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PCPFS Research Digests

Nutritional Erogogenics & Sports Performance

A Note From The Editors

Over the past few years, The President's Council on Physical Fitness and

Sports Physical Activity and Fitness Research Digest has focused primarily

on physical activity as it relates to good health and fitness. In this issue, we

deviate a bit from that traditional theme. We have asked Dr. Mel Williams

to write about nutritional ergogenics and sport performance. We did this

because the use of nutritional products in attempts to increase performance

has become so widespread. We thought it was important to provide a review

of the latest evidence to provide readers with the latest evidence on these

various products alleged to enhance performance.

This review will show that there is evidence to support the performance

enhancement of a few supplements, but to use Dr. William's words,

"...supplementation with various essential nutrients or commercial dietary

supplements will NOT, in general, enhance exercise performance in wellnourished and physically active individuals."

As editors, we solicited this paper for a second reason. Many non-athletes

interested in increasing muscle mass or reducing body fat levels look to

athletes for advice on dietary supplements. Even though they are not

particularly interested in performance enhancement, they will mimic the

behaviors of high profile athletes using the strategy "...if they use it, it must

be good." This paper allows teachers, coaches, fitness leaders, and all other

readers to find out the facts about dietary supplements. While some of the

information in this paper is somewhat technical, Dr. Williams has made

every effort to provide the information in a format that is easy to

understand. Table 1 provides a good summary of the evidence available for

the dietary supplements discussed in this paper.

Introduction

Most individuals participate in mild to moderate physical activity to improve

their physical appearance or health. Many others, however, engage in highintensity physical activity to prepare for sport performance. They are

athletes. Whatever the level of competition, be it for an Olympic gold

medal or an age-group award in a local road race, the two major keys to

successful athletic performance are genetic endowment and proper training.

In order to optimize the genetic potential of the elite athlete, scientists at

the United States Olympic Training Center design specific individualized

physiological training programs to increase physical power, psychological

training programs to enhance mental strength, and biomechanical training

programs to provide a mechanical edge. Many of these training strategies

are increasingly available to nonelite athletes to help increase their ability

to perform their best athletically within their genetic potential.

Although there are multiple purposes for engaging in sport, one of the

primary objectives of athletic competition is supremacy, to win the contest.

The most appropriate means to achieve this objective is optimal

physiological, psychological, and biomechanical training. However, some

athletes believe that they have maximized their ability to improve their
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sport performance through training and may seek other methods to gain a

competitive edge on their opponents.

Ergogenic aids, or ergogenics, are substances, strategies or treatments that

are theoretically designed to improve physical performance above and

beyond the effects of normal training. Some ergogenics are used during

training to enhance the training effect over time, while others are used just

before or during the sport event to provide an immediate competitive edge.

In general, ergogenics are designed to enhance the athlete's physical power

(physiological ergogenics), mental strength (psychological ergogenics), or

mechanical edge (mechanical ergogenics).

Physiological ergogenics, particularly pharmacological and nutritional

substances, are designed to increase physical power by enhancement of

metabolic processes involved in energy production during exercise. For

example, anabolic/androgenic steroids (drugs) and creatine monohydrate

(nonessential nutrient) have both been used in attempts to increase

strength and power.

Psychological ergogenics are devised to enhance mental strength by

favorably affecting psychological processes before or during competition. For

example, hypnosis and mental imagery have been used to induce

psychological sensations of relaxation or stimulation, depending on the

nature of the sport.

Mechanical ergogenics are used to provide a mechanical edge by improving

energy efficiency. For example, a skintight racing suit will reduce wind

resistance and help increase velocity at a given energy expenditure during

sports such as downhill skiing and speed skating.

Within the regulations of the specific sport, use of most psychological and

mechanical ergogenics is legal. However, use of many physiological

ergogenics, particularly drugs and methods such as blood doping, is

prohibited because they may provide an unfair competitive advantage or

pose serious health risks to the athlete. A comprehensive list of prohibited

substances and methods is available from the United States Olympic

Committee (1996). Conversely, use of most nutritional substances is legal,

and literally hundreds of dietary supplements have been promoted as

ergogenic aids for sports performance. Table 1 provides a partial listing of

individual nutrients or nutritional products that have been studied or

marketed for their ergogenic potential. However, some commercial products

include multiple ingredients. For example, Up Your Gas, advertised as a

natural energy pill, includes the following among its many ingredients: Bee

pollen, Cayenne Pepper, Ginkgo Biloba, Guarana, Inosine, Kola Nut, Korean

ginseng, Niacin, Octacosanol, Spirulina blue-green algae, Vitamin E, and

Yerba Mate.

