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Sports and Fitness Support: Enhancing Performance
In the competitive world of sports, the smallest advantage can make an enormous difference in the outcome of a contest. A substance that improves an athlete's strength, speed, or endurance is called an ergogenic aid.
The most effective ergogenic aids are both dangerous and illegal: stimulants, anabolic steroids, and human growth hormone. Numerous natural options are marketed as alternatives. In this article, we explore the many supplements used in the hopes of improving sports performance.
Principal Proposed Natural Treatments TOP
Creatine, one of the best-selling and best-documented supplements for enhancing athletic performance, is a naturally occurring substance that plays an important role in the production of energy in the body. The body converts creatine to phosphocreatine, a form of stored energy used by muscles. In theory, taking supplemental creatine will build up a reserve of phosphocreatine in the muscles to help them perform on demand. Supplemental creatine may also help the body make new phosphocreatine faster when it has been used up by intense activity.
However, the balance of current evidence suggests that that if creatine supplements have any benefit for sports performance, it is slight and limited to highly specific forms of exercise.
Several small double-blind studies have found that creatine can improve performance in exercises that involve repeated short bursts of high-intensity activity with intervening rest periods of adequate length.
For example, a double-blind, placebo-controlled study investigated creatine and swimming performance in 18 men and 14 women.1 Men taking the supplement had significant increases in speed when doing six bouts of 50-meter swims started at 3-minute intervals, compared to men taking placebo. However, their speed did not improve when swimming 10 sets of 25-yard lengths started at 1-minute intervals. Researchers theorize that the shorter rest time between laps was not enough for the swimmers' bodies to resynthesize phosphocreatine.
Interestingly, none of the women enrolled in the study showed any improvement with the creatine supplement. The authors of this study noted that women normally have more creatine in their muscle tissue than men do, so perhaps creatine supplementation (at least at this level) is not of benefit to women, as it appears to be for men. Further research is needed to fully understand the difference between the genders in response to creatine.
In an earlier double-blind study, 16 physical education students carried out ten 6-second bursts of extremely intense exercise on a stationary bicycle, separated by 30 seconds of rest.2 The results showed that the students who took 20 g of creatine for 6 days were better able to maintain cycle speed throughout the repetitions. Many other studies showed similar improvements in performance capacity involving repeated bursts of action.2-4 However, there have been negative results as well; in general, minimal to no benefits have been seen in studies involving athletes engaged in normal sports rather than contrived laboratory tests.2-7,143-146
In contrast, studies of endurance or nonrepetitive aerobic burst exercise generally have not shown benefits from creatine supplementation.6,8-11,147-148 Therefore, creatine probably will not help you with marathon running or single sprints.
Besides repetitive burst exercise, creatine has also shown promise for increasing isometric exercise capacity (pushing against a fixed resistance), in some, but not all studies.4,12-13,149-151 In addition, two double-blind, placebo-controlled studies, each lasting 28 days, provide some evidence that creatine as well as creatine plus hydroxymethyl butyrate (HMB) (see below) can increase lean muscle and bone mass.14 However, one double-blind trial failed to find creatine helpful for enhancing general fitness, including resistance exercise performance, in male seniors.125
The contradictory results seen in these small trials suggest that creatine offers at most a very modest sports performance benefit. For more information, including dosage and safety issues, see the full Creatine article.
Technically beta-hydroxy beta-methylbutyric acid, HMB is a chemical that occurs naturally in the body when the amino acid leucine breaks down. Leucine is found in particularly high concentrations in muscles. During athletic training, damage to the muscles leads to the breakdown of leucine as well as increased HMB levels. Some evidence suggests that taking HMB supplements might signal the body to slow down the destruction of muscle tissue.15 On this basis, HMB has been studied as a sports performance supplement for enhancing strength and muscle mass.
According to many (but not all) of the small double-blind trials that have been reported, HMB appears to improve muscle-growth response to weight training.14-20
For example, in a controlled study, 41 male volunteers aged 19 to 29 were given either 0, 1.5, or 3 g of HMB daily for 3 weeks.17 The participants also lifted weights 3 days a week according to a defined (rather severe) schedule. The results suggested that HMB can enhance strength and muscle mass in direct proportion to intake.
In another controlled study reported in the same article, 32 male volunteers took either 3 g of HMB or placebo daily, and then lifted weights for 2 or 3 hours daily, 6 days a week for 7 weeks. The HMB group saw a significantly greater increase in bench-press strength than the placebo group. However, there was no significant difference in body weight or fat mass by the end of the study.
Similarly, a double-blind, placebo-controlled trial of 39 men and 36 women found that over 4 weeks, HMB supplementation improved response to weight training.19
Two placebo-controlled studies of women found that 3 g of HMB had no effect on lean body mass and strength in sedentary women, but it did provide an additional benefit when combined with weight training.18 In addition, a double-blind study of 31 men and women, all 70 years old and undergoing resistance training, found significant improvements in fat-free mass attributable to the use of HMB (3 g daily).21
However, there have been negative studies as well.14,20,22
All of these studies were small and therefore, their results are ultimately not terribly reliable. Larger studies will be necessary to truly establish whether HMB is helpful for power athletes working to enhance strength and muscle mass.
For more information, including dosage and safety issues, see the full HMB article.
Other Proposed Natural Treatments TOP
Numerous other supplements are marketed as ergogenic aids, said to improve speed, strength, or endurance. Unfortunately, the evidence that they work is marginal at best, and in many cases the best available evidence indicates that these substances are not effective.
There are three different herbs commonly called ginseng: Asian or Korean ginseng ( Panax ginseng), American ginseng ( Panax quinquefolius), and Siberian "ginseng" ( Eleutherococcus senticosus). The latter is actually not ginseng at all, but the Russian scientists responsible for promoting it believe that it functions identically. According to some experts, a fourth herb, ciwujia, is actually Eleutherococcus, while others claim it is a related but different species.
Panax ginseng has shown some promise as a mild ergogenic aid, but published evidence remains at best incomplete and contradictory. Other forms of ginseng generally lack any meaningful supporting evidence.
For example, an 8-week, double-blind, placebo-controlled trial evaluated the effects of Panax ginseng with and without exercise in 41 people.24 The participants were given either ginseng or placebo, and then underwent exercise training or remained untrained throughout the study. The results showed that ginseng improved aerobic capacity in people who did not exercise, but offered no benefit in those who did exercise.
In a 9-week, double-blind, placebo-controlled trial of 30 highly trained athletes, treatment with Panax ginseng or Panax ginseng plus vitamin E produced significant improvements in aerobic capacity.25 Another double-blind, placebo-controlled trial of 37 participants also found some benefit.26 Also, a double-blind, placebo-controlled study of 120 people found that ginseng gradually improved reaction time and lung function over a 12-week treatment period among participants from 40 to 60 years old.27 (No benefits were seen in younger people.)
On the other hand, in an 8-week, double-blind trial that followed 60 healthy men in their 20s, no benefit with Panax ginseng could be demonstrated.179 Many other small trials of Panax ginseng have failed to find evidence of benefit.28-36,126
These mixed outcomes suggest that Panax ginseng is only slightly effective at best.
A double-blind study of 20 endurance athletes over an 8-week period failed to find evidence of benefit with a standard eleutherococcus formulation.37 Lack of benefit was also seen in another small double-blind crossover trial.38 Furthermore, in a small double-blind, placebo-controlled trial of endurance athletes, use of eleutherococcus actually increased physiologic signs of stress during intensive training.36 Ciwujia has not yet been studied in meaningful double-blind trials.
