Nutrition, Body Composition, and Performance. Objectives. Describe the effect of various carbohydrate diets on muscle glycogen and on endurance performance during heavy exercise. - PowerPoint PPT Presentation
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Scott K. Powers • Edward T. HowleyScott K. Powers • Edward T. HowleyScott K. Powers • Edward T. HowleyScott K. Powers • Edward T. Howley
Theory and Application to Fitness and PerformanceTheory and Application to Fitness and PerformanceSEVENTH EDITION
5. Contrast the evidence that protein is oxidized at a faster rate during exercise with the evidence that the use of labeled amino acids may be an inappropriate methodology to study this issue.
6. Describe the need for protein during the adaptation to a new, more strenuous exercise level with the protein need when the adaptation is complete.
7. Defend the recommendation that a protein intake that is 12 to 15% of energy intake is sufficient to meet an athlete’s need.
8. Describe the recommended fluid replacement strategies for athletic events of different intensities and durations, citing evidence to support your position.
9. Describe the salt requirement of the athlete compared to that of the sedentary individual, and the recommended means of maintaining sodium balance.
10.List the steps leading to iron deficiency anemia and the special problem that athletes have in maintaining iron balance.
11.Provide a brief summary of the effects of vitamin supplementation on performance.
12. Characterize the role of the pregame meal on performance and the rationale for limiting fats and proteins.
13. Describe the various components of the somatotype and what the following rating signify: 171, 711, and 117.
14. Describe what the endomorphic and mesomorphic components in the Heath-Carter method of somatotyping represent in conventional body composition analysis.
15. Explain why one must be careful in recommending specific body fatness values for individual athletes.
• Classical method– Prolonged strenuous exercise to deplete glycogen stores– A high-fat/protein diet for three days while continuing to train– 90% CHO diet for three days with inactivity
• Modified plan– Tapering workouts (90 to 40 minutes) over several days while
eating 50% CHO diet– Two days of 20 minute workouts while eating 70% CHO diet– Day of rest eating 70% CHO diet before event
• Both methods increase muscle glycogen to high levels• Only one day with carbohydrate intake of 10 g/kg body weight
from high glycemic index foods required for very high muscle glycogen levels– Elevated muscle glycogen can last as long as five days
Performance in endurance events is improved by a diet high in carbohydrates due primarily to the increase in muscle glycogen.
When workouts are tapered over several days while additional CHO (70% of dietary intake) is consumed, a “supercompensation” of the glycogen store can be achieved.
• Pre-exercise– 1–5 grams CHO•kg–1 body weight – 1–4 hours before exercise– Easily digestible solid or liquid food– Test for sensitivity to carbohydrate load in training
• Carbohydrate intake immediately prior to exercise may impair performance– Hypoglycemia in sensitive individuals– Faster rate of muscle glycogen utilization
Pre-exercise feedings should contain 1 to 5 g of carbohydrate per kilogram of body weight and should be taken one to four hours prior to exercise.
Muscle glycogen is depleted at the same rate, whether or not glucose is ingested during prolonged performance.
The ingestion of glucose solutions during exercise extends performance by providing carbohydrate to the muscle at a time when muscle glycogen is being depleted.
The protein requirement for those engaged in light-to-moderate endurance exercise is equal to the RDA of 0.8 g•kg–1•d–1; however, it is 1.2–1.4 g•kg–1•d–1 for athletes who participate in high-intensity endurance exercise.
For resistance training, there is more dispute about the requirement. It may be only 0.9 g•kg–1•d–1 for those maintaining strength or as high as 1.6–1.7 g•kg–1•d–1 for those adding lean mass and strength.
Bottom line: The average protein intake of an athlete exceeds 1.5 g•kg–1•d–1, more than enough to cover the higher protein requirement.
– Events of 1–3 hours (60–90% VO2 max) Contain 10–20 mEq•L–1 NaCl and 6–8% carbohydrate 500–1,000 ml to meet carbohydrate need 800–1,600 ml water to meet fluid need
– Events >3 hours Contain 10–20 mEq•L–1 NaCl and 6–8% carbohydrate 500–1000 ml to meet carbohydrate and fluid need
– For rapid rehydration ~1.5 L fluid for every kg of weight loss
Fluid replacement during exercise reduces the heart rate, body temperature, and perceived exertion responses to exercise, and the greater rate of fluid intake, the lower the responses.
Cold drinks are absorbed faster than warm drinks, and when exercise exceeds 65% to 70% VO2 max, gastric emptying decreases.
For exercise lasting less than one hour, the focus is on water replacement only. When exercise duration exceeds one hour, drinks should contain Na+, Cl–, and carbohydrate.
Iron deficiency in American athletes may be related to an inadequate intake of dietary iron as well as a potentially greater loss in sweat and feces. In spite of this deficiency, athletes may absorb less than half of what a sedentary group of anemic individuals absorbs. Iron supplementation may be recommended for female athletes as a result of an annual clinical assessment of iron status.
Vitamin supplementation is unnecessary for an athlete on a well-balanced diet. However, for those with a clear deficiency, supplementation is warranted.
• Purposes– Provide adequate hydration– Provide carbohydrates to “top off” liver stores– Avoid the sensation of hunger– Minimize GI tract problems– Allow the stomach to be relatively empty at start of
The pregame meal should provide for hydration and adequate carbohydrate to “top off” stores while minimizing hunger symptoms, gas, and diarrhea. Varieties of commercially available liquid meals are consistent with these goals.
• Optimal body fatness for health– Males: 10–25%– Females: 15–25%
• Optimal body fatness for performance – Differs between men and women – Varies within gender and sport– It is natural for some athletes to have higher body
fatness than others in order to perform optimally– Should be based on individual health status, not on
team average– Be aware of error in measurement of percent fat
A somatotype is a numerical representation on a 1 to 7 scale of the degree to which a person possesses a high level of endomorphy, mesomorphy, or ectomorphy. Athletes are clearly different from the ordinary population, indicating a natural predisposition needed for success.
The body fat percentage consistent with excellence in performance is different for men and women, and varies within gender from sport to sport. Average values should not be applied to any single individual without regard to overall health status as seen in diet, sleep, and mental outlook. Further, it is “natural” for some athletes to have a higher body fatness than others in order to perform optimally.