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Athletes engaged in heavy endurance training often seek additional nutritional strategies to help maximize performance. Specific nutritional supplements exist to combat certain factors that limit performance beginning with a sound everyday diet. Research has further demonstrated that safe, effective, legal supplements are in fact available for today’s endurance athletes. Several of these supplements are marketed not only to aid performance but also to combat the immunosuppressive effects of intense endurance training. It is imperative for each athlete to research the legality of certain supplements for their specific sport or event. Once the legality has been established, it is often up to each individual athlete to decipher the ethics involved with ingesting nutritional supplements with the sole intent of improving performance. Key wordsExercise–Nutrition–Endurance–Supplements–Ergogenics
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11 Nutritional Supplements
for Endurance Athletes
Christopher J. Rasmussen
Athletes engaged in heavy endurance training often seek additional nutritional
strategies to help maximize performance. Specific nutritional supplements
exist to combat certain factors that limit performance beginning with a
sound everyday diet. Research has further demonstrated that safe, effective,
legal supplements are in fact available for today’s endurance athletes.
Several of these supplements are marketed not only to aid performance but
also to combat the immunosuppressive effects of intense endurance training.
It is imperative for each athlete to research the legality of certain supple-
ments for their specific sport or event. Once the legality has been established,
itisoftenuptoeachindividualathlete to decipher the ethics involved
with ingesting nutritional supplements with the sole intent of improving
Key words
Exercise Nutrition Endurance Supplements Ergogenics
The endurance athlete has special nutritional needs that go above
and beyond those of the normal sedentary individual. To optimize
performance the endurance athlete needs a solid foundation that
includes proper training and nutrition. Proper training should be
based on the principles of training and largely depends on the goals
of the individual athlete and the point in time within the training
cycle (preseason, in-season, postseason). Proper nutrition should
focus on a variety of whole foods that adequately meet the demands
of the athlete. Supplementing the diet with additional nutrients is
From: Nutritional Supplements in Sports and Exercise
Edited by: M. Greenwood, D. Kalman, J. Antonio,
DOI: 10.1007/978-1-59745-231-1_11, ÓHumana Press Inc., Totowa, NJ
becoming increasingly important for those engaged in heavy endur-
ance training because it is often difficult to obtain the proper amount
of macronutrients through whole foods alone. This chapter largely
addresses the specific nutritional needs of the endurance athlete and
more specifically nutritional supplements for the endurance athlete.
Several studies have documented that endurance athletes can
improve their training sessions and performance with a combination
of proper everyday nutrition and effective supplementation (17).
To gain a better understanding of how supplementation can
improve performance for the endurance athlete it is important to
realize what drives their performance. Therefore, the chapter begins
with a description of the factors associated with optimal perfor-
mance of the endurance athlete and the factors that limit their
performance. The second section focuses on specific supplements
for endurance athletes and how they can prepare the athlete for
action and enhance the training response. The third section dis-
cusses how supplementation can aid the immune system to keep it
functioning during even the most intense phases of training. The
fourth section briefly dives into additional legal and ethical issues.
Finally, a brief summary reviews the most important points of the
chapter and brings it to a close.
Various types of training are utilized by endurance athletes
depending on whether they are aiming to improve anaerobic capa-
city, maximal aerobic power (MAP)—power output when VO
is reached—or endurance capability. It is important to point out
that the term ‘‘endurance athlete’’ in athletic circles today tradition-
ally refers to those participating in running, cycling, swimming, and/
or combinations of these activities, although other activities may
certainly be considered. Combinations of training including speed,
interval, tempo, resistive, and long slow distance (LSD) are common
for the endurance athlete. Manipulating the principles of training
depending on the overall goals while coinciding with the respective
training season helps optimize training and subsequent performance.
The nutritional supplements discussed in this chapter focus primarily
370 Rasmussen
on their effectiveness, or lack thereof, in athletes who are involved in
running, cycling, and/or swimming events.
Prior to discussing specific supplements for endurance athletes, it is
important to understand the factors that limit endurance performance.
Dehydration, the depletion of muscle glycogen, and limited blood
glucose availability can all play a role in fatigue during long-duration
aerobic exercise. The body transfers heat to the environment through
conduction, convection, radiation, evaporation, or a combination of
these methods. Conduction involves the transfer of heat from one
material to another through direct molecular contact, and convection
is the transfer of heat from one place to another by the motion of a gas
or a liquid across the heated surface. Radiation involves the dissipation
of heat in the form of infrared rays, and evaporation is best defined as
the evaporation of sweat from the skin’s surface.
Evaporation is the primary avenue for heat dissipation during
exercise, accounting for roughly 80% of the total heat loss during
exercise. With prolonged exercise or exercise in a hot and humid
environment, blood volume is reduced by a loss of water through
sweat. As exercise continues in a hot, humid environment, a redistribu-
tion of blood from the core to the periphery takes place to cool the
body. Cardiac filling is reduced as the total blood volume gradually
decreases with an increase in the duration of exercise. This leads to a
decrease in venous return to the right side of the heart. Subse-
quently, stroke volume is reduced. The heart rate then tries to
compensate for the decreased stroke volume by increasing in an
effort to maintain cardiac output. Collectively, these alterations are
referred to as the cardiovascular drift. The benefit of this phenom-
enon is that one is able to continue exercising at a low to moderate
intensity. The drawback is that the body is unable to compensate
fully for the decreased stroke volume at high exercise intensities
owing to the fact the heart rate attains its maximum value at a much
lower exercise intensity. A loss of body fluid equal to 1% of body
weight (approximately 2.0 lb for a 200 lb athlete) can significantly
reduce blood volume, placing undue stress on the cardiovascular
system and limiting physical performance (8).Whendehydration
reaches 4%, endurance athletes can experience heat cramps and
heat exhaustion (9); and when it reaches upwards of 6%, there may
be cessation of sweating, a rise in body temperature, and eventually
heat stroke (10).
Nutritional Supplements for Endurance Athletes 371
Collectively the depletion of muscle glycogen and the decline in
blood glucose can put a damper on endurance athletic performance.
Plasma fatty acids and muscle triglycerides are able to supply the
needed energy during low-intensity exercise (i.e., 25% VO
max) (11).
Carbohydrate use is relatively low and comes from blood glucose.
Exercise at lower intensities can be maintained for several hours
owing to the fact that the liver is able to continually supply glucose
to the working muscles. As the intensity of exercise increases, the
amount of carbohydrate necessary to keep pace with the increased
demand also increases. A combination of blood glucose and muscle
glycogen contributes a large percentage of the energy requirements
at moderate exercise intensities (i.e., 65% VO
max) (11). At the
beginning of exercise, muscle glycogen is the preferred fuel source;
but as these levels decline there is increased dependence on blood
glucose by the exercising muscles. Higher-intensity exercise (85%
max) is performed at a level that promotes an even higher rate
of muscle glycogen breakdown and carbohydrate oxidation (11).
This results in an accelerated rate of lactic acid production and
ultimately accumulation in muscle and blood. Contrary to popular
belief, lactic acid and lactate—the scapegoats for the pain athletes
experience—are not responsible for all the ills for which they are
blamed (see sidebar: The Truth About Lactate). Higher-intensity
exercise represents the highest level an athlete can maintain for
approximately 60 minutes. At these high intensities, carbohydrate
oxidation accounts for more than two-thirds of the required energy,
with the remainder coming from a combination of plasma fatty
acids and intramuscular triglycerides. Given the fact that most
competitive endurance athletes often train and compete at a higher
intensity, it is easy to reason why the depletion of muscle glycogen
and subsequent decline in blood glucose can be such a deterrent to
endurance athletic performance. Maintaining adequate hydration
and energy supplies is therefore essential to the performance of the
endurance athlete.
2.1. The Truth About Lactate
Lactic acid and lactate are not the same compound. Lactate is any
salt of lactic acid that enters the blood during high-intensity efforts.
Recall that lactic acid is a by-product of glycolysis. Although most
372 Rasmussen
people believe that it is responsible for fatigue and exhaustion dur-
ing all types of exercise, lactic acid accumulates in muscle fibers only
during relatively brief high-intensity efforts. Athletes, and endur-
ance athletes in particular, have been told for years that the primary
reason they cannot ‘‘push’’ any more during intense exercise is that
lactic acid has built up in their muscles. This is not entirely true, and
there is evidence to disprove it. It is possible to experience muscle
fatigue while the lactic acid concentration in the muscle remains low.
Marathon runners, for example, may have near-resting lactic acid
versely, there can be an absence of fatigue when the lactic acid
concentration in the muscle is high. Exhausting isometric efforts
with the quadriceps, for example, can cause fatigue and ultimately
terminate the exercise. Minutes after completion the athlete can
once again produce the initial force despite the fact that the degree
of acidity in the muscles decreases to normal rather slowly. There-
fore, it is difficult to accept the idea that an increase in lactic acid
in the muscle causes fatigue as a high degree of acidity without
fatigue can be observed. Lactate can also serve as an important fuel
source by other tissues by converting it to pyruvate and oxidizing it
in the mitochondria. For example, during exercise lactate serves as
a significant fuel source for the heart (12). Therefore, the fatigue
experienced by the endurance athlete is largely caused by a combi-
nation of dehydration and inadequate energy supplies, not excess
lactic acid.
To combat the damaging and depleting effects of intense endur-
ance training and further help the body respond to training, a well
planned diet and supplement strategy that meets energy intake needs
and incorporates proper timing of essential nutrients is vital. It is
important to differentiate between the two popular terms ‘‘supple-
ments’’ and ‘‘ergogenic aids’’ when discussing athletes and nutrition.
Although the two are often used interchangeably, there are subtle
differences. A nutritional supplement is usually thought of as some-
thing that completes or makes an addition to something else. On
the other hand, the scientific literature refers to substances that
Nutritional Supplements for Endurance Athletes 373
athletes use to help enhance performance as ergogenic aids or sports
ergogenics. The term ergogenic is derived from the Greek words ergon
(work) and gennan (to produce). Thus, an ergogenic usually refers to
something that produces or enhances work. To avoid confusion, this
chapter uses the two terms interchangeably, although specific clas-
sifications of the sports ergogenics are mentioned. Countless supple-
ments now exist for athletes of all kinds. This chapter addresses
the most popular nutritional supplements available to endurance
athletes today.
