oxygen consumed while the subject performs a particular exercise at a set power output or speed
• plays an enormous role in the outcome of most endurance events
• 65% of the total variation in 10 km running performance among athletes can be explained by the variations in running economy
• economy of cycling has been shown to be correlated to the % of type I muscle fiber because cycling is usually performed at an rate that approximates 1/3 of max shortening velocity
• book claims that type I fibers act with greater mechanical efficiency than the type II fiber, but this is only true at 1/3 of its own shortening velocity

 

Mechanical Efficiency

• mechanical efficiency is the percentage of total chemical energy expended that contributes to external work, the remainder being lost as heat
• mechanical efficiency(%) = actual mechanical work / input of energy x 100
• on a bicycle ergometer, the average person exhibits an efficiency of about 25% ; as with all machines, the efficiency of the human body for producing mechanical work is considerably less than 100%
• in general, the efficiency of human locomotion in walking, running and cycling ranges between 20-30%

 

Energy Expenditure During Walking

• the most common form of exercise
  • See Figure 10.2
• notice economy is relatively linear between 3.0-5.0 km / hour

 

Influence of Body Mass

between 2.0-4.0 mph walking speeds, body mass tables can be used to calculate the energy expenditure (accurate to within 15%)

 

Effects of Terrain and Walking Surface

• grass track or paved surface makes little if any difference
• walking in sand double caloric expenditure
• walking in soft snow triples the energy expenditure
• walking on a treadmill or on a paved surface are the same

 

Downhill Walking

• considered negative work
• less costly in terms of energy expenditure to walk downhill
• only expends greater energy downhill when the speed is relatively great and the cost of "braking"

 

Effects of Footwear

• it is considerably more costly to carry weights on the feet or ankles than to carry a similar weight attached to the torso
• this makes the energy cost of wearing boots considerably higher than when wearing running shoes
• softer-soled shoes reduce the oxygen cost of running by about 2.4% when compared to a similar shoe with firm soles even if the soft soled shoes are heavier

 

Use of Hand-Held and Ankle Weights

• the impact force on the leg while running is equal to about 3 times the body mass, whereas the level of leg shock walking is only 30% of this value
• walking with ankle weights can increase the energy cost of walking to values usually observed for running without the impact forces (hand weights elevate SBP)
• running with ankle or hand weights is generally not recommended (benefit is not greater than risk)

 

Competition Walkers

See Figure 10.5

 

Energy Expenditure During Running

• the demarcation between jogging and running is dependent upon the fitness level of the individual
• it is more economical to discontinue walking and begin running at speeds greater than about 5 mph

 

The Economy of Running Fast or Slow

• because the relationship between oxygen uptake and running speed is linear, the total caloric cost or running a given distance at a steady-rate oxygen uptake is about the same regardless of whether the pace is fast or slow
• it is the equivalent of :
• 1 kcal / kg / km or .75 kcal / lb / mile
• it is more costly to run than to walk any given distance because running is slightly less economical

 

Energy Cost Values

See Table 10.3

 

Stride Length, Stride Frequency, and Speed

running speed can be increased in one of three ways:

 

1. by increasing the # of steps each minute (stride frequency)

2. increasing distance between steps (stride length)

3. increasing both the length and the frequency

 

• as a general rule, running speed is increased mostly by stride length and very little by stride frequency; only at faster speeds does stride frequency become important
• most of speed increases with speed walking is from increased stride frequency

 

Optimum Stride Length

• depends a great deal on the individual's mechanics or style
• it is generally more costly to overstride than to understride
• an athlete generally chooses the stride length that is most optimum without being coached to do so

 

Running Economy: Children and Adults, Trained and Untrained

 

• children are less economical than adults because they require 20-30% more oxygen per unit of body mass to run at a particular speed
  • See Figure 10.9
• mostly attributed to increased stride frequency and decreased stride length
• the best runners in the world are the athletes that are able to cover more distance at the same oxygen consumption (i.e. they are the most economical)

 

Air Resistance

 

is affected by three factors:

 

1. air density

2. the runner's projected surface area

3. the square of the runner's velocity

 

even when running in calm air, overcoming air resistance can account for 3-9% of the total energy cost

 

 

Drafting: Often a Wise Position

• can reduce the energy cost of running a marathon race for a great athlete by about 5%, or close to 3.5 seconds on every mile run for 26 miles (1.5 minutes; win or lose)
• the effect is far greater for a cyclist in a 40 km time trial
• 90% of the power generated is used to overcome air resistance
• drafting in such a cycling race could reduce energy expenditure by as much as 25-35%

 

Treadmill vs. Track Running

• are only different in that running on a track includes fighting wind resistance

 

Marathon Running

• 1988 - Ethiopian - Belayneh Densimo set the world record in the marathon averaging just under 4:53 / mile for 26.2 miles
• this equates to an estimate of about 2,400 kcals in just about 2 hours
• training for this event would consume about 10,000 kcals /week

 

Swimming

• energy expended for buoyancy and horizontal movement
• overcoming drag forces depends on:

