Treatment
Principal Proposed Treatments for Sports Performance:
In this section, we discuss sports supplements with some real evidence behind
them: creatine, HMB, vitamin C, and sports beverages. Each has its own
recommended use for athletes. We also address nutrition and training, the
best-established ergogenic aids of all.
Creatine: Ergogenic Aid For Repetitive, High-Intensity, Short-Burst Exercise
and, perhaps, Resistance Exercise
Creatine is one of the best-selling and best-documented supplements for
enhancing athletic performance, although the scientific evidence that it works
is still far from complete. The evidence that does exist points to benefits in
forms of exercise that require repeated short-term bursts of high-intensity
exercise, such as soccer and basketball. Creatine has also been proposed to
promote weight loss and reduce the proportion of fat to muscle in the body, but
there is little evidence that it is effective for these purposes.
Creatine is a naturally occurring substance that plays an important role in the
production of energy in the body: the body converts it 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.
Creatine is not an essential nutrient because your body can make it from the
amino acids L-arginine, glycine, and L-methionine. Provided that you eat enough
protein (the source of these amino acids), your body will make all the creatine
you need for good health. However, because meat is the most important dietary
source of creatine and its amino acid building blocks, vegetarian athletes may
potentially have difficulty producing enough creatine themselves.
What Is the Scientific Evidence for Creatine?
Several small double-blind studies suggest that creatine can improve performance
in exercises that involve repeated short bursts of high-intensity activity. The
evidence is better for men than for women.
A double-blind study investigated creatine and swimming performance in 18 men
and 14 women. Men taking the supplement had significant increases in speed when
doing 6 bouts of 50-meter swims started at 3-minute intervals, as compared with
men taking placebo. However, their speed did not improve when swimming 10 sets
of 25-yard lengths started at 1-minute intervals. It may be 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 this
gender difference in response to creatine.
In an earlier double-blind study, 16 physical education students exercised 10
times for 6 seconds on a stationary cycle, alternating repetitions with a
30-second rest period. The results showed that individuals 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, although there have been negative
results as well.
In contrast, studies of endurance or nonrepetitive exercise have not shown
benefits from creatine supplementation. Therefore, creatine probably wont help
you with marathon running or single sprints.
Isometric exercise capacity (pushing against a fixed resistance), however, may
improve with creatine. In addition, two double-blind, placebo-controlled
studies, each lasting 28 days, provide some evidence that creatine and creatine
plus HMB can increase lean muscle and bone mass. The first enrolled 52 college
football players during off-season training, and the other followed 40 athletes
engaged in weight training.
For more information, including dosage and safety issues, see the full creatine
article.
HMB: Ergogenic Aid For Strength and Power Athletes
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. Evidence suggests that taking HMB supplements might signal
the body to slow down the destruction of muscle tissue. However, while
promising, the research record at present is contradictory and marked by an
absence of large studies.
HMB is not an essential nutrient, so there is no established requirement. HMB is
found in small amounts in citrus fruit and catfish. To get a therapeutic dosage,
however, you need to take a supplement in powder or pill form.
What Is the Scientific Evidence for HMB?
According to many but not all of the small double-blind trials performed thus
far, HMB may improve response to weight training. HMB might help prevent muscle
damage during prolonged exercise.
Muscle Building Studies on chick and rat muscles suggest that HMB reduces the
amount of muscle protein that breaks down during exercise.
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. The participants also lifted weights 3
days a week for 90 minutes. 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 daily or placebo, 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 its 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.
Another double-blind placebo-controlled trial of 39 men and 36 women found that
over 4 weeks HMB supplementation improved response to weight training.
Two placebo-controlled studies in 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. In addition, a double-blind study of
31 men and women, 70 years old, undergoing resistance training found significant
improvements in fat-free mass attributable to the use of HMB (3 g daily).
However, other studies have found marginal or no benefits with HMB for enhancing
body composition or strength. HMB may have greater effects on lean body mass and
muscle strength when combined with creatine.