Nutritional ergogenic aids serve as the foundation for endurance
performance and primarily include the macronutrients and micro-
nutrients. Athletes that do not consume enough calories and/or do
not consume enough of the right type of calories may hinder training
adaptations and subsequent performance. However, athletes who
consume a well planned diet during training can help the body adapt
to training and more than likely notice improved performance.
Furthermore, maintaining a diet that is deficient of the essential
macronutrients over time may lead to a loss of body mass and muscle
mass, increased susceptibility to illness, and an increase in the symp-
toms associated with overtraining. Practicing good dietary habits on a
daily basis is essential to help optimize training adaptations and
subsequent performance.
Preexercise nutrition should consist largely of moderate to low
glycemic index (GI) foods/supplements (Table 1) that provide a
slow, sustained release of carbohydrates and protein necessary to
fuel a workout (see sidebar: What Is the Glycemic Index?). It gen-
erally takes about 4 hours for dietary carbohydrate to be digested
and begin to be stored as muscle and liver glycogen. Thus, preex-
ercise meals should be consumed about 4 to 6 hours prior to exercise
(13). Putting this into an average everyday scenario means that for
an athlete who trains in the afternoon breakfast is the most impor-
tant meal to top off muscle and liver glycogen levels. If the athlete
trains first thing in the morning, the meal the evening before is vital.
Recent research has also indicated that ingesting a light carbohy-
drate and protein snack 30 to 60 minutes prior to exercise (e.g., 50 g
carbohydrate and 5–10 g protein) further increases carbohydrate
availability toward the end of an intense exercise bout owing to
the slight increase in glucose and insulin levels (14,15). This can
serve to increase the availability of amino acids and decrease
374 Rasmussen
Table 1
Partial list of the glycemic index of foods using glucose as the standard
Low GI Moderate GI High GI
Food GI Food GI Food GI
Chana dal 8 Apple juice 40 Life Savers
Peanuts 14 Snickers
41 White bread 70
Plain yogurt 14 Peach 42 Bagel 72
Soy beans 18 Pudding 43 Watermelon 72
Rice bran 19 Pinto beans 45 Graham
Peas 22 Orange juice 46 French fries 75
Cherries 22 Baked beans 48 Total
Barley 25 Strawberry jam 51 Vanilla wafers 77
Grapefruit 25 Sweat potato 54 Gatorade
Kidney beans 27 Pound cake 54 Fava beans 79
Link sausages 28 Popcorn 55 Jelly beans 80
Black beans 30 Brown rice 55 Tapioca
Lentils 30 Fruit cocktail 55 Rice cakes 82
Butter beans 31 Pita bread 57 Team Flakes
Soy milk 31 PowerBar
58 Pretzels 83
Lima beans 32 Honey 58 Corn Chex
Skim milk 32 Blueberry
59 Corn flakes
Split peas 32 Shredded wheat 62 Baked white
Fettucini 32 Black bean
64 Mashed
Chickpeas 33 Macaroni and
64 Dark rye 86
33 Raisins 64 Instant rice 87
Chocolate milk 34 Canteloupe 65 Crispix
Vermicelli 35 Mars Bar
65 Boiled Sebago 87
Whole wheat
37 Rye bread 65 Rice Chex
(Continued )
Nutritional Supplements for Endurance Athletes 375
exercise-induced protein catabolism (1416). Insulin inhibits protein
degradation and apparently offsets the catabolic effects of other
hormones (e.g., cortisol) (17). Anabolic actions of insulin appear
to be related to its nitrogen-sparing effects and promotion of nitro-
gen retention (17). The choice of foods and supplements selected is
largely up to individual athlete and their personal preferences. It is
recommended that the endurance athlete consume something famil-
iar on the day of competition rather than experimenting with a new
food or supplement.
3.1. What Is the Glycemic Index?
The glycemic index (GI) is a ranking of foods based on their
postprandial blood glucose response compared to a reference
food, either glucose or white bread. The GI concept was first devel-
oped in 1981 to help determine which foods were best for people
with diabetes. The GI of a food is based on several factors, including
the physical form of the food, the amylose/amylopectin ratio (two
types of starch), sugar content, fiber content, fat content, and the
acidity of a food. The index consists of a scale from 0 to 100 with 0
Table 1
Low GI Moderate GI High GI
Food GI Food GI Food GI
Apple 38 Pineapple 66 Gluten-free
Pear 38 Grapenuts
67 Baked red
Tomato soup 38 Angel food cake 67 French
Ravioli 39 Stoned wheat
67 Peeled Desiree 101
Pinto beans 39 Taco shells 68 Dates 103
Plums 39 Whole wheat
69 Tofu frozen
GI, glycemic index
376 Rasmussen
(water) representing the lowest ranking and 100 (pure glucose) the
highest ranking. The GI is obtained through use of an oral glucose
tolerance test (OGTT) utilizing 50 g of carbohydrate from the test
food. Blood samples are then obtained periodically throughout a
2-hour time period, glucose levels are measured, and the area under
the curve is calculated (18).
The GI of a carbohydrate has a profound effect on subsequent
glucose and insulin responses. High-GI carbohydrates (i.e., dex-
trose, maltose) produce large increases in glucose and insulin levels.
Moderate-GI carbohydrates (i.e., sucrose, lactose) traditionally
produce only modest increases in glucose and insulin. Finally, low-
GI carbohydrates (i.e., fructose, maltodextrin) have little if any
effect on glucose and insulin responses. It has been suggested that
manipulating the GI of a sports supplement may optimize carbohy-
drate availability for exercise, particularly prolonged intense exer-
cise. Caution should be used when applying the GI to whole foods
that contain several ingredients. The GI is more accurate for indivi-
dually packed foods/supplements because of the fewer ingredients
and the standardization that exists with the processing of these
snacks/supplements. The GI is not as applicable to whole foods/
meals and has not been established for many of these whole foods/
Nutrition during an intense endurance training session can aid
in the quality of the workout especially if the workout exceeds 60
to 90 minutes. Nutrition during exercise for the endurance athlete
usually centers on supplementation more than pre- and postexercise
nutrition if for no other reason than the convenience supplements
provide. Convenience supplements include glucose-electrolyte solu-
tions (GES), meal replacement powders (MRPs), ready-to-drink
supplements (RTDs), energy bars, energy gels, and fitness waters.
They are typically fortified with various amounts of vitamins and
minerals and differ on the amount of carbohydrate, protein, and fat
they contain. The beneficial effects of solid and liquid carbohydrate/
protein supplements are similar when thermal stress is not a factor.
Liquid supplements do provide the added benefits of aiding
rehydration and tend to digest easier for most athletes while exercis-
ing. Cyclists can generally empty from the stomach up to 1000 ml of
fluid per hour, and therefore 40 to 60 g of carbohydrate can be easily
ingested while consuming a large volume of fluid (19). On the other
Nutritional Supplements for Endurance Athletes 377
hand runners generally consume less than 500 ml of fluid per hour
(20). This is because of the difficulty of drinking on the run and the
potential discomfort of running with a full stomach. Therefore,
runners tend to use more concentrated solutions than do cyclists in
order to consume adequate amounts of carbohydrate. For cyclists, a
carbohydrate solution of 4% to 6% is generally sufficient when fluid
replacement is important. For runners, this concentration may have
to be 8% to 10% to provide adequate carbohydrate. Glucose con-
centrations in excess of 10% seem to delay gastric emptying and
compromise fluid replacement (Fig. 1). Adequate sodium intake is
also important to combat potential electrolyte imbalances during
exercise. Most GES solutions contain sufficient quantities of
sodium. If sodium is lacking in the supplement, however, electrolyte
tablets (i.e., Heat Guard) are also available. The bottom line is that
rapid nutrient availability is especially important during a workout
to maintain energy levels and training intensity. Thus, high-GI
sources should make up most of the supplements ingested during
an endurance-type workout. Once again, athletes should experiment
with different formulations to find the one that works best for them
prior to competition.
Fig. 1. Effect of carbohydrate (CHO) concentration on the rate of gastric
emptying of fluids and carbohydrate from the stomach during exercise. Car-
bohydrate concentrations of 8% to 10% maximize carbohydrate gastric emp-
tying without substantially reducing fluid delivery. From Gisolfi and Lamb
(100), with permission.
378 Rasmussen
It is now well established that with prolonged continuous exercise
the time-to-fatigue at moderate submaximum exercise intensities is
related to preexercise muscle glycogen concentrations—thus the
importance of everyday nutrition along with preexercise nutrition
(21). In addition, a GES has been the recommended supplement of
choice for decades during exercise to preserve muscle glycogen and
maintain blood glucose levels. With short-term, high-intensity exer-
cise, the relation between the availability of muscle glycogen and
performance is less clear. One study that utilized 15 high-intensity
6-second bouts on a cycle ergometer concluded that a high carbohy-
drate regimen over 48 hours helped subjects maintain a higher
power output than did the exercise and dietary regimen that
included a low carbohydrate content (22). This study demonstrated
the importance of a high carbohydrate diet in relation to short-term,
high-intensity exercise.
Recent research has shown that the addition of protein can have
added benefits to a supplement ingested during exercise by reducing
muscle protein degradation and speeding postexercise recovery.
Carbohydrate and protein intake significantly alters circulating
metabolites and the hormonal milieu (i.e., insulin, testosterone,
growth hormone, cortisol) as well as the response of muscle protein
and glycogen balance (23). Furthermore, the addition of protein
to a carbohydrate supplement enhances the insulin response of a
carbohydrate supplement compared to a placebo (24), which can
ultimately lead to performance gains (25).
Saunders et al. (7) examined the effects of a carbohydrate-
protein beverage on cycling endurance and muscle damage. They
utilized 15 male cyclists who were randomly administered either a
carbohydrate or carbohydrate-protein beverage (4:1 ratio) every
15 minutes during exercise and immediately upon completion of a
ride to volitional exhaustion. The carbohydrate-protein beverage
produced significant improvement in time-to-fatigue and reduction
of muscle damage in the selected endurance athletes. The authors
concluded that the benefits observed were the result of a higher total
caloric content of the carbohydrate-protein beverage or were due to
specific protein-mediated mechanisms.
