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  Last updated: 1/26/2016



Competitive cyclists (and other athletes) who have achieved maximal results from their training programs will often turn to performance aids (also called ergogenic aids) to enhance get that competitive edge. These include equipment tweaks, psychological programs (visualization techniques, hypnosis, even psychotherapy), pharmacological manipulation (erythropoietin and all the hoopla with Lance Armstrong are a case in point) and nutritional additives (creatine phosphate, vitamins, minerals for example).

The use of performance enhancing dietary supplements can be traced back as the Romans who reportedly drank lion's blood to improve their strength and courage. Unfortunately nutritional supplements are frequently promoted with unsubstantiated claims - in magazine advertisements and health food stores, by coaches, and by entrepreneurs who stand to gain financially from their use. And in many cases potential harmful effects have not been studied or are not pointed out.

I couldn't have said it better - "As an amateur athlete I realize how powerful that urge is to want to take something that promises to help improve your performance without having to practice harder. But Iím always amazed at how many products are available, and as someone who does evidence-based medicine, Iíve always been somewhat skeptical of the benefits they provide."

This quote is from an on-line blog and refers to a British Medical Journal article in which researchers examined 615 sports advertisements in magazines. Of these, 54 contained claims that the product enhanced performance, but only three offered references. The 53 Web sites for these sports products contained an additional 141 references.

Further analysis found only three studies that were offered by the manufacturers were of high quality and at low risk of bias.... Two were studies of the effect of linoleic acid supplementation, and the other was a controlled trial of magnesium citrate in the treatment of leg cramps. All three had NEGATIVE results.


Following are six common errors in researching performance boosting claims in advertisements and personal stories.

  1. an absence of a comparison or "control" group using an inert or inactive agent to eliminate any bias or placebo effect (more below)
  2. the use of anecdotal or personal testimonials (once again there is the risk of a positive bias or placebo effect
  3. a failure to understand the strengths and weaknesses of statistics to rationally sort out conflicting results
  4. misinterpretation of data
  5. forgetting the original study's parameters, then applyingthe findings or conclusions to a different situation.
  6. cherry picking, or slanting information, to confirmone's preconceived notions.

I. The placebo effect

A placebo effect is evident when an inert compound produces results similar to those of the a prove active agent. It results from our optimism and belief that a medication, supplement, or training program will be beneficial, biasing us toward a positive impression of the results. This is what often occurs when a sugar pill (a placebo) is used in studying disease treatment. When told that the placebo will help, a large percentage of subjects report significant benefits. However this beneficial effect usually lasts for only a few doses and then rapidly wears off.

We can avoid confusing a placebo effect with the real, reproducible benefit of a supplement by comparing two groups of athletes in carefully monitored or "controlled" studies - one group being given the active ingredient being investigated and the other group given an inactive or sham agent, and not telling either group which agent they are receiving. This type of study is considered double blinded as neither group knows what they are receiving.Only if we as individuals are" blinded" (i.e. not told whether we are using an active agent) and then rigorously compare our personal results as subjects with both an active and inert agent (or use two groups of subjects as in a double blinded study) will we be able to eliminate the placebo bias.

II. Anecdotes

The placebo effect also points out the risks of using anecdotal information (personal testimonials) to make decisions on training programs and products. It explains why an athlete, optimistic about the benefits of a product he/she using, usually provides a positive testimonial based on his/her own perception of its benefit.

III. Use of statistics and data

A third error results from a misunderstanding of the fact that random positive results can occur when studying supplements, even when they may be of no physiologic benefit. Clinical studies use statistical methods to minimize the chance of interpreting random success as a reproducible effect (both positive or negative) of a supplement. But as the threshold is generally p< .05 or a 1 chance in 20 of the result being from random chance alone even in the best of studies, with good statistical analysis, the potential remains for publishing random, non-reproducable results. So if you find several studies on a training aid, but only one supports a positive or beneficial effect, be skeptical that the single positive outcome may have been by chance alone (and thus not reproducible). Likewise, be wary of the single, often quoted study, with results which no one else can duplicate.

IV. Misinterpretation of valid data

And of course you might have a valid scientific study, but the results are taken outof context. The article I am going to discuss is a great example of the way valid scientificresults can be mis interpreted leading to the abuse of supplements - as well as exposingusers to potential toxicity along the way (elemental iron is not a benign supplement).

First, the original articlewhich, I feel, misrepresents the conclusions of the referenced study: Iron Levels and Altitude.Taking supplements may increase the benefits of thin-air training. Which it wasthen reprinted for cyclists in Bicycling:This Common Supplement Could Help You Ride Better at Altitude"

This was a pretty strong claim so I thought I'd look for more detailsin the original article in PLOS. Although the PLOS article was quoted as supporting improved athletic performance at altitude withiron supplements, as far as I can determine it only found that IRON DEFICIENT athletesincorporate more substrate (iron) into their blood cells if they were given supplements - whichmakes sense. They need iron (even at sea level as they are iron deficient), so given iron plus thestimulus of altitude, it is only reasonable to assume that they will absorb more of it. Andas iron is in many enzymes (along with iron in blood cells), one might also expect some performanceimprovement (non heme level related) in the iron deficient athletes as well. And of course there isno evidence that the iron deficient group actually improved performance - only that the blood cell mass increased and thus it was assumed they would perform better as well.

So in my reading, this is a great example of an unfounded interpretation in the lay press that willlead to iron supplementation abuses by athletes who have adequate iron stores, and expose those lookingfor that performance edge to the toxicity of iron supplements.