Medium-chain triglycerides (MCTs) are fats with an unusual chemical structure that allows the body to digest them easily. Most fats are broken down in the intestine and reassembled into a special form that can be transported in the blood. However, MCTs are absorbed intact and taken to the liver, where they are used directly for energy. In this sense, they are processed very similarly to carbohydrates. For that reason, MCTs have been proposed as an alternative to "carbo-loading" (consumption of a large quantity of carbohydrates prior to intense physical exercise) for providing a concentrated source of easily utilized energy.
A number of double-blind studies have evaluated MCTs’ effects on high-intensity or endurance exercise performance, but the results have been thoroughly inconsistent.39-44 This is not surprising because all of the studies were too small to properly eliminate the effects of chance.
For more information, including dosage and safety issues, see the full MCTs article.
The majority of athletes are probably not iron-deficient, and you should not take iron supplements if you already have enough iron in your body. However, if you are deficient in this essential mineral, iron supplements may enhance athletic training.
A double-blind, placebo-controlled trial of 42 nonanemic women with evidence of slightly low iron reserves found that iron supplements significantly increased the benefits gained from exercise.45 Participants were put on a daily aerobic training program for the latter 4 weeks of this 6-week trial. At the end of the trial, those receiving iron showed significantly greater gains in speed and endurance than those given placebo.
In addition, a double-blind, placebo-controlled study of 40 nonanemic elite athletes with mildly low iron stores found that 12 weeks of iron supplementation enhanced aerobic performance.46
Benefits with iron supplementation for marginally iron-depleted athletes were observed in other double-blind trials as well.127,128 However, several other studies failed to find significant improvements.129-131 These contradictory results suggest that the benefits of iron supplements for nonanemic, iron-deficient athletes is small at most.
For more information, including dosage and safety issues, see the full Iron article.
Colostrum is the fluid that new mothers' breasts produce during the first day or two after birth. Colostrum contains growth factors, such as IGF-1, that could enhance muscle development, and on this basis, it has been tried as a sports supplement.
In addition, a small double-blind study found that colostrum, as compared to whey protein, increased lean mass in healthy men and women undergoing aerobic and resistance training.47 However, no improvements in performance were seen in this trial.
Finally, in a double-blind, placebo-controlled study, use of colostrum over an 8-week training period did not improve performance on an exercise-to-exhaustion test; however, it did improve performance on a repeat bout 20 minutes later.48
Interestingly, research suggests that the growth factor IGF-1 in colostrum is not directly absorbed into the body,134 yet consumption of colostrum nonetheless increases IGF-1 levels in the blood, perhaps by stimulating its natural release.134,135
For more information, including dosage and safety issues, see the full Colostrum article.
Pyruvate, also called dihydroxyacetone pyruvate (DHAP), supplies the body with pyruvic acid, a natural compound that plays important roles in the manufacture and use of energy. Pyruvate supplements have become popular with bodybuilders and other athletes based on slim evidence that pyruvate can improve body composition.49-52 However, at the present time, the evidence regarding pyruvate as an ergogenic aid is weak and contradictory at best.53-56 One study failed to find that pyruvate supplements improved body composition or exercise performance; furthermore, pyruvate appeared to negate the beneficial effect of exercise on cholesterol profile.152
For more information, including dosage and safety issues, see the full Pyruvate article.
Policosanol is a mixture of waxy substances manufactured from sugarcane. It contains octacosanol, which is also made from wheat germ oil. Both are marketed as performance-enhancing dietary supplements said to increase muscle strength and endurance and improve reaction time and stamina. However, the only evidence for policosanol as a performance enhancer comes from one small double-blind trial with marginal results.57
Phosphatidylserine (PS) is a phospholipid and a major component of cell membranes. Good evidence suggests that PS can improve mental function, especially in the elderly. However, PS has also been marketed as a sports supplement, said to help bodybuilders and power athletes develop larger and stronger muscles.
This claim is based on modest evidence indicating that PS slows the release of cortisol following heavy exercise.58-60 Cortisol is a hormone that causes muscle tissue to break down. For reasons that are unclear, the body produces increased levels of cortisol after heavy exercise. Strength athletes who believe natural cortisol release works against their efforts to rapidly build muscle mass hope that PS will help them advance more quickly. However, only two double-blind, placebo-controlled studies of PS as a sports supplement have been reported, and neither one found effects on cortisol levels. Of these small trials, one found a possible ergogenic benefit, and the other did not.153-154
Another study evaluated use of phosphatidylserine for improving the performance of golfers.184 While improvement in perceived stress levels failed to reach statistical significance, participants who were given phosphatidylserine did tee-off successfully at a greater rate than those given placebo.
For more information, including dosage and safety issues, see the full Phosphatidylserine article.
Branched-chain Amino Acids: Leucine, Isoleucine, and Valine TOP
Amino acids are molecules that form proteins when joined together. Three of them—leucine, isoleucine, and valine—are called branched-chain amino acids (BCAAs), describing the shape of the molecules. Muscles have a particularly high BCAA content.
Both strength training and endurance exercise use greater amounts of BCAAs than normal daily activities,61 perhaps increasing an athlete's need for dietary intake of these amino acids. Sports such as mountaineering and skiing may cause even greater depletion of BCAAs because of metabolic changes that occur at higher altitudes. Athletes have tried BCAA supplements to build muscle, improve performance, postpone fatigue, and cure overtraining syndrome (prolonged fatigue and other symptoms caused by excessive exercise). However, most of the evidence suggests that BCAAs are not helpful for these purposes.62-69,155
Whey protein is rich in BCAAs, and on this basis, it has also been proposed as a bodybuilding aid. However, there is little evidence that whey protein is more effective for this purpose than any other protein. One small double-blind study found evidence that both casein and whey protein were more effective than placebo at promoting muscle growth after exercise, but whey was no more effective than the far less expensive casein.156 Another study failed to find benefits with combined whey and soy protein supplementation.174 However, a single small study did find ergogenic benefits with whey as compared to casein.175
For more information, including dosage and safety issues, see the full Branched-chain Amino Acids article.
Other Amino Acids TOP
Besides BCAAs, athletes use a number of other amino acids, sometimes individually and sometimes in combination. Amino acids believed by some to have ergogenic effects include arginine, glutamine, and ornithine (ornithine and glutamine combined form ornithine alpha-ketoglutarate, or OKG), as well as the branched-chain amino acids leucine, isoleucine, and valine, discussed above.
However, evidence supporting the use of amino acids as ergogenic aids is sparse to nonexistent. The few clinical trials performed generally do not show positive results.69,70-72
Carnitine, a substance closely related to amino acids, is used by the body to convert fat into energy. Even though the body can manufacture all it needs, supplemental carnitine could, in theory, improve the ability of certain tissues to produce energy, leading to its promotion as a sports performance enhancer. To date, however, there is no meaningful evidence that this is the case.187
The mineral chromium has been sold as a "fat burner" and is also said to help build muscle tissue. However, studies evaluating its benefits as a performance enhancer or an aid to bodybuilding have yielded almost entirely negative results.73-82
Coenzyme Q 10 TOP
Coenzyme Q10 (CoQ 10 ubiquinone) is a natural substance that plays a fundamental role in the mitochondria, the parts of the cell that produce energy from food. On this basis, CoQ 10 has been proposed as a performance enhancer for athletes. However, most clinical trials have found no significant improvement with CoQ 10.83-89,157
For more information, including dosage and safety issues, see the full Coenzyme Q10 article.