Controversy exists among numerous studies examining the addition
of protein due to the fact that such addition increases the total caloric
content of the supplement. Anytime a larger amount of calories is
Nutritional Supplements for Endurance Athletes 379
consumed an athlete is likely to perform and recover more rapidly.
Therefore, when examining studies that are not based on isocaloric
data, one should give them careful consideration.
Whey is the preferred protein to ingest during exercise because of
its rapid absorption rates and the fact that is contains all of the
essential amino acids (refer to Table 3) as well as a high percentage
of leucine and glutamine, which are amino acids the body uses
during sustained exercise (26). High-GI carbohydrates (glucose,
sucrose, maltodextrin) should be combined with the protein in a
4:1 ratio to provide optimal benefits. Table 2 gives an example of the
ideal nutrient composition for a sports drink during exercise (27).
Sports drinks such as that shown in Table 2 should be ingested every
20 minutes during an endurance training session to help improve
performance and reduce muscle protein breakdown.
Postexercise nutrition for the endurance athlete is vital to restore
muscle glycogen stores, enhance skeletal muscle fiber repair and
growth, and maintain overall health and wellness. After an intense
exercise bout, the body is in a catabolic state (thus key muscle
Table 2
Ideal Nutrient Composition for a Sports Drink During Exercise
Nutrient objectives
Replace fluids and electrolytes
Preserve muscle glycogen
Maintain blood glucose levels
Maintain hydration
Minimize cortisol increases
Set the stage for a faster recovery
Satisfy thirst
Ideal composition (per 12 oz water)
High-glycemic carbohydrates (e.g., glucose, sucrose, maltodextrin):
20–26 g
Whey protein: 5–6 g
Vitamin C: 30–120 g
Vitamin E: 20–60 IU
Sodium: 100–250 mg
Potassium: 60–120 mg
Magnesium: 60–120 mg
Adapted from Ivy and Portman (27), with permission
380 Rasmussen
nutrients are being broken down). However, the opportunity exists
to alter the catabolic state into a more anabolic hormonal profile
where the athlete begins to rebuild muscle and thus initiates a much
faster recovery. Exercise that results in glycogen depletion activates
glycogen synthase, the enzyme responsible for controlling the trans-
fer of glucose from UDP-glucose to an amylase chain (28,29). This
also happens to be the rate-limiting step of glycogen formation. The
degree of glycogen synthase activation is influenced by the extent of
glycogen depletion (28). Complete resynthesis of muscle glycogen,
however, ultimately depends on adequate carbohydrate intake. Car-
bohydrates composed of glucose or glucose polymers are the most
effective for replenishing muscle glycogen, whereas fructose is most
beneficial for replenishing liver glycogen (30,31). Glucose and fruc-
tose are metabolized differently. They have different gastric empty-
ing rates and are absorbed into the blood at different rates (29,32).
Furthermore, the insulin response to a glucose supplement is gen-
erally much greater than that of a fructose supplement (33). The
fact that approximately 79% and 14% of total carbohydrate is
stored in skeletal muscle and the liver, respectively, is further indica-
tion of the importance of consuming glucose or glucose polymers
after exercise (13).
Blom et al. (34) found that ingestion of glucose and sucrose was
twice as effective as fructose for restoring muscle glycogen. The
maximum stimulatory effect of oral glucose intake on post-exercise
muscle glycogen synthesis was reached at a dose of 0.70 g/kg taken
every second hour following exercise in which the muscle glycogen
concentration was reduced by an average of 80%. In addition,
the rate of post-exercise muscle glycogen synthesis increases with
increasing oral glucose intake, up to a maximum rate of approxi-
mately 6 mmol/kg/hr. Blom et al. indicated that the differences
between glucose and fructose supplementation were the result of
the way the body metabolized these sugars. Fructose metabolism
takes place predominantly in the liver, whereas most glucose
appears to bypass the liver and is stored or oxidized by muscle (31).
Subsequent research by Burke and associates (35) found that the
intake of high-GI carbohydrate foods after prolonged exercise pro-
duces significantly more glycogen storage than consumption of low-
GI carbohydrate foods 24 hours after exercise. Although the meal
immediately after exercise elicited exaggerated blood glucose and
Nutritional Supplements for Endurance Athletes 381
plasma insulin responses that were similar for the low-GI and high-
GI meals, for the remainder of the 24 hours the low-GI meals elicited
lower glucose and insulin responses than the high-GI meals. As
previously mentioned, protein has shown additive effects to that of
carbohydrate alone in regard to the rate of muscle glycogen resynth-
esis and overall post-exercise recovery. The addition of protein to a
carbohydrate supplement increases insulin levels more than that
produced by carbohydrate or protein alone (36). Tarnopolsky
et al. showed that post-exercise carbohydrate and carbohydrate-
protein-fat nutritional supplements can increase glycogen resynth-
esis during the first 4 hours after exercise to a greater extent than
placebo for both men and women (37). The supplements adminis-
tered were both isoenergetic and isonitrogenous. Insulin has been
demonstrated to have profound anabolic effects on skeletal muscle.
In the resting state, insulin has been demonstrated to decrease the
rate of muscle protein degradation (38).
To summarize, in addition to the macronutrients selected, the
timing of nutrient ingestion can greatly affect the speed of recovery.
Research has clearly shown that muscle glycogen resynthesis occurs
more quickly if carbohydrate is consumed immediately following
exercise in contrast to waiting for several hours (39). Whereas most
of the everyday diet for the endurance athlete should be a low- to
moderate-GI diet, the post-exercise diet should be centered on mod-
erate- to high-GI sources. This nutritional approach has been found
to accelerate glycogen resynthesis and promote a more anabolic
hormonal state, which may speed recovery (37).
The increased protein and glycogen synthesis is believed to be due
to insulin secretion from the pancreas combined with an increase in
muscle insulin sensitivity (40). This was demonstrated in a study
(Fig. 2) showing that a carbohydrate-protein combination was
38% more effective in stimulating protein synthesis than a protein
supplement and more than twice as effective as a carbohydrate
supplement (41). Insulin appears to stimulate biosynthetic path-
ways that lead to increased glucose utilization, increased carbohy-
drate and fat storage, and increased protein synthesis. This metabolic
pattern is characteristic of the absorptive state. The rise in insulin
secretion during this state is responsible for shifting metabolic path-
ways to net anabolism (13). In contrast, when insulin secretion is
low, the opposite effect occurs. The rate of glucose entry into the
382 Rasmussen
cells is reduced and net catabolism occurs, rather than net synthesis
of glycogen, triglycerides, and protein. This pattern is reminiscent of
the postabsorptive state.
In addition to the major macronutrients, phosphorus, an essen-
tial mineral distributed widely in foods, may also be classified as
a nutritional sports ergogenic. Phosphorus is distributed widely in
foods, particularly meat, seafood, eggs, milk, cheese, whole-grain
products, nuts, and legumes. The Recommended Dietary Allowance
(RDA) is 800 mg for adults and 1200 mg for those 11 to 25 years of
age (42). Phosphate salts in both inorganic and organic forms play
important roles in human metabolism, particularly as related to
sports performance. They may influence all three human energy
systems by acting as intracellular buffers. Another theory suggests
that phosphate salts increase the formation of 2,3-diphosphoglycerate
(2,3-DPG), a compound in the red blood cells (RBCs) that facilitates
the release of oxygen to tissues.
An early study on phosphate loading examined highly trained
runners who took 1 g sodium phosphate four times daily for 6 days.
The phosphate salts increased the concentration of 2,3-DPG in
Protein Synthesis (mg/3 hr/leg)
Carbohydrate Protein Carb/Protein
Effect of Protein and Carbohydrate Alone and in Combination on Protein Synthesis Following
Fig. 2. Effect of protein and carbohydrate alone and in combination on
protein synthesis, measured after exercise. From Tarnopolsky et al. (37),
with permission.
Nutritional Supplements for Endurance Athletes 383
RBCs by 6.6%, which subsequently resulted in an increase in
max (43). This study also reported decreased production of
lactate and reduced sensation of physiological stress. A later study
utilizing highly trained crosscountry runners found that 1 g sodium
phosphate four times daily for 6 days resulted in a 10% increase in
max and an 11.8% increase in the anaerobic threshold (5). The
authors attributed the improvements in exercise performance to
increased metabolic efficiency. Well controlled studies support the
theory that phosphate salt supplementation may enhance function
of the oxygen energy system. Furthermore, studies show that phos-
phate salt supplementation increases VO
max and improves perfor-
mance in endurance exercise tasks, including a greater number of
stages completed in a progressive treadmill running test, increased
time-to-exhaustion on a bicycle ergometer, and a decreased time to
complete a 40-km cycling test (42). However, if phosphate salts are
in fact ergogenic, the underlying mechanism has yet to be deter-
mined (42). The scientific literature suggests that phosphates may
have an ergogenic effect on endurance athletes, but there is little
support for its effectiveness during anaerobic exercise (44). More
research with tight methodological control is needed to support
claims made in regard to phosphorus supplementation in both
aerobic and anaerobic events.
Another popular nutritional ergogenic aid is the branched-chain
amino acids (BCAAs): leucine, isoleucine and valine. They are
prevalent in both protein/meal replacement powders and energy
drinks. Table 3 shows the typical amino acid composition of some
common protein preparations. The RDA for BCAAs is less than 3 g
per day, although supplementation studies frequently utilize 5 to
20 g per day in tablet form and 1 to 7 g per liter in solutions (42). The
theory behind BCAA supplements relates to a phenomenon known
as central fatigue, which holds that mental fatigue in the brain can
adversely affect physical performance in endurance events. The
central fatigue hypothesis suggests that low blood levels of
BCAAs may accelerate the production of the brain neurotransmit-
ter serotonin, or 5-hydroxytryptamine (5-HTP), and prematurely
lead to fatigue (45). Tryptophan, an amino acid that circulates in
the blood, is a precursor of serotonin and can be more easily
transported into the brain to increase serotonin levels when
BCAA levels in the blood are low because high blood levels of
384 Rasmussen
BCAAs can block tryptophan transport into the brain (46).Dur-
ing endurance exercise, as muscle and liver glycogen are depleted
for energy the blood levels of BCAAs also decrease, and fatty acid
levels increase to serve as an additional energy source (47).The
issue with extra fatty acids in the blood is that they need to attach
to albumin as a carrier protein for proper transport. In doing so,
the fatty acids displace tryptophan from its place on albumin and
facilitate the transport of tryptophan into the brain for conversion
to serotonin (48). Thus, the combination of reduced BCAAs and
elevated fatty acids in the blood causes more tryptophan to enter
the brain and more serotonin to be produced, leading to central
fatigue (49).
