Caffeine is part of a regular diet for most people and is legal to a certain level. The ergogenic dose is approximately one half of this— to mg three cups of coffee or six to eight sodas. Many athletes take caffeine in pill form. Sympathomimetics such as ephedrine, pseudoephedrine, phenylpropanolamine and herbal ephedrine ma huang are used for their stimulant properties.
A double-blind study 24 of eight patients showed prolonged time to exhaustion and decreased perception of exertion with a caffeine and ephedrine combination. Studies 24 , 25 of sympathomimetics alone have not shown benefit.
The combined adverse effects of these stimulants include restlessness, nervousness, tachycardia, arrhythmias and hypertension. As of August , at least 17 deaths have been linked to use of these products in combination. Use of ephedrine products and elevated levels of urinary caffeine, as noted above, are banned by the IOC. Protein and its constituent, amino acids, are the building blocks of muscle.
Protein supplements are used by some athletes to enhance muscle repair and growth. Inadequate protein intake does cause a negative nitrogen balance, which slows muscle growth and causes fatigue. Athletes in training have increased protein needs.
A study 27 examining the protein requirements of experienced resistance-training athletes found that those consuming the recommended daily allowance for protein 0. The protein intake required for a zero balance was 1. Another study 28 using novice resistance-training athletes found their requirements to be 1. Both studies found that protein intakes in excess of these recommendations did not provide additional gains in strength or mass.
In an athlete with normal renal function, there are no notable adverse effects to increased protein consumption. It may be more healthy, however, to avoid acquiring protein from foods that also contain increased amounts of fat and cholesterol. While fat stores constitute the largest reservoir of stored energy, carbohydrates are the body's main source of rapidly available energy.
It has been suggested that taking proper quantities of carbohydrates at the right time could improve athletic performance by ensuring adequate energy stores are available when necessary. Loading, or increasing the carbohydrate content of the diet for several days before an event, has been promoted as a means to prolong exercise endurance. One study 29 evaluated its impact on continuous, short-term events of less than one hour and found no benefit, because muscle glycogen content was not depleted at the end of the exercise.
A meal prior to exercise will ensure that muscle and liver glycogen stores are maximized. Evaluation of six endurance athletes ingesting carbohydrates only 45 minutes prior to a two-hour exercise test revealed no benefit. Replenishment with carbohydrate-containing fluids during an endurance event may help to delay fatigue. Thirty marathon runners in a double-blind study 33 described decreased subjective exertion when ingesting 60 g per hour of a liquid carbohydrate solution during a two and one-half hour run.
Another study 34 found that ingesting a carbohydrate-electrolyte drink during one hour of high-intensity exercise improved performance in 19 bicyclists. Many studies have demonstrated similar results. One study 35 that evaluated solid versus liquid carbohydrate replenishment showed no difference, as long as adequate water intake was maintained. Eating a mixture of carbohydrates and protein within two hours after an activity has also been associated with benefits, including replenishment of depleted muscle and liver glycogen stores and decreased muscle catabolism.
A study 36 of nine weight lifters showed increased levels of plasma growth hormone and insulin when athletes ingested protein and carbohydrate immediately and two hours after exercise, which would theoretically provide a physiologic environment favorable for muscle growth. Another placebo-controlled study 37 of endurance athletes ingesting a carbohydrate-containing solution after exercise reported increased glycogen resynthesis.
Theoretic disadvantages have been reported with carbohydrate supplementation. Increased insulin levels after carbohydrate consumption were shown to significantly decrease blood glucose levels in some athletes, though not all athletes seem to be subjectively sensitive to these decreased levels. Many other dietary supplements have been advertised for their purported ergogenic properties, and the list grows each year.
Table 3 provides a brief summary of the most common agents that physicians may hear about from their patients who are athletes. When counseling patients about ergogenic aids, it is important that the physician be knowledgeable about the topic. The intervention that carries the most impact is ensuring optimal dietary habits.
Supplying adequate energy intake, carbohydrates and protein in the diet, and timing these to be efficiently used by the body, will provide the most effective and safe results. If a patient asks about a specific ergogenic aid, he or she should be told what is known and unknown about the product based on current research, including the side effect profile.
The danger is that once athletes start using a commercial supplement, they will continue to use more, eventually trying something that may not be safe. Many athletes feel pressured to use supplements to maintain a competitive advantage over their supplement-using peers. If physicians can guide athletes away from disproven and dangerous supplements, while maintaining open and honest lines of communication, then more serious health risks may be prevented.
Already a member or subscriber? Log in. Interested in AAFP membership? Learn more. Address correspondence to Dale M. Ahrendt, M. Reprints are not available from the author. The author thanks Christopher Dillon, M.
The opinions expressed in this article reflect the views of the author and do not reflect the opinion of the Department of Defense or the United States Government. Supplementary data tables USDA's — continuing survey of food intakes by individuals. Sobal J, Marquart LF. Int J Sports Nutr. Nesheim MC. What is the research base for use of dietary supplements?
Public Health Nutr. Williams MH. Rating the sports ergogenics. In: Williams MH. The ergogenics edge: pushing the limits of sports performance. Champaign, Ill Human Kinetics, — Anabolic steroids: a review of the literature. Am J Sports Med. The effects of supraphysiologic doses of testosterone on muscle size and strength in normal men. N Engl J Med.
Effects of creatine supplementation on body composition, strength, and sprint performance. Med Sci Sports Exerc. Effects of in-season 5 weeks creatine and pyruvate supplementation on anaerobic performance and body composition in American football players.