First and foremost, a varied, healthful diet balanced in energy and nutrient

content is the nutritional mainstay for most athletes. Sports nutritionists

contend that athletes should obtain the energy and nutrients they need

through wise selections within and among the various food groups, including

whole grains, fruits, vegetables, and meat and milk products. Dietary

supplements are designed to complement a balanced, healthful diet, not

substitute for it.

The purpose of this review is to provide a broad overview of selected

individual nutrients and dietary supplements purported to possess ergogenic

properties. Space does not permit a detailed analysis of all specific studies,

so most of the references cited are either principal studies or review papers

that may provide the interested reader with more detail.

Table 1. Efficacy of some purported nutritional ergogenics

Nutritional ergogenics may be used in attempts to enhance physical power,

mental strength, and mechanical edge for various sports. Research support

for nutritional ergogenics may be classified as strong (meaning studies

generally support effectiveness), uncertain (meaning some positive findings

are available, but confirming research is needed), or weak (meaning little or

no positive data are available). The following is a brief summary of the

research-based efficacy of some purported nutritional ergogenics on physical
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power (PP), mental strength (MS), or mechanical edge (ME) in wellnourished subjects.

Strong evidence

Alkaline salts: PP - aerobic endurance

Caffeine: PP - aerobic endurance

Carbohydrates: PP - aerobic endurance

Creatine: PP - muscular strength

Water: PP - aerobic endurance during heat stress conditions

Uncertain evidence

Alcohol: MS - neuromuscular relaxation

Antioxidants ME - muscle tissue damage prevention

Antioxidants PP - aerobic endurance

Choline: PP - aerobic endurance

Dihydroxyacetone pyruvate: PP - aerobic endurance

Glycerol: PP - aerobic endurance

Phosphates: PP - aerobic endurance

Vitamin E: PP - aerobic endurance at altitude

Vitamins B1,B6, B12 MS - neuromuscular relaxation

Weak evidence:

 Amino acids:

Arginine, ornithine, lysine

Branched-chain (leucine,

isoleucine, valine)

Glutamine

Glycine

Tryptophan

Bee pollen

Carnitine (L-carnitine)

Ciwujia (Endurox)

Coenzyme Q10 (Ubiquinone)

Conjugated linoleic acid (CLA)

Dehydroepiandrosterone (DHEA)

Ephedrine, ephedra (Ma Huang)

Fructose 1,6-diphosphate

Gamma oryzanol (Ferulic acid,

 FRAC)

Ginkgo biloba

Ginseng

Inosine

Medium chain triglycerides (MCTs)

Minerals

Boron

Chromium

Iron

Selenium

Vanadium

Octacosanol

Omega-3 fatty acids

Polylactate

Protein

Smilax officianalis

Vitamins

B-complex

- Thiamin (B1)

- Riboflavin (B2)

- Niacin

- Pyridoxine (B6)

- Cyanocobalamin (B12)

- Folacin

- Pantothenic acid

Antioxidants

- Beta carotene

- Vitamin C

Vitamin B15

Wheat germ oil

Yohimbine (Yohimbe)

Carbohydrate and carbohydrate metabolites
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Carbohydrate is the primary dietary energy source for high-intensity aerobic

endurance exercise (> 65-70% VO2max), but endogenous supplies such as

muscle and liver glycogen are limited and may become suboptimal within

90 minutes. Carbohydrate loading procedures may elevate endogenous

glycogen stores, postponing fatigue and improving performance in which a

set distance is covered as quickly as possible (such as a marathon) by 2-3

percent (Hawley et al., 1997). Additionally, numerous studies support the

efficacy of carbohydrate supplementation prior to and/or during such

prolonged aerobic exercise tasks to improve performance (Williams, 1998B).

Metabolic by-products of carbohydrate are theorized to provide a more

efficient fuel than other carbohydrate sources. Several well-controlled

studies by researchers at the University of Pittsburgh have shown that

pyruvate, administered as dihydroxyacetone and pyruvate (DHAP), may

increase muscle glycogen levels or blood glucose uptake by exercising

muscles and enhance exercise performance in untrained subjects. However,

these findings have not been duplicated by other scientists and the

ergogenic effect of pyruvate for trained athletes is questionable (Anderson,

1997; Williams, 1998B). Other metabolites, such as fructose 1,6-

diphosphate and lactate salts (polylactate) do not provide any ergogenic

effect beyond that provided by more natural carbohydrate sources, such as

glucose (Swensen, et al., 1994; Williams, 1998B).