Table 3
Typical amino acid composition of whey, casein, and soy isolates
Amino acid Whey Casein Soy
Alanine 4.6 2.7 3.8
Arginine 2.3 3.7 6.7
Aspartic acid 9.6 6.4 10.2
Cysteine/cystine 2.8 0.3 1.1
Glutamic acid 15.0 20.2 16.8
Glycine 1.5 2.4 3.7
1.6 2.8 2.3
4.5 5.5 4.3
11.6 8.3 7.2
9.1 7.4 5.5
2.2 2.5 1.1
3.1 4.5 4.6
Proline 4.4 10.2 4.5
Serine 3.3 5.7 4.6
4.3 4.4 3.3
2.3 1.1 1.1
Tyrosine 3.3 5.7 3.3
4.5 6.5 4.5
Values are expressed per 100 g of product
Essential amino acid
Branched-chain amino acid
Nutritional Supplements for Endurance Athletes 385
For endurance athletes competing in long races (more than 2 hours),
BCAA supplements can help delay central fatigue and maintain mental
performance (50). One study looked at BCAA supplementation dur-
ing a marathon and showed improved performance for slower runners
(3.05þhours) but no effect on faster runners (less than 3.05 hours) (2).
Chronic BCAA supplementation (2 weeks) has also been shown to be
effective in improving time-trial performance in trained cyclists (6).In
addition to their effects on prolonging endurance and delaying central
fatigue, BCAA supplements have been associated with a reduced rate
of protein and glycogen breakdown during exercise and an inhibition
of muscle breakdown following exhaustive endurance exercise (2,51).
A number of studies in trained and untrained subjects, however, have
shown no effect of BCAA supplements on exercise performance or
mental performance (52). In some cases, BCAAs have been compared
with carbohydrate supplementation during exercise, with results show-
ing they both delay fatigue to similar degrees (53). The data on BCAA
supplements are mixed, but they clearly do not harm endurance per-
formance. Some studies have shown positive adaptations, whereas
others have displayed no effect. Biological variations may determine
whether BCAAs are effective for the individual athlete and the parti-
cular sport or event.
Pharmacological sports ergogenics are drugs designed to func-
tion like hormones or neurotransmitter substances that are found
naturally in the human body. Like some nutritional sports ergo-
genics, pharmacological sports ergogenics may enhance physical
power by affecting various metabolic processes associated with
sport success. The most popular pharmacological sports ergogenics
used by endurance athletes today are caffeine and ephedrine.
Caffeine is theorized to enhance endurance performance by first
stimulating the central nervous system (CNS) and increasing psy-
chological arousal. Caffeine also stimulates the release of epinephr-
ine from the adrenal glad, which may further enhance physiological
processes such as cardiovascular function and fuel utilization. The
caffeine-mediated increase in free fatty acid mobilization and spar-
ing of muscle glycogen is the primary theory underlying the ergo-
genic effects of caffeine on prolonged endurance activities. Lastly,
caffeine increases myofilament affinity for calcium and/or increases
the release of calcium from the sarcoplasmic reticulum in skeletal
muscle, resulting in more efficient muscle contractions.
386 Rasmussen
In one of the first studies conducted on caffeine’s ergogenic effect,
subjects consumed decaffeinated coffee or decaffeinated coffee com-
bined with 330 mg pure caffeine 60 minutes prior to exercise. Time to
exhaustion was more than 19% longer in the caffeine trial than in
the decaffeinated trial (54). The authors concluded that the perfor-
mance increase was more than likely due to the increase in fat
oxidation as muscle glycogen was not measured. Another study
measured muscle glycogen utilization and found that caffeine prior
to exercise reduced muscle glycogen utilization by 30% (4). A later
study supported the muscle glycogen-sparing hypothesis by report-
ing a 55% decrease in muscle glycogenolysis during the first 15 min-
utes of exercise in the caffeine trial (55). The decrease in
glycogenolysis during the initial stages of exercise allowed more
glycogen to be available during the final stages, subsequently lead-
ing to an increased time to exhaustion. Further support of caffeine
supplementation was demonstrated in a study examining the effects
of acute caffeine ingestion (6 mg/kg) on prolonged, intermittent
sprint performance on a cycle ergometer. The total amount of sprint
work performed during the caffeine trial was 8.5% greater than that
performed during the placebo trial (56). The authors concluded
that acute caffeine ingestion can significantly enhance performance
of prolonged, intermittent sprint ability in competitive male, team-
sport athletes.
Despite the overwhelming ergogenic evidence of caffeine supple-
mentation, caution should be exercised when considering its use.
A recent study showed that in healthy volunteers a caffeine dose
corresponding to two cups of coffee (200 mg) significantly decreased
blood flow to the heart during exercise by 22%. That percentage
increased to 39% for people exercising in a high-altitude chamber,
which the researchers used to simulate the way coronary artery
disease (CAD) limits the amount of oxygen that gets to the heart
(57). Because an increase in blood to the heart is necessary for
aerobic activity, the findings theoretically suggest that caffeine
could slow the body down. The study’s purpose, however, was not
to look at whether caffeine could help athletes go faster or farther.
Instead, it set out to investigate the effect caffeine has on blood flow
to the heart. It can thus be concluded that people with CAD or those
at a high risk for heart disease should avoid loading up on caffeine
before a run or at least check with their primary care physician first.
Nutritional Supplements for Endurance Athletes 387
A final note in regard to caffeine supplementation is that the
International Olympic Committee lists caffeine as a banned substance.
Although some amount of caffeine is allowed because of its occur-
rence in foods, a urinary level that exceeds 12 mg/ml results in a doping
violation and possible disqualification or suspension. Therefore, it is
recommended to keep the daily caffeine intake to less than 3 mg/kg
body weight (i.e., 50–200 mg of caffeine) (44). Table 4 lists typical
caffeine content in common beverages, pills, and other products.
Although ephedrine is typically thought of as a weight loss sup-
plement, evidence supports its role in enhancing endurance exercise
performance. Ephedrine is a general sympathomimetic agent, which
means that it stimulates the CNS by mimicking the effects of many
of the body’s own sympathetic hormones [e.g., epinephrine (adrena-
line), norepinephrine] (50).
Ephedrine is found in various antiasthmatic and cold or cough
medications in pill, tablet, or inhaler form. It is also found in herbal
teas and dietary supplements containing Ma Huang (Chinese ephedra
or herbal ephedrine) as well as in dietary supplements marketed for
weight loss and for increasing energy. All cold medications with
decongestants are likely to contain prohibited sympathomimetics.
Typical doses used in research range from 20 to 25 mg ephedrine (42).
Table 4
Typical Caffeine Content in Common Beverages, Pills, and Other Products
Brewed coffee (cup)
= 100 mg
Decaffeinated coffee (cup) = 3 mg
Medium-brewed tea (cup) = 50 mg
Cocoa (cup) = 5 mg
Starbucks’ Coffee Grande (cup) = 90
Excedrin (one tablet) = 65 mg
No Doz (one tablet) = 100 mg
Vivarin (one tablet) = 200 mg
Guarana (100 mg) = 100 mg
SoBe No Fear (16 oz) = 159 mg
Cola-type soda (can) = 40 mg
Adapted from M.H. Williams (42), with permission
cup = 5–6 ounces
388 Rasmussen
Ephedrine is commonly combined with caffeine when assessing
its ergogenic potential. One study examined ephedrine and caffeine
separately and in combination in 12 subjects running a 10-km race.
The run times for the ephedrine-containing trials were significantly
shorter than those in the caffeine-only and placebo trials. In addi-
tion, heart rate and pace for the ephedrine-containing trials were
significantly lower than in the caffeine-only and placebo trials (58).
Another study examined the effects of caffeine and ephedrine on
running times of nine male subjects performing the Canadian Forces
Warrior Tests (WT). This is a standard test that all land forces soldiers
must perform within 22 minutes. Time to exhaustion was significantly
improved in the treatment group versus the placebo (1). The caffeine
and ephedrine enabled the subjects to exercise at a higher percentage
of the maximum aerobic power for a longer period of time when
compared with the placebo trials. These observations suggest that the
improved performance may have been due to the CNS stimulatory
effects of both caffeine and ephedrine (44). Ephedrine has a track
record of safe use at the recommended amount. Abuse of ephedrine,
however, can lead to amphetamine-like side effects, including elevated
blood pressure, rapid heart beat, nervousness, irritability, headache,
urination disturbances, vomiting, muscle disturbances, insomnia, dry
mouth, heart palpitations, and even death caused by heart failure
(59). It is important to note that ephedra use is banned by most
sports governing bodies (e.g., International Olympic Committee).
Additional research on the safety and efficacy of caffeine and ephe-
drine alone and in combination is warranted.
Physiological sports ergogenics are substances or techniques
designed specifically to augment natural physiological processes
that generate physical power. Two popular examples are glycerol
and creatine. Physiological sports ergogenics are not drugs per se. In
a strict sense, however, some may be regarded as drugs because they
are prescribed substances.
Glycerol is also known as glycerin and is an alcohol compound
that is more commonly found in the diet as a component of fat or
triglycerides. It serves as a backbone onto which fatty acid molecules
are attached and is marketed as an aid for ‘‘hyperhydrating’’ the body
by increasing blood volume and helping to delay dehydration. Thus,
glycerol may aid endurance athletes training or competing in hot,
humid environments by hydrating tissues, increasing blood volume,
Nutritional Supplements for Endurance Athletes 389
and ultimately delaying fatigue and exhaustion associated with dehy-
dration. Glycerin dosages used in research are based on body weight
or total body water and have approximated 1 g/kg body weight, with
each gram diluted in about 20 to 25mL of water or similar fluid (42).