 

1. fluid medium

2. size, shape, and velocity of swimmer

 

• total mechanical efficiency of swimming ranges between 5 and 9.5%
• the energy cost of swimming is about four times greater than the cost of running the same distance

 

Methods of Measurement

• short swims do not require that the subject breath during the swim (energy expenditure is estimated during 40 minutes of recovery)

 

longer swims require one of three methods:

 

1. the experimenter walks along side the pool with the portable gas collection equipment

2. the subject is attached to a tether system so that they stay in one place

3. the subject swims in a flume or "swimming treadmill"

 

 

Energy Cost and Drag

 

total drag force consists of three components:

 

1. wave drag- caused by waves that build up in front of, and from hollows behind the swimmer

2. skin friction drag- water against skin

3. viscous pressure drag- reduced by "streamlining" stroke mechanics (like an oar through water)

 

Ways to Reduce Effect of Drag Force

• wet suits worn by triathletes help considerably
• drafting (following closely behind the wake of a lead swimmer)

 

Energy Cost, Swimming Velocity, and Skill

• elite swimmers can swim a particular stroke at a given velocity with lower oxygen uptakes than relatively untrained or recreational swimmers

 

Effects of Water Temperature

• in water temperatures below 77 degrees F there is an added oxygen cost of swimming which is used provide the energy for shivering and body heat production
• the leanest swimmers suffer the most from this response
• swimmers of average body fat perform the best in pool temperatures of 82 - 86 F

 

Effect of Buoyancy: Men vs. Women

• due to body fat, the average female swimmer expends less energy to stay afloat than the average male swimmer
• for this reason, women swim a given distance at about 30% lower total energy cost than men
• in addition, greater peripheral distribution of body fat in women compared to men causes their legs to float high in the water, making them more horizontal or "streamlined"
• this effect is most prominent in long distance events; those that have swum the English Channel in the shortest time have been of significantly high body fat

 

Endurance Swimmers

• has an extreme cost metabolically
• swimming the English Channel is equivalent to running two marathons back to back

---

Individual Differences and Measurement of Energy Capacities

 

People vary a great deal with respect to their metabolic capacities. This is often referred to as individual differences.

There is also a specificity of metabolic capacity which is dependent upon the specific exercise task.

 

Others exhibit a generality of aerobic or anaerobic capacity.

 

See Figure 11.1

 

The effects of exercise training are highly specific for neuromuscular patterning and metabolic demand.

 

"Speed" , "Power", "Endurance" - terms should be used carefully

 

Overview of Energy-Transfer Capacity During Exercise

All out exercise for up to 2 minutes powered by immediate or short-term energy systems.

 

See Figure 11.2

 

Anaerobic Energy Transfer: The Immediate and Short-Term Energy Systems

Evaluation of the Immediate Energy System

Sports such as football and weightlifting which rely almost exclusively on high-energy phosphate systems.

 

Field Tests for anaerobic power are based on 2 assumptions:

 

1.

 

2.

 

These types of tests are referred to as "Power Tests"

 

P = (F x D) / t

 

Usually expressed in Watts:

1 Watt = .73756 ft-lb / sec or .01433 kcal / min or 6.12 kg-m / min

 

Stair Sprinting Power Tests

Easy to determine:

 

1. F = mass in kg

2. D = 1.05 m (standard for 9 stairs)

3. T = length of time it takes subject to reach 9 stairs

• in seconds and convert to minutes
• units = kg-m / min
• limitation of interpreting results is that body mass will heavily influence power output; if two people cover the same ground in the same time, the heavier person will have a greater power output
• there is no evidence to support that the heavier individual has a more developed ATP-CP system
• should use this test for evaluation of individuals with similar body mass or pre- and post- testing

 

Jumping Power Tests

Sargent jump-and-reach test

standing broad jump

 

Other Power Tests

• Sprint Running or Cycling can also be used a criteria to determine the immediate energy capacity
• low correlation among power tests shows that most of the power tests are task specific and do not necessarily indicate the ATP-CP levels of the tissues used

 

Physiological Evaluation of the ATP-CP System

1. estimating size of the ATP-CP pool

2. depletion rates of ATP and CP in response to all-out exercise of short duration ****

3. oxygen deficit calculated from the oxygen uptake curve

4. fast component of the recovery oxygen uptake

 

Evaluation of the Short-Term Energy System

• The level of blood lactate is the most common indicator of the activation of the short-term energy system.
• This does not mean that the aerobic energy system is not providing any of the energy for the task.
• More difficult to quantify than max aerobic capacity

 

Performance Tests for Anaerobic Power

• Requires test of up to 3 minutes of maximal effort.
• Cycling, running and repetitive lifting have all been used
• High intramuscular glycogen levels affect test performance or the final level of lactate accumulation.
• The performance test should be similar to the activity for which energy capacity is being measured.
• Two most common tests are the Katch and Wingate tests, both of which deal with short term all-out cycling.