Lipids and lipid metabolites

Lipids represent an energy source for mild-to-moderate intensity aerobic

endurance exercise (less than 50-65% VO2max), but unlike carbohydrate,

endogenous stores of lipids as adipose and muscle tissue triglycerides are

abundant. Triglycerides provide free fatty acids (FFA), the primary lipid

energy source during exercise. Lipid dietary strategies or supplements

attempt to increase FFA oxidation and reduce reliance on endogenous

carbohydrate stores, sparing muscle glycogen use and delaying fatigue

during prolonged exercise. Other supplements, such as L-carnitine and

caffeine supplementation (discussed below) are theorized to exert similar

effects.

Fat loading is a dietary strategy involving increased consumption of dietary

fats, up to 70 percent of daily energy intake, in attempts to increase the

contribution of endogenous fats as an energy source during exercise.

Several preliminary studies have shown some beneficial effects of fat

loading, but either the experimental design was not appropriate or the

exercise tasks used do not appear to have any application to contemporary

sports events (Williams, 1998B). In a major review, Sherman and Leenders

(1995) noted that although the fat loading hypothesis is intriguing, the

current scientific literature is not supportive. Medium-chain triglycerides

(MCT), oral water soluble supplements that may enter the circulation more

readily than normal dietary fats, have been theorized to be a more efficient

lipid energy source during exercise. However, recent research by scientists

from the Netherlands has not shown any significant contribution of oral MCT

to energy metabolism during exercise, and two recent studies have shown

that MCT supplementation could actually impair 40-kilometer cycling

performance (Williams, 1998B). Nevertheless, in a recent review, Berning

(1996) noted that some preliminary research findings were promising,

particularly when MCT were ingested with carbohydrate supplements during

exercise. Confirming research is needed.

Proteins, amino acids, and related metabolites

Protein supplements have been recommended to athletes to enhance

nitrogen retention and increase lean body (muscle) mass, to prevent protein

catabolism during prolonged exercise, and to support an increased synthesis

of hemoglobin, myoglobin, oxidative enzymes, and mitochondria during

aerobic training. Current research suggests that athletes may need slightly

more protein than the Recommended Dietary Allowance (RDA). Values

suggested for strength-type athletes approximate 1.6-1.8 grams per

kilogram body weight, while recommended amounts for endurance athletes

approximate 1.2-1.6 grams per kilogram body weight (Lemon, 1996; 1995).

Such values may be obtained easily in a typical western diet with adequate
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animal and plant protein. In general, research with protein supplements in

excess of these dietary quantities has shown no beneficial effects on

strength, power, hypertrophy of muscle, or physiological work capacity

(Williams, 1998B). Amino acid supplements have also been marketed to

increase muscle mass and enhance aerobic endurance capacity via various

mechanisms.

Arginine and ornithine have been used in attempts to increase human

growth hormone (HGH) and/or insulin production, the theory being to

increase muscle mass and strength via enhanced hormonal activity. Limited

data are available, but a number of well-controlled studies, including several

with experienced weightlifters, reported that amino acid supplementation

elicited no significant increases in serum HGH, insulin levels, or various

measures of muscular strength or power (Fogelholm, 1993; Kreider et al.,

1993; Williams, 1998B).

Potassium and magnesium aspartates are salts of aspartic acid, an amino

acid. They have been used as ergogenics, possibly by mitigating the

accumulation of ammonia during exercise. The effect of aspartate

supplementation on physical performance is equivocal, but about 50 percent

of the available studies have indicated enhanced performance (Williams,

1998A). Additional research is needed to study their potential ergogenicity

and underlying mechanisms.

Tryptophan (TRYP) and branched chain amino acids (BCAA) are thought to

affect the formation of serotonin, a neurotransmitter believed to be involved

in the etiology of central nervous system (CNS) fatigue during exercise.

However, according to proponents of either TRYP or BCAA supplementation,

the hypotheses underlying the serotonin effect on the development of

fatigue are diametrically opposite.

In one hypothesis, TRYP serves as a precursor for serotonin, a brain

neurotransmitter theorized to suppress pain. Free tryptophan (fTRYP) enters

the brain cells to form serotonin. Thus, TRYP supplementation has been

used to increase fTRYP and serotonin production in attempts to increase

tolerance to pain during intense exercise, thus delaying fatigue. Limited data

involving TRYP supplementation are available, but one study reported

significant improvements in time to exhaustion at 80 percent VO2max,

accompanied by significant reductions in the psychological rating of

perceived exertion (RPE). However, research with a more appropriate

experimental design did not replicate these findings when subjects ran to

exhaustion at 100 percent VO2max. Moreover, other investigators reported

no effect of TRYP supplementation on aerobic endurance performance at 70-

75 percent VO2max (Williams, 1998B). In a recent review, Wagenmakers

(1997) concluded that TRYP supplementation had no effect on endurance

performance.