V. Forgetting the study parameters

And finally, try to put the claims (proven of course) in perspective. A nicely done review of three classes of ergogenic aids (stimulants, tremor reducing agents, and anabolic steroids) in 1997 pointed out that Most studies of drug for improving performance have not used athletes as subjects. Thus the effectiveness of many drugs may be reduced in highly trained athletes with their lower margin for improvement. And there is always the cross sport applicability to be considered - will an improvement of a few percent obtained in repetitive sprints to exhaustion on a bike trainer be relevant to an endurance or recreational athlete?

Here is an example. I recently ran across this article in the NYT and my first response was "wow, what a simple way to get a 2 or 3 % edge in a competitive event". Then I decided to read the supporting literature. An article referencedwas peer reviewed. But as you get down into the details you find the rub. "....The studies showing a performance enhancement have all entailed subjectscommencing exercise following an overnight fast... a common feature of investigations that fail to report an ergogenic action from carbohydratefeeding during high-intensity exercise is that subjects receive a meal designed to Ďtop-upí endogenous carbohydrate stores, ~2 h prior to exercise ..."

The moral of the story (example) is that you cannot blithely believe all that you read and should always be a bit skeptical of the interpretation and application to your situation of even well done scientific studies. In this case, even with what appeared to be a scientifically supported benefit, the design of the study implied a performance benefit that is probably not there in a real life situation.If you are eating smart, you WILL be topping off your carbohydrates before a ride, and you WILL probably start taking oral supplements early in the ride to maintain your muscle glycogen stores for as long as possible (knowing that glycogen is the essential fuel to maximize your performance). And if you are, then the piece in the NYT, and the scientific study supporting it, are relegated to the "interesting, but..." bin.

VI. Confirmation bais

Confirmation bias occurs when people cherry pick or slant information to confirmtheir preconceived notions. To quote the scientist Francis Bacon:"We prefer to believe what we prefer to be true." For those interested inunderstanding how performance and health mythsdevelop and are perpetuated, this is anexample of confirmation bias.(click on "read transcript" to avoid the video).

The theme of this section is to be skeptical about unbelievable claims for performance improving products. And unless they are proven in well designed, blinded studies, assume that a claim which sounds too good to be true, probably is. There are few shortcuts for a well designed training program supported with sound nutrition. And although there may be little risk in trying supplements in addition, there is a monetary cost for those on a limited budget for their athletic pursuits, as well as the potential to lose focus on the need for a good training program.

It can be a long and tedious search to find the products and programs that might actually help you gain that competitive edge. It is more often the application of tried and true training basics, not shortcuts, that will get you to your goals.

Following is a listing of ergogenic aids that have been used for years, and some that are relatively new on the scene. There is an overlap between nutritional and pharmacologic ergogenic aids - caffeine is the best example being found in coffee and also available in tablet form as NoDoz. Following are a compilation of various dietary supplements that have been advocated as ergogenic aids over the last few years. Whenever possible the original scientific studies were reviewed to validate the claims and are so noted, but in many cases only anecdotal and testimonial evidence was available. If you would like to check on the most up to date literature, PubMed contains over 9 million citations in the MEDLINE database.

Based on my reviews, I have tried to identify those supplements that I feel are clearly helpful and beneficial (++) for improving cycling performance. The text will be clear for those that have nothing other than anecdotal information to recommend them. For the others? Caveat Emptor (the buyer beware) - the author

The following question from a reader is one I commonly receive:

Q: I am a beginner cyclist, and it is sometimes difficult to find time for cycling with college (Bio/Chem double major). However, I have became better at finding time and now it seems that I am in need of finding a nice, well-rounded muscle building/endurance enhancing supplement. I am rather slender (160lbs, 6'1"), and have trouble building the muscle needed for explosive power and lasting endurance. JT

A. There is no evidence that protein (powders or otherwise) beyond a fairly minimal 100 - 120 grams a day as a maximum are of any benefit. Likewise for carbs. Weight gain would be about adding daily Calories (fat has the most) and muscle mass is from stressing the muscles - that is exercise.

My advice is a good training program and a balanced diet - no supplements areneeded (or are adding any value for your $$ spent).


in alphabetical order.



Occasional articles will appear touting the benefits of alcohol as an energy source for vary sports activities. Although alcohol does contain more energy per gram (7 Cal/gram) than carbohydrates, and is rapidly absorbed from the intestinal tract, the available evidence suggests these Calories are not utilized to any significant extent during exercise. Thus its negative effects outweigh any theoretical positive ones. These include

In a recent study from Penn State, 10 women were given a mixed drink equal to a moderate drink. They then rode stationary bikes for 30 minutes at 70% of their maximum heart rate. Compared to their own baseline performance off alcohol, cycling after alcohol required more energy, produced a higher heart rate, and stimulated a higher cardiovascular demand. Even moderate drinking while exercising placed increased demands on the cardiovascular system.

The bottom line is a definite negative influence on performance.


Purified amino acids (particularly arginine, ornithine, lysine, and tyrosine) have become a popular, if expensive, form of protein supplementation. Five well performed studies have failed to demonstrate that either singly, or in combination, there is any significant effect on human growth hormone secretion (postulated to be the method of action) or direct measures of muscular development, strength, or power.

Amino acids are the building blocks of proteins and are present in almost all the foods we eat. As with vitamins, a balanced diet which replaces Caloric expenditures should provide more than enough of the essential amino acids. Amino acids sold in the health food stores at $25 to $30 per bottle have no added advantage over a peanut butter sandwich and a glass of milk, and don't have nearly the taste appeal.

