chapter 9 - nutrition and performance

Chapter 9 - Nutrition and Performance

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Nieman DC. Exercise Testing and Prescription: A Health-Related Approach. 6/e. Copyright ©2007 McGraw-Hill Higher Education. All rights reserved.

Principles of Sports Nutrition

• Prudent diet is the cornerstone• Increase total energy intake• Keep dietary carbohydrate intake

high (55-70%)• Drink large amounts of fluid• Keep a close watch on iron

deficiency• Vitamin & mineral supplements

are not needed• Protein supplements do not benefit• Rest and emphasize carbohydrates

prior to endurance events• Use of ergogenic aids is unethical• Fat loading is not recommended

>1 hour/day exercise changes

• Increase energy intake

• Increase grams per kilogram of body weight coming from carbohydrate

• Increase fluid intake


Nutrition Basics

FOOD AS ENERGY• Kilocalorie – unit of heat

– 14.5 to 15.5 degrees celsius

• 1600-2500 calories per day

• We poor Americans



Year 2005---Dietary Guidelines for Americans

• 1. WEIGHT MANAGEMENT• 2. PHYSICAL ACTIVITY• 3. FOOD GROUPS TO ENCOURAGE• 4. CARBOHYDRATES• 5. FOOD SAFETY• 6. FATS • 7. ADEQUATE NUTRIENTS WITHIN

CALORIE NEEDS• 8. SODIUM AND POTASSIUM• 9. ALCOHOLIC BEVERAGES


2005---USDA Dietary Guidelines• WEIGHT MANAGEMENT;

PHYSICAL ACTIVITY

Key Recommendations• To maintain body weight in a healthy

range, balance calories from foods and beverages with calories expended.

• To prevent gradual weight gain over time, make small decreases in food and beverage calories and increase physical activity.


2005 Guidelines:WEIGHT MANAGEMENT; PHYSICAL ACTIVITY (cont)

• Engage in regular physical activity and reduce sedentary activities to promote health, psychological well-being, and a healthy body weight. – To reduce the risk of chronic disease in adulthood: Engage in at least 30

minutes of moderate-intensity physical activity, above usual activity, at work or home on most days of the week.

– For most people, greater health benefits can be obtained by engaging in physical activity of more vigorous intensity or longer duration.

– To help manage body weight and prevent gradual, unhealthy body weight

gain in adulthood: Engage in approximately 60 minutes of moderate- to vigorous-intensity activity on most days of the week while not exceeding caloric intake requirements.

– To sustain weight loss in adulthood: Participate in at least 60 to 90 minutes of daily moderate-intensity physical activity while not exceeding caloric intake requirements. Some people may need to consult with a healthcare provider before participating in this level of activity.


*2005 Guidelines:FOOD GROUPS TO ENCOURAGE

• Consume a variety of fruits and vegetables (2 cups fruit, 2 ½ cups vegetables per day for a 2,000-calorie intake (higher or lower depending on the calorie level).

• In particular, select from all 5 vegetable subgroups (dark green, orange, legumes, starchy vegetables, and other vegetables) several times a week.

• Consume 3 or more ounce-equivalents of whole-grain products per day, with the rest of the recommended grains coming from enriched or whole-grain products (at least half the grains should come from whole grains).

• Consume 3 cups per day of fat-free or low-fat milk or equivalent milk products.


*2005 Guidelines:FOOD GROUPS TO ENCOURAGE

(cont.)

• The MyPyramid Food Guidance System provides food-based guidance to help implement the recommendations of the Guidelines. Taken together, they would result in the following changes from a typical diet (Figure 9.1, Box 9.3):– Increased intake of vitamins, minerals, dietary fiber, and other essential

nutrients, especially of those that are often low in typical diets.– Lowered intake of saturated fats, trans fats, and cholesterol and increased intake

of fruits, vegetables, and whole grains to decrease risk for some chronic diseases.

– Calorie intake balanced with energy needs to prevent weight gain and/or promote a healthy weight.


Visit www.mypyramid.gov for details (and to choose your food intake plan).

Physical activity

Grains

vegetables

fruits oils

milk

meat and beans

http://www.mypyramid.gov/


*2005 Guidelines:CARBOHYDRATES

• Choose fiber-rich fruits, vegetables, and whole grains often (Table 9.3).