  • See Figure 11.5

• Children have considerably less anaerobic capacity.
• Women also exhibit less short-term anaerobic capacity than men even when differences in body mass and muscle mass are taken into effect.

 

Blood Lactate Levels

• starts to accumulate at above approximately 55% VO₂ max
• continues to rise linearly with duration of all-out exercise of up to 3 minutes (can reach 140 mg/ 100 ml blood)

 

Glycogen Depletion

See Figure 11.7

• fiber specific depletion of glycogen depends on the mode of exercise
• during intervals of high intensity, fast twitch fibers become depleted of glycogen faster (less ability for aerobic E)

 

Individual Differences in Anaerobic Energy-Transfer Capacity

Three main factors contribute to individual differences in the capacity for anaerobic training:

 

1. previous training

2. motivation

3. capacity to buffer acid metabolites

 

 

Effects of Training

 

trained individuals can use more of their muscle glycogen and accumulate more lactic acid before fatigue sets in

 

 

Buffering of Acid Metabolites

• the consensus is that trained people have a buffering capability that is within the range expected for healthy untrained individuals
• ingestion of sodium bicarbonate solution to help buffer acid during intense anaerobic exercise improves exercise performance

 

 

Motivation

 

individuals with higher pain tolerance are capable of generating more anaerobic work; can achieve much greater levels of lactic acid

 

 

Aerobic Energy: The Long-Term Energy System

VO₂ max is a fundamental physiological measure in exercise physiology

See Figure 11.9

Measurement of Maximal Oxygen Uptake

• treadmill running and stationary cycling are the most common, but it is often exercise-task specific
• swimming, speed skating, etc. can also be used
• running on a treadmill is the method which has the most degree of overlap among athletes

 

Criteria for VO₂ max

 

1. leveling off of peak oxygen uptake ( if leveling off is not achieved then it is referred to as peak VO₂)

2. a level of lactic acid of 70-80 mg / 100 ml

3. reaching age-predicted max heart rate

4. max RER in excess of 1.00

 

Tests of Maximal Oxygen Uptake

• numerous tests have been designed
• usually consists of progressively graded exercise
• particularly difficult for untrained individuals

 

Comparison of Tests

• can be continuous or discontinuous: most researchers and subjects prefer the continuous due to brevity
• running causes very little local fatigue
• cycling often causes too much local fatigue

 

comparison of 6 treadmill tests

See Figure 11.11

 

 

Factors That Affect Maximal Oxygen Uptake

1. mode of exercise

2. heredity

3. state of training

4. body size and composition

5. sex

6. age

 

Mode of Exercise

• affects VO₂ max according to the quantity of muscle mass recruited during the activity
• treadmill and bench-step modes are similar
• cycling and swimming is dependent upon the level of skill of the athlete
• cycling can approach #'s attained with treadmill, but even trained swimmers VO₂ max #'s during swimming is 11% below that obtained during treadmill testing

 

Heredity

• heredity as determined by fraternal vs. identical twins can determine as much as 93% of the variation in VO2 max, and 81% of the variation in glycolytic capacity

  • See Table 11.4

 

Trainability of Genes

• of two people performing the same exercise program, one individual may show 10 times the improvement of the other
• this is due to the interaction effect between training and genetics

 

State of Training

• VO₂ max will increase between 5 and 20% depending on whether the individual is "in shape" or "out of shape"

 

Gender

• the VO₂ max of women is generally 15-30% below that of men
• with trained endurance athletes the gap is slightly smaller
• mostly due to hemoglobin and body composition differences

 

Body Size and Composition

• 69% of differences are due to body size and composition

 

An Argument for Biological Differences between Sexes

 

even after removal of differences in:

 

1. body mass

2. muscle mass

3. hemoglobin concentration

4. training history

 

there is still a "biologically inherent" difference between men and women with VO₂ max

 

 

Age

 

See Figure 11.14

 

• gap between males and females increases with age between 12 and 16 years
• after age 25, VO₂ max declines steadily at a rate of about 1% per year so that, by age 55, it is about 27% below values reported for 20 year olds
• this effect is mostly dependent upon activity levels, but the age effect is still present

 

Tests to Predict Aerobic Capacity

must consider:

 

1. extensive lab equipment

2. high subject motivation

3. health hazards

 

therefore predictive measures have been developed

 

VO₂ max can be predicted from:

 

walking tests, running endurance tests, step tests, and from heart rate

 

Predictions Based on Heart Rate

• gather submaximal data regarding VO₂ and HR and make a linear graph
• calculate your hypothetical max HR and extend line to predict VO₂ max

  See Figure 11.15

 

Limitations to the HR-VO₂ max relationship within one mode of exercise:

1.

2.

3.

4.