Protein should provide approximately 20% of our daily Caloric intake. It normally provides less than 5% of the energy expended during exercise and is used as a source of energy for normal cell functions only during starvation or extreme malnutrition. Studies in athletes have shown that 1.2 grams of protein per kilogram per day is adequate for muscle development in most sports, and protein in excess of 2 grams per kilogram per day will be turned into fat. Most cyclists get more than enough protein for cell building and repair from the foods they eat, and any excess - whether from supplements or in the diet - will be either converted to body fat or burned inefficiently as fuel.

In addition, excess protein:


Common wisdom holds that taking anti-inflammatories or aspirin before cycling or other vigorous activity can reduce muscle soreness. However a study at the University of Georgia concluded that even at large doses (20 mg per kg or 4 standard aspirin for the average rider), aspirin did not delay the onset of muscle pain during exercise or reduce the perceived intensity when it occurred. In addition there is good evidence that using agents such as Motrin (ibuprofen) or aspirin on a regular basis increases the incidence of ulcers and can cause kidney and liver damage. How much is too much? If it's a regular part of your program, it's probably too much, and may be a sign that you are riding or training too hard.


There is evidence supporting the long term benefits of antioxidants. However,short term studies are more controversial. But at least one has suggested that the use of antioxidants in the form of vitamins C, E, and beta carotene decreased muscle damage in a group of runners as compared to a control group, and there are numerous anecdotal reports that vitamin C taken before a ride diminished the amount of muscle soreness the next day. However, none have suggested a positive effect of any of the antioxidant vitamins on actual exercise performance although one study from the University of Birmingham in England did suggest that a group of riders that took 500 mg of Vit C and exercised strenuously for 60 minutes recovered 85% of their muscle strength at 24 hours vs 75% in the placebo group.

The bottom line is that very little evidence to support the short term benefit of antioxidants for the competitive athlete - and plenty of controversy remains as to the long term health benefits. But there is no evidence that they will do you any harm.

More information on antioxidants.



Aspartic acid salts may improve aerobic endurance - perhaps by sparing muscle glycogen utilization. Conflicting studies (no effect of 3 grams of aspartate ingested 24 hrs before a ride to exhaustion at 75% VO2max; 15% increase in endurance at 75% VO2max after 10 grams of aspartate over the 24 hr period before the ride) suggest a possible role in endurance performance. Low doses are considered safe.

ASPIRIN (see anti-inflammatories)


A root herb from the Mongolian wilderness. Reported to increase the body's capacity to handle stress, and help reduce fatigue and enhance endurance. There are no studies with specifics. aAll information is purely anecdotal.

ATP (oral)

ATP is the chemical compound which provides the energy for muscle action. It is composed of a base (adenosine), a sugar (ribose) and three phosphate groups. It is the high energy phosphate bonds that contains the chemical energy which is stored in this molecule, and it is the breaking of these bonds during cellular metabolism that power muscle contractions and other vital cellular functions.

An oral supplement of this compound is available. The only controlled study available demonstrated a 7 % increase in mean power as demonstrated by a Wingate performance test (a 30 second interval of maximal performance, ie anaerobic, on a bicycle ergometer) after taking a 14 day supplement of 0.2 grams per kg body weight per day of ATP-E. How this translates to improvement in actual cycling performance or a positive impact on an end of race sprint is yet to be determined. Until further studies confirm this preliminary impression, and translate any benefits into actual improved cycling performance, this supplement should be considered as unproven.

BETA-CAROTENE (see antioxidants)

BICARBONATE (see sodium bicarbonate (baking soda))

BLOOD DOPING (see also erythropoietin)

Another name for red blood cell reinfusion. In this procedure 1 to 4 units (one has about 10 units of whole blood circulating normally) of blood are removed, the red blood cells separated from the plasma and stored, and the plasma reinfused. Three to four weeks later (when the body has replaced the red blood cells removed) and just prior to the event, the stored red blood cells are reinfused with a rise in the hematocrit (or red blood cell percentage of the whole blood) from a normal 40-45% to 60%. The increased hematocrit will persist for 14 days or so before the body readjusts through decreased red blood cell production.

Since red blood cells carry oxygen from the lungs to the muscles, this increase in the total red blood cell mass is beneficial to the endurance athlete for whom oxygen transport and delivery to the muscle are often limiting factors in performance. In controlled studies this translates into a 5 to 13% increase in aerobic capacity, reduced submaximal heart rate and blood lactate, and augmented endurance.

The opposite side of this issue is the definite deterioration in performance that results from donating a unit of blood. Research has shown that both VO2max and endurance suffer after blood donation. There is an immediate drop in plasma volume of 7 to 13% which persists for up to 24 hours, and the loss of hemoglobin may not be corrected for several weeks, even with an iron supplemented diet.

A new blood doping testing methodology introduced in 2004 can identify "inconsistencies" in blood samples. This was the case made against Olympic time trial winner Tyler Hamilton. Hamilton's tests revealed a "mixed red blood cell population", which, if confirmed, would indicate a homologous blood transfusion (from another person). Simply put, the tests suggest the presence of blood that is not Hamilton's own, and point toward the original form of "blood doping"in which an athlete receives a transfusion of his or her own stored blood, or that of a compatible person. As of 10/15/2004, the final results are pending.


Boron has been reported to increase serum testosterone levels and subsequently the lean body mass and strength of male athletes. However, a carefully controlled study of 19 male body builders, half of whom received 2.5 mg of boron per day for 7 weeks, demonstrated no significant difference in total testosterone, lean body mass, or strength. A normal diet will provide 10 mg/day of boron; 50 mg per day appears to be a toxic level.


Caffeine is one of a few proven performance enhancers. It is both a central nervous system as well as a metabolic stimulant used to reduce fatigue and as an endurance aid for some activities. In the trained athlete it can give a 2 - 3 % edge in performance.

