Gatorade
Sports
Science
Institute ®
50
VOLUME 7 (1994)
NUMBER 3
SPORTS SCIENCE EXCHANGE
FLUID AND CARBOHYDRATE REPLACEMENT DURING EXERCISE: HOW MUCH AND WHY?
Edward E Coyle, Ph.D.
Director., Human Performance Laboratory
Department of Kinesiology and Health Education,
The University of Texas at Austin
Austin, Texas
Member, Sports Medicine Review Board
Gatorade Sports Science Institute
KEY POINTS
1. During prolonged exercise in the heat, people can become dehydrated at a rate of 1-2 L every hour (about 2-4 lbs of body weight loss per
hour). The rate of dehydration can be monitored by recording changes in nude body weight. Each pound of weight loss corresponds to 450
mL (15 fluid ounces) of dehydration.
2. Even a slight amount of dehydration causes physiological consequences. For example, every liter (2.2 lbs) of water lost will cause heart rate to
be elevated by about eight beats per minute, cardiac output to decline by 1 L/min, and core temperature to rise by 0.3o C when an individual
participates in prolonged exercise in the heat.
3. When it is important to minimize disturbances in cardiovascular function and body temperature and to reduce the perceived difficulty of exercise, people should attempt to drink fluids at close to the same rate that they are losing body water by sweating.
4. Unfortunately, runners generally drink only 300-500 mL of fluids per hour and thus allow themselves to become dehydrated at rates of 5001,000 mL/h. Dehydration compromises cardiovascular function and places the runner at risk for heat-related injury. The runner must answer
the question, Will the time I lose by drinking larger volumes of fluid be compensated for by the physiological benefits the extra fluid produces that may cause me to run faster during the last half of the race?
5. For an exerciser who weighs about 68 kg (150 lb), the requirements for both carbohydrate (i.e., 30-60 g/h) and fluid during prolonged exertion
can be met by drinking 625-1,250 mL/h of beverages containing 4-8% carbohydrate. This volume must be adjusted for persons of different
body weights. For example, an individual who weighs 50 kg should multiply the above recommendation by 50/68 or 0.74, i.e., 462.5-925
mL/h.
INTRODUCTION
The prevalent thinking from the turn of the century until the 1970's was that participants in endurance sports did not need to replace fluids lost
during exercise (Noakes et al., 1991a; Noakes, 1993). This misconception has now given way to the knowledge that drinking fluids reduces the
increase in body temperature (hyperthermia) and the amount of stress on the cardiovascular system, especially when exercising in hot environments (Coyle & Montain, 1993). However, the extent to which even a slight degree of dehydration adversely affects bodily function during exercise and the situations in which adding carbohydrate and salt to water provides added benefit are not generally appreciated. The volume of fluid
that most athletes choose to drink voluntarily during exercise replaces less than one-half of their body fluid losses (Noakes, 1993). The purpose of
this paper is to review the physiology of fluid and carbohydrate replacement during exercise and the likely effects of such replacement on the performance of pro-longed exercise. It is hoped that this knowledge might encourage competitors to drink more during exercise.
FLUID INGESTION DURING
PROLONGED EXERCISE
The decision as to how much fluid to
ingest during exercise should be based upon
a risk-benefit analysis. Undoubtedly, the
most serious consequence of inadequate
fluid replacement, i.e., dehydration, during
exercise is hyperthermia, which when severe
will cause heat exhaustion, heat stroke, and
even death. The risks of too much fluid
ingestion are gastrointestinal discomfort
(Rehrer et al., 1990) and a reduced pace during competition associated with the physical
difficulty of drinking large volumes of fluid
while exercising. The benefits of fluid ingestion are reduced cardiovascular stress and
reduced hyperthermia that, by themselves,
can probably improve exercise performance.