 

taking all of these factors into consideration, VO2 max predicted from submaximal HR is generally within 10-20% of the actual value

---

Training for Anaerobic and Aerobic Power

• throughout the book there is an emphasis on particular activities and their reliance on particular energy pathways
  • See Figure 21.1
• relative contributions of each energy system depends on intensity and duration of the activity
• training for anaerobic and aerobic activities is the same for men and women across a broad age range

 

Principles of Training

major objective is to facilitate biological adaptation with many variables which can be controlled

 

Overload Principle

exercise overload - is stimulus which induces training response

involves manipulation of:

 

1. Frequency

2. Intensity

3. Duration

4. Mode

 

Specificity Principle

specific exercise elicits specific adaptations, creating specific training effects

 

 

Specificity of VO₂ max

• following training, little improvement when aerobic capacity is measured during a dissimilar exercise: improvements are significant when the test exercise is the same exercise used in training
• some overlap is usually observed, but not much

 

Specificity of Local Changes

microcirculation and distribution of blood as well as enzymatic enhancement only occurs in trained musculature

 

Individual Differences Principle

• training response depends on starting level of fitness
• training benefits are optimized when programs are planned to meet the individual needs and capacities of the participants

 

Reversibility Principle

• after only 1 to 2 weeks of detraining, significant reduction in metabolic and exercise capacity occur
• 5 subjects confined to bed for 20 consecutive days, VO₂ max decreased by 25%

 

Physiological Consequences of Training

See Table 21.3

Summary of Physiological and Metabolic Changes with Training

 

Anaerobic System Changes

1. increases in resting levels of anaerobic substrates

2. increases in the quantity and quality of key enzymes

3. increases in the capacity for generating high levels of blood lactate during all out exercise

 

Aerobic System Changes

Metabolic Adaptations

 

Metabolic Machinery

larger mitochondria

more numerous mitochondria

 

Enzymes

two fold increase in level of aerobic enzymes

 

Lipid Metabolism

increased capacity to mobilize, deliver, and oxidize lipid

 

See Figure 21.4

 

Carbohydrate Metabolism

greater capacity to oxidize carbohydrate

 

Muscle Fiber Type

slight shifts in fiber type (especially with respect to LC)

all fibers maximize already existing potentials

 

Muscle Fiber Size

selective hypertrophy of slow twitch muscle fibers

 

 

Cardiovascular and Pulmonary Adaptations

Heart Size

increased weight and volume of the heart

 

Plasma Volume

increased plasma volume (i.e. increased O2 carrying)

 

Heart Rate

decreased resting and submaximal heart rate

 

Stroke Volume

increased stroke volume at rest and during exercise

 

Cardiac Output

increase in maximal cardiac output is the most significant change in cardiovascular function with aerobic training

 

Oxygen Extraction

increase in a-v O2 difference

 

Blood Flow and Distribution

more efficient blood flow distribution

 

Blood Pressure

reduced systolic and diastolic blood pressure both at rest and during submaximal exercise

 

Pulmonary Function

breathing rate is reduced in an trained subject at the same absolute level of exercise due to more efficient oxygen pressure gradients at the lungs; less ventilation requires less energy from the respiratory muscles

 

 

Other Adaptations

1. body composition changes - more muscle less fat

2. body heat transfer - improved sweating response

3. performance changes - obvious

4. psychological benefits - reduced anxiety, depression with improved self esteem

 

• practical implications
  • See Figure 21.6
• cellular adjustments probably account for a trained person being able to perform steady-rate exercise at a large percentage of VO₂ max

 

Factors That Affect The Aerobic Training Response

1. Initial level of aerobic fitness

2. Intensity of training

3. Frequency of training

4. Duration of training

 

 

Initial Level of Aerobic Fitness

more room for improvement if you start without much aerobic capacity

 

Exercise Intensity

training-induced physiologic changes depend primarily on the intensity of the overload

seven ways to express exercise intensity:

 

1. calories/ unit time

2. absolute power output

3. % of max capacity (% of VO₂ max)

4. below or above lactate threshold

5. particular exercise HR or % of max HR

6. multiples of resting metabolic rate (METS)

7. rating of perceived exertion (RPE)

 

 

Train at a Percentage of HRmax

• as a general rule, aerobic capacity improves if exercise is sufficiently intense to increase heart rate to about 70% of maximum
• alternative method: train at 60% of difference between resting and maximum heart rate:
• HR threshold = HR rest + .60(HRmax - HRrest)
• 70% of HR max is not strenuous, yet it still provides significant improvement over time
• referred to as "conversational exercise"
• relative strenuousness must be maintained as one adapts to the exercise or the exercise program becomes a "maintenance program"

 

Is Strenuous Training More Effective ?

there is a ceiling effect to the gains which a person achieves with greater intensity: a general rule of thumb is that exercise intensity of 85% is the upper limit, but this is not determined yet scientifically

 

 

The "Training-Sensitive Zone"

See Figure 21.8

 

 

Is Less Intense Training Effective ?

generally, a lower exercise intensity can be offset by a longer exercise duration

 

 

Train at a Perception of Effort

 

See Figure 21.9

 

13-14 RPE = 70% VO₂ max

 

Training Duration

more is not better, but 20-30 minutes is usually recommended for the general population to achieve gains in aerobic capacity

 

Training Frequency

• when considered for improvements in aerobic capacity, training frequency made little difference
• when considered for weight loss, training frequency makes a large difference (recommend 60 minutes or 300 kcals / day)

 

Exercise Mode

many different modes of training will tax the aerobic system as long as they involve large musculature

 

 

How Long Does It Take Before Improvements Are Noted ?