All of these studies were small, and therefore, their results are not 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.
Vitamin C: May Aid Recovery by Preventing the "Post-Marathon Sniffle"
While being active in sports can improve your physical (and mental) well-being,
it also places higher stresses on your body, and can end up damaging your
system. Preventative maintenance to the rescue! In addition to eating right and
getting enough sleep, taking vitamin C may help as well.
Apart from providing some of our basic nutritional needs, this vitamins
greatest benefit to athletes is its potential for preventing colds. Extremely
intense exercise, such as training for and running in a marathon, is known to
lower immunity, and endurance athletes frequently get sick after maximal
exertion. When we exercise at a highly competitive level or train intensely for
a competitive athletic event, we stress our bodies as we push them to perform,
and sickness may be the result. Vitamin C might help prevent this, although not
all studies agree. (See also Glutamine in Supplements for Recovery, below.)
As an additional bonus, vitamin C may also help reduce muscle soreness due to
exertion.
What Is the Scientific Evidence for Vitamin C?
According to a double-blind placebo-controlled study involving 92 runners,
taking 600 mg of vitamin C for 21 days prior to a race made a significant
difference in the incidence of sickness afterwards. Within 2 weeks after the
race, 68% of the runners taking placebo developed cold symptoms, versus only 33%
of those taking the vitamin C supplement. As part of the same study, non-runners
of similar age and gender to those running were also given vitamin C or placebo.
Interestingly, for this group, the supplement had no apparent effect on the
incidence of upper respiratory infections. Vitamin C seemed to be specifically
effective in this capacity for those who exercised intensively.
Two other studies found that vitamin C could reduce the number of colds
experienced by groups of people involved in rigorous exercise in extremely cold
environments. One study involved 139 children attending a skiing camp in the
Swiss Alps, while the other enrolled 56 military men engaged in a training
exercise in Northern Canada during the winter months. In both cases, the
participants took either 1 g of vitamin C or placebo daily at the time their
training program began. Cold symptoms were monitored for 1 to 2 weeks following
training, and significant differences in favor of vitamin C were found.
However, one very large study of 674 marine recruits in basic training found no
such benefit. The results showed no difference in the number of colds between
the treatment and placebo groups.
Whats the explanation for this discrepancy? There are many possibilities.
Perhaps basic training in the marines is significantly different from the other
forms of exercise studied. Another point to consider is that the marines didnt
start taking vitamin C right at the beginning of training, but waited 3 weeks.
The study also lasted a bit longer than the positive studies mentioned above,
continuing for 2 months; maybe vitamin C is more effective at preventing colds
in the short term. Of course, another possibility is that it doesnt really
work. More research is needed to know for sure.
One double-blind trial compared vitamin C, vitamin E, and placebo for muscle
soreness in 24 male volunteers. Vitamin C was found to relieve muscle soreness,
while vitamin E did not. However, larger trials are needed to resolve whether or
not vitamin C is effective in preventing muscle soreness.
For more information, including dosage and safety issues, see the full vitamin C
article.
Nutrition and Training: Good for All Athletes
We may be stating the obvious, but supplements alone will not improve your
strength or endurance in the absence of a good training program and a healthy
diet. Increased muscle mass or stamina is the result of an appropriate exercise
program supported by adequate intake of calories and essential nutrients,
including fuel for energy, protein, fluids, vitamins, and minerals.
Just like your car requires more gasoline if you drive farther, your body
requires more fuel if you exercise more. In addition to carbohydrates and fats
which provide fuel during a workout, you need adequate protein to prevent the
muscles that youre working so hard to build up from breaking down. One
researchers recommendation for protein intake is 1.2 to 1.4 g of protein per
kilogram of body weight (1 kilogram equals about 2.2 pounds) if you pursue
endurance-type sports, such as marathon running. If you are involved in
strength-building sports such as weight lifting, 1.4 to 1.8 g per kilogram body
weight is suggested. These amounts are higher than the current recommended daily
intakes for protein, which may be more appropriate for people with a less active
lifestyle. Protein supplements such as soy or whey powders, or protein
hydrosylates, are sometimes used to boost protein intake. However, taking
protein in the form of separate amino acids does not appear to offer any
additional benefit (see Amino Acids in Ergonomic Aids, below).