• Choose and prepare foods and beverages with little added sugars or caloric sweeteners, such as amounts suggested by the USDA MyPyramid and the DASH Eating Plan (see Chapter 10).

• Reduce the incidence of dental caries by practicing good oral hygiene and consuming sugar- and starch-containing foods and beverages less frequently.


2005 Guidelines:CARBOHYDRATES (cont.)

• Carbohydrates are part of a healthful diet. Choose fiber-rich fruits, vegetables, and whole grains often (Table 9.3).

• The recommended intake of carbohydrates is 45 to 65% of total Calories.

• For an individual eating 2,000 calories a day, this would be 900-1,300 Calories or 225-325 grams of carbohydrate (divide by 4, the number of Calories per gram of carbohydrate).

45 65

20 35

10 35

Percent of Total Energy Intake0 10 20 30 40 50 60 70

Fat

Protein

Carbohydrate


2005 Guidelines:CARBOHYDRATES (cont.)

• As mapped out by MyPyramid, more servings of grain products should be consumed at each meal than any other type of food, followed by fruits and vegetables.

• Although dietary fiber provides no energy, it has many beneficial actions in the body and promotes a low risk of colon cancer, heart disease, and diabetes.

• There are two kinds of dietary fiber: soluble fiber which is soluble in water and forms a gel, and insoluble fiber which is insoluble in water.

• Soluble fiber is found in many fruits and vegetables, and in some grains like oats. Insoluble fiber is found in many vegetables and whole grains (e.g., wheat bran).


*The Food Label (Figure 9.3)

• In 1990, the FDA approved a procedure for nutrition labeling of processed foods and authorized appropriate health claims.

• The food label focuses on the shortcomings of Americans, total fat, saturated fat, cholesterol, sodium, dietary fiber, and sugars.

• The Nutrition Facts food label uses the Daily Values to help consumers plan healthy diets.

• The Daily Values are based on a 2,000 calorie diet. A Daily Value of 20% for total fat means that a serving of this particular food provides 20% of the total fat allowed for the average adult.


*2005 Guidelines:FOOD SAFETY

• To avoid microbial foodborne illness: – Clean hands, food contact surfaces, and fruits and vegetables.

Meat and poultry should not be washed or rinsed.– Separate raw, cooked, and ready-to-eat foods while shopping,

preparing, or storing foods.– Cook foods to a safe temperature to kill microorganisms.– Chill (refrigerate) perishable food promptly and defrost foods

properly.– Avoid raw (unpasteurized) milk or any products made from

unpasteurized milk, raw or partially cooked eggs or foods containing raw eggs, raw or undercooked meat and poultry, unpasteurized juices, and raw sprouts.


2005 Guidelines: FATS• Consume less than 10% calories from saturated fatty acids

and less than 300 mg/day of cholesterol, and keep trans fatty acid consumption as low as possible.

• Keep total fat intake between 20 to 35% of calories, with most fats coming from sources of polyunsaturated and monounsaturated fatty acids, such as fish, nuts, and vegetable oils.

• When selecting and preparing meat, poultry, dry beans, and milk or milk products, make choices that are lean, low-fat, or fat-free.

• Limit intake of fats and oils high in saturated and/or trans fatty acids, and choose products low in such fats and oils (see Figure 9.4).


*2005 Guidelines:ADEQUATE NUTRIENTS WITHIN

CALORIE NEEDS • Consume a variety of nutrient-dense foods and beverages

within and among the basic food groups while choosing foods that limit the intake of saturated and trans fats, cholesterol, added sugars, salt, and alcohol.

• Meet recommended intakes within energy needs by adopting a balanced eating pattern, such as the USDA Food Guide or the DASH Eating Plan.


2005 Guidelines:SODIUM AND POTASSIUM

• Consume less than 2,300 mg (approximately 1 tsp of salt) of sodium per day.

• Choose and prepare foods with little salt. At the same time, consume potassium-rich foods, such as fruits and vegetables (see Table 9.4).

• Individuals with hypertension, blacks, and middle-aged and older adults. Aim to consume no more than 1,500 mg of sodium per day, and meet the potassium recommendation (4,700 mg/day) with food.


2005 Guidelines: ALCOHOLIC BEVERAGES

• Those who choose to drink alcoholic beverages should do so sensibly and in moderation—defined as the consumption of up to one drink per day for women and up to two drinks per day for men.