CARBOHYDRATE INGESTIO
DURING PROLONGED INTENSE
EXERCISE
The primary purpose of carbohydrate
ingestion during strenuous exercise lasting
longer than one hour is to maintain a sufficient concentration of blood glucose and to
sustain a high rate of energy production
from blood glucose and glycogen stored in
muscles (Coggan & Coyle, 1991; Coyle et
al., 1986), which can allow competitors to
exercise longer and sprint faster at the end of
exercise (Coggan & Coyle, 1991 ). Most
studies demonstrating improved performance with carbohydrate feedings have
given subjects 25-60 g of carbohydrate during each hour of exercise (Coggan & Coyle,
1991; Murray et al., 1991). We therefore
recommend that individuals consume solutions that provide 30-60 g of carbohydrate
per hour in the form of glucose, sucrose, or
starch (Coggan & Coyle, 1991 ).
It was previously thought that the addition of carbohydrate to solutions impaired
fluid replacement because carbohydrate is
known to slow the rate at which fluids empty
from the stomach (gastric emptying).
However, the most important factor regulating gastric emptying and fluid replacement
is the volume of fluid ingested; the carbohydrate concentration of the solution is of secondary importance (Coyle & Montain,
1992a; Coyle & Montain, 1992b, Mitchell et
al., 1989; Noakes et al. 1991b; Rehrer et al.
1990). Practically speaking, solutions containing up to 8% carbohydrate appear to
have little deleterious influence on the rate
of gastric emptying, especially when the
drinking schedule adopted maintains a high
gastric volume (Coyle & Montain, 1992b;
Houmard et al., 1991; Mitchell et al., 1988;
Noakes et al., 1991b). Thus, it is quite possible to ingest 30-60 g of carbohydrate per
hour and still replace 600-1,250 mL of
fluid per hour. Our experience is that
cyclists have no difficulty drinking 1,200
mL/h of a 6% carbohydrate solution.
Difficulties in Drinking Large Volumes
of Fluids While Running
Large gastric volumes will no doubt
cause discomfort in some runners.
Therefore, in runners, it remains to be
deter-mined if the performance benefits of
high rates of fluid replacement outweigh
the discomfort it may cause. We suspect
that many marathon runners allow themselves to become dehydrated to some extent
because they feel their stomachs cannot tolerate the large volumes of fluid that must
be drunk to totally offset sweat losses. In
general, most runners drink less than about
500 mL of fluid per hour (Noakes et al,
1991 a; Noakes, 1993). Because sweat rates
often average 1,000-1,500 mL/h, marathon
runners commonly become dehydrated at a
rate of 500-1,000 mL/h, although dehydration rates can be much higher when the
fastest runners compete in hot environments. Unfortunately, drinking large volumes of fluid cost the runner additional
seconds in approaching the aid-station table
and in attempting to drink and breathe
while running. Furthermore, the added gastrointestinal discomfort may cause the
competitor to run at a slower pace until the
discomfort subsides. The runner must
answer the question of whether the time
lost while drinking larger volumes of fluid
will be compensated for by the physiological benefits the extra fluid produces that
may cause me to run faster during the last
half of the race. However, if the goal is
safety, which means minimizing hyperthermia, it is clear that the closer that the rate
of drinking can match the rate of dehydration, the better.
To our knowledge, no studies have
directly compared the effects on running or
cycling performance of fluid replacement at
rates that prevent dehydration versus rates
voluntarily chosen by many endurance athletes (e.g., 500 mL/h) who replace only 3050% of fluid losses. The cardiovascular
benefits of full compared to partial fluid
replacement when cycling are discussed
below, and it is likely that the same cardiovascular benefits are derived when running.
LOW INTENSITY EXERCISE AND
FLUID REPLACEMENT
In experiments conducted about the
time of World War II, it was repeatedly
found that fluid ingestion during prolonged
low-intensity exercise such as walking and
stair stepping attenuated deep body (core)
temperature and improved exercise performance (Adolph, 1947; Bean & Eichna,
1943; Eichna et al. 1945; Pitts et al., 1944).