Whether adding vitamins and minerals over and above the amount suggested by the
recommended daily intake is necessary or beneficial to athletes is an unresolved
issue. Several vitamins and minerals are used as sports supplements, and well
discuss them in the sections below.
Sports Beverages
Sports beverages may also be beneficial. Most obviously, they provide fluids,
helping to avoid exercise-induced dehydration. In addition, they contain varying
amounts of carbohydrates and electrolytes. These carbohydrates can be important
because once your body has burned up all the fuel that was available in your
bloodstream, it will begin to use the glycogen stored in your muscles, which can
cause muscle wasting. Consuming carbohydrates has been found to prevent loss of
muscle tissue during intense exercise, to delay fatigue, and even to improve
performance times in some cases.
The electrolytes in most sports drinks help to prevent dehydration and other
potential problems related to electrolyte imbalances. Major electrolytes in your
body include potassium, sodium, and chloride, with potassium and sodium working
together like a molecular seesaw: when the level of one goes up, the other goes
down. All together, these three dissolved minerals play an essential chemical
role in every function of your body. Making sure you have enough of them will
enhance your performance and improve your recovery.
Other Proposed Treatments for Sports Performance:
Numerous other supplements are commonly recommended for athletes. Unfortunately,
the evidence that they work is marginal at best.
Some supplements are marketed as ergogenic aids, said to improve speed,
strength, or endurance.
These include medium-chain triglycerides (MCTs), ginseng, branched-chain amino
acids (BCAAs), stimulants (ephedrine and caffeine), pyruvate (DHAP),
nicotinamide adenine dinucleotide (NADH), B vitamins, coenzyme Q10, carnitine,
inosine, ribose, trimethylglycine (TMG), suma, phosphate, policosanol,
schisandra, certain minerals (copper, magnesium, iron, and zinc), and a Chinese
medicine called cordyceps. Certain commercial preparations that combine herbs
and supplements are also marketed as ergogenic aids.
Supplements reputed to increase muscle mass or improve muscle/fat ratio include
phosphatidylserine (PS), pyruvate, BCAAs, conjugated linoleic acid, lipoic acid,
ipriflavone, gamma oryzanol, the herb Tribulus terrestris, and chromium.
Some sports supplements arent aimed at improving performance directly but are
instead intended to speed recovery time, whether by helping injuries to heal
more quickly or restoring the bodys natural balance after the stress of
exertion. Like vitamin C, glutamine may help prevent colds following intense
exercise. Various antioxidants may reduce muscle soreness. Other supplements are
said to help prevent or treat athletic injuries, including glucosamine,
oligomeric proanthocyanidins (OPCs), bromelain, other proteolytic enzymes, and
horse chestnut.
In the following sections, well discuss many of these substances briefly,
describing the level of evidence behind them.
Other Proposed Ergogenic Aids
Many substances besides those mentioned earlier are marketed as ergogenic aids,
but there is little to no evidence that they work.
Medium-Chain Triglycerides (MCTs)
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 remade into a special form that can be transported in the blood.
But 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" for providing a concentrated source of easily utilized energy.
A number of double-blind trials using MCTs for improving high-intensity or
endurance exercise performance have been conducted, but the results have been
thoroughly inconsistent. This is not surprising, as none of these studies
enrolled enough participants to provide trustworthy results.
Phosphatidylserine
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.
Recently, PS has also been marketed as a sports supplement, said to help
bodybuilders and power athletes develop larger and stronger muscles. This is
based on modest evidence that PS slows the release of cortisol following heavy
exercise. 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, there is no direct evidence yet to support claims
that PS actually helps to build muscles more quickly and with less training
effort.