• significant improvements can be noted within several weeks
• relatively linear improvement over 10 weeks
• levels off near genetically predisposed maximums

 

Maintenance of Aerobic Fitness

• improvements in aerobic capacity involve somewhat different training requirements than its maintenance
• if intensity is held constant, the frequency and duration of exercise required to maintain a certain level of aerobic fitness is much less than that required for its improvement
• a small drop off in intensity is associated with a reduction in VO₂ max
• other factors such as glycogen storage are not maintained with a decrease in volume (duration and frequency)

 

Methods of Training

• with increased opportunities for participation, individuals with natural abilities are more likely to be exposed to a particular sport

 

Anaerobic Training

• ATP and CP system can be overloaded by repeatedly engaging in maximum bouts of effort for 5-10 seconds
• recovery is rapid and 30 seconds rest is usually enough
• movement speed and desired power output must be considered due to recruitment of motor units etc.

 

Lactic Acid Generating Capacity

• anaerobic training is both physiologically and psychologically taxing and requires considerable motivation
• includes repeated bouts of 1 minute specific maximum exercise followed by 3-5 minutes of recovery

 

Aerobic Training

See Figure 21.12

three major methods:

1. Interval training

2. Continuous training

3. Fartlek training

 

Interval Training

high intensity with rest periods; can vary from a few seconds to several minutes

 

4 considerations:

1. intensity of exercise

2. duration of exercise interval

3. length of recovery

4. number of repetitions of the exercise-recovery interval

 

in interval training, the intensity of exercise should be geared to the particular energy systems to be trained

 

 

Exercise Interval and Relief Interval (practical application)

 

See Table 21.7

 

Continuous Training (long slow distance)

• moderate or high aerobic intensity performed at 60-80% of the VO₂max
• one advantage of this type of training is that the athlete can train at approximately the same intensity as the competition

 

Fartlek Training (Fartlek - Swedish word = speed play)

• adaptation of interval and continuous training
• especially well suited for exercise out of doors and over natural terrain
• can be adjusted to be very scientific, but is usually adjusted by how the exerciser feels (allows freedom and variety in training sessions)

 

Overtraining: Too Much of a Good Thing

1. overtraining often equated with "staleness"

2. unexplained and persistent poor performance with increased difficulty recovering from a workout

3. disturbed mood states characterized by general fatigue, depression, and irritability

4. elevated resting pulse, painful muscles, and an increased susceptibility to upper respiratory infections and gastrointestinal distress

5. insomnia

6. weight loss

7. overuse injuries

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Muscular Strength: Training Muscles to Become Stronger

 

Part I : Strength Measurement and Resistance Training

• through the 1950's athletes refrained from weightlifting for fear that they would become to "muscle bound" and lose their flexibility
• myth dispelled in early 1960's

 

Measurement of Muscle Strength

muscle strength - maximum force or tension generated by a muscle or muscle groups

measured in four ways:

 

1. Tensiometry

2. Dynanometry

3. One-repetition max (1 RM)

4. Computer-assisted force and power output determination

 

Cable Tensiometry

light weight and allows versatility of recording force measurements at all angles in the range of motion (ROM)

 

Dynanometry

operate on the principle of compression

 

One-Repetition Maximum (1RM)

• self explanatory, but #'s are usually lower than trained subjects would predict due to necessary correct form
• often estimate max from submax performance in preadolescents, elderly, hypertensives or cardiac patients

 

Computer-Assisted, Electromechanical, and Isokinetic Methods

• force transducers or force platforms
• isokinetic machines control the speed of the movement and the subject varies the effort applied throughout that movement

  See Figure 22.2

 

Strength Testing Considerations

1. standardized instructions

2. uniform warm-up

3. minimize learning effect

4. consistent angle of measurement

5. average of several trials or just max score

6. use tests with high reproducibility

7. express strength with absolute or relative #'s

 

Learning Factors in Assessing Muscular Strength

• several attempts should be allowed before a true maximum is attained due to a learning effect involving neural adjustment
• (especially true in untrained individuals)

 

Gender Differences in Muscle Strength

Strength in Relation to Muscle Cross Section

• 16-30 Newtons of force / cm² (variability due to testing conditions)
• force output depends on this # and arrangement of bony levers and muscle architecture
• if expressed in strength / cross-sectional area, men and women are very similar at the same age

 

Absolute Muscle Strength

differences between the genders primarily due to LBM especially in the upper body

 

 

Sex Differences in Weightlifting Championships

• See Table in Class
• note* the differences here are due to body composition and participation in the sport

 

Relative Muscle Strength

• can be expressed relative to body mass or fat-free body mass
• no differences in "quality" of muscle, just quantity
• however, strength differences still exist when expressed in terms of relative strength