Relative to the second hypothesis, some investigators believe that increased

levels of serotonin may induce fatigue by depressing central nervous system

functions (Newsholme et al., 1992). During prolonged aerobic endurance

exercise, muscle glycogen may become depleted and the muscle may

increase its reliance on branched chain amino acids (BCAA) for fuel,

decreasing the plasma BCAA:fTRYP ratio. Because BCAA compete with fTRYP

for entry into the brain, a low BCAA:fTRYP ratio would facilitate the entry of

fTRYP to the brain, increasing serotonin formation and inducing fatigue.

Hypothetically, BCAA supplementation may delay fatigue in prolonged

aerobic endurance events by maintaining a high BCAA:fTRYP ratio to

mitigate the formation of serotonin. Although several studies support this

hypothesis both Wagenmakers (1997) and Davis (1996), in recent reviews,

concluded not enough evidence indicates BCAA supplementation is

ergogenic. Davis also noted that carbohydrate supplementation during

exercise, by delaying the reliance on BCAA as a fuel, would serve the same

purpose as BCAA supplementation.

Vitamins

Research indicates that a vitamin deficiency may adversely affect physical

performance, but the overall review of the literature supports the viewpoint

that vitamin supplements are unnecessary for physically-active individuals
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who are on a well-balanced diet with adequate calories. Most studies report

that athletes who consume high calorie diets containing the RDA of all

nutrients have few vitamin or mineral deficiencies (Armstrong and Maresh,

1996). Several excellent studies have shown that multivitamin/mineral

supplementation over prolonged periods, up to eight months, have no

significant effects on both laboratory and sport-specific tests of physical

performance (Singh et al., 1992; Telford et al., 1992). Nevertheless,

vitamin/mineral supplementation may be recommended for athletes

consuming a low-calorie diet for weight control sports (Williams, 1998B).

Some studies have shown that specific vitamins supplements may benefit

sports performance in events where excess anxiety may be disruptive. For

example, thiamin (B1), pyridoxine (B6), and cobalamin (B12)

supplementation has been shown to enhance performance in pistol shooting,

possibly because of beneficial effects on brain neurotransmitter functions

(Bonke, 1986). Additional research is merited.

Supplementation with several antioxidant vitamins (beta-carotene; vitamin

C; vitamin E) has been theorized to prevent muscle tissue damage

associated with generation of oxygen free radicals during high-intensity

exercise. However, recent reviews suggest that research regarding the value

of antioxidant therapy for athletes is ambivalent. Some reviewers (Goldfarb,

1993; Kanter, 1995) note that further investigations are needed to

determine the viability of antioxidant supplements in preventing exerciseinduced lipid peroxidation and muscle damage. Conversely, other reviewers

(Dekkers et al., 1996; Packer, 1997) indicate substantial research suggests

that dietary supplementation with antioxidant vitamins has favorable effects

on lipid peroxidation and exercise-induced muscle damage. All reviewers

indicate more research is needed to address this issue and to provide

guidelines for recommendations to athletes.

Antioxidant vitamins, particularly vitamins C and E, have also been

theorized to enhance sport performance. Although vitamin C

supplementation has been shown to improve physical performance in

vitamin C-deficient subjects, research supports the general conclusion that

vitamin C supplementation does not enhance physical performance in wellnourished individuals (Gerster, 1989). Vitamin E supplementation may

increase tissue or serum vitamin E concentration, but a recent review

indicates that there is no discernable effect on training or performance in

either recreational or elite athletes (Tiidus and Houston, 1995).

Nevertheless, Packer (1997) indicates that if antioxidant supplementation

ameliorates exercise-induced muscle tissue damage, such supplementation

may be beneficial in the long term. Additionally, some studies have shown

that vitamin E supplementation may enhance exercise performance at

altitude, but confirming research is needed (Williams, 1998B).

Minerals

As with vitamins, research indicates that a mineral deficiency may adversely

affect physical performance. Iron deficiency is the most common mineral

deficiency among athletes, particularly female athletes in weight-control

sports, and curing an athlete's iron-deficiency anemia with iron

supplementation will return performance to normal. However, in general,

research also indicates that mineral supplements, including

multivitamin/mineral compounds, are unnecessary for physically-active

individuals who are on a well-balanced diet with adequate calories.