• Alcoholic beverages should not be consumed by some individuals, including those who cannot restrict their alcohol intake, women of childbearing age who may become pregnant, pregnant and lactating women, children and adolescents, individuals taking medications that can interact with alcohol, and those with specific medical conditions.

• Alcoholic beverages should be avoided by individuals engaging in activities that require attention, skill, or coordination, such as driving or operating machinery. (See Table 9.5, page 302).


Principle 1: Prudent Diet Is the Cornerstone (Table 9.7): Dietary Practices of Athletes

• Athletes tend to have high energy intakes (dependent on size and sport energy demands). (See Table 9.6).

• Diet quality is similar to that of general population (too high in fat, low in carb), falling short of standards established for athletes.

• Vitamin and mineral intake generally exceeds RDA standards, primarily because of high energy intake.

• Athletes at risk of nutrient deficiency: sports that emphasize leanness (gymnasts, wrestlers, ballet dancers, body builders, female runners). See Box 9.4 for recommendations for wrestlers.

Notes on Athletes

• Studies support the idea that sports training does not have a negative effect on nutritional status of athletes. Performance is not decreased and nutrients are adequate for what is necessary. In short, supplements are not needed.

• Athletes will consume more calories per kg of body weight.



Principle 2: Increase Total Energy Intake

• Athletes are capable of amazingly high levels of energy output (see Figure 9.5).– In UK 24-h cycling time trial in a lab, one cyclist expended

20,166 kcal

• Athletes are high energy expenders for two reasons:– High working capacities

– Ability to work at a high % of maximal capacity (70-90%)

• Expended in short period of time– High glycogen depletion

– High sweat rates

– Muscle and GI trauma

• Energy and ATP Production (Figures 9.6, 9.7, 9.8) later

• Table 9.4

Nutritional needs for athletes

• Higher carbohydrate needs (utilization of glycogen)

• High water needs (high sweat rates)

• Protein and iron needs may increase (musculoskeletal trauma)

• Iron balance (GI disturbance)

Tips for Refueling - Protein Needs

• Sedentary 0.8g/kg• Fitness Enthusiast 1 g/kg• Elite Endurance Athlete 1.2 - 1.4 g/kg

– Fuel– Muscle Repair

• Elite Strength Athlete 1.4 – 2.0 g/kg– Muscle Repair– Accretion of Lean Mass

Energy and ATP Production• ATP (small amount stored in muscles)

– Constantly replinished.

• ATP-PC or _________. – Time ____.– Activities?

• Lactate Pathway or AKA ________.– Time ____.– Activities?

• ATP produces at a high rate from glycogen via glycolysis. LA byproduct that causes fatigue.


Energy and ATP Production• Oxygen system or ________.

– Time ________.– Activities?

• Stores of fatty acids and CHO

• ATP produced at a slower rate than LA path

• Mitochondrial respiration

• O2 is the limiting factor

• Longer distances this pathway is the main provider


Figure 9.7, page 308Aerobic and anaerobic systems work together. Fat and CHO are the primary fuel sources of endurance exercise.

Fat stores = 140,000 calories CHO = 1,450



Factors That Influence Fuel UtilizationIntensity and duration of exercise

% carb usage greater during high intensity exercise, with fat usage increasing as duration increases (Tables 9.8, 9.9; Figures 9.9, 9.10).

Fitness statusAt any given workload, fit people use a greater %fat for

fuel, sparing glycogen (Figure 9.11).

Previous diet If pre-event meal is high in carb, relatively more is

stored and available, increasing exercise time (Figure 9.12).

Figure 9.11 – Relationship between intensity of exercise and fitness status and use of glycogen

Increased glycogen used with an increase in intensity. Increased fitness levels spare glycogen and use fat as a fuel source.


Fig 9.9: Fuel Utilization during 1 mile run at 70% VO2max

Gradual utilization of fat as a fuel source to produce ATP



Principle 3: Increase intake of carbohydrate (55-70%)

• Glycogen found to play important role in intense exercise (70-85%) (e.g., running, cycling, soccer) (Figures 9.11 and Table 9.9).

• Endurance training leads to a higher level of stored carbohydrate and a greater utilization of fat (Table 9.8, Figure 9.11).