Int J Sport Nutr. Long-term creatine intake is beneficial to muscle performance during resistance training. J Appl Physiol. Creatine supplementation differentially affects maximal isometric strength and time to fatigue in large and small muscle groups. Creatine supplementation enhances muscular performance during high-intensity resistance exercise.
J Am Diet Assoc. Effects of creatine monohydrate ingestion in sedentary and weight-trained older adults. Acta Physiol Scand. Creatine supplementation in endurance sports. Poortmans JR, Francaux M. Long-term creatine supplementation does not impair renal function in healthy athletes. Dehydroepiandrosterone replacement in aging humans.
J Clin Endocr Metab. The effect of six months treatment with a mg daily dose of dehydroepiandrosterone DHEA on circulating sex steroids, body composition and muscle strength in age-advanced men and women. Clin Endocr. Effect of oral androstenedione on serum testosterone and adaptations to resistance training in young men: a randomized controlled trial. Oral androstenedione administration and serum testosterone concentrations in young men. Performance and metabolic responses to a high caffeine dose during prolonged exercise.
Kalmar JM, Cafarelli E. Effects of caffeine on neuromuscular function. Caffeine increases maximal anaerobic power and blood lactate concentration. Thermoregulatory effects of caffeine ingestion during submaximal exercise in men. Aviat Space Environl Med. Effects of caffeine, ephedrine and their combination on time to exhaustion during high-intensity exercise.
Do pseudoephedrine or phenylpropanolamine improve maximum oxygen uptake and time to exhaustion? Clin J Sports Med. Ephedrine pharmacokinetics after the ingestion of nutritional supplements containing ephedra sinica ma huang. Ther Drug Monitoring. Evaluation of protein requirements for trained strength athletes. Effects of 3 days of carbohydrate supplementation on muscle glycogen content and utilization during 1-h cycling performance. The effect of a preexercise meal on time to fatigue during prolonged cycling exercise.
Influence of high and low glycemic index meals on endurance running capacity. CHO feeding before prolonged exercise: effect of glycemic index on muscle glycogenolysis and exercise performance. Effect of carbohydrate substrate availability on ratings of perceived exertion during prolonged running. Carbohydrate-electolyte feedings improve 1 h time trial cycling performance. Int J Sports Med. Blood glucose and glucoregulatory hormone responses to solid and liquid carbohydrate ingestion during exercise.
Dietary supplements affect the anabolic hormones after weight-training exercise. Postexercise protein-carbohydrate and carbohydrate supplements increase muscle glycogen in men and women J Appl Physiol.
Sherman WM. However, in large doses, it can be harmful to the kidneys. CLA is a type of fat that athletes take to help reduce muscle damage and increase lean body mass after exercise.
The supplement is especially popular with bodybuilders, who use it to enhance recovery. A review of six research studies published in the journal Nutrients concluded that taking CLA supplements can have an effect on reducing body fat in those who also engage in a resistance training exercise program. However, CLA can cause side effects, including upset stomach, nausea, and fatigue.
It can also impact how well the body uses insulin. CLA can interact negatively with certain medications, like antipsychotics. Carnitine transports long-chain fatty acids into the mitochondria. This allows them to be burned for energy, which can help boost exercise performance.
Even so, many athletes continue to take the supplement. Taking more than 3 grams of carnitine per day can cause side effects like nausea, vomiting, stomach cramping, and diarrhea. Carnitine can also interact harmfully with some medications, such as thyroid medications and the blood thinner warfarin.
Drugstores often sell the mineral as chromium picolinate. Muscles use creatine to release energy, which enhances lean muscle mass and increases muscle energy. Those who take creatine often do so as a means to build muscle mass. Taking creatine is also not without its side effects.
For example, creatine can cause weight gain, muscle cramping, and stomach cramping. Additionally, the liver and kidneys must filter creatine. Taking an excessive amount can put a strain on these important organs, which could potentially damage them. Individual results may vary for all of these supplements. Talk with your doctor or athletic trainer about the safety and effectiveness of individual supplements.
The NCAA and the Olympics commission have banned some substances because they offer an unfair advantage or can cause harm to the athlete.
Anabolic and other steroids are illegal in sporting events and according to the law. The side effects are numerous and potentially fatal. Examples include androstenedione, stanozolol, axiron, and fortesta. DHEA is possibly the most abundant steroid in humans. Using synthetic versions to increase steroid production is potentially dangerous. Diuretics are medications that cause a person to urinate more frequently.
Athletes face intense training and fierce competition when working to get to the top of their game. With supplements claiming to improve strength, agility, speed and weight, it can be tempting to try something to help improve competitive edge.
Unfortunately, not all supplements live up to their claims. Dietary supplements are regulated by the U. Food and Drug Administration, or FDA, but the process is different than the regulation of conventional foods and drugs.
Manufacturers are responsible for ensuring their products are reasonably safe and not misleading, however, they are not required to prove a supplement works before marketing it, or even that it contains what it says it does.
Some organizations test supplements to verify what is inside of them, such as US Pharmacopeia, Informed Choice or NSF International, whose label may be found on the container of supplements that have been tested. The FDA is also able to remove or restrict the sale of a supplement, but only after it has been on the market and been shown to be unsafe or mislabeled.
Another concern with supplements is that evidence is often conflicting or insufficient. They can be costly and if taken in excess, may have negative side effects or even result in an athlete from being banned from an event. Before taking a supplement, talk with your health care provider first.
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