Several minerals have been marketed as potent anabolic agents. Chromium

is an insulin cofactor, and its theorized ergogenic effect is based on the role

of insulin to facilitate BCAA transport into the muscle. Chromium has been

advertised for strength-type athletes. The available research with chromium

is limited, and the data available have not been subjected to a critical

scientific review. Some early research data do suggest an increase in lean

body mass and decreased body fat with chromium picolinate

supplementation (Evans, 1989). However, this report was based on flawed

studies. More contemporary research with better experimental protocols

replicated these studies and have shown that chromium picolinate

supplementation does not increase lean muscle mass or decrease body fat

(Clancy et al., 1994; Hallmark et al., 1996; Trent and Thieding-Cancel,
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1995). Other research also indicated different forms of chromium, such as

chromium chloride, had no effect on body composition (Lukaski et al.,

1996). Boron and vanadium have also been advertised for their anabolic

potential. However, the limited data available do not support an anabolic

effect of either boron (Ferrando and Green, 1993) or vanadium (Fawcett et

al., 1996).

Phosphorus is an essential nutrient present in the diet as a phosphate salt,

or phosphate. Phosphate is a component of several high energy compounds,

is essential for the functioning of several B vitamins, and is part of 2,3-

DPG, essential for oxygen release from hemoglobin. An increased 2,3-DPG

level is the prevalent theory underlying phosphate supplementation to

endurance athletes. Current research is equivocal as to whether or not

phosphate loading may improve physiological functions important to

endurance performance. However, no study has reported decreases in

performance, and several recent studies from independent laboratories have

shown remarkable similarities relative to increased levels of VO2max (about

10%) following phosphate supplementation. Increases in physical

performance have also been documented in four of these studies (Cade et

al., 1984; Kreider et al., 1990; Kreider et al., 1992; Stewart et al., 1990).

However, a number of confounding variables in previous research have been

identified and more controlled research has been recommended (Tremblay

et al., 1994).

Food drugs

Although doping (the use of pharmacological ergogenics to improve sports

performance) is prohibited, the International Olympic Committee does

permit limited use of several nutritionally-related drugs, such as caffeine,

alcohol, and alkaline salts.

Caffeine, found naturally in certain foods or beverages, such as cocoa,

coffee, and cola drinks, consumed by athletes, has been studied extensively

for its ergogenic potential. Caffeine is a stimulant that may improve various

metabolic and psychological functions during exercise, and several recent

reviews indicate that legal doses of caffeine may enhance performance in a

variety of exercise tasks (Graham and Spriet, 1996; Spriet, 1995). Many

studies that have evaluated the ergogenic effect of caffeine on prolonged

aerobic endurance tasks greater than one hour have shown beneficial

effects. For example, a series of studies from Guelph University in Canada

has suggested caffeine may enhance prolonged aerobic endurance

performance through increased levels of epinephrine and sparing of muscle

glycogen (Graham and Spriet, 1991; Spriet, et al., 1992). Other recent

research suggests caffeine may exert an ergogenic effect in shorter

endurance events through neurological mechanisms. For example, caffeine

supplementation has been shown to improve performance in a 1,500-meter

run, an event which is not dependent on muscle glycogen sparing (Wiles et

al., 1992), and caffeine supplementation also has increased work output on

a cycle ergometer at a set RPE (Cole, et al., 1996). Because caffeine

appears to be an effective ergogenic in legal doses, some investigators have

suggested the IOC should reconsider the legal limits determinant for a

positive drug test (Spriet, 1995)

Alkaline salts, such as sodium bicarbonate and sodium citrate, are described

as antacids in the United States Pharmacopeia (USP) and have been studied

as nutritional ergogenics. Taken orally prior to high-intensity anaerobic

exercise, alkaline salts may increase the alkaline reserve and help buffer

lactic acid in the muscle cell, an effect that theoretically could improve

performance in exercise tasks dependent primarily on anaerobic glycolysis.

Research indicates that alkaline salt supplementation will increase the serum

pH and may enhance performance in exercise tasks, particularly repetitive

exercise tasks, that maximize energy production for 1-6 minutes. Numerous

laboratory and field studies support a positive ergogenic effect of sodium

bicarbonate supplementation, and several comprehensive reviews

(Linderman and Fahey, 1991; Williams, 1992), including a meta-analysis

reporting an effect size greater than 0.40 favoring sodium bicarbonate when

compared to placebo conditions (Matson and Tran, 1993), conclude that

sodium bicarbonate is an effective ergogenic. Studies conducted subsequent

to these reviews have provided mixed results but, in general, about half of
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these more recent studies have revealed ergogenic effects of sodium

bicarbonate or sodium citrate on exercise performance. Some beneficial

effects have even been noted on prolonged aerobic endurance tasks, a

finding that merits additional research (Williams, 1998B)

Dietary supplements

Numerous dietary supplements are marketed to physically-active individuals.