Inosine is an important chemical found throughout the body. It plays many roles, one of which is helping to make ATP, the body's main form of usable energy. Based primarily on this fact, inosine supplements have been proposed as an energy booster for athletes. However, most of the available evidence suggests that it does not work.90-94
For more information, including dosage and safety issues, see the full Inosine article.
Ribose is a carbohydrate that is also vital for the manufacture of ATP. Ribose has shown some promise for improving exercise capacity in people with certain enzyme deficiencies and other rare conditions that cause muscle pain during exertion.95,96 On this basis, it has been touted as an athletic performance enhancer; however, six small double-blind, placebo-controlled trials in humans failed to find any benefit.97,136-137,158-159,173 In one of these studies, dextrose (a form of ordinary sugar), proved effective while ribose did not.160
For more information, including dosage and safety issues, see the full Ribose article.
Gamma Oryzanol TOP
Very preliminary evidence suggests that gamma oryzanol, a substance derived from rice bran oil, may increase endorphin release and aid muscle development.98,99 These findings have created interest in using gamma oryzanol as a sports supplement. However, a 9-week, double-blind, placebo-controlled trial of 22 weight-trained males found no difference between placebo or 500 mg daily of gamma oryzanol in terms of performance, body composition, or hormone levels.100
For more information, including dosage and safety issues, see the full Gamma Oryzanol article.
Trimethylglycine (TMG) is a naturally occurring compound that may help to prevent atherosclerosis and is, therefore, sometimes taken as a supplement. In the course of its metabolism in the body, TMG is turned into another substance, dimethylglycine (DMG).
In Russia, DMG is used extensively as an athletic performance enhancer, and it has recently become popular among American athletes. TMG is cheaper, and it may have the same effects as DMG as it changes into DMG in the body. However, there is no evidence that DMG is effective, and some evidence that it is not.101
For more information, including dosage and safety issues, see the full Trimethylglycine article.
Athletes have used DHEA on the belief that (like phosphatidylserine) it might limit the body's response to cortisol and thereby cause an increase in muscle tissue growth. However, study results have conflicted on whether or not DHEA really interferes with cortisol.106,107 Furthermore, studies of DHEA as an aid to increasing muscle mass or enhancing sports performance have produced mixed results at best.108-110,161,182
For more information, including dosage and safety issues, see the full DHEA article.
Tribulus Terrestris TOP
Tribulus terrestris is a tropical plant with a long history of medicinal use. It has been tried for low libido in both men and women, and for impotence and female infertility.
One theory regarding how T. terrestris might help with sexual problems is that a component from the plant called protodioscine is converted to the hormone DHEA in our bodies.102 DHEA is used by the body as a building block for both testosterone and estrogen (as well as other hormones). This finding has led bodybuilders and strength athletes to try T. terrestris for increasing muscular development. So far, however, the scientific evidence seems to be against it. This is not surprising because DHEA itself has not been found effective as a sports supplement.
One study involving 15 men compared the effects of T. terrestris (3.21 mg per kilogram of body weight—for example, 292 mg daily for a 200-pound man) against placebo on body composition and endurance among men engaged in resistance training.103 At the end of the 8-week study, the only significant difference between the treatment and placebo groups was that the placebo group showed greater gains in endurance.
Another double-blind, placebo-controlled study, which enrolled 22 athletes and followed them for five weeks, failed to find benefit.178 The dose used in this trial was fixed at 450 mg daily for all participants.
For more information, including dosage and safety issues, see the full Tribulus terrestris article.
Because phosphate plays a fundamental role in the body's energy-producing pathways, it has been suggested that taking high doses of phosphate (phosphate loading) prior to athletic activities might enhance performance. Phosphate-containing chemicals are also part of the process that allows oxygen release from hemoglobin, and this too has intrigued researchers looking for ergogenic aids. However, while some studies have found that phosphate loading improves maximum oxygen utilization, others have not. Flaws in study design cast doubt on the positive results.104,105,171,172
For more information, including dosage and safety issues, see the full Phosphorus article.
Commercial Preparations TOP
A small double-blind study of a mixture of various herbs and supplements marketed as SPORT® found no evidence that it can improve sports performance in trained athletes.111
Stimulants: Ma Huang and Caffeine TOP
A number of plant-derived stimulants are used by some athletes to improve their performance, including ephedrine from the Chinese herb ma huang (also called ephedra) and caffeine from coffee, tea, maté, cola, or guarana (a plant native to South America). Both ephedrine and caffeine are central nervous system stimulants. Caffeine also appears to change the way your body burns calories, possibly allowing it to burn fats first and preserve muscle glycogen for later in the competition—sort of like "saving the best for last."112
Caffeine does appear to improve performance during endurance-type exercises.112
Note: The International Olympic Committee has set a tolerance limit for caffeine in the urine at 12 mcg/ml. If you are competing in a sport that follows similar regulations, you may want to have a cup of coffee or tea, but do not drink the whole pot.
Ephedrine's value in enhancing sports performance has not been established; at the same time, there are serious safety issues associated with its use.138 (See the Safety Issues section in the full article on Ephedra.) Some sports federations have determined that specific amounts of ephedrine in an athlete's system are grounds for disqualification.
One small double-blind trial found that use of the herb Rhodiola rosea improved endurance exercise performance.162 However, another study failed to find benefit with a combination of cordyceps and rhodiola.163
A variety of antioxidants have been proposed for enhancing recovery after heavy exercise. One study found weak evidence that a combination of vitamin E (400 mg daily) and vitamin C (1,000 mg daily) taken for 3 weeks can improve aerobic performance.185
Heavy exercise causes increased calcium loss through sweat, and the the body does not compensate for this by reducing calcium loss in the urine.180 The result can be a net calcium loss great enough so that it presents health concerns for menopausal women, who are already at risk for osteoporosis. One study found that use of an inexpensive calcium supplement (calcium carbonate), taken at a dose of 400 mg twice daily, is sufficient to offset this loss.180
A small study found endurance exercise benefits with the herb Panax notoginseng.164
Galactose is a type of sugar that the body combines with glucose to create lactose (“milk sugar”). For various theoretical reasons, it has been hypothesized that use of galactose might enhance endurance exercise performance. However, the one small study designed to test this hypothesis found, instead, that consumption of galactose prior to endurance exercise actually proved detrimental.181
A small, double-blind study failed to find any performance or training-enhancing benefits with a newly marketed silicate product.140 Astaxanthin, fish oil, N-acetylcysteine (NAC), soy isoflavones, and tyrosine have also failed to show benefit in preliminary trials.141,165-168
Numerous other natural substances have been marketed as ergogenic aids, despite essentially an absolute absence of evidence that they help, including cordyceps, Cystoseira canariensis, deer antler, ipriflavone, lipoic acid, methoxyisoflavone, NADH, and suma. One study found that L-citrulline, another purported ergogenic aid, actually decreases exercise capacity.169
Many websites advertise products that they claim act like human growth hormone, often called HGH enhancers. However, these products are entirely speculative because there are no natural treatments proven to raise human growth hormone levels.
Similarly, there are no herbs or supplements known to act as “natural anabolic steroids.” (See also the discussion of androstenedione in the Not Recommended Treatments section.)
The amino acid beta-alanine is said to raise levels of carnosine, which in turn is hypothesized to enhance performance in athletes undergoing resistance training. However, a double blind study of 26 athletes failed to find benefit with 6 g of alanine daily.186
Not Recommended Treatments TOP
The mineral vanadium has been suggested for use by bodybuilders based on its effects on insulin, but there is no evidence that it helps. A double-blind, placebo-controlled study involving 31 weight-trained athletes found no benefit of supplementation at more than 1,000 times the nutritional dose.113 Furthermore, there are serious safety concerns about taking vanadium at such high doses. See the full article on Vanadium for more information.