Ginseng
There are actually 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, another herb, ciwujia,
is actually Eleutherococcus, while others claim it is a related but different
species.
The evidence for Panax ginseng as a sports supplement is mixed. An 8-week
double-blind placebo-controlled trial evaluated the effects of Panax ginseng
with and without exercise in 41 individuals. 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 individuals 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. Another double-blind
placebo-controlled trial of 37 individuals also found some benefit. A
double-blind placebo-controlled study of 120 individuals found that ginseng
gradually improved reaction time and lung function over a 12-week treatment
period among those 40 to 60 years old. No benefits were seen in younger
individuals.
However, no benefit could be demonstrated with Panax ginseng in an 8-week,
double-blind trial that followed 31 healthy men in their twenties. Many other
small trials of Panax ginseng have failed to find evidence of benefit.
A double-blind study of 20 endurance athletes over an 8-week period failed to
find evidence of benefit with a standard Eleutherococcus formulation. Lack of
benefit was also seen in another small double-blind crossover trial.
Furthermore, in a small double-blind, placebo-controlled trial of endurance
athletes, use of eleutherococcus actually increased physiological signs of
stress during intensive training.
Branched-Chain Amino Acids (BCAAs): Leucine, Isoleucine, and Valine
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 up greater amounts of BCAAs
than normal daily activities, perhaps increasing an athletes 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" (see Supplements
for Recovery below); however, most of the evidence suggests that they do not
work.
Conjugated Linoleic Acid (CLA)
Conjugated linoleic acid (CLA) is a mixture of different isomers, or chemical
forms, of linoleic acid. Although linoleic acid itself is an essential fatty
acid—a type of fat that your body needs as much as it needs vitamins—there is no
evidence that you need CLA in your diet. If you choose to include it,
supplements are the only practical source.
The evidence that CLA can help you lose fat while retaining muscle remains
highly preliminary.
Amino Acids
Athletes use a number of amino acids as supplements for a variety of purposes,
sometimes individually and sometimes in combination. Amino acids are sometimes
taken as protein supplements, as they are the components from which proteins are
formed. Some individual amino acids are also biochemically active, and taking
them alone might alter your metabolism or change your hormone balance. However,
evidence supporting the use of amino acids as ergogenic aids is sparse to
nonexistent. The few clinical trials performed generally dont show positive
results, and there is no evidence that amino acids are better than whole
protein.
Those amino acids believed by some to be ergogenic include arginine, glutamine,
and ornithine (ornithine and glutamine combined form ornithine alpha-ketoglutarate,
OKG), as well as the branched-chain amino acids leucine, isoleucine, and valine,
discussed above. Glutamine is also used for overtraining syndrome (see
Supplements for Recovery below).
Stimulants: Ma Huang (Ephedra), Caffeine (Coffee, Tea, Guarana, Cola, etc.)
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, 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
on in the competition—sort of like "saving the best for last."
Ephedrines value in enhancing sports performance has not been established; at
the same time, there are serious safety issues associated with its use (see
Safety Issues in the full article on ephedra). Some sports federations have
determined that specific amounts of ephedrine in an athletes system are grounds
for disqualification.
Caffeine does appear to improve performance during endurance-type exercises.
Note: The International Olympic Committee has set a tolerance limit for caffeine
in the urine at 12 mcg/ml. If youre competing in a sport that follows similar
regulations, you may want to have a cup of coffee or tea, but dont drink the
whole pot.
Pyruvate (Dihydroxyacetone Pyruvate, DHAP)
Pyruvate 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. However, at the present time, the
evidence regarding pyruvate as an ergogenic aid is weak and contradictory.
Nicotinamide Adenine Dinucleotide (NADH)
Short for nicotinamide adenine dinucleotide, NADH is an important cofactor
("assistant") that helps enzymes in their work throughout the body. NADH
particularly plays a role in producing energy (ATP or adenosine triphosphate,
your bodys preferred fuel). Its possible that taking supplemental NADH could
help speed up ATP synthesis. However, NADH has to undergo some chemical changes
to participate in ATP formation, and we dont really know if supplemental NADH
gets processed in a way that allows it to be effective. NADH is one of those
supplements that appeared on the market before it was sufficiently evaluated.
