Athletic performance is the culmination of genetics, proper training, adequate nutrition, hydration, desire, and rest. Understanding sport-specific physiologic requirements for training and competition is integral to obtaining sufficient energy, optimal levels of macronutrients and micronutrients, and adequate levels of fluids. Healthy eating habits and supplements, and sports foods may be necessary to support energy needs for training hard, achieving performance goals, and reducing the incidence of illness and injury.
SPORTS NUTRITION:
Sports nutrition is the study and practice of nutrition and diet, improving one's athletic performance. Nutrition is an important part of many sports training regimens, popular in strength sports (e.g.weightlifting and bodybuilding) and endurance sports (e.g., cycling, running, swimming, rowing). Sports nutrition focuses on the type, the number of fluids, and food taken by an athlete. In addition, it deals with the consumption of nutrients such as vitamins, minerals, supplements, and organic substances that include carbohydrates, proteins, and fat.
EXERCISE AT ALTITUDE:
- Altitude training is the practice by some endurance athletes of training for several weeks at high altitudes, preferably over 2,400 meters (8,000 ft) above sea level, though more commonly at intermediate altitudes due to the shortage of suitable high-altitude locations.
- In high-altitude environments, less oxygen per breath than at lower altitudes. That means each breath will deliver less oxygen to the muscles. This may sound negative, but living in higher altitudes and getting used to breathing “thinner” air can enhance elite athletes’ athletic performance in competitions at lower altitudes.
- A high-altitude environment produces physiological stress in humans. The changes can occur at moderate altitude, between 2,000 and 3,000 m, and high altitude, above 3,000 m.
NUTRIENT REQUIREMENTS AT HIGH ALTITUDES
Energy requirement at altitude for moderately active individuals is 2 to 2.3 times sea-level basal requirements. Further adjustments must be made for other strenuous activities performed, such as marching or climbing. Successful consumption of this energy intake may require strong incentives, frequent encouragement, and special high-calorie, nutrient-dense, palatable products. Calorie goal – 2500 to 5000 kcal per day. These calorie requirements vary for different sports at higher altitudes.
The energy and nutrient requirements depend upon the total energy expenditure and metabolic rate of the individual. Total energy expenditure (TEE) has three components, i.e., basal metabolic rate (BMR), diet-induced energy expenditure, and expenditure related to activities.
Short-term measurements or gas exchange during field studies suggest that altitude hypoxia increases BMR. Some studies show these acute increases (20-30%) to be sustained for 1-2 weeks, while others show elevation to be maintained throughout a three-week stay.
The decline in BMR with acclimatization sees ills to result from an inadequate energy intake and a decrease in metabolically active tissue that accompanies weight loss. The decrease in metabolic rate is expected to be approximately 20-25 Kcal/dl kg lean tissue lost.
Finally, the stress of high altitude (HA) decreases over a period of time, as indicated by a decrease in the epinephrine levels in both men and women.
Regarding the energy cost of various activities under stationary conditions, there is no variation compared to the sea levels. Increased energy expenditure ranging from 6.9 to 25% has been reported. Increased energy expenditure may be due to the heavier load carried by the troops, as cold protective garments and efforts in walking in snowbound hilly terrain.
The energy expenditure of 3250 Kcal/day is reported in climbers to Mt. Everest using the doubly labeled water technique; out of this, 1610 Kcal/day was required just for climbing activities. The physical activity level (PAL) calculated using doubly labeled water and expressed as a multiple of BMR in trained subjects during climbing reached 2.0-2.7, lower than the upper limit (4.0-5.0) at sea level.
Education about the causes and consequences of weight loss at altitude may be essential for ensuring compliance. Compliance with this recommendation should essentially eliminate weight loss at altitude.
The composition of diet should be as follows:
Protein intake of 8 g/kg for sedentary individuals; 1.2 to 1.5 g/kg for those performing strenuous endurance activities (result is about 12 to 15 percent of total energy intake).
Carbohydrate intake should supply around 60 percent of total energy intake to cover the increased need for carbohydrates in the adequately fed individual. This carbohydrate should be consumed in complex forms to minimize gastrointestinal distress.
Fat intake could be as low as 25 to 28 percent, and such intake levels may decrease some of the intestinal distress that may accompany large intakes of simple carbohydrates.
Vitamins: In humans, exposure to high altitudes has been reported to cause a marked increase in lipid peroxidation. Antioxidant nutrients such as vitamin E, C, and A, β-Carotene) and selenium, copper, zinc, and manganese may be required in greater amounts in cold and high-altitude environments to prevent oxidative stress.
These antioxidants act in a concerted manner to combat the oxidative stress arising from different sources; β-carotene protects against photo immuno-suppression caused by long-wave UV radiation encountered outdoors.
During rough weather, when the supply of fresh fruits and vegetables becomes limited at high altitudes, vitamin C supplements are recommended due to their antioxidant role. Free radical damage to cells increases with altitude because anaerobic metabolism predominates and ultraviolet exposure increases.
Free radical damage is a main cause of aging. Humans make their own natural protective antioxidants, but these levels can go down when exercising intensely at high altitudes unless the individual is “trained.” Trained athletes can counteract the damaging effects of free radicals because they produce more natural antioxidants. Vitamin E supplementation at high altitudes has shown positive effects in mountain climbing, skiing, etc.
Minerals: Increased urinary excretion of Na+ and K+ on exposure to hypoxia is reported, while some workers have found only an increase in Na+ with a decrease in K+ excretion. Though there is always a balance between blood formation and destruction at high altitudes, there is still no evidence for increased dietary iron requirements. The requirements of increased hemoglobin synthesis during the early phase of stay at altitude are fulfilled by redistributing body stores and from dietary iron. Urinary excretion of Zn2 + is more during physical exertion, as observed during an expedition to Mt Everest. Reduced zinc levels are associated with anorexia.
HYDRATION: Develop a drinkable, high-carbohydrate, moderate protein and a fat supplement containing about 500 kcal; including such a product in the rations of sojourners at altitude will help to remedy the consequences of increased need and decreased appetite. Determine the amount of diuresis that is necessary for optimal adaptation to altitude.
Provide fluid sufficient to cover high insensible losses and diuresis (4 litre/d). Sweating adds to the water loss. Drink a minimum of 1 quart of water every three hours. Putting a pinch of salt in plain water or using a sports drink. Make sure the sports drink has sodium listed on the label. Making of own sports drink by adding 1/2 tsp sea salt, three tablespoons of sugar or honey, and a ¼ cup of fresh lemon or orange juice to one quart of water.
Determine the possible positive effects of feeding on the development of symptoms of acute mountain sickness. Evaluate the effect of meal composition on these symptoms.
The altitude exposure leads to considerable weight loss due to an initial loss of water and subsequently loss of fat and muscle tissue. Up to altitudes around 5000m, the loss of fat and muscle may be avoidable by increasing food intake. Primary anorexia, discomfort, lack of palatable food detained, and possible direct effects of hypoxia on protein metabolism seem to lead to weight loss at higher altitudes inevitably. To minimize losses, it is advisable to acclimatize properly, reduce the length of stay at extreme altitudes as much as possible, and keep the nutrient intake high and varied.
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