CALCIUM (see also minerals)

Calcium metabolism in the athlete is still not completely understood. The question of an increased calcium requirement is linked to concerns about osteoporosis in women athletes who, because of the intensity of their training, have become amenorrheic. The hormonal changes that occur with amenorrhea (associated with intense training programs) affect bone formation and are thought to be one of the causes of osteoporosis. Recent evidence has suggested that the positive effects of weight bearing exercise on bone formation may counteract and cancel out bone loss. At this time, there is no consensus on the need for calcium supplements.

We're discovering that cycling may contribute to bone loss in both men and women because it's not a weight-bearing activity. So cyclists should crosstrain for bone health. Weight training and jumping (like rope skipping) are helpful.

CARNITINE (see l-carnitine)

CHLORIDE (see sodium chloride, minerals)


An amine widely distributed in food, as well as synthesized in the body, choline has been postulated to increase the production of the neurotransmitter acetylcholine and thus prevent fatigue in endurance events. Even with increased blood levels (ingestion of choline bitartrate, 2.34 grams), two separate studies failed to demonstrate any significant improvement in cycling times to exhaustion at 70% VO2max.


A chemical compound reported to potentiate the effect of insulin, and help build muscle and dissolve fat. However, 8 different studies, using up to 200 micrograms of chromium picolinate daily, have failed to demonstrate any changes in body composition or strength compared to control groups administered a placebo. Current information indicates that daily intakes of up to 400 micrograms are not toxic.

CITRATE (Sodium Citrate) (++)

Sodium citrate was evaluated in a 30 km high intensity time trial event at a dose of 0.5 grams per kg body weight. Total power output, but not peak power output, was greater in this treated group. At 30 km, the riders using sodium citrate had an average 100 second lead. The cyclists using the sodium citrate had a higher venous blood pH throughout the ride, and it is presumed that this buffering effect led to the improved performance (by optimizing the pH within the muscle cell and enhancing contractility).

Sodium citrate has also been shown to increase peak power over a placebo control group during short, high intensity cycle ergometry of 120 and 240 seconds duration. Again, this is thought to be related to optimizing the pH within the active muscle cell.

CIWUJIA (Endurox tm)

Ciwujia is an herb derived from a root grown in the northeast section of China and used in traditional Chinese medicine for over 1700 years to treat fatigue and bolster the immune system. It is commercially prepared and marketed under the trade name Endurox in the United States, and is claimed to shift energy metabolism in the exercising muscle from carbohydrate to fat, thus sparing carbohydrate and slowing lactic acid buildup. There is also a decrease in heart rate during moderate exercise.

However, there are several important caveats:

So for the moment, there is no proof that this supplement is of any benefit to athletes exercising near their VO2 max (or at prolonged moderate levels as well).


Clenbuterol is used by athletes in many sports for its purported anabolic effects and reduction of subcutaneous fat. It is a beta-2 (beta 2) agonist prescribed outside the US as a bronchodilator, but not approved for use in this country. It is on the banned substance list of the United States Olympic Committee.

A review of the animal husbandry literature (Clenbuterol: a substitute for anabolic steroids? Med Sci Sports Exerc. 1995 Aug;27(8):1118-21)reveals that this drug, when administered in doses far greater than those required for bronchodilation, does increase the deposition rate of lean mass and retard adipose gain. However, there are no human studies available and no investigation into long-term cardiovascular side effects has been undertaken. Thus the extrapolation from animal studies to unsupervised human usage is alarming.

For example, a laboratory study (Clin Sci (Lond). 2000 Mar;98(3):339-47) demonstrated significantly undesireable effects on heart muscle - The hearts of sedentary rats treated with clenbuterol exhibited extensive collagen infiltration surrounding blood vessels and in the wall of the left ventricle. The results indicate strongly that chronic clenbuterol administration deleteriously affects exercise performance in rats, potentially due to alterations in cardiac muscle structure and function.

CoQ10 (coenzyme Q10; ubiquinone)

A lipid found in mitochondria, as well as an anti-oxidant. In a recent review of research on this compound, supplementation of 100-150 mg/day for 4 - 8 weeks elicited no enhancement on metabolic responses to submaximal or maximal exercise, VO2max or cycle time to exhaustion.


Performance claims are not supported by published research studies.

COFFEE BEAN/COFFEE (see caffeine)

COLA NUT (see also caffeine)

A natural source of caffeine. Used in the energy gel GU, which contains the equivalent of 20 mg of caffeine per 1.1 ounce packet.

COPPER (see minerals)


An organic compound which, when combined with phosphate, yields creatine phosphate, an intermediary in the energy transfer pathway in the muscle cell which resynthesizes ATP. Creatine is available through nutritional supply stores in the form of creatine monohydrate, and will increase body weight (whether this is water retention of true muscle mass is still unproven). It is claimed to improve performance during maximal strength or power tests (weight lifting) and in repetitive high intensity bouts with short recovery intervals (short sprints of 5 to 15 second duration). However, the literature is split evenly on the question of benefits for the competitve cyclist, and there are some questions as to whether long term use of high doses might affect the kidneys. No short term toxicity has been reported at doses of 20 to 30 grams per day.

This compound may be effective in limited situations. It is doubtful that it is of any benefit for sprints of lasting more than 30 to 45 seconds. The study most like a real life cycling situation, an 18 mile time trial that included 6-15 second sprints, demonstrated no difference between riders receiving creatine or a placebo. So if you are being beaten by competitiors using this supplement, it is probably for other reasons.


