American College of Sports Medicine roundtable. The physiological and health effects of oral creatine supplementation.

Creatine (Cr) supplementation has become a common practice among professional, elite, collegiate, amateur, and recreational athletes with the expectation of enhancing exercise performance. Research indicates that Cr supplementation can increase muscle phosphocreatine (PCr) content, but not in all individuals. A high dose of 20 g x d(-1) that is common to many research studies is not necessary, as 3 g x d(-1) will achieve the same increase in PCr given time. Coincident ingestion of carbohydrate with Cr may increase muscle uptake; however, the procedure requires a large amount of carbohydrate. Exercise performance involving short periods of extremely powerful activity can be enhanced, especially during repeated bouts of activity. This is in keeping with the theoretical importance of an elevated PCr content in skeletal muscle. Cr supplementation does not increase maximal isometric strength, the rate of maximal force production, nor aerobic exercise performance. Most of the evidence has been obtained from healthy young adult male subjects with mixed athletic ability and training status. Less research information is available related to the alterations due to age and gender. Cr supplementation leads to weight gain within the first few days, likely due to water retention related to Cr uptake in the muscle. Cr supplementation is associated with an enhanced accrual of strength in strength-training programs, a response not independent from the initial weight gain, but may be related to a greater volume and intensity of training that can be achieved. There is no definitive evidence that Cr supplementation causes gastrointestinal, renal, and/or muscle cramping complications. The potential acute effects of high-dose Cr supplementation on body fluid balance has not been fully investigated, and ingestion of Cr before or during exercise is not recommended. There is evidence that medical use of Cr supplementation is warranted in certain patients (e.g.. neuromuscular disease); future research may establish its potential usefulness in other medical applications. Although Cr supplementation exhibits small but significant physiological and performance changes, the increases in performance are realized during very specific exercise conditions. This suggests that the apparent high expectations for performance enhancement, evident by the extensive use of Cr supplementation, are inordinate.

Facts and fallacies of purported ergogenic amino acid supplements.

Although current research suggests that individuals involved in either high-intensity resistance or endurance exercise may have an increased need for dietary protein, the available research is either equivocal or negative relative to the ergogenic effects of supplementation with individual amino acids. Although some research suggests that the induction of hyperaminoacidemia via intravenous infusion of a balanced amino acid mixture may induce an increased muscle protein synthesis after exercise, no data support the finding that oral supplementation with amino acids, in contrast to dietary protein, as the source of amino acids is more effective. Some well-controlled studies suggest that aspartate salt supplementation may enhance endurance performance, but other studies do not, meriting additional research. Current data, including results for several well-controlled studies, indicated that supplementation with arginine, ornithine, or lysine, either separately or in combination, does not enhance the effect of exercise stimulation on either hGH or various measures of muscular strength or power in experienced weightlifters. Plasma levels of BCAA and tryptophan may play important roles in the cause of central fatigue during exercise, but the effects of BCAA or tryptophan supplementation do not seem to be effective ergogenics for endurance exercise performance, particularly when compared with carbohydrate supplementation, a more natural choice. Although glutamine supplementation may increase plasma glutamine levels, its effect on enhancement of the immune system and prevention of adverse effects of the overtraining syndrome are equivocal. Glycine, a precursor for creatine, does not seem to possess the ergogenic potential of creatine supplementation. Research with metabolic by-products of amino acid metabolism is in its infancy, and current research findings are equivocal relative to ergogenic applications. In general, physically active individuals are advised to obtain necessary amino acids through consumption of natural, high-quality protein foods.

Creatine supplementation and exercise performance: an update.

Creatine, a natural nutrient found in animal foods, is alleged to be an effective nutritional ergogenic aid to enhance sport or exercise performance. Research suggests that oral creatine monohydrate supplementation may increase total muscle creatine [TCr], including both free creatine [FCr] and phosphocreatine [PCr]. Some, but not all, studies suggest that creatine supplementation may enhance performance in high-intensity, short-term exercise tasks that are dependent primarily on PCr (i.e., < 30 seconds), particularly laboratory tests involving repeated exercise bouts with limited recovery time between repetitions; additional corroborative research is needed regarding its ergogenic potential in actual field exercise performance tasks dependent on PCr. Creatine supplementation has not consistently been shown to enhance performance in exercise tasks dependent on anaerobic glycolysis, but additional laboratory and field research is merited. Additionally, creatine supplementation has not been shown to enhance performance in exercise tasks dependent on aerobic glycolysis, but additional research is warranted, particularly on the effect of chronic supplementation as an aid to training for improvement in competitive performance. Short-term creatine supplementation appears to increase body mass in males, although the initial increase is most likely water. Chronic creatine supplementation, in conjunction with physical training involving resistance exercise, may increase lean body mass. However, confirmatory research data are needed. Creatine supplementation up to 8 weeks has not been associated with major health risks, but the safety of more prolonged creatine supplementation has not been established. Creatine is currently legal and its use by athletes is not construed as doping.