Its use is completely speculative at present.
B-Complex Vitamins
The recommended daily intakes for B vitamins are based on caloric intake.
Because people who are exercising rigorously on a regular basis are likely to
consume more calories than the average person, supplementation with B vitamins
may thus be appropriate. Vitamin B2 (also called riboflavin) and vitamin B5 (pantothenic
acid) have also been proposed as performance enhancers for athletes, but there
is no real evidence that either is effective for this.
Lipoic Acid
Lipoic acid is now being used by some athletes as an "insulin mimicker" because
it appears to increase the bodys utilization of blood sugar, which in turn
might help build muscle glycogen. However, no studies have yet been done to
determine whether or not lipoic acid supplementation actually increases muscle
glycogen, so this use is purely theoretical at present.
Coenzyme Q10 (CoQ10, or Ubiquinone)
Coenzyme Q10 (CoQ10), also known as ubiquinone, is an antioxidant discovered by
researchers at the University of Wisconsin in 1957. Its name comes from the word
ubiquitous, meaning "found everywhere." Indeed, CoQ10 is found in every cell in
the body, where it plays a fundamental role in the mitochondria, the parts of
the cell that produce energy from food. Its best-established use is for
congestive heart failure. CoQ10 has also been used as a performance enhancer for
athletes, but most clinical trials have found no significant improvement with
CoQ10, and one group reported significant worsening of performance with the
supplement compared to placebo.
Coenzyme Q10 might be of some value as a recovery supplement because of its
antioxidant properties (see Supplements for Recovery, below).
Carnitine
Carnitine is a compound the body uses to turn fat into energy. It is not
considered an essential nutrient, because the body can manufacture all it needs.
However, supplemental carnitine may improve the ability of certain tissues to
produce energy. Principal dietary sources of carnitine are meat and dairy
products, but a supplement is necessary to obtain therapeutic dosages. Carnitine
is widely touted as a physical performance enhancer, but there is no real
evidence that it is effective, and some research indicates that it does not work
in this capacity.
Inosine
Inosine is an important chemical found throughout the body. It plays many roles,
one of which is helping to make ATP, the bodys 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 doesnt work for this purpose.
Ipriflavone
Ipriflavone is a semisynthetic version of an isoflavone (water-soluble chemicals
found in many plants) from soy. Ipriflavone is also touted as a bodybuilding
aid, but no real evidence supports this use.
Ribose
Ribose is a carbohydrate also vital for the manufacture of ATP. Ribose has been
tried for improving exercise capacity in individuals with certain enzyme
deficiencies and other rare conditions that cause muscle pain during exertion.
There is weak evidence that it may help people with some of these conditions—but
not others—to exercise without pain.
Ribose has recently been touted as an important new athletic performance
enhancer; however, there is as yet no evidence at all that it works. Although at
least one animal study seems to show that skeletal muscle replenishes ATP
("ready to go" chemical energy for your cells) more quickly when ribose is added
to the blood, the one reported double-blind trial in humans found neither
enhanced sports performance nor improved ATP resynthesis.
Gamma Oryzanol
Very preliminary evidence suggests that gamma oryzanol, which is derived from
rice bran oil, may increase endorphin release and aid muscle development. 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.
Trimethylglycine (TMG)
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 doing its work to keep your blood vessels clear, TMG is turned into
another substance, dimethylglycine (DMG).
In Russia, DMG is used extensively as an athletic performance enhancer and has
recently become popular among American athletes. TMG is cheaper, and may have
the same effects as DMG, as it changes into DMG in the body. However, one small
study suggests that DMG does not work, making the use of TMG as a sports
supplement seem rather pointless.