Cytochromes are iron containing cellular enzymes which facilitate energy transfer.The only controlled study of this compound examined the effects of a supplement containing 500 mg cytochrome C on eleven trained triathletes. The performance test included a treadmill for 90 minutes at 70% VO2 max. followed by cycling to exhaustion again at 70% VO2 max. There was no significant improvement over the

D15 (see Pangamic Acid)

DHEA (dehydroepiandrosterone)

DHEA is a steroid, related to cortisone, produced by the adrenal gland. Maximum production occurs during the third decade of life and then gradually declines with aging. Studies to date on it's "anti-aging" effects are only preliminary and have given conflicting results. Doses of 25 to 100 mg per day have been given for 6 months to subjects over 60 years of age with variable results on muscle strength and lean body mass. It appeared that men had more of a response than women. At this time there is absolutely no evidence that physical performance is modified in young, healthy individuals.

ELECTROLYTES (see also minerals, sodium chloride)

The minerals sodium, potassium, and chlorine are collectively referred to as electrolytes. They are dissolved in the intra (within) and extra (outside) cellular water as charged particles (ions) and are responsible for maintaining a proper electrical gradient across the cellular membrane - required for the proper functioning of each cell.

A normal diet contains these three minerals in excess, and the kidneys control the loss from the body. As a result there is no requirement for diet supplementation except in extreme conditions.

DHAP (dihydroxyacetone pyruvate)

A metabolic byproduct of glycolosis which includes dihydroxyacetone and pyruvate in a 3:1 ratio. Several studies have sugggested that 100 grams per day of DHAP for 7 days increased arm ergometer endurance at 60% VO2max and cycle ergometer endurance time at 70%VO2max. These studies are yet to be confirmed in well trained athletes.


Performance claims are not supported by published research studies.


ENDUROX (see ciwujia)

EPHEDRA & EPHEDRINE ( additional information)

A short acting stimulant found in the traditional Chinese herb tea Ma Huang, ephedra mimics adrenaline. The synthetic version, ephedrine, is found in asthma and nasal decongestant (pseudoephedrine) products. It has been used in tandem with other natural caffeine sources such as kola nut and guarana. In fact, the only study that assessed the the effects of ephedrine and caffeine in combination reported that ephedrine must be supplemented with caffeine to affect athletic performance. In higher doses it can cause tremors, rapid breathing, nervousness and insomnia - common side effects of caffeine as well.

Although it appears to be safe in small amounts (up to 50 mg of ephedrine or 2 cups of Ma Huang tea per day), a tolerance will develop (ie it becomes less effective as time passes), and its use in any amount is banned by the International Olympic Committee. In fact the USOC advises athletes to eliminate all herb based teas and diet supplements for one week prior to a race (and urine testing) if they are unsure whether they might contain ephedra. Likewise check on any decongestant and asthma medications to see if they contain ephedrine.

ERYTHROPOIETIN (EPO)(see also blood doping)

EPO is a hormone, produced by the kidney, which stimulates the bone marrow to produce red blood cells. It is available in injectable form and can be self administered to "hyper"stimulate the bone marrow. The result is an abnormally high red blood count (hct, hematocrit) which effectively creates the same physiologic conditions as blood doping. Unfortunately, when administered in an unmonitored manner, the hematocrit can increase above 60% increasing blood viscosity and predisposing to the formation of blood clots (also aggravated by the dehydration which occurs in competitive cycling). This clotting tendency is speculated to be the explanation for the cases of "sudden death  which have been reported after hard training or racing - most likely from a heart attack or a pulmonary embolism.

Athletes training at altitude will increase their hematocrit by about 1% per week for the first 12 weeks, an effect partially moderated by an increase in erythropoietin release from the kidneys which is stimulated by the lower oxygen levels at altitude. However, as the result of counterbalancing factors from a decrease in maximum exercise capacity, training at altitude this increase in hct does NOT lead to an equal improvement (compared to EPO injections) in sea level performance.

EPO is banned in sanctioned events. But as it is almost impossible to monitor for an excess of a hormone that is naturally produced, it is the hct. that is monitored, not the hormone itself. Any cyclist with a hct greater than 50% is not allowed to compete, regardless of the mechanism of the increased hct. Unfortunately this is not as fair as a test for EPO, but health concerns were felt to override those of fairness.

FAT(DIETARY) - see also

Over the last few years it has been suggested that a diet composed of at least 30% fat Calories improves competitive aerobic performance over a high carbohydrate diet - relatively restricted in fat Calories (20-25%).

There are a number of physiologic studies that demonstrate fat CANNOT sustain high level (high VO2 max.) aerobic and anaerobic activity (the cause of the "bonk" as glycogen stores are depleted). And others that have shown that a high carbohydrate diet is best for maintaining glycogen stores while a chronic deficit in replacing carbohydrates has been proven to lead to chronic fatigue. In addition it has been proven beyond any doubt that a long term high fat diet leads to heart disease. And for those who still aren't convinced, it should be remembered that even the leanest athlete has plenty of stored fat available without any need for diet supplements.

A variation on this theme is reflected in the energy bars which contain fat and are alleged to improve performance, SELECTIVELY increase fat metabolism, and aid in weight loss. While there has been some evidence that an occasional long slow recovery ride in your training program MIGHT improve the ability to metabolize or use stored fat Calories for muscle energy, there is no scientific basis for the claims made by these products that eating any particular food or food type (i.e. fat) will enhance fat metabolism.


Ferulic acid is derived from the natural plant sterol, frac, and has been claimed to assist the body in maintaining greater workloads. However these performance claims are not supported by published research studies.


Fiber is a general term for non digestible carbohydrate in the diet and refers mainly to the cellulose, lignin, and pectin found in fruits, grains, and vegetables. Currently there is no recommended minimum for dietary fiber and no special requirements for cyclists or other athletes. On the other hand, there is good evidence that too much fiber may bind minerals such as zinc in the intestinal tract, resulting in poor absorption. A high fiber diet also may lead to abdominal bloating and cramping. The most reasonable approach seems to be a well balanced diet with enough fruits, grains, and vegetables to maintain regular bowel function.


