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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 well-nourished 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
high-intensity 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 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 power (PP), mental strength (MS),
or mechanical edge (ME) in well-nourished subjects.
Alkaline salts:
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PP - aerobic endurance
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Caffeine:
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PP - aerobic endurance
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Carbohydrates:
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PP - aerobic endurance
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Creatine:
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PP - muscular strength
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Water:
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PP - aerobic endurance during heat stress
conditions
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Alcohol:
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MS - neuromuscular relaxation
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Antioxidants
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ME - muscle tissue damage prevention
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Antioxidants
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PP - aerobic endurance
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Choline:
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PP - aerobic endurance
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Dihydroxyacetone pyruvate:
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PP - aerobic endurance
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Glycerol:
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PP - aerobic endurance
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Phosphates:
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PP - aerobic endurance
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Vitamin E:
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PP - aerobic endurance at altitude
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Vitamins B1,B6, B12
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MS - neuromuscular relaxation
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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)
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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)
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Carbohydrate and carbohydrate
metabolites
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 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 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 exercise-induced 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 well-nourished 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, 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 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 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 glycerol-containing 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 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 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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