Advertisements insinuate that such supplements may improve energy

production, increase muscle mass, decrease body fat, or induce some other

possible ergogenic outcome. By and large, many commercial products have

not been studied scientifically to validate such advertising claims. However,

some data are available for several specific ingredients marketed individually

or as part of a multiple-ingredient product. Choline - Choline, an amine, is

found naturally in a variety of foods. A sports drink powder containing

carbohydrates, electrolytes, and choline has been marketed recently.

Choline is involved in the formation of acetylcholine, a neurotransmitter

whose reduction in the nervous system may be theorized to be a

contributing factor to the development of fatigue. Because plasma choline

levels have been reported to be significantly reduced following events such

as marathon running, choline supplementation has been theorized to

prevent fatigue in aerobic endurance tasks. Research has shown that choline

supplementation will increase blood choline levels at rest and during

prolonged exercise, and some preliminary field and laboratory research has

suggested increased plasma choline levels are associated with a significantly

decreased time to run 20 miles. However, other well-controlled laboratory

research has revealed that choline supplementation, although increasing

plasma choline levels, exerted no effect on either brief, high-intensity

anaerobic cycling tests or more prolonged aerobic exercise tasks (Williams,

1998B). These findings are equivocal and reviewers have recommended

more research with choline supplementation, particularly research involving

prolonged aerobic endurance exercise tasks (Kanter and Williams, 1995).

Coenzyme Q10 (Ubiquinone) - Coenzyme Q10 (CoQ10), also known as

ubiquinone, is a lipid with characteristics common to a vitamin. CoQ10 is

found in the mitochondria in all tissues, particularly the heart and skeletal

muscles. CoQ10 is also an antioxidant. CoQ10 supplementation has been

used therapeutically for the treatment of cardiovascular disease because it

may improve oxygen uptake in the mitochondria of the heart. Theoretically,

improved oxygen usage in the heart and skeletal muscles could improve

aerobic endurance performance.

Although research data suggests CoQ10 supplementation may benefit

cardiac patients, several studies have shown that CoQ10 supplementation to

healthy young or older physically-active subjects did not influence lipid

peroxidation, heart rate, VO2max, or cycling endurance performance (Braun,

et al., 1991; Laaksonen, et al., 1995; Snider, et al., 1992; Weston, et al.,

1997). One study reported that CoQ10 supplementation was associated with

muscle tissue damage and actually impaired cycling performance compared

to the placebo treatment (Malm, et al., 1996).

Creatine - Creatine is a nitrogen-containing substance, found naturally in

small amounts in animal foods. Acute oral creatine supplementation, daily as

creatine monohydrate for approximately 5-7 days, has been reported to

increase muscle concentrations of total creatine, both as free creatine and

creatine phosphate, a high-energy phosphagen. Several reviews indicate

creatine supplementation may be an effective sport ergogenic (Balsom, et

al., 1994; Greenhaff, 1995). Subsequent to these reviews, numerous

studies have reported a positive ergogenic effect of creatine

supplementation, particularly in repetitive, short-duration, high-intensity,

short-recovery isokinetic and isometric resistance tests or cycle ergometer

protocols. However, in such tests, although some body parts are exercising,

the total body mass is stationary. Thus, the ergogenic effect of acute

creatine supplementation may be limited to laboratory tasks in which the

body mass does not need to be moved. Acute creatine supplementation also

appears to increase body mass (Williams and Branch, 1998). In exercise

tasks in which the body mass is moved, research generally has not

supported an ergogenic effect of creatine supplementation on sprint swim
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performance (Burke, et al., 1996) or sprint run performance (Redondo, et

al., 1996), and actually may be ergolytic (impair performance) in endurance

running because of the acute increase in body mass (Balsom et al., 1993),

which may simply be water associated with the oncotic effect of creatine in

the muscle. Creatine supplementation has been shown to improve rowing

performance (Rossiter et al., 1996), an exercise task in which the body

mass is supported, and may theoretically enhance performance in cycling

tasks for similar reasons.