Many companies add food colorings to make their products look more appealing, not to improve nutritional value. These are felt to be harmless although the purist can read the label and will be able to find almost any commercial product in a "natural" form, if they are willing to spend the time and energy to look.


A 6 carbon carbohydrate derived from fruit often touted as superior to glucose as an energy source for the endurance athlete. However, there is little evidence that fructose alone has any advantages over glucose and may in fact have less of a glycogen sparing effect. There is some evidence that its benefits lie in a combination fructose/glucose sports drink.


Performance claims are not supported by published research studies.


Ginsengs are herbal preparations extracted from the roots of plants in the family Araliaceae, and contain a wide variety of chemical substances. Thus all ginsengs are not equivalent as far as ergogenic potential. Some may work at the higher centers of the central nervous system to enhance both mental and physical stamina.

A commonly advertised commercial product, Ginsana, claims to produce lower lactate levels and increase VO2 max. However, as with many of the herbal products, there are as many studies supporting the claims as refuting them - a common situation with ineffective claims. And the most recent, which are the most carefully contolled, failed to demonstrate any change in maximal aerobic performance after two and three weeks of supplementation.

At recommended doses, ginseng can produce the "ginseng abuse syndrome" - high blood pressure, nervousness, and confusion. Although this compound may be considered as "possibly" effective, needing further study, try it at your own risk!


An over the counter agent derived from shark cartilage, glucosamine sulfate is helpful in decreasing the joint pain from degenerative or wear and tear arthritis (osteoarthritis). There is no evidence that it decreases the muscular pain associated with over training.


A chemical compound that together with fatty acids forms triglycerides (the most plentiful lipid in the body and the major form of lipid stored in fat cells), glycerol is a clear, syrupy, and extremely sweet substance which also has water retaining effects when taken orally. In 1987, it was shown that resting subjects drinking a glycerol solution retained 50% more fluid than when drinking a similar volume of water alone. This led to investigation of its ability to help prevent dehydration under extreme conditions of exercise, heat, and high humidity.


Human growth hormone, also known as somatotrophin, is now competing on the illicit market with anabolic steroids a tissue building and performance enhancing drug. Although there have been studies suggesting a decrease in body fat and an increase in muscle mass with growth hormone supplements, these reults have been mainly in men more than 60 years old, and there is no evidence it improves muscle mass in athletes less than 60 years old. Growth hormone must be given by injection as the molecule is too big to be absorbed if taken orally. It is still only conjecture (unproven) whether oral amino acid mixtures (available without a prescription) can stimulate your own, internal, GH release from the pituitary gland.

Side effects include insulin resistance (diabetes), water retention, and carpal tunnel syndrome. At this time, injectable growth hormone should be considered potentially dangerous and its benefits still to be proven.


A South American herb used as a natural source of caffeine. Used in the energy gel Pocket Rocket, which contains the equivalent of 50 mg of caffeine per 1.2 ounce packet. The caffeine effect of one teaspoon (100 mg) of guarana is equivalent to one cup of coffee.

HERB TEA (see also Ma Huang)

The biggest short coming of herb teas is the inability to identify the active ingredients, increasing the possibility of taking a substance banned by the IOC or USOC. Strength of these teas is directly related to the brewing time, making calculation of a "safe" dose difficult and increasing the chances of a toxic side effect.

HMB (beta-hydroxy-beta-methylbutyrate)

This metabolite of the amino acid leucine was studied in a group of serious weight lifters (1.5 hours a day, 3 days a week) on their "normal" diet of 117 grams of protein per day (twice the Recommended Daily Requirement) and a high protein diet of 175 grams per day.

HMB (1.5 and 3.0 grams per day) decreased the products of muscle breakdown (muscle damage) found in the urine during the training period, and increased the amount of weight lifted in each week of the study when compared to a control group not using the supplement. There was a dose related effect, that is the 1.5 gram per day dose of HMB was beneficial but greater improvement was noted on 3.0 grams perday. There was no benefit of a high protein diet compared to a normal protein diet (117 grams per day) either in the control (no HMB) or HMB groups. Lower body strength improved more than upper. The average increase in overall (averaged) strength compared to the control (no HMB) group at week 3 was 13% for the 1.5 gram per day HMB supplement and 18% for the 3.0 gram per day HMB supplemented group. No adverse effects were noted during the study period.

HMB is of use in a program of regular resistance training amd appears to work by minimizing the muscle damage that normally occurs. It's role in aerobic conditioning or cycling where strength is less of a factor has not been studied.


Humic substances (including humic acid) are ubiquitous in the environment and may constitute as much as 95% of the total dissolved organic matter in aquatic systems Although they have been touted as a health supplement, their use at this time should be considered risky.


Inosine is a nucleoside theorized to enhance oxygen delivery during exercise. However, the only available study in 9 highly trained runners after 6 grams per day for 2 days reported no significant benefit either during submaximal running or peak oxygen uptake and performance in a treadmill run to exhaustion.

IODINE (see also minerals)

IRON (see also minerals)

Iron is important as a component of hemoglobin in red blood cells which transports oxygen from the lungs to the muscle cells, and iron deficiency can cause fatigue and weakness. Although some riders use iron supplements to alleviate the beat feeling they experience after a long ride, a balanced diet easily meets the RDA for iron (10 mg for men and 15 mg for women). Four ounces of red meat contains 8 - 10 mg. As excess iron can be toxic, any questions of a deficiency state are best resolved with a screening blood test before resorting to supplements - any self prescribing has definite risks.