• Exhaustion is tied to low muscle glycogen levels and is limiting in bouts lasting longer than 60-90 minutes (Figure 9.14).

• When muscle and liver glycogen is low, a high work output cannot be maintained.


Principle 3: Carbohydrate (cont.)• During the first hour, most of the carb and fat

come from within the muscle (Figures 9.10, 9.15). As exercise continues, more and more demands are placed on fat stores and blood glucose.

• During strenuous training, muscle glycogen stores undergo rapid day-to-day fluctuation (Figures 9.16, 9.17). 70% CHO diet required.

• Ingest 8-10 g/kg carbohydrate soon after long-term exercise to restore glycogen quickly (and consider high-glycemic-index foods (Figure 9.18, Box 9.5).

• High Glycemic Index foods (such as simple carbohydrates) will increase the body’s sugar levels rapidly. See Box 9.5, page 313 for GI.

Figure 9.16, page 312

Low-carbohydrate diet leads to muscle glycogen depletion. Each successive 2 hour workout the next days leads to decreased performance and the exercise feels harder than normal.


- Refueling - Post ExerciseReplacement of Glycogen Stores

• High glycemic index – bread, potatoes, fruit– Low in fiber– No fructose

• Beginning 15 min postexercise• Repeat every 2 hr if you did not eat a meal• Protein 40% of CHO dose (?)


Principle 4: Increase Fluid Intake

• As the muscle burns fuel, 70-80% is transformed into heat (body heat can rise 1°C/5 min, causing death in 20-30 min).

• During exercise, sweat evaporation accounts for >80% of heat loss (1 liter of sweat evaporation on the skin removes 600 kcal heat) (Figures 9.19, 9.20).

• Sweat losses can range from 0.5-3.7 Liter/hr of exercise, depending on the workrate and environmental conditions (Figure 9.21).

• Loss of >2% body water impairs performance due to decreased endurance capacity, increased core temperature and decreased cardiac output. (see Table 9.12, Figure 9.22).

Components of Body Water

60% of Body Weight• Intracellular fluid (67%)

• Interstitial fluid (27%)

• Plasma Volume (6%)

• Loss of >2% body water impairs performance due to decreased endurance capacity, increased core temperature, increased heart rate and decreased cardiac output.

• Early Warning Signs: clumsiness, stumbling, excessive sweat, cessation of sweating, headache, nausea, or dizziness


Core Temperature Responsesto Exercise of Different Intensities

Primary method the body cools itself is sweating. Other methods are convection, radiation, conduction, and respiration.


Importance of Evaporation As Heat-Loss Mechanismin High Environmental Temperatures

Importance of Evaporation As Heat-Loss Mechanism in Heavy Exercise

• "ConvectionWhen wind blows against the skin, it helps speed up the processes of evaporation, making the person feel much colder (often known as the wind chill factor).

ConductionHeat may be lost through contact with surfaces at a lower temperature than that of the body.

RadiationHeat is lost through radiation from all over the body.

EvaporationHeat is lost through the body's natural cooling system (perspiration) which evaporates from the skin.

•RespirationThe only other way in which heat is lost is through respiration (breathing).


Hydration• 2 cups of water immediately prior to exercise• 1 cup every 15 mins• Postexercise – water replacement

– Drink 2 cup/lb lost– Drink 3 cup/lb if exercise again same day

• Heat – electrolytes + water• Endurance exercise >1.0 hr

– CHO supplements to maintain glucose levels and delay fatigue (GU, Gatorade, bars, etc.)– 30-60 gms/hr of CHO– 0.5-0.7 gms/L of water of sodium

Figure 9.21, Page 317

Sweat rates are affected by running pace and weather conditions.



Box 9.6 ACSM Position Stand on Exercise & Fluid Replacement

• Emphasize fluid intake before exercise by drinking adequate fluids during the day before the event, and drink about 500 ml 2 hours before exercise.– Urine should be light-colored, good volume, no strong smell.

• Athletes should start drinking early and at regular intervals during exercise to replace nearly all the water lost from sweating.– 2% drop in body wt from fluid impairs exercise– 0.5-2 cups fluid / 10-15 min of exercise – 2 cups / pound of weight loss – Gastric emptying is promoted by >600 ml gastric volume

(maintain largest fluid volume in stomach that is tolerable)– Fluids should be sweetened (6-8% carb), flavored, and cooled to

stimulate intake.