The mineral boron has been proposed as a sports supplement because it is thought to increase testosterone levels. However, studies performed thus far have failed to provide meaningful evidence that it helps increase muscle mass or enhances performance.114,115 Furthermore, clinical studies suggest that boron supplementation is more likely to increase estrogen than testosterone.116-118 Increased estrogen is not likely to have a sports performance benefit in men, while in women it might increase risk of breast cancer. Therefore, we do not recommend taking supplemental boron as a sports supplement. See the full article on boron for more information.
The hormone androstenedione is said to enhance athletic performance and strength by increasing testosterone production, thereby building muscle. However, in double-blind studies, when androstenedione was given to men, it neither altered total testosterone levels, nor improved sports performance, strength, or lean body mass.109,119-123 It did, however, increase estrogen levels, an effect that would not be considered favorable. Interestingly, androstenedione does appear to raise testosterone levels in women, but it is not clear whether this would produce favorable results.23,142 For more information, see the full Androstenedione article.
References[ + ]
1. Leenders N, Sherman WM, Lamb DR, et al. Creatine supplementation and swimming performance. Int J Sport Nutr. 1999;9:251-262.
2. Balsom PD, Ekblom B, Soderlund K, et al. Creatine supplementation and dynamic high-intensity intermittent exercise. Scand J Med Sci Sports. 1993;3:143-149.
3. Mujika I, Padilla S. Creatine supplementation as an ergogenic aid for sports performance in highly trained athletes: a critical review. Int J Sports Med. 1997;18:491-496.
4. Williams MH, Branch JD. Creatine supplementation and exercise performance: an update. J Am Coll Nutr. 1998;17:216-234.
5. Mujika I, Padilla S, Ibanez J, et al. Creatine supplementation and sprint performance in soccer players. Med Sci Sports Exerc. 2000;32:518-525.
6. Gilliam JD, Hohzorn C, Martin D, et al. Effect of oral creatine supplementation on isokinetic torque production. Med Sci Sports Exerc. 2000;32:993-996.
7. Finn JP, Ebert TR, Withers RT, et al. Effect of creatine supplementation on metabolism and performance in humans during intermittent sprint cycling. Eur J Appl Physiol. 2001;84:238-243.
8. Balsom PD, Harridge SDR, Soderlund K, et al. Creatine supplementation per se does not enhance endurance exercise performance. Acta Physiol Scand. 1993;149:521-523.
9. Burke LM, Pyne DB, Telford RD. Effect of oral creatine supplementation on single-effort sprint performance in elite swimmers. Int J Sport Nutr. 1996;6:222-233.
10. Mujika I, Chatard JK, Lacoste L, et al. Creatine supplementation does not improve sprint performance in competitive swimmers. Med Sci Sports Exerc. 1996;28:1435-1441.
11. Cooke WH, Grandjean PW, Barnes WS. Effect of oral creatine supplementation on power output and fatigue during bicycle ergometry. J Appl Physiol. 1995;78:670-673.
12. Volek JS, Kraemer WJ, Bush JA, et al. Creatine supplementation enhances muscular performance during high-intensity resistance exercise. J Am Diet Assoc. 1997;97:765-770.
13. Bemben MG, Bemben DA, Loftiss DD, et al. Creatine supplementation during resistance training in college football athletes. Med Sci Sports Exerc. 2001;33:1667-1673.
14. Kreider RB. Dietary supplements and the promotion of muscle growth with resistance exercise. Sports Med. 1999;27:97-110.
15. Slater G, Jenkins D. Beta-hydroxy beta-methylbutyric acid (HMB) supplementation and the promotion of muscle growth and strength. Sports Med. 2000;30:105-116.
16. Ostaszewski P, Kostiuk S, Balasinska B, et al. The effect of leucine metabolite 3-hydroxy-3-methylbutyrate (HMB) on muscle protein synthesis and protein breakdown in chick and rat muscle [abstract]. J Anim Sci. 1996;74(suppl 1):138.
17. Nissen S, Sharp R, Ray M, et al. Effect of leucine metabolite beta-hydroxy-beta-methylbutyrate on muscle metabolism during resistance-exercise training. J Appl Physiol. 1996;81:2095-2104.
18. Nissen S, Panton L, Fuller J, et al. Effect of feeding beta-hydroxy-beta-methylbutyrate (HMB) on body composition and strength of women [abstract]. FASEB J. 1997;11:A150.
19. Panton LB, Rathmacher JA, Baier S, et al. Nutritional supplementation of the leucine metabolite beta-hydroxy beta-methylbutyrate (HMB) during resistance training. Nutrition. 2000;16:734-739.
20. Gallagher PM, Carrithers JA, Godard MP, et al. Beta-hydroxy-beta-methylbutyrate ingestion, Part I: effects on strength and fat free mass. Med Sci Sports Exerc. 2000; 32:2109-2115.
21. Vukovich MD, Stubbs NB, Bohlken RM. Body composition in 70-year-old adults responds to dietary beta-hydroxy-beta-methylbutyrate similarly to that of young adults. J Nutr. 2001;131:2049-2052.
22. Thom E, Wadstein J, Gudmundsen O. Conjugated linoleic acid reduces body fat in healthy exercising humans. J Int Med Res. 2001;29:392-396.
23. Kicman AT, Bassindale T, Cowan DA, et al. Effect of androstenedione ingestion on plasma testosterone in young women; a dietary supplement with potential health risks. Clin Chem. 2003;49:167-169.
24. Cherdrungsi P, Rungroeng K. Effects of standardized ginseng extract and exercise training on aerobic and anaerobic capacities in humans. Korean J Ginseng Sci. 1995;19:93-100.
25. Forgo I. Effect of drugs on physical exertion and the hormonal system of athlete [translated from German]. MMW Munch Med Wochenschr. 1983;125:822-824.
26. McNaughton LG, Egan G, Caelli G. A comparison of Chinese and Russian ginseng as ergogenic aids to improve various facets of physical fitness. Int J Clin Nutr Rev. 1989;9:32-35.
27. Forgo I, Kayasseh L, Staub JJ. Effect of a standardized ginseng extract on general well-being, reaction time, lung function and gonadal hormones [translated from German]. Med Welt. 1981;32:751-756.
28. Engles HJ, Wirth JC. No ergogenic effects of ginseng ( Panax ginseng) during graded maximal aerobic exercise. J Am Diet Assoc. 1997;97:1110-1115.
29. Engels HJ, Said JM, Wirth JC, et al. Failure of chronic ginseng supplementation to affect work performance and energy metabolism in healthy adult females. Nutr Res. 1996;16:1295-1305.
30. Morris AC, Jacobs I, McLellan TM, et al. No ergogenic effect of ginseng ingestion. Int J Sport Nutr. 1996;6:263-271.
31. Teves MA, Wright JE, Welch MJ, et. al. Effects of ginseng on repeated bouts of exhaustive exercise [abstract]. Med Sci Sports Exerc. 1983;15:162.
32. Allen JD, McLung J, Nelson AG, et al. Ginseng supplementation does not enhance healthy young adults' peak aerobic exercise performance. J Am Coll Nutr. 1998;17:462-466.
33. Lifton B, Otto RM, Wygand J. The effect of ginseng on acute maximal aerobic exercise [abstract]. Med Sci Sports Exerc. 1997;29(suppl 5):S249.
