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Aside from training, nutrition may be the most important influence on athletic performance.1 However, in seeking a competitive edge, athletes are often susceptible to fad diets or supplements that have not been scientifically validated. Nevertheless, there is much useful research to guide the exerciser toward optimum health and performance.
 
bullet 
Lifestyle changes that may be helpful
Many athletes use exercise and weight-modifying diets as tools to change their body composition, assuming that a lower percent body fat and/or higher lean body mass is desirable in any sport. There is no single standard for body weight and body composition that applies to all types of athletic activities. Different sports, even different roles in the same sport (e.g., running vs. blocking in football), require different body types. These body types are largely determined by genetics. However, within each athlete’s genetic predisposition, variations occur due to diet and exercise that may impact performance. In general, excess weight is a disadvantage in activities that require quickness and speed. However, brief, intense bursts of power depend partly on muscle size, so this type of activity may favor athletes with higher body weights due to increased lean body mass. On the other hand, participants in endurance sports, which require larger energy reserves, should not attempt to lower their body fat so much as to compromise long-term performance.2
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bullet 
Dietary changes that may be helpful
Calorie requirements for athletes depend on the intensity of their training and performance. The athlete who trains to exhaustion on a daily basis needs more fuel than one who performs a milder regimen two or three times per week. Calorie requirements can be as much as 23–39 kcal per pound of body weight per day for the training athlete who exercises vigorously for many hours per day.3 4 Many athletes compete in sports having weight categories (such as wrestling and boxing), sports that favor small body size (such as gymnastics and horse racing), or sports that may require a specific socially-accepted body shape (such as figure skating). These athletes may feel pressured to restrict calories to extreme degrees to gain a competitive edge.5 Excessive calorie restriction can result in chronic fatigue, sleep disturbances, reduced performance, impaired ability for intensive training, and increased vulnerability to injury.6

Carbohydrate is the most efficient fuel for energy production and can also be stored as glycogen in muscle and liver, functioning as a readily available energy source for prolonged, strenuous exercise. For these reasons, carbohydrate may be the most important nutrient for sports performance.7 Depending on training intensity and duration, athletes require up to 4.5 grams per day of carbohydrate per pound of body weight or 60–70% of total dietary calories from carbohydrate, whichever is greater.8 9 Emphasizing grains, starchy vegetables, fruits, low-fat dairy products, and carbohydrate-replacement beverages and reducing intake of fatty foods results in a relatively high carbohydrate diet.

Carbohydrate beverages should be consumed during endurance training or competition (30–70 grams of carbohydrate per hour) to help prevent carbohydrate depletion that might otherwise occur near the end of the exercise period. At the end of endurance exercise, body carbohydrate stores must be replaced to prepare for the next session. This replacement can be achieved most rapidly if 40–60 grams of carbohydrate are consumed right after exercise, repeating this intake every hour for at least five hours after the event.10 Standard sport drinks containing 6–8% carbohydrate can be used during exercise, while high-density carbohydrate beverages containing 20–25% carbohydrate are useful for immediate post-exercise repletion. Addition of protein or a blend of essential amino acids to these products may increase their effectiveness for carbohydrate repletion,11 may help athletes recover from anaerobic (short-term and intense) exercise,12 and, according to preliminary research,13 14 may facilitate muscle growth during weight-training.

Carbohydrate-loading, or “supercompensation,” is a pre-event strategy that improves performance for some endurance athletes.15 16 Carbohydrate-loading can be achieved by consuming a 70% carbohydrate diet (or 4.5 grams per pound of body weight) for three to five days before competition, while gradually reducing training time, and ending with a day of no training while continuing the diet just before the event date.

Protein requirements are often higher for both strength and endurance athletes than for people who are not exercising vigorously; however, the increased food intake needed to supply necessary calories and carbohydrate also supplies extra protein. As long as the diet contains at least the typical 12–15% of calories as protein, or up to 0.75 grams per day per pound of body weight, protein supplements are neither necessary nor likely to be of benefit.17 18

Some athletes have speculated that consuming a high-fat diet for two or more weeks prior to endurance competition might cause the body to shift its fuel utilization toward more abundant fat stores (“fat adaptation”). In general, high-fat diets have not been found to consistently improve performance, and may even be detrimental;19 20 21 however, one study did report that a high-fat diet supported endurance training and performance as effectively as a high carbohydrate diet after two to four weeks of adaptation to the diets.22