Athletes involved in contact sports (including runners) are more likely to be anemic as a result of iron deficiency than cyclists, but even regular cyclists have an additional need of around 18 mg of iron per month (equal to one menstrual period). As you might expect, iron deficiency is more of a problem in women athletes because of monthly menstrual blood loss. When the US Olympic team was studied, it was found that 20-30% of the female athletes did not get enough iron from diet alone. If you ride regularly, taking a multivitamin with iron will help to prevent anemia. An alternative is to eat extra portions of iron containing foods (dark green vegetables, prune juice, figs, and raisins).

KOLA NUT (see caffeine)

The caffeine effect of one teaspoon (100 mg) of kola nut is equivalent to one cup of coffee.


An nitrogenous compound found mainly in meats (a non-vegetarian diet contains 100-300 mg per day), but also synthesized in the kidney and liver from lysine and methionine. Theorized to enhance aerobic endurance by increasing the oxidation of glucose, decreasing the accumulation of lactic acid, and enhancing fatty acid metabolism by the cellular mitohondria.


MA HUANG (see also ephedra)

MAGNESIUM (see minerals)

MANGANESE (see minerals)

MINERALS (see also electrolytes, sodium chloride)

Minerals are chemical elements found in the body either in their elemental form or complexed with organic compounds. Like vitamins, they are essential for normal cell functioning. The two most prevalent minerals, calcium and phosphorus, are major components of bone while sodium and potassium are found in all tissue fluids, both within and around cells. Magnesium, chloride, sulfur, and zinc are other minerals that play a key role in cell function. The trace elements iron, manganese, copper, and iodine are found in much smaller quantities, but play essential roles as catalysts in basic cellular chemical processes.

These minerals, found in all foods, are kept in balance through internal regulation of absorption and excretion. As a result, adequate tissue levels are easily provided by a balanced diet. Multiple studies of body tissue mineral status in athletes failed to identify any deficiencies in those ON A BALANCED DIET compared to people engaged in normal daily activities. Athletes who are restricting energy intake to achieve a lower body weight (endurance runners for example) are the exception, and may need supplements.

It has been alleged that athletes need higher than normal levels of minerals to maintain maximum performance. However numerous studies of mineral and micronutrient diet supplementation (with the exception of iron in athletes who were clearly anemic with iron deficiency) have failed to demonstrate an improvement in performance whenever studied.

Only calcium (for long term bone strength) and iron (in clearly deficient individuals) may be required by some athletes in increased amounts. Because of toxic side effects when taken in large amounts, minerals as a group are not recommended as routine supplements for athletes on a balanced diet that meets their Caloric needs.


The concentration (and thus availability) of fatty acids in the blood is believed to directly influence their uptake and oxidation by skeletal muscle. The use of niacin as a vitamin supplement results in a lowering of blood free fatty acids levels at rest and a blunting of the rise in free fatty acid levels normally associated with prolonged exercise. Theoretically this should reduce the use of free fatty acids as an energy source for skeletal muscle during exercise, and require a compensatory increase in the amount of carbohydrate metabolized from muscle glycogen stores or blood glucose supplies. And one might even expect a potential decrease in TOTAL muscle energy output because of a decrease in the total energy Calories available to the muscle cell (fatty acids and glucose).

However, as measured in actual controlled studies, the effects on performance have been inconsistent. One investigator reported impaired "run to exhaustion" times with nicotinic acid supplements while another reported no impairment in performance in a 10 mile run. As to cycling performance, one study failed to demonstrate a difference in "cycling time to exhaustion" while another reported a decrease in physical work capacity to exhaustion in a one legged cycling model.

These conflicting results suggest that any decrease in overall performance is probably small, affecting at most only a minority of elite cyclists. However, as with all medications, there is the occasional individual with a particular sensitivity and exaggerated response in which case this medication could have an adverse effect on their personal performance.


Performance claims are not supported by published research studies.


These "eicosanoids" are speculated to stimulate human growth hormone release, and are marketed in several energy bars containing a blend of fish and vegetable oils with omega3 fatty acids. There is currently no support for an anabolic or performance enhancing effect. Excesses may interfere with blood clotting.



A plant extract claimed to have anabolic effects, this is a ferulic acid compound derived from rice bran oil. Recent studies have indicated it may actually decrease testosterone production. Any effect on performance is purely speculative.


Touted by many athletes as a performance enhancer ( increased aerobic capacity, increased endurance, decreased blood lactate levels), there is no evidence from controlled studies as to any benefits in athletic performance. Concern has been expresses as to possible harmful effects to humans, and the FDA has made it illegal to sell this as a diet supplement or drug.


A blood phosphate compound (2,3 diphosphoglycerate, DPG) binds with hemoglobin to facilitate the release of oxygen at the level of the muscle capillary. Thus oral phosphate, a building block of DPG, has been investigated as a performance enhancer. However results have been conflicting and although there is some suggestive evidence, this compound should be considered as unproven as an ergogenic aid at this time.

Usual doses are 3 to 4 grams of calcium or sodium phosphate for 3-6 days. Phosphate supplements may cause gastrointestinal distress unless consumed with ample fluids or food, and chronic consumption may interfere with calcium balance.

PHOSPHORUS (see minerals)

PRITIKIN DIET (see vegetarian diet)


A procyanidin extracted from the tree bark of the pine, Pinus maritima. It is a free radical scavenger and antioxidant when studied in the test tube. However there have been limited animal studies and no human studies of this compound. There is no proof as to benefits of this compound compared to the antioxidant effects of Vitamins C or E.