ACSM Position Stand on Exercise & Fluid Replacement (cont.)

• If the event is longer than 1 hour, carbohydrates and electrolytes should be included in fluids ingested (F 9.24).– Peformance enhanced (fatigue delayed) (Figures 9.25, 9.26)– Water delivery to body not impaired – Enhance palatability

• Carbohydrates should be ingested at a rate of 30-60 g/hr (0.6-1.2 lof most sports drinks with 4-8% carb) (T 9.13).– The carbohydrates can be glucose, sucrose, or maltodextrin

(fructose can cause GI distress)

• Inclusion of sodium (0.5-0.7 g/l water) enhances palatability, promotes fluid retention (less urination), and helps prevent hyponatremia in certain athletes who drink excessive plain water during ultra events– 1 liter sweat has 0.4-1 g sodium


Figure 9.25

Acclimatization• Takes 5-10 days

• Increased plasma volume (400-700 ml)

• Increased sweat earlier in exercise with less loss of sodium

• Heart rate and body temperature are lower for a given workload.

• Slow progression is ideal



Principle 5: Watch for Iron Deficiency

• In the human body, iron is present in all cells and has several vital functions. Too little iron can interfere with these vital functions and lead to morbidity and mortality. Iron has these functions:– carrier of oxygen to the tissues from the lungs in the form of

hemoglobin

– facilitator of oxygen use and storage in the muscles as myoglobin

– transport medium for electrons within the cells in the form of cytochromes

– integral part of enzyme reactions in various tissues.


Principle 5: Watch for Iron Deficiency

• 10-80% female athletes (depending on sport and study design) have mild iron deficiency (serum ferritin <12 g/l). Reasons:– Inadequate dietary iron– Increased hemolysis (trauma, temperature, increased blood flow,

acidosis, catecholamines)– Increased iron loss in sweat and feces (GI bleeding most important

cause)

• Extremely rare to find that athletes have anemia (hemoglobin <12 mg/dl for females) (Figure 9.28). (See Table 9.14 & Figure 9.27 for review of iron deficiency).

• Mild iron deficiency does not impair health or performance in most female athletes (unlike anemia).


Principle 6: Vitamin and Mineral Supplements Are Not Needed

In a joint statement, the American College of Sports Medicine, American Dietetic Association, and Dietitians of Canada have stated,

“In general, no vitamin and mineral supplements should be required if an athlete is consuming adequate energy from a variety of foods to maintain body weight. If an athlete is dieting, eliminating foods or food groups, is sick or recovering from injury, or has a specific micronutrient deficiency, a multivitamin/mineral supplement may be appropriate. No single nutrient supplements should be used without a specific medical or nutritional reason (e.g., iron supplements to reverse iron deficiency anemia).”


Figure 9.29


Principle 6: Vitamin & mineral supplements are not needed

• Most studies show that intake of major vitamins and minerals by athletes exceeds 67% RDA (but 50- 80% still use supplements on a regular basis). (Fig 9.30).

• Exercise does increase the requirement for some nutrients (e.g., iron, zinc, copper, magnesium, chromium, B6, riboflavin), but can by met by consuming a balanced diet that matches energy expenditure.

• Nutrient deficiencies can impair physical performance, but these are rare among athletes.

• Studies do not back the claim that performance is enhanced when nutrient intake exceeds recommended levels (in well-nourished athletes).


Principle 7: Protein supplements do not benefit the athletes Protein and Exercise Historical Background

• 19th century – Belief that protein was the major exercise

fuel

• Most of 20th century– Thought that exercise had little effect on

protein needs

• 1970 to present– Research has shown that protein needs of

those who exercise heavily exceeds that of sedentary individuals (see Figure 9.31 for a review of protein/amino acid metabolism).


Acute Exercise-Induced Changes in Protein Metabolism

• Decrease in protein synthesis (but then an increase during recovery). (Figure 9.32).

• Increase in branched-chain amino acid (BCAA) oxidation, especially during prolonged endurance exercise (enhanced by an increase in skeletal muscle branched chain 2-oxoacid dehydrogenase enzyme activity).

• Increase in protein degradation.• Increase in gluconeogenesis (liver converts amino

acids into glucose).