 

Allometric Scaling

• the relationship between body mass and muscular strength is not linear, so strength per unit body mass is usually expressed with a correction factor

  See Figure 22.7

 

Training Muscles to Become Stronger

as a general rule, a muscle worked close to its force - generating capacity will increase in strength

 

Resistance Training for Children

• major concern over the well being of children undergoing resistance training
• usually, high repetitions and relatively low resistance can significantly improve the muscle strength of children with no adverse effect on bone, muscle or connective tissue

 

Progressive Resistance Weight Training

• the most popular of the methods of resistance training
• 3 sets of 10 repetition workout started with rehabilitation during World War II

 

variations in progressive resistance exercise:

 

1. 3-12 reps improves strength the most

2. one max per week will increase the strength of an untrained individual

3. variations in the # of reps makes very little difference in terms of strength gain

4. performing more sets (up to 5 or more) will increase strength faster than performing one set per workout

5. optimum # of days per week varies with the individual

6. training the same body part too frequently can obviously lead to overtraining and decreased strength

7. lifting at a faster velocity may provide more gains than lifting at a slower velocity

8. neither free weights nor machines are inherently better for developing strength

 

 

Periodization

macrocycles (1 year)

mesocycles (3 months)

microcycles (4 weeks)

 

manipulate intensity, volume, frequency, sets, repetitions, and rest periods

 

See Figure 22.9

 

consists of:

1. preparation phase

2. first transition phase

3. competition phase

4. second transition phase (recuperation period)

 

 

preparation phase - specific strength development with high volume (3-5 set of 8-12 reps) and low intensity (50-80% of 1 RM)

 

 

first transition phase - specific strength development with moderate volume (3-5 sets of 5-6 reps) and moderate intensity (80-90% of 1RM)

 

 

competition phase - specific strength development is emphasized with low volume, and high intensity (3-5 sets of 2-4 reps at 90-95% of 1RM)

 

 

second transition phase (recuperation period) - emphasizes recreational activities, low-intensity, nontaxing workouts;

at the end of the second transition phase, the periodization cycle can be repeated in preparation for the next competition

 

 

Practical Recommendations for Initiating a Weight-Training Program

a load that is equal to about 60-80% of a muscle's force generating capacity is sufficient to increase strength

12-15 reps for a beginner will usually avoid joint injuries

 

Lower Back Pain

• weak abdominal region, and poor joint flexibility in the lower back and legs often leads to lower back pain syndrome
• proper application of exercises for the abdomen and lower back often facilitates the recovery from lower back pain syndrome
• especially important to wear a weightlifting belt during near maximal lifts (even more important if a lifter usually uses a belt)

 

Resistance Training Plus Aerobic Training Often Equals Less Strength Improvement

added energy (and perhaps protein) demands of such heavy endurance training may impose a limit on muscle growth and responsiveness to resistance training

 

 

Isometric Strength Training

• gains in strength with isometric resistance training are highly specific and do not carry over to concentric or eccentric training
• it is also specific to the joint angle and body position trained
• isometric training can be useful especially in rehabilitation

 

Which Are Better, Static or Dynamic Methods ?

• both create increases in muscle strength, but the key is the specificity of the training response
• this is mostly due to changes in both the musculoskeletal system as well as the nervous system

 

 

Supplemental Resistance Training with Modified Sports Equipment

• example given in book consisted of pitching baseballs of greater and lesser mass than normal simulating greater resistance and greater speed respectively
• both programs resulted in increased pitching velocity confirming the notion that programs should incorporate modified sports equipment into the actual movement pattern

 

Specificity Not Always Observed

if the movement pattern of two training methods are similar enough, both will create gains in strength

(example: free weights vs. isokinetic squats in one study)

 

 

Isokinetic Resistance Training

• is based on resistance exerted against a load at a constant speed
• in comparison to standard weightlifting, isokinetics allows for variable resistance which attempts to match the force capacity at certain joint angles
  • See Figure 22.12
• this is an attempt to allow a successful lift whereas standard weightlifting may cause failure at a "sticking point"
• drawback is that the machines design is based on the average levers etc. of the average population

 

Experiments with Isokinetic Exercise and Training

• at greater velocities of movement, greater torque per unit body mass is achieved by individuals with higher percentages of fast-twitch fibers
• should try to train at a similar velocity to the exercise task, but most isokinetic machines will not allow movements which approach the speeds of pitching, etc.