34. Kolokouri I, Englels HJ, Cieslak T, et al. Effect of chronic ginseng supplementation on short duration, supramaximal exercise test performance [abstract]. Med Sci Sports Exerc. 1999;31(suppl 5):S117.
35. Engels HJ, Kolokouri I, Cieslak TJ 2nd, et al. Effects of ginseng supplementation on supramaximal exercise performance and short-term recovery. J Strength Conditioning Res. 2001;15:290-295.
36. Gaffney BT, Hugel HM, Rich PA. The effects of Eleutherococcus senticosus and Panax ginseng on steroidal hormone indices of stress and lymphocyte subset numbers in endurance athletes. Life Sci. 2001;70:431-442.
37. Dowling EA, Redondo DR, Branch JD, et al. Effect of Eleutherococcus senticosus on submaximal and maximal exercise performance. Med Sci Sports Exerc. 1996;28:482-489.
38. Eschbach LF, Webster MJ, Boyd JC, et al. The effect of Siberian ginseng ( Eleutherococcus senticosus) on substrate utilization and performance. Int J Sport Nutr Exerc Metab. 2000;10:444-451.
39. Bach AC, Babayan VK. Medium-chain triglycerides: an update. Am J Clin Nutr. 1982;36:950-962.
40. Jeukendrup AE, Saris WHM, Schrauwen P, et al. Oxidation of orally ingested medium chain triglyceride (MCT) during prolonged exercise [abstract]. Med Sci Sports Exerc. 1995;27(suppl 5):S101.
41. Anderson O. Putting medium-chain triglycerides in your sports drink can increase your endurance. Nutrition Science News. 1994;6:6-7.
42. Misell LM, Lagomarcino ND, Schuster V, et al. Chronic medium-chain triacylglycerol consumption and endurance performance in trained runners. J Sports Med Phys Fitness. 2001;41:210-215.
43. Satabin P, Portero P, Defer G, et al. Metabolic and hormonal responses to lipid and carbohydrate diets during exercise in man. Med Sci Sports Exerc. 1987;19:218-223.
44. Van Zyl CG, Lambert EV, Hawley JA, et al. Effects of medium-chain triglyceride ingestion on fuel metabolism and cycling performance. J Appl Physiol. 1996;80:2217-2225.
45. Hinton PS, Giordano C, Brownlie T, et al. Iron supplementation improves endurance after training in iron-depleted, nonanemic women. J Appl Physiol. 2000;88:1103-1111.
46. Friedmann B, Weller E, Mairbaurl H, et al. Effects of iron repletion on blood volume and performance capacity in young athletes. Med Sci Sports Exerc. 2001;33:741-746.
47. Antonio J, Sanders MS, Van Gammeren D. The effects of bovine colostrum supplementation on body composition and exercise performance in active men and women. Nutrition. 2001;17:243-247.
48. Buckley JD, Abbott MJ, Brinkworth GD, et al. Bovine colostrum supplementation during endurance running training improves recovery, but not performance. J Sci Med Sport. 2002;5:65-79.
49. Stanko RT, Reynolds HR, Hoyson R, et al. Pyruvate supplementation of a low-cholesterol, low-fat diet: effects on plasma lipid concentrations and body composition in hyperlipidemic patients. Am J Clin Nutr. 1994;59:423-427.
50. Stanko RT, Arch JE. Inhibition of regain in body weight and fat with addition of 3-carbon compounds to the diet with hyperenergetic refeeding after weight reduction. Int J Obes Relat Metab Disord. 1996;20:925-930.
51. Stanko RT, Tietze DL, Arch JE. Body composition, energy utilization, and nitrogen metabolism with a severely restricted diet supplemented with dihydroxyacetone and pyruvate. Am J Clin Nutr. 1992;55:771-776.
52. Kalman D, Colker CM, Wilets I, et al. The effects of pyruvate supplementation on body composition in overweight individuals. Nutrition. 1999;15:337-340.
53. Ivy JL. Effect of pyruvate and dihydroxyacetone on metabolism and aerobic endurance capacity. Med Sci Sports Exerc. 1998;30:837-843.
54. Stanko RT, Robertson RJ, Galbreath RW, et al. Enhanced leg exercise endurance with a high-carbohydrate diet and dihydroxyacetone and pyruvate. J Appl Physiol. 1990;69:1651-1656.
55. Stanko RT, Robertson RJ, Spina RJ, et al. Enhancement of arm exercise endurance capacity with dihydroxyacetone and pyruvate. J Appl Physiol. 1990;68:119-124.
56. Morrison MA, Spriet LL, Dyck DJ. Pyruvate ingestion for 7 days does not improve aerobic performance in well-trained individuals. J Appl Physiol. 2000;89:549-556.
57. Saint-John M, McNaughton L. Octacosanol ingestion and its effects on metabolic responses to submaximal cycle ergometry, reaction time and chest and grip strength. Int Clin Nutr Rev. 1986;6:81-87.
58. Fahey TD, Pearl M. Hormonal effects of phosphatidylserine during 2 weeks of intense training [abstract]. Med Sci Sports Exerc. 1998;30(suppl 5).
59. Monteleone P, Maj M, Beinat L, et al. Blunting by chronic phosphatidylserine administration of the stress-induced activation of the hypothalamo-pituitary-adrenal axis in healthy men. Eur J Clin Pharm. 1992;43:385-388.
60. Fahey TD, Pearl MS. The hormonal and perceptive effects of phosphatidylserine administration during two weeks of resistive exercise-induced overtraining. Biol Sport. 1998;15:135-144.
61. Wagenmakers AJM. Amino acid metabolism, muscular fatigue and muscle wasting. Speculations on adaptations at high altitude. Int J Sports Med. 1992;13:S110-S113.
62. Kelly GS. Sports nutrition: a review of selected nutritional supplements for bodybuilders and strength athletes. Alt Med Rev. 1997;2:184-201.
63. Bigard AX, Lavier P, Ullmann L, et al. Branched-chain amino acid supplementation during repeated prolonged skiing exercises at altitude. Int J Sport Nutr. 1996;6:295-306.
64. Struder HK, Hollmann W, Platen P, et al. Influence of paroxetine, branched-chain amino acids and tyrosine on neuroendocrine system responses and fatigue in humans. Horm Metab Res. 1998;30:188-194.
65. Davis JM, Welsh RS, De Volve KL, et al. Effects of branched-chain amino acids and carbohydrate on fatigue during intermittent, high-intensity running. Int J Sports Med. 1999;20:309-314.
66. Mero A. Leucine supplementation and intensive training. Sports Med. 1999;27:347-358.
67. van Hall G, Raaymakers JS, Saris WH, et al. Ingestion of branched-chain amino acids and tryptophan during sustained exercise in man: failure to affect performance. J Physiol (Lond). 1995;486:789-794.
68. Williams MH. Facts and fallacies of purported ergogenic amino acid supplements. Clin Sports Med. 1999;18:633-649.
69. Wagenmakers AJ. Amino acid supplements to improve athletic performance. Curr Opin Clin Nutr Metab Care. 1999;2:539-544.
70. Yaspelkis BB, Ivy JL. The effect of a carbohydrate-arginine supplement on postexercise carbohydrate metabolism. Int J Sport Nutr. 1999;9:241-250.
71. Candow DG, Chilibeck PD, Burke DG, et al. Effect of glutamine supplementation combined with resistance training in young adults. Eur J Appl Physiol. 2001;86:142-149.
72. Antonio J, Sanders MS, Kalman D, et al. The effects of high-dose glutamine ingestion on weightlifting performance. J Strength Cond Res. 2002;16:157-160.