Although acute creatine supplementation may enhance exercise performance

under certain laboratory conditions, more research is needed to evaluate its

efficacy to enhance actual sports performance. Additionally, well-controlled

research is needed to evaluate the effect of chronic creatine

supplementation on the training response and subsequent competitive sport

performance.

Ginseng - Extracts derived from the plant family Araliaceae contain

numerous chemicals that may influence human physiology, the most

important being the glycosides, or ginsenosides. Collectively, these extracts

are referred to as ginseng. Numerous commercial forms of ginseng products

are available, including Chinese or Korean (Panax ginseng), American

(Panax quinquefolium), and Russian/Siberian (Eleutherococcus senticosus),

but the ginseng content may vary considerably (Cui et al., 1994).

Ginseng supplementation has been theorized to mitigate the stress of

exercise and possess ergogenic qualities, but the underlying mechanisms

have not been determined. Although some earlier studies reported

ergogenic effects of ginseng supplementation on exercise performance, a

recent comprehensive review by Bahrke and Morgan (1994) indicated that

ginseng research with humans has been characterized by numerous

methodological and statistical shortcomings. They concluded, in 1994, that

there is an absence of compelling research evidence demonstrating the

ability of ginseng to consistently enhance physical performance in humans,

and that there remains a need for well-designed research.

Several well-controlled studies subsequent to the review by Bahrke and

Morgan reported no significant effect of either Panax ginseng,

Eleutherococcus senticosus Maxim L (regarded to be Siberian Ginseng), or a

standardized ginseng extract on cardiovascular, metabolic, or psychologic

responses to either submaximal or maximal exercise performance, or on

maximal performance capacity (Dowling, et al., 1996; Engels and Wirth,

1997; Morris, et al., 1996).

Glycerol - Water ingestion is essential to help optimize body water balance

and body temperature regulation during exercise under warm environmental

conditions. Rehydration during exercise in the heat has been shown to

decrease physiological stress as evidenced by a decreased heart rate

response, lesser rise in the core temperature, and increased endurance

performance. Hyperhydration before exercise may also be helpful, but has

not been shown to be as effective as rehydration (Williams, 1998B). Glycerol

(glycerin), an alcohol byproduct of fat hydrolysis, has been studied as a

means to enhance the hyperhydration effect. Small amounts of glycerol are

mixed with water in set proportions and the water is consumed following

normal hyperhydration procedures. Glycerol capsules and a glycerolcontaining sports drink are marketed to athletes.

Glycerol-induced hyperhydration, when compared to water hyperhydration

alone, has been shown to increase total body water in some (Freund, et al.,

1995; Koenigsberg, et al., 1995), but not all (Latzka, et al., 1997) studies.

Several studies have shown that glycerol-induced hyperhydration improves

cardiovascular responses, temperature regulation, and cycling exercise

performance under warm/hot environmental conditions (Lyons, et al., 1990;

Montner, et al., 1996). However, other research has shown that both

glycerol and carbohydrate supplementation improved cycling endurance

compared to a placebo solution, suggesting carbohydrate supplementation

was as effective as glycerol supplementation as a means to enhance

performance (Lamb, et al., 1997). Additional research is needed to resolve

these equivocal findings, particularly so in sports such as distance running in

which the extra body mass (water weight) must be moved as efficiently as
PCPFS Research Digests

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possible.

Inosine - Inosine is a nucleoside with a variety of proposed ergogenic

effects, including enhancement of aerobic endurance performance by

facilitating the delivery of oxygen to the muscles during exercise. Although

scientific research is limited, two well-controlled studies did use the

recommended supplementation protocol for endurance athletes and reported

no beneficial effects of inosine on cardiovascular-respiratory or metabolic

functions during submaximal or maximal exercise, nor was there any effect

on time to complete a simulated three mile race on a treadmill. Both

studies actually suggested inosine could be ergolytic for certain athletic

endeavors involving anaerobic glycolysis (Starling, R., et al., 1996; Williams,

M., et al., 1990).

L-carnitine - L-carnitine is a vitamin-like compound found naturally in

animal foods, particularly meats, and may also be formed in the liver from

various amino acids. L-carnitine facilitates the transport of fatty acids into

the mitochondria for oxidation and also facilitates the oxidation of several

amino acids and pyruvate, functions that theoretically could lead to a

sparing of muscle glycogen during exercise and a decreased production of

lactate. However, recent reviews of the available research do not support an

ergogenic effect of L-carnitine supplementation on fuel utilization during

exercise, maximal heart rate, anaerobic threshold, maximal oxygen uptake,

time to exhaustion in various anaerobic or aerobic exercise tasks, or

performance in either a marathon or 20-kilometer run (Heinonen, 1996;

Wagenmakers, 1991; Williams, 1998B).