Fluid ingestion equal to the rate of sweating was more effective than voluntary or
partial fluid replacement (Bean & Eichna,
1943; Eichna et al., 1945; Pitts et al.,
1944). Furthermore, voluntary fluid ingestion during low-intensity exercise is more
effective in attenuating hyperthermia than
when fluid intake is totally prohibited or is
restricted to small volumes (Eichna et al.
1945; Pitts et al. 1944). Thus, during prolonged, low-intensity, intermittent exercise,
the optimal rate of fluid replacement for
attenuating hyperthermia appears to be the
rate that most closely matches the rate of
sweating.
CARDIOVASCULAR AND
THERMOREGULATORY BENEFITS
OF HIGH RATES OF FLUID
REPLACEMENT DURING INTENSE
CYCLING IN THE HEAT
To gain some insight into the effects of
various fluid replenishment schemes on
exercise at the high intensities typically
experienced in sport competition, we determined the effect of different rates of fluid
replacement during prolonged intense
cycling on hyperthermia, cardiac output,
and heart rate (Coyle & Montain, 1992a).
On four different occasions endurancetrained cyclists exercised in a warm environment (33 _ C, 50% relative humidity) at
62-67% VO2max, which was the highest
intensity that could be maintained for 2 h
when no fluid was ingested. During 2 h of
exercise, the cyclists randomly received
either no fluid or drank small (300 mL/h),
moderate (700 mL/h), or large (1,200
mL/h) volumes of a sport drink containing
6% carbohydrate and low concentrations of
electrolytes. These fluid volumes replaced
approximately 20%, 50%, and 80%,
respectively, of the fluid lost in sweat during exercise. The protocol resulted in
graded magnitudes of dehydration; body
weight declined 4%, 3%, 2% and 1%,
respectively, when drinking either no fluid
or small, moderate, or large volumes of
fluid. The increases in core temperature,
heart rate, and perceived exertion during
the 2 h of exercise were progressively
diminished as more and more fluid was
consumed (Figure 1 ). The magnitude of
dehydration accrued after 2 h of exercise in
the four trials was the major factor associated with hyperthermia and cardiovascular
stress. Figure 2 demonstrates that the rise in
core temperature, the rise in heart rate, and
the fall in cardiac output observed after 2 h
of exercise were inversely related to the
rate of fluid ingestion and directly related
to the extent of dehydration experienced.
Specifically, every 1 L loss of sweat (2.2 lb
of body weight) caused heart rate to
increase by eight beats per minute, cardiac
output to decline by 1 L/min, and core temperature to increase by 0.3o C. Therefore,
we maintain that there is no acceptable
amount of dehydration that can be tolerated
before cardiovascular function and thermoregulation are impaired. Drinking 1,200
mL/h was better than drinking 700 mL,
which in turn was better than drinking 300
mL/h.
Perception of Effort
Although performance was not actually
measured in the study just described, several subjects were barely able to complete 2 h
of exercise without fluid ingestion
(Montain & Coyle, 1992). Drinking progressively larger volumes of fluid reduced
the subjective rating of perceived exertion,
as shown in Figure 1. After 2 h of exercise,
these cyclists rated the exercise as being
"very hard" when no fluid was ingested and
"hard" when only 300 mL/h of fluid was
ingested. (Competitors often drink only a
small volume of fluid (e.g., 300 mL/h),
which may give a false sense of security by
somewhat reducing their sense of perceived
exertion while providing only minimal
physiological benefit.) However, when
fluid was consumed at a rate of 700 mL/h
or 1,200 mL/h, the exercise never was rated
"hard." It is likely that these perceptions of
effort provide indirect information about
performance ability after 2 h of cycling
with different amounts of fluid replacement. Additionally, none of the cyclists
complained of gastrointestinal discomfort
or of difficulty drinking 1,200 mL/h. We
therefore conclude that this rate of fluid
replacement is tolerable during cycling, but
we do not know whether it is acceptable
when running.