Numerous studies support the theory that glycerol added to
fluids increase tissue hydration compared with drinking fluid with-
out glycerol added. Following glycerol consumption, the heart rate
and body core temperature are lower during exercise in the heat
(60), suggesting an ergogenic effect. In endurance type of activities a
larger supply of stored water may lead to a delay in dehydration and
exhaustion (61). More specifically, one study examined the effect of
glycerol (1 g/kg) supplementation on body temperature while exer-
cising on a treadmill (60% VO
max) at 428C at 25% relative humid-
ity for 90 minutes 2.5 hours after ingestion of the glycerol. Results
showed that the urine volume decreased before exercise, the sweat
rate increased, and the rectal temperature was lower during exercise
(62). These findings imply that glycerol ingestion was helpful in
maintaining normal body temperature during exercise in the heat.
Another study reporting positive results gave 11 fit adults gly-
cerol (1.2 g/kg in a 26 ml/kg body weight solution) or a placebo
(26 mg/kg body weight aspartame-flavored solution) 1 hour prior
to cycle exercise to exhaustion at 60% of maximum workload
(temperature 23.58–24.58C, humidity 25%–27%). The heart rate
for those taking glycerol was 2.8 bpm lower, and endurance time
was 21% longer (63). In a follow-up study, these same researchers
wanted to determine whether the same preexercise routine followed
by a carbohydrate oral replacement solution during exercise had any
further effect. Once again, they found that when glycerol had been
taken the endurance time was 25% longer (63).
It is important to note that not all studies show an ergogenic
effect and that the benefits—although noted for trained endurance
athletes exercising in hot, humid environments—are not necessarily
observed in athletes who are less well trained or are exercising in
more temperate climates (61,64). These factors should be taken into
account when considering glycerol supplements.
Although creatine supplements are typically marketed as body-
building and ‘‘strength-boosting’’ supplements, growing evidence
suggests that they may prove beneficial for endurance athletes as
well. Normally, about 1 to 2 g of creatine daily are produced in the
390 Rasmussen
body from the amino acids arginine, glycine, and methionine. Diet-
ary sources (Table 5), including meat and fish, add another 1 to 2 g
of creatine per day, although overcooking destroys most of the
creatine (the 1 g of creatine in an 8-oz steak may fall to zero if that
steak is well done).
In the body, creatine plays a vital role in cellular energy produc-
tion as creatine phosphate (phosphocreatine) in regenerating ATP
in skeletal muscle (50). Most studies utilize doses approximating 20
to 30 g/day, consumed in four or five equal doses throughout the day
for 5 to 7 days followed by a maintenance dose of 5 g/day (42).
One of the earliest creatine studies utilized well trained distance
runners and demonstrated improved cumulative, repeated running
times following four 300-m sprints (65). Another study demon-
strated significant increases in time to exhaustion during intense
cycle ergometry with creatine supplementation (66). Yet another
study reported that creatine loading in both male and female ath-
letes resulted in a 12% increase in the anaerobic threshold as well
as a decrease in blood lactate during incremental cycle tests (67).
One other study showed continued support by delaying the onset of
neuromuscular fatigue (a parameter similar to anaerobic threshold)
Table 5
Creatine Content in Select Foods
Food Creatine content
g/lb g/kg
Adapted from Williams MH, Kreider RB, Branch D. Creatine:
The Power Supplement (p 15). Human Kinetics, Champaign,
IL, 1999
Nutritional Supplements for Endurance Athletes 391
by 13% in highly trained female athletes (68). Most scientists agree
that creatine’s effectivenss can be attributed to one of two scenarios:
1) Phosphocreatine may aid ATP resynthesis for up to 3 minutes,
albeit in a decreasing role with time and intensity of work (69);2)it
may act as an energy shuttle between the mitochondria and muscle
fibers, which suggests that creatine may help produce ATP aero-
bically (70). Regardless, increasing muscle creatine phosphate
levels through creatine supplementation may decrease the reliance
on anaerobic glycolysis and reduce intramuscular lactate accumula-
tion, thereby delaying the onset of fatigue (44). More research on
the effects of creatine supplementation on endurance performance is
needed before definitive conclusions can be drawn.
Endurance athletes engaged in intense training run the risk of
overtraining. Overtraining is usually encountered after several days
of intense training and is generally associated with muscle fatigue.
During the training period, transient signs and symptoms may occur
including changes in the profile of mood state (POMS) where ten-
sion, depression, anger, fatigue, and confusion may be present.
Other signs include depleted muscle glycogen stores, increased rest-
ing heart rate, increased cortisol secretion, decreased appetite, sleep
disturbances, head colds, and immunosuppression. Most of the
symptoms that result from overtraining, collectively referred to as
overtraining syndrome, are subjective and identifiable only after the
individual’s performance has suffered. Unfortunately, these symp-
toms can be highly individualized, which can make it difficult for
athletes, trainers, and coaches to recognize that performance decre-
ments are brought on by overtraining. The first indication of over-
training syndrome is a decline in physical performance. The athlete
can sense a loss in muscle strength, coordination, and maximal
working capacity.
The immune system provides a line of defense against invading
bacteria, parasites, viruses, and tumor cells. The system depends on
the actions of specialized cells and antibodies. Unfortunately, one
of the most serious consequences of overtraining is the negative
effect it has on the body’s immune system. Recent studies confirm
392 Rasmussen
that excessive training suppresses normal immune function, increas-
ing the overtrained athlete’s susceptibility to infections (71,72).
Numerous studies show that short bouts of intense exercise can
temporarily impair the immune response, and successive days of
heavy training can amplify this suppression (73). Several investiga-
tors have reported an increased incidence of illness following a
single, exhaustive exercise bout. Also, intense exercise during illness
might decrease one’s ability to fight off infection and increases the
risk of even greater complications. In some cases, supplementation
may help attenuate the immunosuppression typically seen with
overtraining and in doing so may help prevent overtraining.
To bolster the first line of defense, an endurance athlete must
ensure that adequate calories are being consumed. Endurance ath-
letes maintaining heavy volume training often do not consume
enough calories to keep up with energy demands because of the
suppressive effect exercise can have on the appetite (74). This
point can be especially concerning for endurance athletes engaged
in prolonged training or competition sessions on the same or suc-
cessive days. Multiple training sessions on the same day have now
become the norm more than the exception for the elite endurance
athlete owing to the ever-increasing level of competition and pres-
sure to perform at optimal levels. An example is performing a long,
slow, distance (LSD) run in the morning only to follow-up with a
strength training session that evening. Although it is unlikely that
muscle glycogen stores can be completely resynthesized within a few
hours by nutritional supplementation alone, it would behoove all
endurance athletes to maximize the rate of muscle glycogen storage
after exercise. This ultimately results in faster recovery from train-
ing, possibly allowing a greater training volume (75).
To demonstrate the importance of nutrient timing, Flakoll et al.
(76) provided either a placebo, carbohydrate, or carbohydrate/
protein supplement to U.S. Marine recruits immediately after exer-
cise during 54 days of basic training to test the long-term impact of
postexercise carbohydrate/protein supplementation on variables
such as health, muscle soreness, and function. Compared to the
placebo and carbohydrate groups, the combined carbohydrate/pro-
tein group had 33% fewer total medical visits, 28% fewer visits due
to bacterial/viral infections, 37% fewer visits due to muscle and joint
problems, and 83% fewer due to heat exhaustion. Muscle soreness
Nutritional Supplements for Endurance Athletes 393
was also reduced immediately after exercise by the carbohydrate/
protein supplement. The authors postulated that post-exercise car-
bohydrate/protein supplementation not only may enhance muscle
protein deposition but also have significant potential to affect
health, muscle soreness, and tissue hydration positively during
prolonged intense exercise training. This suggests a potential ther-
apeutic approach for the prevention of health problems in severely
stressed exercising populations.
Hence, it is essential for the endurance athlete to consume an
adequate balance of macro and micronutrients at the proper times
throughout the day especially during periods of heavy training.
Athletes involved in intense training not only have greater macro-
nutrient needs but, more specifically, greater dietary protein needs
than individuals who do not train. Intense training has been shown
to decrease the availability of certain essential amino acids. Chronic
depletion of essential amino acids may slow the rate of tissue repair
and growth. Therefore, athletes involved in intense training need to
ingest enough high quality protein in the diet to maintain essential
amino acid availability during training. Dietary supplementation of
protein has been a common practice among athletes. More recently,
advances in food processing have allowed extraction of high quality
proteins from food. These proteins have been used in numerous
food products and have been marketed to athletes as a convenient
means of increasing the quality of protein in their diet.
Several ergogenic aids have been reported to aid the immune
system. Colostrum is the clear or cloudy ‘‘premilk’’ that female
mammals secrete after giving birth and before producing milk.
Colostrum for dietary supplements is usually derived from bovine
sources and contains various immunoglobulins (also called antibo-
dies) and antimicrobial factors (i.e., lactoferrin, lactoperoxidase, lyso-
zyme) as well as insulin-like growth factors (e.g., IGF-I, IGF-II).
Bovine colostrum is among the highest quality sources of protein.
The most prevalent claims for dietary supplements containing
colostrum are in the area of generalized immune function and
improved recovery from intense exercise. One study examined the
effects of consuming colostrum (60 g/day) or placebo (whey protein)
during an 8-week running program, running three times a week for
45 minutes per session (77). Participants conducted two treadmill
runs to exhaustion, with 20 minutes of rest between runs, at baseline
394 Rasmussen
and 4 and 8 weeks into the study. No differences existed in treadmill
running performance at baseline, and at week four both groups had
similar improvements in running performance. At week 8, however,
the colostrum group ran significantly farther and did more work
than the placebo group during the treadmill test. In addition, the
colostrum supplemented group exhibited lower serum creatine
kinase (CK) levels. CK is an important muscle cell enzyme that
some scientists believe can be used as a marker of muscle cell
damage. High CK levels often indicate that significant muscle
damage has occurred. However, some scientists believe that if CK
levels remain fairly normal, the athlete has experienced little muscle
trauma (77).