Water is the most abundant substance in the human body and is essential for normal physiological function. Water loss due to sweating during exercise can result in decreased performance and other problems. The athlete should not wait until thirst occurs before drinking water but should instead drink before the need is felt. Fluids should be ingested prior to, during, and after exercise, especially when extreme conditions of climate, exercise intensity, and exercise duration exist.23 Approximately two glasses of fluid should be consumed two hours before exercise and at regular intervals during exercise; fluid should be cool, not cold, (59–72 degrees F). Flavored sports drinks containing electrolytes are not necessary for fluid replacement during brief periods of exercise, but they may be more effective in encouraging the athlete to drink frequently in larger amounts.24 water

bulletNutritional supplements that may be helpful

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Sports Supplements
Many athletes do not eat an optimal diet, especially when they are trying to control their weight while training strenuously.25 These athletes may experience micronutrient deficiencies that, even if marginal, could affect performance or cause health problems.26 27 28 29 However, athletes who receive recommended daily allowances of vitamins and minerals from their diet do not appear to benefit from additional multivitamin/mineral supplements with increased performance.30 31 32 The importance of individual vitamins and minerals is discussed below.

Electrolyte replacement is not as important as water intake in most athletic endeavors. It usually takes several hours of exercise in warm climates before sodium depletion becomes significant, and even longer for potassium, chloride, and magnesium.33 However, the presence of sodium in fluids will often make it easier to drink as well as retain more fluid.34

Most research has demonstrated that strenuous exercise increases production of harmful substances called free radicals, which can damage muscle tissue and result in inflammation and muscle soreness. Exercising in cities or smoggy areas also increases exposure to free radicals. Antioxidants, including vitamin C and vitamin E, neutralize free radicals before they can damage the body, so antioxidants may aid in exercise recovery. Regular exercise increases the efficiency of the antioxidant defense system, potentially reducing the increased intake otherwise needed for protection. 

However, supplements of antioxidant vitamins may be at least theoretically beneficial in older or untrained individuals or athletes who are undertaking an especially vigorous training protocol or athletic event, although research focusing on recovery from exercise is lacking.35 36 Placebo-controlled research, some of it double blind, has shown that taking 400–3,000 mg of vitamin C per day may reduce pain and speed up muscle strength recovery after intense exercise.37 38 Reductions in blood indicators of muscle damage and free radical activity have also been reported for supplementation with 400–1,200 IU per day of vitamin E in most studies,39 40 41 but no measurable benefits in exercise recovery have been reported.42 A combination of 90 mg per day of coenzyme Q10 and a very small amount of vitamin E did not produce any protective effects in one double blind study,43 while in another double blind study, a combination of 50 mg per day of zinc and 3 mg per day of copper significantly reduced evidence of post-exercise free radical activity.44

In most well-controlled studies, exercise performance has not been shown to benefit from supplementation of vitamin C, unless a deficiency exists.45 46 Similarly, vitamin E has not benefited exercise performance,47 except possibly at high altitudes.48 49

The B-complex vitamins are important for athletes, because they are needed to produce energy from carbohydrates. Exercisers may have slightly increased requirements for some of the B vitamins, including vitamin B2, vitamin B6, and pantothenic acid;50 athletic performance can suffer if these slightly increased needs are not met.51 However, most athletes obtain enough B vitamins from their diet without supplementation,52 and supplementation studies have found no effect on performance measures for vitamin B2,53 54 niacin,55 or vitamin B6.56

Chromium, primarily in a form called chromium picolinate, has been studied for its potential role in altering body composition. Preliminary research in animals57 and humans58 59 suggested that chromium picolinate increases fat loss and lean muscle tissue gain when used with a weight-training program. However, several recent studies have found little to no effect of chromium on body composition or strength,60 61 62 though one group of researchers has reported significant reductions in body fat measured with precise techniques in double blind trials using 200–400 mcg per day of chromium for six to twelve weeks in middle aged adults.63 64

Iron is important for the athlete because it transports oxygen to and within muscle cells. Some athletes, especially women, do not get enough of this mineral, and endurance athletes, such as marathon runners, frequently have low body iron levels for reasons that are unclear.65 66 67 A severe deficiency of iron can impair performance, but mild deficiency appears harmless; as a result, supplementing non-anemic athletes does not usually improve performance.68 Anemia in athletes is often not due to iron deficiency and may be a normal adaptation to the stress of exercise.69 Therefore, it is unwise to supplement with iron unless a significant deficiency has been diagnosed. Athletes who experience undue fatigue (an early warning sign of iron deficiency) should have their iron status evaluated by a nutritionally oriented physician.  