Figure 1. Core temperature (esophageal temperature), heart rate, and perceived exertion during 120
min of exercise when ingesting no fluid, or small (300 mL/h), moderate (700 mL/h) and large (1,200
mL/h) volumes of fluid. A rating of 17 for perceived exertion corresponds to "Very Hard," 15 is "Hard,"
and 13 is "Somewhat Hard". Values are means-SE. * Significantly lower than no fluid, P < 0.05.
Significantly lower than small
POSSIBLE REASONS FOR THE
CARDIOVASCULAR BENEFIT OF
FLUID REPLACEMENT DURING
EXERCISE
The most serious consequence of exercise-induced dehydration is hyperthermia,
which places added stress on the cardiovascular system and creates a vicious
cycle. Dehydration during exercise causes
fluid to be lost throughout the body. As a
result, dehydration increases the concentration of dissolved particles in bodily fluids (osmolality), including the
concentration of sodium in the blood
serum. These increases in osmolality and
in sodium concentration seem to play
some role in slowing heat loss by reducing
blood flow to the skin and by reducing the
rate of sweating. An addition-al important
effect of dehydration-induced hyperthermia is a large decline in cardiac output, a
measure of total blood flow throughout the
body. This exacerbates the hyperthermia
by further reducing the transfer of heat
from the body core to the cooler periphery
(Montain & Coyle, 1992a). The most dramatic consequence of dehydration-induced
hyperthermia during exercise is a 25-30%
reduction in stroke volume that is not generally met with a proportional increase in
heart rate; this results in a decline in cardiac output and in arterial blood pressure
(Gonzalez-Alonso et al., 1994; Montain &
Coyle, 1992a).
The primary benefit of sufficient fluid
replacement during exercise is that it helps
to maintain cardiac output and allows
blood flow to the skin to increase to high
levels so as to promote heat dissipation
from the skin, thereby preventing excessive storage of body heat (Montain &
Coyle, 1992a). The exact mechanism by
which fluid replacement pro-motes a high
skin blood flow during exercise is not
clear. Fluid replacement does help to prevent loss of water from the blood plasma,
but in endurance-trained athletes, this
improved maintenance of plasma volume
apparently does not by itself increase
blood flow to the skin to reduce core temperature (Montain & Coyle, 199b). It
seems more likely that fluid replacement
prevents skin blood flow from declining
by preventing dehydration-induced impairments in the neural control of skin blood
flow, by preventing declines in blood pressure, and/or by minimizing the
exercise/dehydration-induced increases in
the blood concentrations of catecholamines, sodium, and other osmotically
active particles.
PERFORMANCE BENEFITS OF
INGESTING FLUIDS AND
CARBOHYDRATE
As discussed previously, fluid replacement during exercise improves work time
in subjects walking in the desert, but surprisingly few studies have documented performance benefits of fluid replacement
during more intense exercise in laboratory
studies or during competitive athletic
events (Armstrong et al., 1985; Costill et
al., 1970). It is to be expected that fluid
replacement would be most beneficial during more prolonged exercise that accentuates the amount of dehydration. As shown
in Figure 1, during 2 h of exercise in the
heat (33 _ C) at 65% VO2max, the physiological benefits of fluid replacement began
to emerge after 1 h of exercise (Montain &
Coyle, 1992b). This prompted us to conduct a performance study during more
intense cycling in the heat, performed for a
duration of approximately 1 h (Below et al.,
In Press). After 50 min of exercise at 80%
VO2max, heart rate and core temperature
were lower by four beats/min and 0.33o C,
respectively (P<O.05), when a large volume (1300 mL) compared to a small volume of fluid (200 mL) was ingested during
the first 35 min of exercise. Performance
was then measured as the number of minutes required to complete a set amount of
work, so as to simulate the closing stages
of a race. Performance time for this last
stage of cycling was 6% faster when the
large volume of fluid was ingested.