73. Clarkson PM. Effects of exercise on chromium levels. Is supplementation required? Sports Med. 1997;23:341-349.
74. Joseph LJ, Farrell PA, Davey SL, et al. Effect of resistance training with or without chromium picolinate supplementation on glucose metabolism in older men and women. Metabolism. 1999;48:546-553.
75. Lefavi RG, Anderson RA, Keith RE, et al. Efficacy of chromium supplementation in athletes: emphasis on anabolism. Int J Sport Nutr. 1992;2:111-122.
76. Clancy SP, Clarkson PM, DeCheke ME, et al. Effects of chromium picolinate supplementation on body composition, strength, and urinary chromium loss in football players. Int J Sport Nutr. 1994;4:142-153.
77. Hallmark MA, Reynolds TH, DeSouza CA, et al. Effects of chromium and resistive training on muscle strength and body composition. Med Sci Sports Exerc. 1996;28:139-144.
78. Campbell WW, Joseph LJ, Davey SL, et al. Effects of resistance training and chromium picolinate on body composition and skeletal muscle in older men. J Appl Physiol. 1999;86:29-39.
79. Walker LS, Bemben MG, Bemben DA, et al. Chromium picolinate effects on body composition and muscular performance in wrestlers. Med Sci Sports Exerc. 1998;30:1730-1737.
80. Lukaski HC, Bolonchuk WW, Siders WA, et al. Chromium supplementation and resistance training: effects on body composition, strength and trace element status of men. Am J Clin Nutr. 1996;63:954-965.
81. Davis JM, Welsh RS, Alerson NA. Effects of carbohydrate and chromium ingestion during intermittent high-intensity exercise to fatigue. Int J Sport Nutr Exerc Metab. 2000;10:476-485.
82. Livolsi JM, Adams GM, Laguna PL. The effect of chromium picolinate on muscular strength and body composition in women athletes. J Strength Cond Res. 2001;15:161-166.
83. Zuliani U, Bonetti A, Campana M, et al. The influence of ubiquinone (CoQ 10) on the metabolic response to work. J Sports Med. 1989;29:57-62.
84. Weston SB, Zhou S, Weatherby RP, et al. Does exogenous coenzyme Q 10 affect aerobic capacity in endurance athletes? Int J Sport Nutr. 1997;7:197-206.
85. Ylikoski T, Piirainen J, Hanninen O, et al. The effect of coenzyme Q 10 on the exercise performance of cross-country skiers. Mol Aspects Med. 1997;18 (suppl):S283-S290.
86. Braun B, Clarkson PM, Freedson PS, et al. Effects of coenzyme Q 10 supplementation on exercise performance, VO2max, and lipid peroxidation in trained cyclists. Int J Sport Nutr. 1991;1:353-365.
87. Malm C, Svensson M, Ekblom B, et al. Effects of ubiquinone-10 supplementation and high intensity training on physical performance in humans. Acta Physiol Scand. 1997;161:379-384.
88. Snider IP, Bazzarre TL, Murdoch SD, et al. Effects of coenzyme athletic performance system as an ergogenic aid on endurance performance to exhaustion. Int J Sport Nutr. 1992;2:272-286.
89. Porter DA, Costill DL, Zachwieja JJ, et al. The effect of oral coenzyme Q 10 on the exercise tolerance of middle-aged, untrained men. Int J Sports Med. 1995;16:421-427.
90. Starling RD, Trappe TA, Short KR, et al. Effect of inosine supplementation on aerobic and anaerobic cycling performance. Med Sci Sports Exerc. 1996;28:1193-1198.
91. Dragan I, Baroga M, Eremia N, et al. Studies regarding some effects of inosine in elite weightlifters. Rom J Physiol. 1993;30:47-50.
92. Williams MH, Kreider RB, Hunter DW, et al. Effect of inosine supplementation on 3-mile treadmill run performance and VO2 peak. Med Sci Sports Exerc. 1990;22:517-522.
93. Rosenbloom C, Millard-Stafford M, Lathrop J, et al. Contemporary ergogenic aids used by strength/power athletes. J Am Diet Assoc. 1992;92:1264-1266.
94. McNaughton L, Dalton B, and Tarr J. Inosine supplementation has no effect on aerobic or anaerobic cycling performance. Int J Sport Nutr. 1999;9:333-344.
95. Zollner N, Reiter S, Gross M. Myoadenylate deaminase deficiency successful symptomatic therapy by high dose oral administration of ribose. Klin Wochenschr. 1986;64:1281-1290.
96. Wagner DR, Gresser U, Zollner N. Effects of oral ribose on muscle metabolism during bicycle ergometer in AMPD-deficient patients. Ann Nutr Metab. 1991;35:297-302.
97. Op 't Eijnde B, Van Leemputte M, Brouns F, et al. No effects of oral ribose supplementation on repeated maximal exercise and de novo ATP resynthesis. J Appl Physiol. 2001;91:2275-2281.
98. Bonner B, et al. Influence of ferulate supplementation on postexercise stress hormone levels after repeated exercise stress. J Appl Sports Sci Res. 1990;4:110.
99. Bucci LR, et al. Effect of ferulate on strength and body composition of weightlifters. J Appl Sports Sci Res. 1990;4:110.
100. Fry AC, Bonner E, Lewis DL, et al. The effects of gamma-oryzanol supplementation during resistance exercise training. Int J Sport Nutr. 1997;7:318-329.
101. Gray ME, Titlow LW. The effect of pangamic acid on maximal treadmill performance. Med Sci Sports Exerc. 1982;14:424-427.
102. Adimoelja A. Phytochemicals and the breakthrough of traditional herbs in the management of sexual dysfunctions. Int J Androl. 2000;23:82-84.
103. Antonio J, Uelmen J, Rodriguez R, et al. The effects of Tribulus terrestris on body composition and exercise performance in resistance-trained males. Int J Sport Nutr Exerc Metab. 2000;10:208-215.
104. Kreider RB. Phosphate loading and exercise performance. J Appl Nutr. 1992;44:29-49.
105. Tremblay MS, Galloway SD, Sexsmith JR. Ergogenic effects of phosphate loading: physiological fact or methodological fiction? Can J Appl Physiol. 1994;19:1-11.
106. Regelson W, Kalimi M. Dehydroepiandrosterone (DHEA)—the multifunctional steroid. II. Effects on the CNS, cell proliferation, metabolic and vascular, clinical, and other effects. Mechanism of action? Ann N Y Acad Sci. 1994;719:564-575.
107. Regelson W, Loria R, Kalimi M. Dehydroepiandrosterone (DHEA)—the "Mother Steroid." I. Immunologic action. Ann N Y Acad Sci. 1994;719:553-563.
108. Brown GA, Vukovich MD, Sharp RL, et al. Effect of oral DHEA on serum testosterone and adaptations to resistance training in young men. J Appl Physiol. 1999;87:2274-2283.
109. Wallace MB, Lim J, Cutler A, et al. Effects of dehydroepiandrosterone vs. androstenedione supplementation in men. Med Sci Sports Exerc. 1999;31:1788-1792.
110. Morales AJ, Haubrich RH, Hwang JY, et al. The effect of six months treatment with a 100 mg daily dose of dehydroepiandrosterone (DHEA) on circulating sex steroids, body composition and muscle strength in age-advanced men and women. Clin Endocrinol (Oxf). 1998;49:421-432.
111. Timmons BW, Newhouse IJ, Thayer RE, et al. The efficacy of SPORT™ as a dietary supplement on performance and recovery in trained athletes. Can J Appl Physiol. 2000;25:55-67.