 

Plyometric Training

• explosive jump training; employed due to the concept of the stretch-shortening cycle and neuromuscular adaptation
• used for basketball, volleyball, football, and track and field
• employed during a two arm swing for a person who jumps off of two feet

 

EMG During Maximal Ballistic Muscle Actions

• breaking of antagonistic muscles during a baseball pitch
• agonist EMG then antagonist EMG then agonist EMG

 

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Part 2: Adaptations With Resistance Training

Six factors which strongly influence development and maintenance of the body's muscle mass:

1. genetics

2. nervous system activation

3. environmental factors

See Figure 22.17

4. endocrine influences

5. nutritional status

6. physical activity and exercise

 

Factors That Modify The Expression of Human Strength

two general modifications for increased humans strength are:

1. psychological (neural) factors

2. muscular factors

 

 

Psychological-Neural Factors

may be the result of:

1. more efficient neural recruitment patterns

2. increased CNS activation

3. improved synchronization of motor units

4. lowering of neural inhibitory reflexes

5. inhibition of Golgi tendon organs

 

hypnosis and other techniques which lower inhibition have been proven to be successful methods of increasing strength

 

 

Muscular Factors

ultimate strength limitation is determined by anatomic and physiologic factors within the joint-muscle itself

power is a combination of muscular strength and speed

 

 

Muscle Hypertrophy

• increase in muscular tension (stretch) is the primary requirement for initiating skeletal muscle growth or hypertrophy
• primarily due to enlargement of individual muscle fibers
• myofibrils thicken and increase in number
• additional sarcomeres are formed by increased protein synthesis and decreased protein degradation
• ATP, CP, and glycogen increase in storage
• mitochondrial volume and enzyme [ ] are actually reduced in hypertrophied muscle
• very old individuals still exhibit the hypertrophic response

 

 

Muscle Hyperplasia: Are New Muscle Fibers Made ?

yes, but increases in fiber # are not thought to contribute to whole muscle hypertrophy to any appreciable extent

 

Changes in Muscle Fiber-Type Composition

• studies employing resistance training have not demonstrated any change in fiber type
• this is not to imply that twitch characteristics can not be modified
• more moderate alterations may occur in type IIa and type IIb fibers as well as the light chains

 

Comparative Training Responses of Men and Women

Muscular Strength and Hypertrophy

• the basic gender difference in response to resistance training appears to be the absolute amount of muscle hypertrophy
• probably due to 20-30 times higher levels of testosterone
• absolute muscle gain is greater in males, but % hypertrophy for males and females is very similar

 

Is Muscle Strength Related to Bone Density ?

• muscular strength in older women is indicative of bone mineral density; could be used as a predictive index

 

Detraining

• little data has been gathered, but a few studies show fast strength loss with detraining
• most likely due to neuromuscular changes, hormonal changes, and lack of stimuli to muscle for hypertrophy
• muscle can be maintained with less frequency and high intensity

 

Metabolic Stress of Resistance Training

little metabolic stress in most programs; not recommended for cardiovascular improvement or weight control

 

Circuit Resistance Training

• circuit resistance training emphasizes the entire body and increases metabolic demand
• 8-15 exercise stations ; 30 seconds of repetitions at 40-55% of 1RM ; 15 seconds rest between stations ; 30-50 minutes of continuous exercise

 

Muscle Soreness and Stiffness

temporary soreness immediately following exercise

 

DOMS (delayed onset muscle soreness)

appears later and may last for several days

 

1. minute tears in the muscle itself due to damage to contractile elements

2. osmotic pressure changes that cause retention of fluids in the surrounding tissues

3. muscle spasms

4. overstretching and perhaps tearing of portions of the muscles connective tissue harness

5. acute inflammation

6. alteration in cell's regulation of calcium regulation

7. combination of the above factors

 

Soreness Occurs Predominantly with Eccentric Actions

 

considerably greater DOMS with eccentric exercise (also a little more DOMS with isometric exercise)

more pronounced with the elderly population

 

 

Actual Cell Damage

 

• serum levels of creatine kinase (CK) and myoglobin increase with DOMS
• fast twitch muscle fibers are more vulnerable
• reduced effect after just one incidence of DOMS; this reduced DOMS may last for as long as 6 weeks

 

An Altered Sarcoplasmic Reticulum (and Sarcolemma?)

• decreased uptake and release of calcium at the SR with DOMS
• also leaky calcium due to damage to the sarcolemma
• eventually results in calcium overload of the damaged cells and destruction of myofilaments
• this leads to a reduction in force-producing capability and eventual muscle soreness

  • See Figure 22.26

---

Special Aids to Performance and Conditioning

 

Ergogenic - refers to the application of a nutritional, physical, mechanical, psychologic, or pharmacologic procedure or aid to improve physical work capacity or athletic performance

 

of the thousands of proposed aids, only a few actually have positive effects on performance

 

Pharmacologic Agents

use and abuse of drugs in sport for high school and junior high school

 

 

Anabolic Steroids

 

used originally for muscle-wasting diseases, and legitimate use for osteoporosis

 

 

Structure and Action

 

• functions in a similar manner to the chief male hormone testosterone
• masculinizing effects can be minimized and anabolic effect can be maximized with synthetic manipulation
• "stacking" is far in excess of the medically recommended doses
• a recent survey of U.S. Powerlifting Team members indicated that 66% of the lifters used androgenic-anabolic steroids
• estimate 200 million dollars / year in illegal trafficking
• in children can result in premature cessation of bone growth; approximately 1 of 15 high school students

 

Are They Effective ?