Effect of Eleutherococcus senticosus on submaximal and maximal exercise performance.

We investigated the effect of Eleutherococcus senticosus Maxim L (ESML) on performance during submaximal and maximal aerobic exercise. Twenty highly trained distance runners randomly assigned in matched pairs to either an experimental (ESML) or placebo (PL) group, participated in an 8-wk double-blind study during which they completed five trails of a 10-min treadmill run at their 10 km (10K) race pace and a maximal treadmill test (T(max)). Following a baseline trail, ESML and PL consumed, respectively, 3.4 ml of ESML extract or placebo daily for 6 wk. Subjects were tested every 2 wk during supplementation and 2 wk following withdrawal. Heart rate (HR), oxygen consumption (VO2), expired minute volume (VE), ventilatory equivalent for oxygen (VE/VO2), respiratory exchange ratio (RER), and rating of perceived exertion (RPE) were measured during the 10K and T(max) tests. Resting, post-10K and post-T(max) blood samples were analyzed for serum lactate. No significant differences were observed between ESML and PL for: HR, VO2, VE, VE/VO2, RER, or RPE; T(max) time to exhaustion; or serum lactate. The data do not support an ergogenic effect of ESML supplementation on selected metabolic, performance, or psychologic parameters associated with submaximal and maximal aerobic exercise tasks.

Antioxidants, carnitine, and choline as putative ergogenic aids.

Three nutritional products that have very different mechanisms of action are antioxidant vitamins, carnitine, and choline. Antioxidant vitamins do not appear to have a direct effect on physical performance in well-fed people but have been touted for their ability to detoxify potentially damaging free radicals produced during exercise. Carnitine purportedly enhances lipid oxidation, increases VO2max, and decreases plasma lactate accumulation during exercise. However, studies of carnitine do not generally support its use for ergogenic purposes. Choline supplements have been advocated as a means of preventing the decline in acetylcholine production purported to occur during exercise; this decline may reduce the transmission of contraction-generating impulses across the skeletal muscle, an effect that could impair one's ability to perform muscular work. However, there are no definitive studies in humans that justify choline supplementation. Much of the scientific data regarding the aforementioned nutrients are equivocal and contradictory. Their potential efficacy for improving physical performance remains largely theoretical.

Nutritional ergogenics in athletics.

Nutritional ergogenic aids may be theorized to improve performance in athletics in a variety of ways, primarily by enhancing energy efficiency, energy control or energy production. Athletes have utilized almost every nutrient possible, ranging from amino acids to zinc, as well as numerous purported nutritional substances, such as ginseng, in attempts to enhance physical performance. This review focuses primarily on nutritional ergogenic aids thought to enhance performance by favourably affecting energy metabolism. Although most purported nutritional ergogenic aids have not been shown to enhance physical performance in well-trained, well-nourished athletes, some reliable scientific data support an ergogenic efficacy of several substances, including caffeine, creatine and sodium bicarbonate, but additional research is needed to evaluate their potential for enhancing performance in specific athletics events.

Ergogenic and ergolytic substances.

Genetic endowment and proper training are the major factors contributing to athletic success in endurance and ultraendurance events. Proper nutrition, primarily adequate carbohydrate and fluid, prior to and during the event is also critical. Endurance athletes often utilize other nutritional substances or practices, often referred to as ergogenics, in attempts to obtain a competitive edge by enhancing energy utilization and delaying the onset of fatigue. Numerous nutritional ergogenics have been used in attempts to enhance endurance performance, but with several exceptions most have been shown to be ineffective, including bee pollen, L-carnitine, CoQ10, inosine, amino acids, alkaline salts, and vitamin E at sea level. Research findings are equivocal relative to the ergogenicity of caffeine, phosphate salts, and vitamin E at altitude. Loss of excess body fat, a nutritional practice, may be an effective ergogenic. Conversely, some agents such as alcohol may impair performance, an ergolytic effect. Additional research is necessary to support the efficacy of several nutritional ergogenics to enhance prolonged endurance performance, such as caffeine, phosphates, specific amino acids, and various commercial products. Such research should involve exercise tasks comparable in intensity and duration to that experienced in the marathon and similar endurance events.

Vitamin supplementation and athletic performance.

Vitamins serve primarily as regulators of metabolic functions, many of which are critical to exercise performance. Depending upon the nature of their sport, e.g., strength, speed, power, endurance, or fine motor control, athletes may use megadoses of various vitamins in attempts to increase specific metabolic processes important to improved performance. Surveys have indicated that most elite athletes do take vitamin supplements, often in dosages greater than 50-100 times the United States Recommended Dietary Allowances. The theoretical basis underlying the use of each vitamin depends upon its specific metabolic function in relation to sport. Vitamin A functions to maintain night vision; thiamin, riboflavin, niacin, and pantothenic acid are all involved in muscle cell energy metabolism; niacin may also block free fatty acid release; pyridoxine is involved in the synthesis of hemoglobin and other oxygen transfer protein; folic acid and vitamin B12 are integrally involved in red blood cell (RBC) development; vitamins C and E are antioxidants, possibly preventing the destruction of the red blood cell membrane during exercise; vitamin D may be involved in muscle cell energetics through its influence on calcium. These are but a few of the possible metabolic functions of vitamins which have been suggested to have ergogenic applications to sport. Research has shown that a vitamin deficiency impairs physical performance. If this deficiency is corrected, performance usually improves. In general, vitamin supplementation to an athlete on a well-balanced diet has not been shown to improve performance. However, additional research with certain vitamins appears to be warranted, such as with the vitamin B complex and fine motor control, and with vitamin E and endurance at high altitudes. Moreover, research with megadose supplementation may also be necessary.