Suma
Suma is a large ground vine native to Central and South America. Sometimes
called "Brazilian ginseng," native people have long used suma to promote robust
health as well as to treat practically all illnesses. They called it Para Toda,
which means "for all things."
Russian Olympic athletes have used suma, along with other adaptogens, in the
belief that it will enhance sports performance. In the United States, suma is
sometimes recommended as a general body strengthener. However, there has been
little formal scientific investigation of suma at this time.
Tribulus terrestris
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, female infertility, and
impotence. In addition, it has been studied as a treatment for heart disease.
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. 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, as 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—292 mg daily for a 200-lb man) against placebo on body
composition and endurance among men engaged in resistance training. 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.
For more information, including dosage and safety issues, see the full Tribulus
terrestris article.
Phosphate
Phosphate has been studied as an ergogenic aid to improve aerobic capacity and
endurance with greatly mixed results. One unanswered question is whether the
findings in some studies resulted from the ingestion of phosphate or from the
other compounds the phosphate was mixed with, such as sodium or calcium. Because
the trials performed so far have used inconsistent methods and measurements, it
isnt possible to know yet whether or not phosphate has any potential benefit as
a sports supplement.
Policosanol
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. They are said to increase muscle
strength and endurance and improve reaction time and stamina, but there is no
reliable scientific evidence as yet to support these claims.
The only evidence for policosanol as a performance enhancer comes from one small
double-blind trial with marginal results.
Glutamine
Two small, double-blind, placebo-controlled trials failed to find the amino acid
glutamine effective for improving response to resistance training (weight
lifting).
Mineral Supplements
Chromium, magnesium, iron, zinc, and copper have all been marketed as having
potential to aid athletes in achieving their goals. However, there is little
evidence that taking these minerals will prove helpful if you are not deficient.
Deficiencies in magnesium, zinc, and chromium are probably most likely.
Chromium has been sold as a "fat burner" and is also said to help build muscle
tissue. While studies evaluating its effects on weight loss are contradictory,
the largest study suggests that it might offer some benefit. However, studies
evaluating its benefits as a performance enhancer or aid to bodybuilding have
yielded almost entirely negative results.
Studies on magnesium supplements have returned contradictory results.
The majority of athletes are probably not iron deficient, and you shouldnt take
iron supplements if you already have enough iron in your body. However, if you
are deficient in this essential mineral, iron supplements may help. A
double-blind placebo-controlled trial of 42 non-anemic women with evidence of
slightly low iron reserves found that iron supplements significantly increased
the benefits gained from exercise. 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 as compared to those given placebo.
In addition, a double-blind placebo-controlled study of 40 non-anemic elite
athletes with mildly low iron stores found that 12 weeks of iron supplementation
enhanced aerobic performance.
There is no real evidence that zinc or copper will improve sports performance.
While zinc deficiency is relatively common, taking too much zinc can be harmful.
For more information on dosage and safety, see the individual articles on
copper, chromium, iron, magnesium, and zinc.
Cordyceps
Cordyceps is a traditional Chinese medicinal substance, part fungus, part
caterpillar. Its use as a sports supplement is based entirely on the belief that
it combats the effects of aging, but there is no scientific evidence to support
this idea.
Commercial Preparations
We dont have scientific evidence on every formula touted for improving sports
performance. However, one 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.
Other Supplements for Recovery
The stresses of sports competitions can sometimes weaken you, and injuries can
keep an athlete out of training and impede performance. The less "down-time,"
the better. The substances discussed in this section have been proposed for
sustaining health or speeding recovery, but none have been proven effective at
this time.
Preventing Infections
Earlier in this article, we discussed the evidence that vitamin C might help
prevent the infections that can follow intense exercise. The amino acid
glutamine may be helpful for this purpose as well. This idea is based on
findings that the amount of glutamine in the blood system of an athlete who has
trained very hard is lower than the norm. Glutamine is an important fuel source
for some of our immune system cells, and it is possible that the drop in
glutamine is associated with the high incidence of infections that occur in
athletes who have overtrained, although not all studies agree.