PYRUVATE (see also DHAP (dihydroxyacetone pyruvate)


This medication is used by cyclists as a cure for leg cramps. However it can cause a drop in blood count and has been linked to 16 deaths, so the FDA is banning it from the market. Cramping cyclists should fight leg cramps with proper hydration, training, and electrolyte replacement instead.

SELENIUM(see also antioxidants)

Thought to have a possible role as an antioxidant, there is little evidence this mineral plays a significant role in minimizing the harmful effects of free radicals. It almost certainly plays a less significant role than Vit C or Vit E, and the occurence of specific selenium deficiency in humans is quite rare. It is found naturally in seafood, meats, and grains, and specific supplementation is not recommended.


A chinese herb, questionably related to ginseng - as in many of these herbal products it is difficult to determine the exact chemical makeup - claimed to have benefit as a brain stimulant. A group of volunteers is reported to have shown an increase in mental alertness and work output, while another study suggested an increase in athletic performance under stressful conditions such as heat and noise. As with other herbal products, these claims are anecdotal and there is no scientific proof of increased athletic performance.

SMILAX (smilax officinalis)

Smilax Officinalis, native to the tropics of Brazil, began as a pharmaceutical base for the production of certain anabolic steroids. However, without the chemical modifications, smilax officinalisis thought to be non-toxic and its use has no known negative side effects. It is alleged to raise the blood content of testosterone - the male growth hormone - and to be equivalent to anabolic steroids in gains of lean muscle mass and defined tissue. However these performance claims are not supported by published research studies.

SODIUM BICARBONATE (baking soda) (++)

A chemical compound available as baking soda or Alka Seltzer, sodium bicarbonate buffers lactic acid allowing longer bouts of near maximal cycling for short, high intensity sprint events lasting 1 to 7 minutes (400m. or 800m. sprints, time trials), but of minimal additional effect compared to the body's natural buffering capacity for lactic acid during very short intense exercise lasting less than 30 seconds or sustained endurance events. Generally, studies that used doses of 300 mg/kg body wt. found an ergogenic effect, while those using less than 200 mg/kg showed no effect.

An early study at Iowa State University demonstrated some improvement in sprinting ability after taking 2 tablespoons of baking soda immediately prior to the event. However, diarrhea and stomach upset were reported, and it appeared to be beneficial only in very short event such as the 4000 meter pursuit. Another demonstrated an increase in average power output on a cycle ergometer during repeated 10 second sprints. A third study at the University of Washington has failed to demonstrate any improvement in a series of one minute intervals at 95% VO2 max. in female cyclists.

Sodium bicarbonate should be considered of probable benefit in very specific circumstances but has certain drawbacks which may outweigh these advantages. (See also Citrate)

SODIUM CHLORIDE (see also minerals, electrolytes)

Over a 24 hour period, the athlete's standard training diet will replace two to three times the normal salt losses. Only under extreme environmental conditions of high temperature or high humidity is a salt supplement needed. An exception might be the cyclist who has not trained for an event and can lose excessive amounts of salt in his/her perspiration. Although exercise cramps were once thought to be the result of salt deficiency, it now appears that they are related to a dehydration and a decreased blood flow to the muscles.

SOMATOTROPHIN (see growth hormone)

SULFUR (see minerals)


Performance claims are not supported by published research studies.


Performance claims are not supported by published research studies.



As most vegetarian diets are already high carbohydrate diets, and also supply enough protein for normal body cellular repair, there are no special supplements needed. In fact, they are the model for continuous carbohydrate loading.


Vitamins are held up as a safe and effective way of improving performance. Although they are often recommended by coaches and trainers, multiple studies of body tissue vitamin status in athletes failed to identify any deficiencies in those on a balanced diet (replacing Calories expended) when compared to people engaged in the normal activities of daily life.

It has been alleged that although deficienceis have not been identified, athletes need higher than normal levels of vitamins to maintain maximum performance. Although supplementation does elevate blood levels of the corresponding vitamins, there is no evidence of an improvement in performance.

And in the face of no proven benefit, there is evidence that mega-vitamin programs can be hrmful. The fat soluble vitamins (A, D, E, and K) are not eliminated in the urine and can accumulate in body fat to reach toxic levels. There have even been reports that the water soluble vitamins (B complex, and C) which are excreted in the urine if excess amounts are taken can be harmful at doses of 10 to 100 times the recommended daily requirements (RDA).

Vitamins are catalysts for the metabolic and biologic pathways that convert fats, carbohydrates, and proteins into Calories or energy. As such, they facilitate the reaction, but are not "used up" or consumed by it. This is why there is a single RDA that is independent of body size, sex, or daily energy expenditures.

The RDA is being reviewed and updated regularly. Recently (2005) it was shown that the current RDA for Vitamin D (400 units) may be too low as a higher dose (1000 units) provides protection from certain cancers. This is particularly important in northern climates where sun exposure (which can provide up to 20,000 units in a single day) is minimal many months of the year.

If there is a concern about how your diet being well balanced, there is no harm (other than to your wallet) in using a simple over the counter multiple vitamin once a day. But vitamins are not the easy answer to increased performance.



No studies have documented enhanced lean muscle mass or strength. It is non toxic even at high doses.


An elegant study in 2005 demonstrated definitively the lack of any benefit from vitamin C supplementation as far as VO2max or maximal cardiac output.


Recently (2005) it was shown that the current RDA for Vitamin D (400 units) may be too low as a higher dose (1000 units) provides protection from certain cancers. This is particularly important in northern climates where sun exposure (which can provide up to 20,000 units in a single day) is minimal many months of the year.



An alkaloid extracted from the bark of the yohimbe tree and claimed to have an anabolic effect through stimulating the release of testosterone or human growth hormone. Performance claims are not supported by published research studies.

ZINC (see minerals)

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