Vitamin and mineral supplements to athletes: do they help?

Although the general implications of this review would be that vitamin and mineral supplements are ineffective as ergogenic aids when added to the diet of an athlete who is well-nourished, there may be certain instances in which supplementation is warranted. For example, wrestlers on low calorie diets and high levels of energy expenditure may not be receiving a balanced intake of nutrients. Young male athletes and female athletes of all ages should be aware of iron-rich foods and include them in the daily diet. The female athlete who experiences a heavy menstrual flow may consider commercial iron preparations; hemoglobin and other hemotologic variables may be evaluated in order to determine the need for supplementation. More research is needed, particularly with large doses of the vitamin B-complex and vitamin C. Although some of the studies cited herein have used large doses, some athletes have been reported to consume massive dosages, for example, 10,000 mg of vitamin C daily. Unfortunately, there may be some adverse side effects of such massive doses, and it may not be ethical to conduct research with humans at those high intake levels. Do these massive dosages elicit a pharmacodynamic effect on some metabolic reactions that are favorable to physical performance? More research with vitamin E at altitude also appears to be warranted, as does iron supplementation to iron-deficient, but not anemic, athletes. As noted earlier, the current data base suggests that vitamin and mineral supplements are unnecessary for the athlete receiving a balanced diet. However, only with additional controlled research may we expand that data base to help answer some of the questions that still remain relative to nutrition and athletic performance. There are still a large number of athletes who believe that the "racers edge" may be found in a tablet.

The effect of induced erythrocythemia upon 5-mile treadmill run time.

The purpose of this experiment was to investigate the effect the infusion of 920 ml equivalent of autologous blood would have upon 5-mile time (5MT) and both local (RPE-L) and cardiovascular-respiratory (RPE-B) ratings of perceived exertion. Twelve long-distance runners undertook a series of four competitive 5MT trials on a treadmill. Four test conditions were utilized: pre-saline trial; post-saline trial after 920 ml saline solution; pre-blood trial; and post-blood trial after 920 ml equivalent of whole blood. All subjects took all trials in this double-blind placebo crossover experimental design. Running time and RPE were recorded at each 0.5 mile split. Blood samples were taken before and after each trial. The data were analyzed via a repeated-measures ANOVA. In general, the following results were noted following the blood infusion when compared with the other three trials: a significantly higher hemoglobin (Hb) concentration; a significantly lower RPE-L and RPE-B during the first two miles of the run; and a significantly faster 5MT. Within the limitations of this experiment, it was concluded that the infusion of 920 ml equivalent autologous blood would increase performance capacity in an athletic event characterized by high levels of aerobic energy expenditure.

The effect of blood infusion upon endurance capacity and ratings of perceived exertion.

The purpose of this investigation was to study the effect of blood infusion upon maximal endurance capacity and ratings of perceived exertaion (RPE). Sixteen long-distance runners, 13 of whom were marathoners, undertook four trials (T1-T4) of a treadmill run to exhaustion over a five week period. Criterion measures were time to exhaustion (TE) and RPE during each T. Data on Hb, Hct and RBCs were collected prior to each trial. Based on TE at T1, Ss were matched and assigned to either the experimental (E) or control (C) group. One week after T1, all Ss had 460 ml blood withdrawn. T2 was undertaken 2 weeks postwithdrawal. One week after T2, or 21 days postwithdrawal, the E group was infused with their own RBCs while the C group received 460 ml normal saline. T3 was taken 2 hours postinfusion and T4 one week later. The results of the factorial repeated measures ANOVA revealed no significant differences (p less than .05) between groups for either TE or RPE, even though the Hb level for the E group was significantly higher (P less than .01) than the C group at T3 and T4.

Effects of post-hypnotic suggestions on muscular endurance.

This study examined the effects of post-hypnotic suggestions upon maximal endurance capacity, Borg ratings of perceived exertion, and heart rate. Experimental subjects were administered post-hypnotic suggestions to improve or decrease performance, and control subjects were given similar instructions during the awake state. Endurance time could be decreased significantly when the fatigue suggestion was given to experimental subjects, but performance could not be enhanced with the facilitating suggestion. Control subjects showed no significant changes across conditions. The Borg ratings indicated that experimental subjects experienced subjective changes as suggested by the hypnotist. In addition, analysis failed to find any significant differences for the heart-rate data.