Carbohydrate ingestion clearly
improves performance in events lasting
longer than 90 min and in which fatigue is
associated with reduced bodily stores of
carbohydrate ( Coggan & Coyle, 1991), but
little is known about the influence of carbohydrate feedings on shorter duration exercise that is more typical of most sport
events. Therefore, in the previously cited
study (Below et al., In Press), we also
determined if ingestion of 70 g of carbohydrate might improve performance of a
brief, high-power cycling test following 50
min of cycling at 80% VO2max. Indeed,
performance was also improved 6% by carbohydrate ingestion. Therefore, both fluid
replacement and carbohydrate ingestion
equally improved high-intensity cycling
performance, each by 6%. Furthermore,
their beneficial effects were additive, i.e.,
there was a 12% improvement in performance when both fluid and carbohydrate
were administered, and these effects appar-
ently operate through independent mechanisms (Below et al., In Press).
EXERCISE/DEHYDRATIONINDUCED HYPERTHERMIA IN
VARIOUS ENVIRONMENTS
The exercise intensity and environmental conditions determine the extent to which
dehydration causes hyperthermia during
exercise and the extent to which fluid
replacement can prevent the hyperthermia.
When an individual exercises at a moderate
intensity, e.g., 60-70% VO2max, in a
warm/hot environment (20-35o C) with
moderate humidity (<50% rh), heat is dissipated primarily by evaporative heat loss.
This heat dissipation is impaired by dehydration, which decreases skin blood flow
and sweating rate. In these environments,
% loss of body weight due to dehydration
causes core temperature to increase by
about 0.15-0.30o C (Coyle & Montain,
1993). However, during exercise m a cool
environment (0-10o C), dehydration
appears to cause a relatively small degree
of hyperthermia, probably because convec-
tive heat loss is sufficiently large to compensate for reduced skin blood flow and
reduced evaporation of sweat.
Body core temperature is the balance
between heat production and heat dissipation, and fluid replacement has its limitations if this balance is skewed. For
example, in very hot and humid environments in which heat dissipation by evaporation and convection is minimal, fluid
replacement will reduce cardiovascular
stress and may improve performance, but it
will have little effect on body temperature.
Likewise, when the exercise intensity is
great enough to cause a very high rate of
heat production, it will not be possible for
even well-hydrated people to increase heat
dissipation enough to prevent excessive
hyperthermia. In these situations, the only
safe option is for individuals to reduce their
heat production by lowering exercise intensity.
TIMING OF FLUID REPLACEMENT
DURING EXERCISE
Is there a time interval during prolonged
Figure 2. The influence of dehydration, as assessed by the percent reduction in body weight after 2 h of
exercise, on the change in rectal temperature, cardiac output, and heart rate. (Reprinted with permission
from Coyle & Montain 1992b).
exercise that is most advantageous for fluid
replacement? Should one drink early in
exercise, throughout exercise, or wait until
near the end of the exercise? In an attempt
to answer these questions, we studied
cyclists who drank about 1 L of fluid at
various times during 140 min of exercise
(Montain & Coyle, 1993). They drank after
either O, 40, or 80 min of exercise or drank
the 1 L intermittently throughout exercise.
In all cases, they incurred the same amount
of dehydration after 140 min, and they
were not different in any of their cardiovascular or THERMOREGULATORY
responses. During the 40 min period immediately after drinking fluid, regardless of
the time of drinking, the subjects stabilized
their heart rates and core temperatures.
During the periods without fluid ingestion,
there was progressive hyperthermia and
increased cardiovascular strain. These
observations suggest that the volume of
fluid ingested is most important, and the
timing of ingestion is secondary.
Individual Trial and Error
Although we generally recommend that
people drink large volumes of fluid and
attempt to totally offset dehydration, we
realize that individuals differ tremendously
in their rates of gastric emptying and, therefore, in their tolerances of large fluid volumes. Each person must devise an
individualized drinking schedule that
appears optimal and should become accustomed to this schedule during practice
(Rehrer et al., 1989 ).
increases in body core temperature, heart
rate, and ratings of the perceived difficulty
of exercise. This same phenomenon probably also applies to running and argues
against the notion that a certain amount of
dehydration (e.g., up to 3% of body weight)
is permissible and without cardiovascular
consequences (Noakes et al., 1991 a).