Factors That Influence Dietary Protein Need for Athletes

• Exercise Intensity– Amino acid oxidation increases with exercise intensity.

• Carbohydrate Availability– The exercising muscle uses more BCAAs for fuel as glycogen

stores become depleted.

• Exercise Type: Aerobic vs. Resistance Exercise– In contrast to prolonged aerobic exercise, resistance exercise

does not stimulate BCAA oxidation (carbohydrate is the primary fuel).

– Diet protein needs are still greater in resistance- compared to aerobic-trained individuals due to larger muscle mass


Practical ImplicationsEstimated dietary protein needs of sedentary individuals and athletes

See Tables 9.16, 9.17

• RDA = 0.8 g/kg/day or 56 g for sedentary individual (actual intake in U.S. is ~90 g/day).

• Strength athletes need about 1.4 g/kg/day to stay in nitrogen balance (1.6-1.7 g/kg/day, safety margin added).

• Endurance athletes need 1.2-1.4 g/kg/day.• Most athletes can obtain the added protein by

ensuring that protein intake is ~15% total energy intake, using foods from the traditional food supply (supplements not needed).


ADA Summary on Protein Intake

• “Recommended protein intakes can generally be met through diet alone, without the use of protein or amino acid supplements, if energy intake is adequate to maintain body weight...Athletes should be aware that increasing protein intake beyond the recommended level is unlikely to result in additional increase in lean tissue because there is a limit to the rate at which protein tissue can be accrued...Although the protein quality of a vegetarian diet is adequate for adults, plant proteins are not as well digested as animal proteins. Thus, to adjust for incomplete digestion, an increase of about 10% in the amount consumed may be made.”


Principle 8: Rest and Emphasize Carbohydrates Before Long

Endurance Events• For events lasting longer than 60-90 minutes:

– Taper exercise gradually during the week before the event (Figure 9.33).

– Consume 8-10 g/kg carbohydrate during the 3 days before the event.

• The pre-event meal should be ingested 3-5 hours before the event, and contain 500-800 Calories of light, low-fiber starch.


Figure 9.33


Principle 10: Fat Loading Is Not Recommended for Enhanced Performance or Health

• Premise: Greater availability of fat during exercise, through supplementation or dietary alternatives (fat loading), can improve performance by further sparing muscle glycogen. Dietary manipulations include high-fat diets for:– 1-5 days before events– 2-4 weeks before events– Immediately before and/or during events

• In general, data do not support “fat loading” for performance enhancement or health.


Principle 9. Use of ergogenic aids is unethical (and usually of no value)

• Ergogenic = substances or methods that tend to increase performance capacity– Nutritional aids (carbohydrates, vitamins,

proteins)– Pharmacological aids (steroids, amphetamines)– Physiological aids (oxygen, blood doping)– Psychological aids (hypnosis, mental imagery)– Mechanical aids (biomechanical aids)


Nutritional Ergogenic Aids (see Table 9.18)

• Prohormones: compounds such as androstenedione, androstenediol, and dehydroepiandrosterone that are purported to increase testosterone, improve recovery, and build muscle mass.

• Creatine preparations: supplements that contain creatine monohydrate, and are advertized to improve power performance and build muscle mass.

• Proteins and amino acids: claimed effects include increases in muscle mass, strength, and endurance.

• Natural and herbal products: ginseng, Echinacea, saw palmetto, tribulus, and kava kava which are claimed to improve energy, strength, endurance, and immune function.


Nutritional Ergogenic Aids (cont.)

• Diuretics: herbal diuretics and stinging nettle which purportedly prevent water retention, swelling, gout, and high blood pressure.

• Energy enhancers, vitamins, and antioxidants: vanadyl sulfate, taurine, and vitamins which are postulated to improve recovery, aid in rehydration and glycogen replenishment, and provide added energy.

• Mental enhancers: plant extracts, amino acids, alkaloids (ephedrines and caffeine), minerals, and vitamins that are alleged to modulate mood, boost metabolism, increase adrenaline output, and provide energy and power.

• Fat burners: L-carnitine, inositol, and choline that are asserted to increase lean muscle mass and burn fat.