One double-blind clinical trial involving 151 athletes found that
supplementation with 5 g of glutamine immediately after heavy exercise, followed
by another 5 g 2 hours later, reduced the incidence of infections quite
significantly. Only 19% of those taking glutamine reported infections, while 51%
of the placebo group succumbed to illness. For more information, including
dosage and safety issues, see the full glutamine article.
Thymus extract is a supplement derived from the thymus gland of cows and is
thought to enhance immune function. However, a double-blind placebo-controlled
trial of 60 athletes failed to find any significant evidence of benefit with
thymus extract. In addition, there are significant safety issues with thymus
extract (see the full article for details).
Traumatic Injuries
Bruises and sprains are common among athletes. There is some evidence that
various supplements may enhance recovery from these injuries. The most popular
are bromelain, other proteolytic enzymes, oligomeric proanthocyanidin complexes
(OPCs), and/or horse chestnut, although the evidence isnt strong. See the full
articles on each of these topics for more information.
In addition, creatine might be helpful for reducing the muscle weakness that
develops when a limb is immobilized following injury.
Some athletes also use glucosamine (best known for its use in treating
osteoarthritis) in the unproven belief that it can help prevent muscle injuries,
relieve tendinitis, and repair damaged cartilage. However, there is no
scientific evidence to support these ideas yet.
Muscle Soreness
Muscle soreness is a common problem among hard-training athletes. A treatment
that could reduce such soreness might help an athlete train harder.
As mentioned previously, exercising increases the presence of free radicals,
naturally occurring substances that can damage tissue. Some researchers have
theorized that such damage may in part cause the muscle soreness, and perhaps
muscle deterioration, that can accompany a strenuous workout. Based on this
theory, various antioxidants have been proposed to help prevent athletic muscle
soreness, including selenium, beta-carotene, vitamin C, vitamin E, OPCs, and
coenzyme Q10.
Vitamin E has also been suggested as a treatment to prevent symptoms that can
occur after endurance running, such as gastrointestinal bleeding, stomach
cramps, nausea, or muscle injury; however, one double-blind trial found no
significant benefit for any of these symptoms.
The supplement phosphatidylserine (PS) might also help treat muscle soreness due
to its effects on cortisol. (See Phosphatidylserine in Ergogenic Aids, above,
for details.)
Not Recommended Treatments:
At least four commonly recommended supplements fall in the "not recommended"
category.
Hormones
Although they are often sold as supplements, androstenedione and
dehydroepiandrosterone (DHEA) are really hormones. The long-term consequences of
using these "supplements" are unknown. They alter your bodys hormone balance,
which may cause unpredictable side effects. For this reason, we do not recommend
the use of these substances. In addition, there is no real evidence that they
work.
Androstenedione is sometimes used by athletes based on the belief that it will
increase the amount of testosterone in the system. However, double-blind studies
of androstenedione have found that it does not alter total testosterone levels,
or improve sports performance, strength, or lean body mass. The most consistent
effect of androstenedione is to increase estrogen levels in the body.
Athletes have used DHEA on the belief that (like phosphatidylserine) it might
limit the bodys response to cortisol and thereby cause an increase in muscle
tissue growth. However, study results have been mixed, so its uncertain whether
DHEA really interferes with cortisol or not. In any case, most (but not all),
studies have found no performance benefits from taking DHEA.
Minerals
The mineral vanadium has been suggested for use by bodybuilders based on its
effects on insulin, but there is no evidence that it works. 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. Furthermore,
there are serious safety concerns about taking vanadium at such high doses (see
full article on vanadium).
The mineral boron has also been proposed as a sports supplement based on its
potential to alter the bodys hormone balance. However, clinical studies suggest
that boron supplementation is more likely to increase your estrogen levels than
help you produce more testosterone. Elevated estrogen levels have been
associated with increased rates of some types of cancer, so we dont recommend
taking supplemental boron. Far more research needs to be done on boron before it
should be considered either safe or effective.