Summary

Adequate dietary intake of carbohydrate, essential fatty acids, protein,

vitamins, minerals and water is necessary to insure optimal physical

performance, because a deficiency of any essential nutrient associated with

energy production may impair physiological or psychological functions during

exercise. As may be discerned from this review, supplementation with

various essential nutrients or commercial dietary supplements will not, in

general, enhance exercise performance in well-nourished, physically-active

individuals. However, research tends to support an ergogenic effect for

some nutritional ergogenics (including alkaline salts, caffeine, carbohydrate

loading, and creatine) under certain conditions or for some athletes.

Additional research is needed to evaluate the possible ergogenic effects of

aspartate salts, choline, glycerol, MCT, phosphates, pyruvate, and certain

vitamins (antioxidants; B1, B6, B12; E) for specific conditions mentioned

above.

Caution is advised when using any nutritional ergogenic in an attempt to

enhance sport performance. As noted above, some products may impair

performance. Also, improper amounts may cause various health problems.

For example, supplements such as alkaline salts may cause gastrointestinal

distress and diarrhea while others, such as ephedrine, have been associated

with fatalities. Individuals who desire to use specific nutritional ergogenics

should consult a sports nutrition expert or physician, and also experiment

with their use in training before use in compe

Please note that the appropriate language for the citation of this resource

is: The President's Council on Physical Fitness and Sports Research Digest.

The President's Council on Physical Fitness and Sports

 The President's Council on Physical Fitness and Sports (PCPFS) was

established in 1956 through an Executive Order by President Dwight D.

Eisenhower as part of a national campaign to help shape up America's

younger generation. Today, the PCPFS serves as an advisory council to

the President and Secretary of the Department of Health & Human

Services on matters involving physical activity, fitness and sports to

enhance and improve the health of Americans of all ages.

 The PCPFS enlists the active support and assistance of individual

citizens, civic groups, private enterprise, and voluntary organizations to
PCPFS Research Digests

http://www.fitness.gov/publications/digests/digest_jun1998.html[12/3/2010 3:01:04 PM]

promote and improve the physical activity and fitness of all Americans

and to inform the public of the important link which exists between

regular activity and good health.

 Twenty (20) individuals from the sports, fitness and health fields are

appointed by the President to serve as members of the Council. They are:

Florence Griffith

Joyner, Co-Chair

Rancho Santa

Margarita, CA

Elizabeth Arendt,

M.D., St. Paul, MN

Jeff Blatnick,

Halfmoon, NY

Ralph Boston,

Knoxville, TN

Don Casey,

East Rutherford, NJ

Timothy Finchem,

Ponte Vedra

Beach, FL

Rockne Freitas, Ed.D.,

Honolulu, HI

Zina Garrison-Jackson,

Houston, TX

Jimmie Heuga,

Avon, CO

Calvin Hill,

Great Falls, VA

Jim Kelly,

Buffalo, NY

Judith Pinero Kieffer,

Los Angeles, CA

Deborah Slaner Larkin,

Pelham, NY

Ira Leesfield, Coral

Gables, FL

Albert Mead III,

Atlanta, GA

Jack Mills,

Columbia, SC

Kevin Saunders,

Corpus Christi, TX

Amber Travsky,

Laramie, WY

Executive

Director-Sandra

Perlmutter

Two (2) vacancies

200 Independence Avenue, S.W., Washington, DC 20201· (202) 690-9000·

FAX (202) 690-5211

Published quarterly by the

President's Council

on Physical Fitness

and Sports

Washington, D.C.

Melvin H. Williams,

PhD Eminent Scholar

Emeritus Department

of Exercise Science,

Physical Education

and Recreation

Old Dominion

University, Norfolk, VA

Co-edited by

Drs. Chuck Corbin

and Bob Pangrazi

Arizona State

University

 

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Physical Activity and Fitness Quote

First and foremost, a varied, healthful diet balanced in

energy and nutrient content is the nutritional mainstay for most

athletes. Although research suggests that a few forms of

nutrient supplementation may enhance physical performance

under specific circumstances, such supplements should

complement a healthful diet, not substitute for it.

Melvin H. Williams, PhD

Eminent Scholar Emeritus Department of Exercise Science,

Physical Education and Recreation Old Dominion University,

Norfolk, VA 23529-0196

Office (757) 683-3355 Fax (757) 683-4270 Home (757) 464-3044

E-mail Mwilliam@odu.edu

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