Magnesium deficiency can reduce exercise performance and contribute to muscle cramps, but it is not clear whether the occasional suboptimal intake found in some athletes is particularly important.70 One recent study found no effect of supplementation with 500 mg per day of magnesium on performance or muscle symptoms in athletes with blood levels of magnesium in the low end of the normal range.71  However, two double blind studies have reported intriguing results. One suggested that magnesium at 3.6 mg per pound body weight per day (including both diet and supplements) may benefit strength training,72 and the other trial used 390 mg per day of magnesium in triathletes and demonstrated reduced swimming, cycling, and running times.73
Very little research has been done to evaluate the ergogenic effects of other vitamins or minerals. Supplementation with selenium had no effect on the results of endurance training in one double blind study.74 Vanadyl sulfate, a form of vanadium that may have an insulin-like action, was given to weight-training athletes in a double blind study using 225 mcg per pound of body weight per day, but no effect on body composition was seen after twelve weeks, and effects on strength were inconsistent.75
Certain amino acids, the building blocks for protein, might be ergogenic aids as discussed below. However, while athletes have an increased need for protein compared with non-exercising adults, the maximum amount of protein suggested by many researchers—0.75 grams per pound of body weight—is already in the diet of most athletes as long as they are not restricting calories. Supplements of amino acids are therefore not needed to fulfill protein requirements for either strength or endurance exercise.76
Some research has shown that supplemental branched-chain amino acids (BCAA) (typically 10–20 grams per day) do not result in meaningful changes in body composition,77 nor do they improve exercise performance78 79 80 81 or enhance the effects of physical training.82 83 However, BCAA supplementation may be useful in special situations, such as the prevention of muscle loss at high altitudes84 and prolonging endurance performance in the heat.85 Studies by one group of researchers suggest that BCAA supplementation may also improve exercise-induced declines in some aspects of mental functioning.86 87 88
L-carnitine, which is normally manufactured by the human body, has been popular as a potential ergogenic aid because of its role in the conversion of fat to energy.89 However, while some studies have found that L-carnitine improves certain measures of muscle physiology, research on the effects of 2–4 grams of carnitine per day on performance have produced inconsistent results.90 L-carnitine may be effective in certain intense exercise activities leading to exhaustion,91 but recent studies have reported that L-carnitine supplementation does not benefit non-exhaustive or even marathon-level endurance exercise,92 93 anaerobic performance,94 or lean body mass in weight-lifters.95
At very high intakes (approximately 250 mg per 2.2 pounds of body weight) the amino acid arginine has increased growth hormone levels,96 an effect that has interested body builders. Large quantities (170 mg per 2.2 pounds of body weight per day) of a related amino acid, ornithine, has also raised growth hormone levels in some athletes.97 High amounts of arginine 98 or ornithine99 do not appear to raise levels of insulin, another anabolic hormone. More reasonable amounts of a combination of these amino acids have not had measurable effects on any anabolic hormone levels during exercise.100 101 Nonetheless, double blind trials combining weight training with either arginine/ornithine (500 mg of each, twice per day, five times per week) or placebo, found that the amino acid combination produced decreases in body fat,102 higher total strength and lean body mass, and reduced evidence of tissue breakdown after only five weeks.103 These remarkable results need independent confirmation before gaining acceptance among healthcare professionals who work with athletes.
Strenuous physical activity lowers blood levels of coenzyme Q10 (CoQ10).112 However, the effects of CoQ10 on how the healthy body responds to exercise have been inconsistent, with several studies finding no improvement.113 114 A few studies using at least four weeks of CoQ10 supplementation at 60–100 mg per day, have reported improvements in measures of work capacity ranging from 3% to 29% in sedentary people and from 4% to 32% in trained athletes.115 However, recent double blind and/or placebo-controlled trials in trained athletes, using performance measures such as time to exhaustion and total performance, have found either no significant improvement116 or significantly poorer results in those taking CoQ10.117 118

