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Protein
The protein requirements of athletes, once the source of great controversy, has settled into a current consensus. Sedentary people and recreational athletes[11] have similar protein requirements, about .8 to 1 gram of protein per kilogram of body mass. These needs are easily met by a balanced diet containing about 56 grams of protein for a 70 kg (150 pound) man or 46 grams of protein for a 60 kg (130 pound )woman.
People who exercise at greater intensity, and especially those whose activity grows muscle bulk, have significantly higher protein requirements. According to Clinical Sports Nutrition (see footnote above), active athletes playing power sports (such as football), those engaged in muscle-development training, and elite endurance athletes, all require approximately 1.6 grams of protein per day per kilogram of body weight, roughly double that of a sedentary persons. Older athletes seeking primarily to maintain developed muscle mass require 1 to 1.2 g/day/kg.
Protein intake in excess of that required to build muscle (and other) tissue is broken-down by gluconeogenesis to be used as energy or stored as fat.
Excess protein consumption in the absence of alkalizing mineral intake (usually from fruits and vegetables) may leads to low grade acididosis in which calcium and glutamine may be leached from bone and muscle respectively to keep the blood pH steady. Where gross caloric intake is adequate, however, a more benign form of ketosis generally results. (This should not be confused with the very harmful ketoacidosis, seen primarily in diabetics and alcoholics.) The overall effect on physical health of a low-carbohydrate diet -- especially concerning blood lipids, bone mass, potential osteoporosis, and possible strain on the liver and kidneys -- is the subject of an impassioned debate, which has not been resolved. All reputable authories agree, however, that excess protein consumption requires additional water intake to prevent dehydration.
The most recent evidence appears to support the beneficial nature of a high-protein, low-carbohydrate diet. A large randomized study at Stanford University found that women following such a diet "lost more weight and experienced more favorable overall metabolic effects at 12 months" than in other diets. The study followed 311 pre-menopausal, non-diabetic women, age 25-50. The women lost significantly more weight (mean 4.7 kg) on the Atkins diet than on 3 higher-carbohydrate diets (LEARN 2.6 kg, Ornish 2.2 kg, and Zone 1.6 kg), without increasing cardiovascular risks. Changes in HDL cholesterol, triglycerides, and mean blood pressure significantly favored Atkins over the other three diets. The authors concluded that "concerns about adverse metabolic effects of the Atkins diet were not substantiated within the 12-month study period."
Water and Salts
Maintaining hydration during periods of physical exertion is key to good performance. While drinking too much water during activities can lead to physical discomfort, dehydration in excess of 2% of body mass (by weight) markedly hinders athletic performance. It is recommended that an athlete drink about 400-600 mL 2-3 hours before activity, during exercise he or she should drink 150-350mL every 15 to 20 minutes and after exercise that he or she replace sweat loss by drinking 450-675 mL for every 0.5 kg body weight loss during activity.[citation needed] Some studies have shown that an athlete that drinks before they feel thirsty stays cooler and performs better than one who drinks on thirst cues, although recent studies of such races as the Boston Marathon have indicated that this recommendation can lead to the problem of overhydration. Additional carbohydrates and protein before, during, and after exercise increase time to exhaustion as well as speed recovery. Dosage is based on work performed, lean body mass, and environmental factors, especially ambient temperature and humidity.
Excess water intake, without replenishment of sodium and potassium salts, leads to hyponatremia, also called water intoxication at more dangerous levels. A well-publicized case occurred in 2007, when Jennifer Strange died while participating in a water-drinking contest. More usually, the condition occurs in long-distance endurance events (such as marathon or triathlon competition and training) and causes gradual mental dulling, headache, drowsiness, weakness, and confusion; extreme cases may result in coma, convulsions, and death. The primary damage comes from swelling of the brain, caused by increased osmosis as blood salinity decreases.
Carbohydrates
The main fuel used by the body during exercise is carbohydrates, which is stored in muscle as glycogen- a form of sugar. During exercise, muscle glycogen reserves can be used up, especially when activities last longer than 90 min. When glycogen is not present in muscles, the muscle cells perform anaerobic respiration producing lactic acid, which is responsible for fatigue and burning sensation, and post exercise stiffness in muscles. Because the amount of glycogen stored in the body is limited, it is important for athletes to replace glycogen by consuming a diet high in carbohydrates. Meeting energy needs can help improve performance during the sport, as well as improve overall strength and endurance.
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Important notice:
The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other
qualified health provider with any questions you may have regarding a medical condition.
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