Another study examined rowing performance in a group of elite
female rowers. Eight rowers completed a 9-week training program
while consuming either colostrum (60 g/day) or whey protein. By
week 9, rowers consuming colostrum had greater increases in the
distance covered and work done than the whey protein group (78).
Additional studies on bovine colostrum consumption suggest that it
can deliver some generalized anti-inflammatory benefits (79,80)
and help prevent and treat the gastric injury associated with non-
steroidal anti-inflammatory drugs (81).
Glutamine is another supplement popular in athletic popula-
tions today. It is the most abundant amino acid in the body,
comprising approximately half of the free amino acids in the
blood and muscle. Glutamine is a nonessential glucogenic amino
acid and an anaplerotic precursor that has been shown to be a vital
fuel for a variety of cells of the immune system (82). In skeletal
muscle, glutamine has an inhibitory role on proteolysis and
branched-chain amino acid catabolism. Recent evidence has placed
emphasis on glutamine as a positive component of immune func-
tion (82,83).
Glutamine has two main functions in the body: It is a precursor in
the synthesis of other amino acids, and it converts to glucose for
energy. Cells of the immune system, small intestine, and kidney are
the major consumers of glutamine, making ‘‘immune boosting’’ and
‘immune maintenance’’ claims for glutamine supplements quite
common. In addition, there are claims for glutamine supplements
in maintaining muscle mass, reducing post-exercise catabolism
(muscle tissue breakdown), and accelerating recovery from intense
Nutritional Supplements for Endurance Athletes 395
exercise. Intense exercise training often exhibited by the endurance
athlete results in a drop in plasma glutamine levels. Chronically low
glutamine levels have been implicated as a possible contributing
factor for athletic overtraining syndrome as well as the transient
immunosuppression and increased risk of infections that typically
affect competitive athletes during intense training and competition.
Under conditions of metabolic stress, the body’s need for glutamine
may become conditionally essential, meaning that the body cannot
produce adequate levels and a dietary source is required to prevent
catabolism of skeletal muscle, the primary source of stored gluta-
mine in the body.
A significant body of scientific literature supports the beneficial
effects of glutamine supplementation in maintaining muscle mass
and immune system function in critically ill patients and in those
recovering from extensive burns and major surgery (84). When
plasma glutamine levels fall, skeletal muscles may enter a state of
catabolism in which muscle protein is degraded to provide free
glutamine for the rest of the body. Because skeletal muscle is the
major source of glutamine (other than the diet), prolonged deficits
in plasma glutamine can lead to a significant loss of skeletal muscle
protein and muscle mass. Postsurgical deposition of collagen (a
marker for wound healing) can be enhanced by amino acid sup-
plementation containing 14 g of glutamine (85), whereas a lower
dose of mixed amino acids containing glutamine (2.9 g) provides
no change in athletic performance or on adaptations to cycling
training (86).
Studies have also been conducted on glutamine supplementation
in athletes, and a strong rationale exists for the efficacy of glutamine
supplements in athletic populations. One study found that athletes
who consumed glutamine immediately and 2 hours after running a
marathon or ultramarathon reported fewer infections than a pla-
cebo group (87). The levels of infection were lowest in the middle
distance runners and highest in the runners after a marathon or
ultramarathon. Glutamine supplements have also been shown to
play a role in counteracting the catabolic effects of stress hormones,
such as cortisol, which are typically elevated by strenuous exercise.
Under conditions of stress-induced protein wasting in adults and
children, including burns, surgery, and some forms of cancer, glu-
tamine supplementation has been associated with reduced protein
396 Rasmussen
breakdown (88), enhanced lymphocyte function (89), reduced gut
permeability (90), and reduced infections (91).
In addition to lowering glutamine levels, prolonged strenuous
exercise has been reported to lower zinc levels apparently owing to
greater zinc loss during training from sweat and/or inadequate
intake of dietary zinc (92). Zinc deficiency has been reported to
diminish serum testosterone levels (93), impair immune function
(94), and decrease strength (95). Zinc is an essential trace mineral
that functions as part of about 300 enzymes. As such, zinc plays a
role in numerous biochemical pathways and physiological pro-
cesses. Because of the varied roles of zinc in the body, claims for
zinc-containing dietary supplements are numerous, including those
for improved wound healing, general immune system support, and
support of various aspects of men’s health.
Zinc lozenges have become one of the most popular natural
approaches to treating the common cold. The scientific evidence
generally supports this use for short periods (1–2 weeks) (96). Zinc
lozenges appear to reduce cold symptoms, such as sore throats,
hoarseness, and coughing, and may even be able to shorten the
duration of colds by a full day.
Exercise performance has been associated with decreased zinc
status, especially in athletes who avoid red meat, who concentrate
their diets too much on carbohydrates, or who follow an overly
restricted dietary regimen. Low zinc intake (<3 mg/day) has been
linked to reduced activity of a zinc-containing enzyme in red blood
cells, carbonic anhydrase, which helps red blood cells transport
carbon dioxide from tissues to the lungs to be exhaled. Mild-to-
moderate zinc deficiency can lead to significant reductions in the
body’s ability to take up and use oxygen, remove carbon dioxide,
and generate energy during high-intensity exercise (50).
One study examined the effects of daily physical training on
serum and sweat zinc concentrations in professional sportsmen
between October and December, during the competition season.
They discovered a significantly higher zinc concentration in sweat
in December than in October. They stated that a daily and main-
tained exercise routine was probably responsible for the altered zinc
metabolism. The authors further concluded that alterations in zinc
metabolism with increases in zinc excretion and stress levels lead to a
situation of latent fatigue associated with decreased endurance (97).
Nutritional Supplements for Endurance Athletes 397
Another study attempted to investigate how exhaustive exercise
affects thyroid hormones and testosterone levels in male wrestlers
who were supplemented with oral zinc sulfate (3 mg/kg/day) for
4 weeks. The results demonstrated that exhaustive exercise led to
significant inhibition of both thyroid hormones and testosterone
concentrations but that 4-week zinc supplementation prevented this
inhibition in wrestlers. The authors concluded that physiological
doses of zinc administration may benefit performance (98). Another
study, however, examined plasma zinc concentrations and markers
of immune function in 10male runners following a moderate increase
in training over 4weeks and found no benefit in zinc concentration,
differential leukocyte counts, lymphocyte subpopulations, or lym-
phocyte proliferation. These authors concluded that athletes are
unlikely to benefit from zinc supplementation during periods of
moderately increased training volume (99).
Overall, then, studies on colostrum, glutamine, and zinc have
provided favorable evidence that they support the immune system
and should be considered by the endurance athlete engaged in
intense training.
Despite the fact that there is solid scientific evidence backing the
safety and efficacy of certain nutritional supplements, some remain
skeptical as to whether they should be used at all. The two most
popular questions raised generally address legal and ethical consid-
erations. Although some drugs may be effective sports ergogenics,
their use might also significantly increase health risks. The Medical
Commission of the International Olympic Committee (IOC) noted
that doping violates the ethics of both sport and medical science and
is prohibited. Most athletic governing bodies, such as the IOC, the
National Basketball Association (NBA), the National Football
League (NFL), The National Collegiate Athletic Association
(NCAA), and the United States Olympic Committee (USOC) have
developed drug-use policies. Any athlete competing under the jur-
isdiction of a specific athletic governing body should be aware of its
drug rules and regulations before consuming any nutritional supple-
ment designed to aid performance.
398 Rasmussen
What are the ethics of sport? According to Webster’s Dictionary,
the definition for ethics includes the following: 1) the discipline
dealing with what is good and bad and with moral duty and obliga-
tion; 2) a theory or system of moral values; 3) the principles of
conduct governing an individual or group; and 4) a guiding philo-
sophy. All four definitions can be operational in sports.
The IOC embraces the idea that athletes should succeed through
their unaided efforts; in other words, the ‘‘Do the best with what
you’ve got’’ approach. However, the athlete whose primary goal is
to win at all costs may be guided by his or her own principles in an
attempt to obtain that unfair advantage. With increasing pressures
to perform and potential scholarships, jobs, endorsements, and
contract extensions on the line, an increasing number of elite ath-
letes participating in both the collegiate and professional ranks are
learning to modify their natural ability by techniques that go beyond
normal training in order to get an advantage—not necessarily an
unfair one—over their competitors. As noted throughout this chap-
ter, safe, effective, legal ergogenics are available. Whether their use is
ethical may depend on the individual athlete’s code of ethics. Some
authorities believe that because a sports ergogenic is legal, its use is
ethical. Others may contend that such a sports ergogenic violates the
ethics of the IOC antidoping rule. In this situation, the ultimate
decision about whether to use a safe, effective, legal ergogenic rests
with the individual athlete.
Proper training, maintaining a positive energy balance, and uti-
lizing effective nutritional supplements form the foundation for
optimal performance. Training for the endurance athlete should be
based on proper utilization of the principles of training, depending
on individual goals and the training season (preseason, in-season,
postseason). The nutritional base should focus on an everyday diet
that emphasizes a combination of all the nutritional ergogenic aids.
The types of macronutrients and micronutrients selected and the
timing of their use are of the utmost importance for developing a
well refined everyday diet. The use of nutritional supplements that
research has shown can help improve energy availability (e.g., sports
Nutritional Supplements for Endurance Athletes 399
drinks, carbohydrate) and/or promote recovery (e.g., carbohydrate,
protein) can provide additional benefits in certain situations. In
addition, a combination of effective pharmacological and physiolo-
gical ergogenic supplements can further propel performance and
support the immune system. Following these training and nutri-
tional recommendations can serve as the foundation for a successful
endurance athlete.
To prepare for competition, endurance athletes should strive to hyper-
hydrate prior to exercise. Full hydration requires that water along with
fluids containing moderate concentrations of carbohydrate and sodium
be ingested regularly starting several days before competition.
Endurance athletes should try to maximize their muscle glycogen stores
prior to competition. This can be accomplished during the training taper
by consuming 7 to 10 g carbohydrates/kg body weight daily.