ADA/ACSM Guidelines• The 1994 Dietary Supplement Health and Education Act

allows supplement manufacturers to make claims regarding the effect of products on the structure/function of the body, as long as they do not claim to diagnose, mitigate, treat, cure, or prevent a specific disease. Performance can be categorized as follows:– Those that perform as claimed.– Those that may perform as claimed but for which there is

insufficient evidence of efficacy at this time.– Those that do not perform as claimed.– Those which are dangerous, banned, or illegal, and

consequently should not be used.• Athletes should be counseled regarding the use of ergogenic aids,

which should be used with caution and only after careful evaluation of the product for safety, efficacy, potency, and legality.


Ergogenic Aids That Work??• Caffeine

– Claim: Increases long-term endurance; improves performance during intense exercise lasting 5 min

– Fact: drinking more than 5 cups of coffee one hour before exercise will enhance performance 10-30%. (IOC bans if urine levels are greater than 12 g/ml, which is >6 cups coffee).

• Soda-loading– Claim: Sodium bicarbonate (Alka Seltzer) counters

lactic acid during intense effort lasting 1-4 minutes– Fact: 300 mg/kg decreases 800 m run time by 2.9

seconds.


Ergogenic Aids That Work??• Blood doping and EPO (erythropoetin)

– Claim: Increases long-term endurance

– Fact: 900 ml blood removed from athlete, stored at 80C for 6-8 wks, and then reinfused 1-7 days before competition increases hemoglobin by 10% (4-11% increase in aerobic power; run 10 sec/mile faster); EPO has similar effect

– A typical regimen is to administer 5000 U of r-EPO three times weekly for four weeks. Hematocrit values will typically increase from 40-43% to 50-53%, increasing VO2max by 8-10%. Once r-EPO administration is discontinued, red cell mass gradually returns to its original state, but this may take weeks. As a result, an “open window” exists where there is no evidence of r-EPO misuse but where performance is enhanced.


Figure 9.36


Ergogenic Aids That Work??

• Steroids and Steroid-Like Compounds – Fact: Claims are true for most people who also engage in intensive

resistance exercise. Side effects are legion (Box 9.9).

– Prohormones are a class of androgenic steroids that either convert to testosterone directly or mimic testosterone by forming androgen-like derivatives (e.g., nandrolone). See Figure 9.37. These compounds include dehydroepiandrosterone (DHEA), androstenedione, 5-androstenediol, and 4-androstenediol, all now sold as prohormones in the U.S. marketplace. Most studies indicate that some androgen supplements convert to testosterone, but also estrogen subfractions. The net effect is no increase in protein synthesis, muscle mass, or strength.

– Claim: Increase muscle mass & strength, decrease fat mass, increase aggressiveness


• Doping with growth hormone:– Reputation of being effective in building skeletal mass,

reducing fat mass, and improving submaximal and maximal aerobic endurance among athletes.

– Crucial in energy metabolism and body anabolism, and has multiple benefits when administered to adults with growth hormone deficiencies.

– Insulin-like growth factor I (IGF-I) mediates the principal effects of growth hormone.

– Currently, the effects of rGH or IGF-I in improving athletic performance, muscle strength, and recovery from intensive exercise are unproven.

– The few controlled studies that have been performed with supraphysiological growth hormone doses to athletes have shown no significant performance effects.


Ergogenic Aids That Work??• Creatine---ACSM consensus statement

– Creatine supplementation can increase muscle phosphocreatine content, but not in all individuals.

– Exercise performance involving short periods of extremely powerful activity can be enhanced with creatine supplementation (e.g., 5-7 d of 20 g/d), especially during repeated bout of activity; does not increase maximal isometric strength, the rate of maximal force production, nor aerobic exercise performance.

– Creatine supplementation leads to weight gain within the first few days; due to water retention.

– Does not(???) cause gastrointestinal, renal, and/or muscle cramping complications.

– Exhibits small but significant physiological and performance changes, but the increases in performance are realized during very specific exercise conditions. This suggests that the apparent high expectations for performance enhancement are inordinate.

Exercise in the Heat

• 5-7 g/kg for athletes daily

• 1 hour before exercise –1.5-2.5 cups water

• Sports Drinks – 10-25 mmoles/liter (concentration)

• 6 to 8% CHO – 8 oz every 15 to 20 minutes

• Electrolyte concentration – sodium and potassium - 4-8% (g CHO/ml)

• Sodium 0.5 -0.7 g/L – salt foods

The End

chapter 9 - nutrition and performance

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