 

pathetic description from your book claims that the effects are equivocal; a comprehensive review of the best studies will indicate a strong anabolic and strength-inducing effect

 

 

Are There Risks ?

• decreased release of endogenous testosterone
• increased release of estradiol
• increased LDL/HDL - increased heart disease
• aggressiveness, hyperactivity, irritability

 

American College of Sports Medicine - Statement on Anabolic Steroids

 

the use of anabolic-androgenic steroids by athletes is contrary to the rules and ethical principles of athletic competition as set forth by many of the sports governing bodies

 

 

Growth Hormone: The Next Magic Pill ?

• somatotropin (hGH)
• enhances fatty acid breakdown, and increases lean muscle mass
• much of the aging response with tissues is due to the decrease in endogenous GH with age
• gigantism vs. acromegaly
• GH works in a similar nature to anabolic steroids and has side effects; the use of GH in an elderly population may be safe, but the determination must be made on an individual basis
• can not be detected with tests because recombinant hGH is the same as our own endogenous GH
• can induce diabetes, joint disorders, cancer, and liver disease

 

Nutritional Supplements for an Anabolic Effect

 

in general, research does not offer evidence of an ergogenic effect of oral amino acid supplements on hormone secretion or exercise performance

 

 

Amphetamines

• powerful stimulating effect on the CNS
• Benzedrine and Dexedrine are the most common
• 5-20 mg usually effect CNS for 30-90 minutes
• increases alertness and wakefulness and decreases the sensation of fatigue; in terms of performance there is little benefit
• many side effects including dependency

 

Caffeine

• a lipid soluble compound which may have positive effects depending on the individual and the event
• approximately 2.5 cups of coffee (350 mg), 60 minutes before exercise has significantly extended time to exhaustion in moderate endurance exercise
• stimulates the breakdown of fat as a method to conserve glycogen
• reduces the RPE for the same VO2 level; could be a CNS (perception of discomfort) effect rather than a metabolic effect (glycogen sparing)
• probably both CNS effect and metabolic effect
• no direct effect on muscle activation (sarcolemma or SR)
• Warning : potent diuretic may lead to dehydration

 

Pangamic Acid

• commonly known as "Vitamin B15"
• supposedly increased oxygen uptake by cells, reduced lactic acid build up and enhanced endurance; no solid research in the U.S. has shown any beneficial ergogenic capacity
• FDA has made the sale and distribution of this substance illegal

 

Buffering Solutions

• may help all out exercise of 30-120 seconds by reducing the amount of H+ that accumulate and cause fatigue
• conflicting results in studies due to difficulty in handling doses which are necessary for possible performance enhancement
• sodium bicarbonate at 300 mg / Kg body weight improved 800 meter race by 2.9 seconds or approximately 19 meters
• sodium citrate (.5 g / kg body weight) will reduce GI distress

 

 

Red Blood Cell Reinfusion- Blood Doping

often called induced erythrocythemia

 

How It Works

• between 450 ml and 1800 ml are taken from the body and the plasma is removed and immediately reinfused
• red blood cells are frozen and stored
• 3-8 weeks are allowed the athlete to naturally restore his/her own RBC count
• 1-7 days before competition, stored blood cells are infused (autologous transfusion)
• RBC count or hemoglobin [ ] may raise from 8-20%
• up to 19 g Hb/ 100 ml blood ; will last up to 2 weeks
• is harmful if blood viscosity increases too much

 

Does Blood Doping Work ?

• blood storage methods often determine if the studies will show a positive effect of blood doping

  • See Figure 23.1

• usually a 5-13% increase in aerobic capacity; also reduced body heat storage and increased sweating responses

 

A New Twist - Hormonal Blood Doping

• erythropoietin - natural hormone which stimulates the bone marrow to produce red blood cells
• can lead to stroke, heart attack, heart failure, or pulmonary edema when hematocrit reaches 60%

 

Warm-Up (Preliminary Exercise)

• provides both a psychological edge and a physiological edge
• warm up should be gradual and sufficient to increase muscle and core temperature without causing fatigue or reducing energy stores
• the effect of prior warm up on EKG and blood pressure response to vigorous exercise indicates a benefit with regard to oxygen supply and demand

 

Oxygen Breathing During Exercise

• there is considerable evidence that breathing hyperoxic gas during submaximal and maximal aerobic exercise enhances physical performance
• 5-10% increase in VO2 max due to expanded a-v O2 difference multiplied by an increased cardiac output

 

Modification of Carbohydrate Intake

• carbohydrate loading - a popular method
• also referred to as glycogen supercompensation; results in 4-5 g of glycogen for each 100 grams of muscle (in contrast to normal #'s of 1.7 g / 100 grams of muscle)
• acts through a change in the glycogen storing enzyme - glycogen synthetase
• only applies to intense and prolonged aerobic activities; not needed for bouts of less than 60 minutes
• negative aspects include increased weight of water storage with CHO storage as glycogen

  • See Figure 21.4 for modified glycogen loading