Prior to competition, it is recommended that 500 to 1000 ml of fluid be
ingested. It may also be beneficial to consume 200 to 300 g of carbohy-
drate if supplementation during exercise is limited or not possible.
During exercise, endurance athletes should try to replace fully any fluid
losses that occur, although during hot and humid conditions this may be
next to impossible.
It is best to consume small volumes of fluid frequently (150–250 ml every
15 minutes) rather than consume high volumes of fluid occasionally
(e.g., 400 ml every 30 minutes).
Electrolyte replacement should be considered by the endurance athlete.
Most sports drinks are formulated adequately to replace electrolyte
losses due to sweating.
To maximize endurance performance, 45 to 60 g of high glycemic index
(GI) carbohydrates should be ingested per hour during exercise. Carbo-
hydrate solutions should not exceed 10% if maintaining hydration is of
Carbohydrate supplementation can be delayed until about 30 to 40 min-
utes prior to the onset of fatigue and still be effective. However, if fluid
replacement is of concern, it is recommended that supplementation with
a dilute carbohydrate solution start as soon as possible and continued
periodically throughout exercise.
The addition of small amounts of protein to a carbohydrate supplement
(4:1 ratio) may also increase the effectiveness of the supplement.
400 Rasmussen
For rapid rehydration following exercise, it is important to start fluid
consumption early and replace at least 150% of the fluid lost during
exercise with a dilute sodium solution.
Requirements for the daily recovery of muscle glycogen depend on exer-
cise intensity and duration. If the training duration is moderate and the
intensity is low, 5 to 7 g of carbohydrate (CHO)/kg/day should be con-
sumed. If the training duration is moderate and the intensity is high, 7 to
12 g CHO/kg/day should be consumed. If the training is extreme
(4–6 hours per day), 10 to 12 g CHO/kg/day should be consumed.
If there is only limited time to replenish the muscle glycogen stores, 1.0
to 1.2 g CHO/kg/hr should be consumed at frequent intervals starting
within the first 30 minutes after exercise.
The addition of protein to the carbohydrate supplement (4:1 ratio)
promotes additional glycogen storage when carbohydrate intake is
suboptimal or when frequent supplementation is not possible.
Post-exercise supplements composed of carbohydrate and protein have
the added benefit of limiting muscle tissue damage, stimulating protein
accretion, and protecting the immune system from exercise-induced
Several pharmacological and physiological ergogenic aids can further
propel performance for the endurance athlete and should be considered
depending on the individual goal of the athlete.
There is strong evidence that colostrum, glutamine, and zinc support the
immune system. Hence, these supplements should be considered by the
endurance athlete engaged in intense training.
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... Athletes who practice endurance disciplines such as running often use supplements that help improve their athletic performance (Rasmussen et al., 2008, Carlsohn et al., 2011. Supplements such as caffeine appear to have an effect on the performance of endurance athletes by stimulating the central nervous system and the release of epinephrine optimizing cardiovascular function. ...
... Its intake seems to influence the levels of central fatigue, mitigating these effects during endurance tests (Blomstrand et al., 1988). Creatine shows improvements in endurance athletes by playing a fundamental role in the production of phosphocreatine (Rasmussen et al., 2008). Another increasingly used supplement is hydrolysed collagen. ...
Full-text available
The main purpose of this observational prospective pilot study was to evaluate the effects of hydrolysed collagen supplementation, in endurance training, in the performance of runners. A cohort of sixty-one subjects (women with an age = 44 ± 5 years; height = 1.65 ± 0.4 m; weight = 58.4 ± 5.2 kg; men with an age = 51 ± 3 years; height = 1.82 ± 0.2 m; weight = 74.4 ± 3.1 kg) received a collagen supplement (11 g / day) during 16 weeks. They performed a 21 kilometre endurance test (21KmET) at baseline and after 16 weeks of follow up. Squat Jump (SJ) and Counter Movement Jump (CMJ) tests were measured before and after each 21KmET and biochemical analyses and a bioimpedance were performed after each 21KmET. Subjects underwent three sport training sessions a week and a supplement intake during the follow up. Regarding the 21KmET time, there were significant differences between before and after supplementation intake (p < .05) and a higher pain perception was assessed with a visual analogue scale at the second 21KmET (p < .05). Significant improvements were observed in handgrip strength, SJ and CMJ after 16 week of supplement intake. Conclusions: A programmed endurance training improves the functionality of the runner in long-distance events and a periodic intake of hydrolysed collagen could help a better performance because it improves the conditions of muscles and joints.
... Creatine can also be sourced, however, in its natural form. Arguably more beneficial in its whole food form due to the additional nutritional value, creatine concentrations can range from 3-5 g/kg of raw meat [47]. Despite these natural sources of creatine, to successfully ingest the recommended "loading" dose of 20 g/day required to rapidly increase skeletal muscle stores [48,49], one would have to consume approximately 4 kg of meat per day. ...
Full-text available
Creatine is an organic compound, consumed exogenously in the diet and synthesized endogenously via an intricate inter-organ process. Functioning in conjunction with creatine kinase, creatine has long been known for its pivotal role in cellular energy provision and energy shuttling. In addition to the abundance of evidence supporting the ergogenic benefits of creatine supplementation, recent evidence suggests a far broader application for creatine within various myopathies, neurodegenerative diseases, and other pathologies. Furthermore, creatine has been found to exhibit non-energy related properties, contributing as a possible direct and in-direct antioxidant and eliciting anti-inflammatory effects. In spite of the new clinical success of supplemental creatine, there is little scientific insight into the potential effects of creatine on cardiovascular disease (CVD), the leading cause of mortality. Taking into consideration the non-energy related actions of creatine, highlighted in this review, it can be speculated that creatine supplementation may serve as an adjuvant therapy for the management of vascular health in at-risk populations. This review, therefore, not only aims to summarize the current literature surrounding creatine and vascular health, but to also shed light onto the potential mechanisms in which creatine may be able to serve as a beneficial supplement capable of imparting vascular-protective properties and promoting vascular health.
... Increased LPL activity in the muscles aer training represents an adaptive advantage that facilitates the supply of energy and increases muscle oxidative capacity which is associated with high lactate threshold , which is characteristic of elite athletes in endurance sports ( ). Analyzing supplements for endurance athletes Antonio and Stout stated that the mechanism of action of colostrum as a supplement through insulin-like growth factor, which stimulates the activity of LPL and inhibits the activity of insulin in fat cells, increases the metabolism of fats and increases the level of free fatty acids in the blood that are necessary for endurance training (Antonio, & Stout, 2002). From the literature it is known that deletions in the LPL gene, LPL S447X truncated variant, lacking the last two amino acids is associated with increased enzyme activity LPL, so it can be assumed that the carriers of these variants of the LPL gene could be successful in endurance sports. ...
Full-text available
The genetic and environmental factors and their interaction contribute to sports performance. So far, it has been identified a large number of genetic markers associated with sports performance and risk of sports injuries. Sports genomics is a relatively young scientific discipline and the necessary additional complex research on a large number of participants is required before scientific results in this field could be applicable in practice. At present, the application of tests based on genetic information for sport talent identification or recommendations for personalized training, in order to achieve optimal sport performance, is not scientifically justified. It is also necessary to carefully consider all the ethical issues related to such testing in children.
... Thus, the combination of reduced BCAAs and elevated fatty acids in the blood causes more tryptophan to enter the brain and more serotonin to be produced, leading to central fatigue [ 72 , 73 ]. Due to these metabolic processes, it has been hypothesized that BCAA supplementation can help delay central fatigue and maintain mental performance in endurance or extremely long-lasting physical activities [ 67 ]. ...
Full-text available
Female athletes tend to choose their supplements for different reasons than their male counterparts. Collegiate female athletes report taking supplements “for their health,” to make up for an inadequate diet, or to have more energy. Multivitamins, herbal substances, protein supplements, amino acids, creatine, fat burners/weight-loss products, caffeine, iron, and calcium are the most frequently used products reported by female athletes. Many female athletes are unclear on when to use a protein supplement, how to use it, and different sources of protein (whey, casein, and soy). This chapter addresses essential amino acid and branched chain amino acid supplementation. Along with recommendations for protein supplementation, creatine supplementation is discussed. Not all female athletes are concerned with building muscle. Burning fat is also a major concern for the female athlete. This may result in the athlete turning to products marketed for weight control (i.e., ginseng or ephedra). A product legal for over-the-counter (OTC) sales, however, can be illegal for athletic competition (i.e., ephedra). Competitive athletes should be aware of the banned substance list for their governing body and that OTC products are not currently regulated by the FDA. This lack of regulation can lead to OTC products that are contaminated with banned substances.
Full-text available
A collaborative study was undertaken in which five international laboratories participated to determine amino acid fingerprints in 39 authentic nonfat dry milk (NFDM)/skim milk powder (SMP) samples. A rapid method of amino acid analysis involving microwave-assisted hydrolysis followed by ultra-high performance liquid chromatography-ultraviolet detection (UHPLC-UV) was used for quantitation of amino acids and to calculate their distribution. The performance of this rapid method of analysis was evaluated and was used to determine the amino acid fingerprint of authentic milk powders. The distribution of different amino acids and their predictable upper and lower tolerance limits in authentic NFDM/SMP samples were established as a reference. Amino acid fingerprints of NFDM/SMP were compared with selected proteins and nitrogen rich compounds (proteins from pea, soy, rice, wheat, whey, and fish gelatin) which can be potential economically motivated adulterants (EMA). The amino acid fingerprints of NFDM/SMP were found to be affected by spiking with pea, soy, rice, whey, fish gelatin and arginine among the investigated adulterants but not by wheat protein and melamine. The study results establish an amino acid fingerprint of authentic NFDM/SMP and demonstrate the utility of this method as a tool in verifying the authenticity of milk powders and detecting their adulteration.