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The amino acid glutamine appears to play a role in muscle function and and in the immune system.104   Intense exercise lowers blood levels of glutamine, which can remain indefinitely low with overtraining.105 Glutamine supplementation raises levels of growth hormone at an intake of 2 grams per day,106 and intravenous glutamine is better than other amino acids at helping replenish muscle glycogen after exercise.107 However, glutamine supplementation (30 mg per 2.2 pounds body weight) has not improved performance of short-term, high-intensity exercise by trained athletes,108 and no studies on endurance performance have been done. Although the effects of glutamine supplementation on immune function after exercise have been inconsistent,109 110 a double blind study giving athletes glutamine (2.5 grams after exercise and again two hours later) reported 81% without subsequent infection compared with 49% in the placebo group.111
One group of researchers has reported on two small placebo-controlled trials showing that 100 grams of a combination of dihydroxyacetone and pyruvate enhanced the endurance of certain muscles.119 120 No follow-up research has appeared in the last decade to confirm these preliminary results.
Aspartic acid is a non-essential amino acid that participates in many biochemical reactions relating to energy and protein. Preliminary, though conflicting, animal and human research suggested a role for aspartic acid (in the form of potassium and magnesium aspartate) in reducing fatigue during exercise.121 However, most studies have found aspartic acid useless in improving either athletic performance or the body’s response to exercise.122 123 124 125 126
Whey protein is a dairy-based source of amino acids. While whey is a high quality source of protein, there is no evidence that currently supports its use for strength-training or body-building.
Creatine (creatine monohydrate) is used in muscle tissue for the production of phosphocreatine, a factor in the formation of ATP, the source of energy for muscle contraction and many other functions in the body.129 130 Creatine supplementation increases phosphocreatine levels in muscle, especially when accompanied by exercise or carbohydrate intake.131 132 It may also increase exercise-related gains in lean body mass, though it is unclear whether this represents more muscle or simply water retention.133 Most controlled studies have shown that 20 grams per day of creatine monohydrate taken for five or six days in sedentary or moderately active people have improved performance and delayed muscle fatigue during short-duration, high-intensity exercise such as sprinting and weight lifting.134 135 However, performance does not appear to be improved for trained athletes supplementing with Creatine in competitive situations, according to most,136 though not all,137 138 studies. Creatine supplementation does not appear to increase endurance performance and may impair it by contributing to weight gain.139 Only one controlled study lasting over one month has been done to evaluate the effects of creatine monohydrate supplementation.140 More long-term research is needed to evaluate creatine’s positive effects on athletic performance, particularly in trained athletes.
Inosine is a purine-like substance that appears in exercising muscle tissue. Its role in various cellular reactions has led to suggestions that it may have ergogenic effects.168 However, two placebo-controlled studies demonstrated no beneficial effects on performance and suggested that inosine may impair some aspects of exercise performance.169 170 Therefore, use of inosine is discouraged.

Caffeine is present in many popular beverages and appears to have an effect on fat utilization.171 Caffeine does not benefit short-term, high-intensity exercise, according to most,172 173 but not all, studies.174 175 However, placebo-controlled research, much of it double blind, has shown that endurance performance does appear to be enhanced by caffeine in many athletes.176 177 178 179 Inconsistency in reported effectiveness of caffeine in some trials can been explained by differences in caffeine sensitivity among athletes, variable effect of caffeine on different forms of exercise and under different environmental conditions, and effects of other dietary components on the response to caffeine.180 181 Effective amounts of caffeine appear to be about 2.5 mg per pound of body weight, which would require 2–3 cups brewed coffee or the equivalent taken one hour before exercise. However, most research has used caffeine supplements in capsules, and a recent study found caffeine was not effective when taken as coffee.182 Caffeine consumption is banned by the International Olympic Committee at levels that produce urinary concentrations of 12 mg/ml or more. These levels would require ingestion of considerably more than 2.5 mg per pound of body weight, or several cups of coffee over a short period of time.183

Are there any side effects or interactions? Refer to the individual supplement for information about any side effects or interactions.

 
bullet 
Herbs that may be helpful
Extensive but often poorly executed studies have been conducted on the use of Asian ginseng (Panax ginseng) to improve athletic performance.186 Some of these studies have reported that Asian ginseng is beneficial187 while others have not.188 One study also found that an extract of the related plant, Asian ginseng (Panax quinquefolium), was not effective at improving exercise performance in untrained people after one week’s supplementation.189 Despite a lack of consistent evidence, some doctors of natural medicine recommend taking extracts containing 5% ginsenosides at a level of 150–200 mg three times per day for at least several weeks.

Siberian ginseng or eleuthero (Eleutherococcus senticosus) has also been investigated as an herb that may improve athletic performance. Research from Russia indicates it may be effective for this purpose.190 Other studies have been inconclusive191 or have shown no beneficial effect.192 Although many doctors of natural medicine suggest taking 1–4 ml (1/4–1/2 tsp) of fluid extract of eleuthero three times per day, supportive evidence remains weak.

Some athletes take guaraná during their training; however, there is no scientific research to support this use. Guaraná contains caffeine, which is discussed above.

Yohimbe Bark is another herbal that helps Athletic Perfomance. In Weight Lifting - 90 percent of those who have try Yohimbe are happy with the results. Incredible gains in lean hard muscle mass with less body fat have been reported. Yohimbe is very effective in increasing the natural production of testosterone (male hormone). High levels of testosterone can make the difference between strong, well-developed muscles and/or a flabby, smooth appearance. Not only does yohimbe help build muscle and strength, but recent research shows it may elevate your mood, slow down the aging process and boost your sex drive.

Are there any side effects or interactions? Refer to the individual herb for information about any side effects or interactions.

 

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