112. Dodd SL, Herb RA, Powers SK, et al. Caffeine and exercise performance. An update. Sports Med. 1993;15:14-23.
113. Fawcett JP, Farquhar SJ, Walker RJ, et al. The effect of oral vanadyl sulfate on body composition and performance in weight-training athletes. Int J Sport Nutr. 1996;6:382-390.
114. Kreider RB. Dietary supplements and the promotion of muscle growth with resistance exercise. Sports Med. 1999;27:97-110.
115. Ferrando AA, Green NR. The effect of boron supplementation on lean body mass, plasma testosterone levels, and strength in male bodybuilders. Int J Sport Nutr. 1993;3:140-149.
116. Nielsen FH, Hunt CD, Mullen LM, et al. Effect of dietary boron on mineral, estrogen, and testosterone metabolism in postmenopausal women. FASEB J. 1987;1:394-397.
117. Naghii MR, Samman S. The effect of boron supplementation on its urinary excretion and selected cardiovascular risk factors in healthy male subjects. Biol Trace Elem Res. 1997;56:273-286.
118. Naghii MR. The significance of dietary boron, with particular reference to athletes. Nutr Health. 1999;13:31-37.
119. Leder BZ, Longcope C, Catlin DH, et al. Oral androstenedione administration and serum testosterone concentrations in young men. JAMA. 2000;283:779-782.
120. Brown GA, Vukovich MD, Martini ER, et al. Endocrine responses to chronic androstenedione intake in 30- to 56-year-old men. J Clin Endocrinol Metab. 2000;85:4074-4080.
121. King DS, Sharp RL, Vukovich MD, et al. Effect of oral androstenedione on serum testosterone and adaptations to resistance training in young men: a randomized controlled trial. JAMA. 1999;281:2020-2028.
122. Ballantyne CS, Phillips SM, MacDonald JR, et al. The acute effects of androstenedione supplementation in healthy young males. Can J Appl Physiol. 2000;25:68-78.
123. Broeder CE, Quindry J, Brittingham K, et al. The andro project: physiological and hormonal influences of androstenedione supplementation in men 35 to 65 years old participating in a high-intensity resistance training program. Arch Intern Med. 2000;160:3093-3104.
124. Wallace MB, Lim J, Cutler A, et al. Effects of dehydroepiandrosterone vs. androstenedione supplementation in men. Med Sci Sports Exerc. 1999;31:1788-1792.
125. Eijnde BO, Van Leemputte M, Goris M, et al. Effects of creatine supplementation and exercise training on fitness in males 55 to 75 years old. J Appl Physiol. 2003;95:818-828.
126. Engels HJ, Fahlman MM, Wirth JC. Effects of Ginseng on secretory IgA, performance, and recovery from interval exercise. Med Sci Sports Exerc. 2003;35:690-696.
127. Brutsaert TD, Hernandez-Cordero S, Rivera J, et al. Iron supplementation improves progressive fatigue resistance during dynamic knee extensor exercise in iron-depleted, nonanemic women. Am J Clin Nutr. 2003;77:441-448.
128. Rowland TW, Deisroth MB, Green GM, Kelleher JF. The effect of iron therapy on the exercise capacity of nonanemic iron-deficient adolescent runners. Am J Dis Child. 1988;142:165-169.
129. Celsing F, Blomstrand E, Werner B, et al. Effects of iron deficiency on endurance and muscle enzyme activity in man. Med Sci Sports Exerc. 1986;18:156-161.
130. Klingshirn LA, Pate RR, Bourque SP, et al. Effect of iron supplementation on endurance capacity in iron-depleted female runners. Med Sci Sports Exerc. 1992;24:819-824.
131. LaManca JJ, Haymes EM. Effects of iron repletion on VO2max, endurance, and blood lactate in women. Med Sci Sports Exerc. 1993;25:1386-1392.
132. Hofman Z, Smeets R, Verlaan G, et al. The effect of bovine colostrum supplementation on exercise performance in elite field hockey players. Int J Sport Nutr Exerc Metab. 2002;12:461-469.
133. Buckley JD. Bovine colostrum: Does it improve athletic performance? Nutrition. 2002;18:776-777.
134. Mero A, Kahkonen J, Nykanen T, et al. IGF-I, IgA, and IgG responses to bovine colostrum supplementation during training. J Appl Physiol. 2002;93:732-739.
135. Mero A, Miikkulainen H, Riski J, et al. Effects of bovine colostrum supplementation on serum IGF-I, IgG, hormone, and saliva IgA during training. J Appl Physiol. 1997;83:1144-1151.
136. Berardi JM, Ziegenfuss TN. Effects of ribose supplementation on repeated sprint performance in men. J Strength Cond Res. 2003;17:47-52.
137. Kreider RB, Melton C, Greenwood M, et al. Effects of oral d-ribose supplementation on anaerobic capacity and selected metabolic markers in healthy males. Int J Sport Nutr Exerc Metab. 2003;13:87-96.
138. Shekelle PG, Hardy ML, Morton SC, et al. Efficacy and safety of ephedra and ephedrine for weight loss and athletic performance: a meta-analysis. JAMA. 2003;289:1537-1545.
139. Ehrlich D, Haber P. Influence of acupuncture on physical performance capacity and haemodynamic parameters. Int J Sport Med. 1992;13:486-491.
140. Purdy Lloyd KL, Wasmund W, Smith L, et al. Clinical effects of a dietary antioxidant silicate supplement, Microhydrin®, on cardiovascular responses to exercise. J Med Food. 2001;4:151-159.
141. Medved I, Brown MJ, Bjorksten AR, et al. N-acetylcysteine infusion alters blood redox status but not time to fatigue during intense exercise in humans. J Appl Physiol. 2003;94:1572-1582.
142. Leder BZ, Leblanc KM, Longcope C, et al. Effects of oral androstenedione administration on serum testosterone and estradiol levels in postmenopausal women. J Clin Endocrinol Metab. 2002;87:5449-5454.
143. Glaister M, Lockey RA, Abraham CS, et al. Creatine supplementation and multiple sprint running performance. J Strength Cond Res. 2006;20:273-277.
144. Cornish SM, Chilibeck PD, Burke DG. The effect of creatine monohydrate supplementation on sprint skating in ice-hockey players. J Sports Med Phys Fitness. 2006;46:90-98.
145. Theodorou AS, Havenetidis K, Zanker CL, et al. Effects of acute creatine loading with or without carbohydrate on repeated bouts of maximal swimming in high-performance swimmers. J Strength Cond Res. 2005;19:265-269.
146. Pluim BM, Ferrauti A, Broekhof F, et al. The effects of creatine supplementation on selected factors of tennis specific training. Br J Sports Med. 2006;40:507-11;discussion 511-512.
147. Astorino TA, Marrocco AC, Gross SM, et al. Is running performance enhanced with creatine serum ingestion? J. Strength Cond Res. 2005;19:730-734.
148. Peyrebrune MC, Stokes K, Hall GM, et al. Effect of creatine supplementation on training for competition in elite swimmers. Med Sci Sports Exerc. 2005;37:2140-2147.
149. Branch JD. Effect of creatine supplementation on body composition and performance: a meta-analysis. Int JSport Nutr Exerc Metab. 2003;13:198-226.
150. Chilibeck PD, Stride D, Farthing JP, et al. Effect of creatine ingestion after exercise on muscle thickness in males and females. Med Sci Sports Exerc. 2004;36:1781-1788.