The use of enzymes from the brush border membrane (BBM) in simulated gastrointestinal digestion of milk proteins has been evaluated. With this purpose, the resistant sequences from casein and milk whey proteins after INFOGEST in vitro digestion with and without BBM have been analyzed by tandem mass spectrometry. The use of BBM revealed additional cleavages to those found with pancreatic enzymes, although the number of total identified peptides decreased due to the reduction of the peptide size. These new cleavages were mainly attributed to the activity of amino- and carboxy-peptidases, which was also reflected in the higher concentration of free amino acids found in the gastrointestinal digests with BBM. The peptidome of the simulated gastrointestinal digests was compared with that previously obtained in digests aspirated from human jejunum after oral administration of the same substrates. The addition of BBM did not change significantly the peptide profile, although it allowed the identification of peptides found in human digests. However, none of the models was able to reproduce the large variety of peptides found in vivo. In addition, in vitro transepithelial transport of six β-casein derived peptides resistant to gastrointestinal digestion, including the opioid β-casomorphin-7, was also evaluated. The results point to the importance of the nature of the N- and C-terminal end for the transport rate through the Caco-2 cell monolayer. Therefore, the use of BBM as a supplementary step after simulated pancreatic digestion can be considered in bioavailability studies since the final sequence can determine the absorption of peptides.
Due to its high nutritional value and increasing consumption trends, plant-based proteins were used in a variety of dietary products, either in their entirety or as partial substitutions. There is indeed a growing need to produce plant-based proteins as alternatives to dairy-based proteins that have good functional properties, high nutritional values, and high protein digestibility. Among the plant-based proteins, both lentil and quinoa proteins received a lot of attention in recent years as dairy-based protein alternatives. To ensure plant-based proteins a success in food applications, food industries and researchers need to have a comprehensive scientific understanding of these proteins. The demand for proteins is highly dependent on several factors, mainly functional properties, nutritional values, and protein digestibility. Fermentation and protein complexation are recognised to be suitable techniques in enhancing the functional properties, nutritional values, and protein digestibility of these plant-based proteins, making them potential alternatives for dairy-based proteins.
Physicochemical characteristics of whey protein concentrate (WPC35, 35% protein), whey protein isolate, sodium, and calcium caseinate powders were studied by storing them at 25, 35, and 45 °C and 11, 44, and 85% relative humidity (RH) for 21 days. Monolayer moisture content (Mo) in these powders increased with increasing protein content. The glass transition temperature (Tg) of all of these powders decreased with increasing RH at all storage temperatures. Lactose crystallization occurred in WPC35 at 85% RH at all temperatures and 44% RH and 45 °C, and this caused caking. Caking was also observed in whey protein concentrate and isolate, and sodium and calcium caseinate powders at 85% RH and 45 °C, despite having low (0.2–1.5%, w/w) lactose content. Surface fat content was higher in powders stored at higher temperatures and RH. All powders developed browning, which was especially pronounced at 85% RH. These findings help better understand the temperature and humidity dependent behavior of whey protein and casein powders during storage.
Female athletes tend to choose their supplements for different reasons than their male counterparts. Collegiate female athletes report taking supplements “for their health,” to make up for an inadequate diet, or to have more energy. Multivitamins, herbal substances, protein supplements, amino acids, creatine, fat burners/weight-loss products, caffeine, iron, and calcium are the most frequently used products reported by female athletes. Many female athletes are unclear on when to use a protein supplement, how to use it, and different sources of protein (whey, casein, and soy). This chapter addresses essential amino acid and branched chain amino acid supplementation. Along with recommendations for protein supplementation, creatine supplementation is discussed. Not all female athletes are concerned with building muscle. Burning fat is also a major concern for the female athlete. This may result in the athlete turning to products marketed for weight control (i.e., ginseng or ephedra). A product legal for over-the-counter (OTC) sales, however, can be illegal for athletic competition (i.e., ephedra).competitive athletes should be aware of the banned substance list for their governing body and that OTC products are not currently regulated by the FDA. This lack of regulation can lead to OTC products that are contaminated with banned substances.
List of Contributors. Preface. Units of Measurement and Terminology. Part 1: Definitions. 1 Basic Definitions for Exercise. H.G. KNUTTGEN AND P.V. KOMI. . Part 2: Biological Basis for Strength and Power. 2 Neuronal control of functional movement. VOLKER DIETZ. 3 Motor Unit and Motor Neuron Excitability during Explosive Movement. TOSHIO MORITANI. 4 Muscular Basis of Strength. R. BILLETER AND H. HOPPELER. 5 Hormonal Mechanisms Related to the Expression of Muscular Strength and Power. WILLIAM J. KRAEMER AND SCOTT A. MAZZETTI. 6 Exercise--related Adaptations in Connective Tissue. RONALD F. ZERNICKE AND BARBARA LOITZ--RAMAGE. 7 Contractile Performance of Skeletal Muscle Fibres. K.A. PAUL EDMAN. 8 Skeletal Muscle and Motor Unit Architecture: Effect on Performance. RONALD R. ROY, RYAN J. MONTI, ALEX LAI AND V. REGGIE EDGERTON. 9 Mechanical Muscle Models and Their Application to Force and Power Production. WALTER HERZOG. 10 Stretch--shortening Cyle. PAAVO V. KOMI. 11 Stretch--shortening Cycle Fatigue and its Influence on Force and Power Production. CAROLINE NICOL AND PAAVO. V. KOMI. . Part 3: Mechanism for Adaptation in Strength and Power Training. 12 Cellular and Molecular Aspects of Adaptation in Skeletal Muscle. GEOFFREY GOLDSPINK AND STEPHEN HARRIDGE. 13 Hypertrophy and Hyperplasia. J. DUNCAN MACDOUGALL. 14 Acute and Chronic Muscle Metabolic Adaptations to Strength Training. PER A. TESCH AND BJORN A. ALKNER. 15 Neural Adaptation to Strength Training. DIGBY G. SALE. 16 Mechanism of Muscle and Motor Unit Adaptation to Explosive Power Training. JACQUES DUCHATEAU AND KARL HAINAUT. 17 Proprocetive Training: Considerations for Strength and Power Production. ALBERT GOLLHOFER. 18 Connective Tissue and Bone Response to Strength Training. MICHAEL H. STONE AND CHRISTINA KARATZAFERI. 19 Endocrine Responses and Adaptations to Strength and Power Training. WILLIAM KRAEMER AND NICHOLASS A. RATAMESS. 20 Cardiovascular Responses to Training. STEVEN J. FLECK. . Part 4: Special Problems in Strength and Power Training. 21 Aging and Neuromuscular Adaptation to Strength Training. KEIJO HAKKINEN. 22 Use of Electrical Stimulation in Strength and Power Training. GARY A. DUDLEY AND SCOTT W. STEVENSON. Part 5: Strength and Power Training for Sports. 23 Biomechanics of Strength and Strength Training. VLADIMIR M. ZATSIORSKY. 24 Vibration Loads: Potential for Strength and Power Development. JOACHIM MESTER P.(?) SPITZENPFEIL AND ZENGYOUAN YUE. 25 Training for Weightlifting. JOHN GARHAMMER AND BOB TAKANO
A randomized, double-blind, placebo controlled design was used in which 13 elite female rowers. all of whom had competed at World Championships, were supplemented with 60 g . day(-1) of either bovine colostrum (BC; n = 6) or concentrated whey protein powder (WP; n = 7) during 9 weeks of pre-competition training. All subjects undertook the study as a group and completed the same training program. Prior to, and after 9 weeks of supplementation and training, subjects completed an incremental rowing test (ROW 1) on a rowing ergometer consisting of 3 X 4-min submaximal workloads and a 4-min maximal effort (4max), each separated by a 1-min recovery period. The rowing test was repeated after a 15-min period of passive recovery (ROW2). The 4max for ROW1 provided a measure of performance, and the difference between the 4max efforts of ROW1 and ROW2 provided an index of recovery. Blood lactate concentrations and pH measured prior to exercise and at the end of each workload were used to estimate blood buffer capacity (beta). Food intake was recorded daily for dietary analysis. There were no differences in macronutrient intakes (p > .56) or training volumes (p > .99) between BC and WP during the study period. Rowing performance (distance rowed and work done) during 4max of ROW2 was less than ROW1 at baseline (p < .05) but not different between groups (P > .05). Performance increased in both rows by Week 9 (p < .001), with no difference between groups (p >.75). However, the increase was greatest in ROW2 (p < .05), such that by Week 9 there was no longer a difference in performance between the two rows in either group (p >.05). beta was not different between groups for ROW1 at baseline (BC 38.3 +/- 5.0, WP 38.2 +/- 7.2 slykes; p > .05) but was higher in BC by Week 9 (BC 40.8 +/- 5.9, WP 33.4 +/- 5.3 slykes; p < .05). beta for ROW2 followed the same pattern of change as for ROW I. We conclude that supplementation with BC improves beta, but not performance, in elite female rowers. It was not possible to determine whether beta had any effect on recovery.
Increasing the plasma glucose and insulin concentrations during prolonged variable intensity exercise by supplementing with carbohydrate has been found to spare muscle glycogen and increase aerobic endurance. Furthermore, the addition of protein to a carbohydrate supplement will enhance the insulin response of a carbohydrate supplement. The purpose of the present study was to compare the effects of a carbohydrate and a carbohydrate-protein supplement on aerobic endurance performance. Nine trained cyclists exercised on 3 separate occasions at intensities that varied between 45% and 75% VO2max for 3 h and then at 85% VO2max until fatigued. Supplements (200 ml) were provided every 20 min and consisted of placebo, a 7.75% carbohydrate solution, and a 7.75% carbohydrate / 1.94% protein solution. Treatments were administered using a double-blind randomized design. Carbohydrate supplementation significantly increased time to exhaustion (carbohydrate 19.7 +/- 4.6 min vs. placebo 12.7 +/- 3.1 min), while the addition of protein enhanced the effect of the carbohydrate supplement (carbohydrate-protein 26.9 +/- 4.5 min, p < .05). Blood glucose and plasma insulin levels were elevated above placebo during carbohydrate and carbohydrate-protein supplementation, but no differences were found between the carbohydrate and carbohydrate-protein treatments. In summary, we found that the addition of protein to a carbohydrate supplement enhanced aerobic endurance performance above that which occurred with carbohydrate alone, but the reason for this improvement in performance was not evident.