However, runners generally drink only 500
mL/h and thus allow themselves to become
dehydrated at rates of 500-1,000 mL/h.
Runners must compare the benefits of
drinking large volumes of fluid during
competition, i.e., the physiological
improvements and the likely improvement
in running speed during the late stages of
the race, with the drawbacks of having to
slow down while drinking and while suffering gastrointestinal discomfort. If the primary goal is safety, which means
minimizing hyperthermia, there is no question that the runner should attempt to match
the rate of drinking to the rate of dehydra-
tion.
SUMMARY
Ingestion of approximately 30-60 g of
carbohydrate during each hour of exercise
will generally be sufficient to maintain high
rates of oxidation of blood glucose late in
exercise and to delay fatigue. Because the
average rates of gastric emptying and
intestinal absorption exceed 1,250 mL/h for
water and for solutions containing up to 8%
carbohydrate, exercising sports competitors
can be supplemented with both carbohydrate and fluids at relatively high rates.
When cyclists exercise at competitive
intensities for 2 h in the heat with sweat
rates of 1,400 mL/h, it is clear that the
closer that fluid consumption matches
sweating rate (at least up to 80% of sweating rate), the better. When fluid consumption is inadequate, increasing dehydration
directly impairs stroke volume, cardiac output, and skin blood flow, resulting in progressive
References
Adolph, E.E Blood changes in dehydration. In: Physiology of Man in the Desert. New York: Interscience Publ., Inc., 1947, pp. 160-171.
Armstrong, L.E., R.W. Hubbard, EC. Szlyk, W.T. Matthew, and I.V. Sils. Voluntary dehydration and electrolyte losses during prolonged exercise in
the heat. Aviat. Space Environ. Med. 56: 765-770, 1985.
Below, ER., R. Mora-Rodriguez, J. Gonzalez-Alonso, and E. E Coyle. Fluid and carbohydrate ingestion independently improve performance during 1 H of intense exercise. Med. Sci. Sports Exerc. (In press).
Bean, W.B., and L.W. Eichna. Performance in relation to environmental temperature. Reactions of normal young men to simuulated desert environment. Fed. Proc. 2: 144-158, 1943.
Coggan, A.R., and E.E Coyle. Carbohydrate ingestion during prolonged exercise: effects on metabolism and performance. Exerc. Sports Sci. Rev.
19: 1-40, 1991.
Costill, D.L., W.E Kammer, and A. Fisher. Fluid ingestion during distance running. Arch. Environ. Health 21: 520-525, 1970.
Coyle, E.E, A.R. Coggan, M.K. Hemmert, and J.L. Ivy. Muscle glycogen utilization during prolonged strenuous exercise when fed carbohydrate. J.
Appl. Physiol. 61: 165-172, 1986.
Coyle, E.E, and S.J. Montain. Carbohydrate and fluid ingestion during exercise: Are there trade-offs? Med. Sci. Sports Exerc. 24: 671-678, 1992a.
Coyle, E.E, and S.J. Montain. Benefits of fluid replacement with carbohydrate during exercise. Med. Sci. Sports Exerc. 24: $324-$330, 1992b.
Coyle, E.E, and S.J. Montain. Thermal and cardiovascular responses to fluid replacement during exercise. In: C.V. Gisolfi and D.R. Lamb (eds.)
Perspectives in Exercise Science and Sports Medicine. Vol 6: Exercise, Heat, and Thermoregulation. Carmel, IN: Brown & Benchmark, 1993, pp.
179-224.
Eichna, L.W., W.B. Bean, W.E Ashe, and N. Nelson. Performance in relation to environmental temperature. Bull. Johns Hopkins Hosp. 76: 25-58,
1945.