151. Eckerson JM, Stout JR, Moore GA, et al. Effect of creatine phosphate supplementation on anaerobic working capacity and body weight after two and six days of loading in men and women. J Strength Cond Res. 2005;19:756-763
152. Koh-Banerjee PK, Ferreira MP, Greenwood M, et al. Effects of calcium pyruvate supplementation during training on body composition, exercise capacity, and metabolic responses to exercise. Nutrition. 2005;21:312-319.
153. Kingsley MI, Wadsworth D, Kilduff LP, et al. Effects of phosphatidylserine on oxidative stress following intermittent running. Med Sci Sports Exerc. 2005;37:1300-1306.
154. Kingsley MI, Miller M, Kilduff LP, et al. Effects of phosphatidylserine on exercise capacity during cycling in active males. Med Sci Sports Exerc. 2006;38:64-71.
155. Crowe MJ, Weatherson JN, Bowden BF, et al. Effects of dietary leucine supplementation on exercise performance. Eur J Appl Physiol. 2005 Oct 29. [Epub ahead of print]
156. Tipton KD, Elliott TA, Cree MG, et al. Ingestion of casein and whey proteins result in muscle anabolism after resistance exercise. Med Sci Sports Exerc. 2004;36:2073-2081.
157. Zhou S, Zhang Y, Davie A, et al. Muscle and plasma coenzyme Q 10 concentration, aerobic power and exercise economy of healthy men in response to four weeks of supplementation. J Sports Med Phys Fitness. 2005;45:337-346.
158. Kerksick C, Rasmussen C, Bowden R, et al. Effects of ribose supplementation prior to and during intense exercise on anaerobic capacity and metabolic markers. Int J Sport Nutr Exerc Metab. 2006;15:653-664.
159. Dunne L, Worley S, Macknin M, et al. Ribose versus dextrose supplementation, association with rowing performance: a double-blind study. Clin J Sport Med. 2005;16:68-71
160. Dunne L, Worley S, Macknin M, et al. Ribose Versus Dextrose Supplementation, Association With Rowing Performance: A Double-Blind Study. Clin J Sport Med. 2005;16:68-71.
161. Villareal D, Holloszy JO. DHEA Enhances Effects of Weight Training on Muscle Mass and Strength in Elderly Women and Men. Am J Physiol Endocrinol Metab. 2006 Jun 20. [Epub ahead of print]
162. De Bock K, Eijnde BO, Ramaekers M, et al. Acute rhodiola rosea intake can improve endurance exercise performance. Int J Sport Nutr Exerc Metab. 2004;14:298-307.
163. Colson SN, Wyatt FB, Johnston DL, et al. Cordyceps sinensis- and rhodiola rosea-based supplementation in male cyclists and its effect on muscle tissue oxygen saturation. J Strength Cond Res. 2005;19:358-363.
164. Liang MT, Podolka TD, Chuang WJ, et al. Panax notoginseng supplementation enhances physical performance during endurance exercise. J Strength Cond Res. 2005;19:108-114.
165. Buckley JD, Burgess S, Murphy KJ, et al. Effects of omega-3 polyunsaturated fatty acids on cardiovascular risk, exercise performance and recovery in Australian Football League (AFL) players. Asia Pac J Clin Nutr. 2005;14(suppl)S57.
166. Bloomer RJ, Fry A, Schilling B, et al. Astaxanthin supplementation does not attenuate muscle injury following eccentric exercise in resistance-trained men. Int J Sport Nutr Exerc Metab. 2005;15:401-412.
167. Sutton EE, Coill MR, Deuster PA, et al. Ingestion of tyrosine: effects on endurance, muscle strength, and anaerobic performance. Int J Sport Nutr Exerc Metab. 2005;15:173-85.
168. Kok L, Kreijkamp-Kaspers S, Grobbee DE, et al. Soy isoflavones, body composition, and physical performance. Maturitas. 2005;52:102-110.
169. Hickner RC, Tanner CJ, Evans CA, et al. L-citrulline reduces time to exhaustion and insulin response to a graded exercise test. Med Sci Sports Exerc. 2006;38:660-666.
170. Fry AC, Bloomer RJ, Falvo MJ, et al. Effect of a liquid multivitamin/mineral supplement on anaerobic exercise performance. Res Sports Med. 2006;14:53-64.
171. Galloway SD, Tremblay MS, Sexsmith JR, Roberts CJ. The effects of acute phosphate supplementation in subjects of different aerobic fitness levels. Eur J Appl Physiol. 1996;72:224-230.
172. Kreider RB, Miller GW, Williams MH, et al. Effects of phosphate loading on oxygen uptake, ventilatory anaerobic threshold, and run performance. Med Sci Sports Exerc. 1990;22:250-256.
173. Peveler WW, Bishop PA, Whitehorn EJ. Effects of ribose as an ergogenic aid. J Strength Cond Res. 2006;20:519-522.
174. Candow DG, Burke NC, Smith-Palmer T, et al. Effect of whey and soy protein supplementation combined with resistance training in young adults. Int J Sport Nutr Exerc Metab. 2006;16:233-244.
175. Cribb PJ, Williams AD, Carey MF, et al. The effect of whey isolate and resistance training on strength, body composition, and plasma glutamine. Int J Sport Nutr Exerc Metab. 2006;16:494-509.
176. Wu CL, Williams C. A low glycemic index meal before exercise improves endurance running capacity in men. Int J Sport Nutr Exerc Metab. 2006;16:510-527.
177. Earnest CP, Lancaster SL, Rasmussen CJ, et al. Low vs. high glycemic index carbohydrate gel ingestion during simulated 64-km cycling time trial performance. J Strength Cond Res. 2004;18:466-472.
178. Rogerson S, Riches CJ, Jennings C, et al. The effect of five weeks of tribulus terrestris supplementation on muscle strength and body composition during preseason training in elite rugby league players. J Strength Cond Res. 2007;21:348-353.
179. Kulaputana O, Thanakomsirichot S, Anomasiri W. Ginseng supplementation does not change lactate threshold and physical performances in physically active Thai men. J Med Assoc Thai. 2007;90:1172-1179.
180. Martin BR, Davis S, Campbell WW, et al. Exercise and calcium supplementation: effects on calcium homeostasis in sportswomen. Med Sci Sports Exerc. 2007;39:1481-1486.
181. Stannard SR, Hawke EJ, Schnell N. The effect of galactose supplementation on endurance cycling performance. Eur J Clin Nutr. 2007 Oct 10. [Epub ahead of print]
182. Igwebuike A, Irving BA, Bigelow ML, et al. Lack of DHEA effect on a combined endurance and resistance exercise program in postmenopausal women. J Clin Endocrinol Metab. 2007 Nov 20. [Epub ahead of print]
183. Roberts MD, Iosia M, Kerksick CM, et al. Effects of arachidonic acid supplementation on training adaptations in resistance-trained males. J Int Soc Sports Nutr. 2007 Nov 28.
184. Jager R, Purpura M, Geiss KR, et al. The effect of phosphatidylserine on golf performance. J Int Soc Sports Nutr. 2007 Dec 4.
185. Ostojic SM, Azarbayjani MA. The effects of vitamin E and vitamin C supplementation on bioenergetics index. Res Sports Med. 2007;15:249-256.
186. Kendrick IP, Harris RC, Kim HJ, et al. The effects of 10 weeks of resistance training combined with beta-alanine supplementation on whole body strength, force production, muscular endurance and body composition. Amino Acids. 2008 Jan 4.
187. Smith WA, Fry AC, Tschume LC, et al. Effect of glycine propionyl-L-carnitine on aerobic and anaerobic exercise performance. Int J Sport Nutr Exerc Metab. 2008;18:19-36.
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