Houmard, J.A., EC. Egan, R. Anderson, ED. Neufer, T.C. Chenier, and R.G. Israel. Gastric emptying during 1 h of cycling and running at 75%
VO2max. Med. Sci. Sports Exerc. 23: 320-325, 1991.
Gonzalez-Alonso, J, R. Mora-Rodriquez, ER. Below, and E.E Coyle. Reductions in cardiac output, mean blood pressure and skin vascular conductance with dehydration are reversed when venous return is increased. Med. Sci. Sports Exerc. 26: S 163, 1994.
Mitchell J.B., D.L. Costill, J.A. Houmard, M.G. Flynn, W.J. Fink, and J.D.Beltz. Effects of carbohydrate ingestion on gastric emptying and exercise perfor-mance. Med. Sci. Sports Exerc. 20: 110-115, 1988.
Mitchell J.B., D.L. Costill, J.A. Houmard, W.J Fink, R.A. Robergs, and J.A. Davis. Gastric emptying influence of prolonged exercise and carbohydrate concen-tration. Med. Sci. Sports Exerc. 21:269-274, 1989.
Mitchell J.B., and K.W. Voss. The influence of volume on gastric emptying and fluid balance during prolonged exercise. Med. Sci. Sports Exerc.
23: 314-319, 1991.
Montain S.J., and E.E Coyle. Fluid ingestion during exercise increases skin blood flow independent of increases in blood volume. J. Appl. Physiol.
73: 903-910, 1992a.
Montain S.J., and E.E Coyle. The influence of graded dehydration on hyperthermia and cardiovascular drift during exercise. J. Appl. Physiol.
73:1340-1350, 1992b.
Montain S.J., and E.E Coyle. Influence of the timing of fluid ingestion on temperature regulation during exercise. J. Appl. Physiol. 75: 688-695,
1993.
Murray, R, D.E. Eddy, T.W. Murray, J.G. Seifert, G.L. Paul, and G.A. Halaby. The effect of fluid and carbohydrate feedings during intermittent
cycling exercise. Med. Sci. Sports Exerc. 19: 597-604, 1987.
Murray, R., G.L. Paul, J.G. Seifert, and D.E. Eddy. Responses to varying rates of carbohydrate ingestion during exercise. Med. Sci. Sports Exerc.
23: 713-718, 1991.
Noakes, T.D., K.H. Myburgh, J. Du Plessia, L. Lang, M. Lambert, C. Van Der Riet, and R. Schall. Metabolic rate, not percent dehydration, predicts
rectal tem-perature in marathon runners. Med. Sci. Sports Exerc. 23: 443-449, 1991a.
Noakes, T.D., N.J. Rehrer, and R.J. Maughan. The importance of volume in regulating gastric emptying. Med. Sci. Sports Exerc. 23: 307-313,
1991b. Noakes, T.D. Fluid replacement during exercise. Exerc. Sports Sci. Rev. 21: 297-330, 1993.
Pitts, G.C., R.E. Johnson, and EC. Consolazio. Work in the heat as affected by intake of water, salt and glucose. Am. J. Physiol. 142: 253-259,
1944.
Rehrer, N.J., E. Beckets, E Brouns, E Ten Hoor, and W.H.M. Saris. Exercise and training effects on gastric emptying of carbohydrate beverages.
Med. Sci. Sports Exerc. 21: 540-549, 1989.
Rehrer, N.J., E.J. Beckers, F. Brouns, ETen Hoor, and W.H.M. Saris. Effects of dehydration on gastric emptying and gastrointestinal distress while
running. Med. Sci. Sports Exerc. 22: 790-795, 1990.
Rehrer, N.J., E Brouns, E. Beckers, ETen Hoof, and W.H.M. Saris. Gastric emptying with repeated drinks during running and bicycling. InL J.
Sports Med. 11: 238-243, 1990.
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