Pre-Exercise Carbohydrate Meal and Endurance Running Capacity
when Carbohydrates are Ingested During Exercise
C. Chryssanthopoulos, C. Williams
Department of Physical Education. Sports Science and Recreation Management, Loughborough University. Loughborough. England
C. Chryssanthopoulos, C . Williams. Pre-Exercise Carbohydrate
Meal and Endurance Running Capacity when Carbohydrates
are Ingested During Exercise. Int. 1. Sports Med.. Vol. 18,
pp. 543 - 548,1997.
This study examined whether combining a pre-exerctse
carbohydrate meal with the ingestion of a carbohydrate-elec-
trolyte solution during exercise is better in improving endur-
ance running capacity than a carbohydrate-electrolyte solution
alone. Ten men completed three treadmill runs at 70% ~0,max
to exhaustion. They consumed 1.) a carbohydrate meal three
hours before exercise and a carbohydrate-electrolyte solution
during exercise (M + C), or 2.) a llquid placebo three hours be-
fore exercise and the carbohydrate-electrolyte solution during
exercise (P+ C), or 3.) a placebo three hours before exercise
and placebo during exercise (P + P). When the meal was con-
sumed (M + C) serum insulin concentrations were higher at the
start of exercise, and carbohydrate oxidation rates were higher
during the first 60min of exercise compared with the values
found in the P+ C and P + P trials (p ~0.01). Exercise time was
longer in the M + C (147.4 f 9.6 rnin) compared with the P + C
(125.3 + 7 min) (p < 0.01). Also, exercise time was longer in
M + C and P + C compared with the P + P (115.1 f 7.6 min)
(p < 0.01 and p < 0.05 respectively). These results indicate that
the combination of a pre-exercise carbohydrate meal and a car-
bohydrate-electrolyte solution further improves endurance run-
ning capacity than the carbohydrate-electrolyte solution alone.
Key words: Pre-exercise meal. carbohydrate-electrolyte solu-
tion, running capacity
Consuming a carbohydrate meal 3-4 hours before prolonged
exercise improves cycling performance (21.29) and running
capacity (1) compared to an overnight fast. Furthermore, the
combination of a pre-exercise meal and a carbohydrate-elec-
trolyte solution during exercise improves endurance running
capacity to a greater extent than a pre-exercise meal alone
(1). However, pre-exercise feeding elevates serum insulin con-
centration before exercise (1.5.29). accelerates carbohydrate
oxidation (1,7,14,15,27,29). and depresses the blood born FFA
concentration (1,5,7,29). Collectively, all these metabolic per-
turbations may not be the most favourable to the endurance
athlete, since they may accelerate the use of the limited mus-
cle glycogen stores (5,22).
Ingesting carbohydrates during exercise delays the onset of fa-
tigue in cycling (4.6,8.29), as well as in running (16.20.24-
26). Also. the ingestion of carbohydrates during exercise does
not alter the carbohydrate oxidation rates, at least during the
first hour of exercise (126.96.36.199-26). and spares muscle glyco-
gen stores during running (23,24).
Therefore, the aim of the present study was to examine whe-
ther the ingestion of carbohydrates before and during exercise
would improve endurance running capacity to a greater extent
than simply ingesting carbohydrates during exercise.
Ten male reaeational/club level runners volunteered to take
part in this study. Their age, height, body weight. \io,rnax,
and maximum heart rate were 34.9 ? 2.5 years, 174.5 * 2.9 cm,
72.4 r 3.6 kg, 58.6 f 1 . 9 ml x k g x min-I. and 186 24 b x min-I
respectively (mean 2 SE). Nine subjects completed all three
trials, and one completed only two trials. All subjects were
fully jnformed about the nature of the experiments and what
was required of them before giving formal consent. The study
had the approval of the Ethical Advisory Committee of Lough-
After subjects became familiar with treadmill running and ex-
perimental procedures, they performed two preliminary tests:
a) a 16-rnin incremental submaximal running test to deter-
mine the relationship between running speed and oxygen
b) an uphill treadmill running test to determine each subject's
maximum oxygen uptake.
Int. 1. Sports Med. 18 (1997) 543-548
O Georg Thieme Verlag Stuttgart . New York
Int.]. Sports Med. 18 (1997)
C. Chryssonthopoulos. C . Williams
All preliminary tests were conducted according to the proce-
dures previously described (28). Subjects also undertook a
60 min treadmill run at 70% ~0,max, about one week before
the first experimental trial in order to become fully familiar-
ised with the drinking pattern and the measurements used
during the main trails.
Subjects were required to record training and to weigh their
food intake during the two days prior to the first trial, and to
replicate these in the next two trials. The dietary information
obtained was then analyzed (18). There were no significant dif-
ferences between the three trials in the average daily energy
intake, or composition in terms of carbohydrate, fat, or protein
consumed during the two days prior to each trial. Subjects
were also required to avoid training the day before each main
Each subject was required to run to fatigue at 70%irOzmaxon a
motorised level treadmill (Quinton, Seattle, USA) on three dif-
ferent occasions separated by one week. On the first occasion a
high carbohydrate meal was eaten three hours before exercise,
and during exercise a carbohydrate-electrolyte solution was
ingested (M + C). On the second and third trials 10 ml x kg1
B W of a liquid placebo were ingested three hours before exer-
cise (P + C and P+ P). During exercise, in the second trial sub-
jects ingested a carbohydrate-electrolyte solution (P+C),
whereas in the third trial a liquid placebo was administered
(P+ P). The order of the three trials was random. Since solid
food was used before exercise a double blind design was im-
possible. In order to make the desjgn single blind subjects
were told that the purpose of the experiment was to compare
solid and liquid carbohydrate food in different combinations
and concentrations before and/or duringexercise and that dur-
ing the three trials they ingested the same amount of carbohy-
drate by adjusting the concentration of the ljquid parts (i.e. li-
quid placebo. or orange juice) of the meals.
After a 12-hour overnight fast subjects arrived at the labora-
tory at 8 : 00 a.m. Duplicate 20 p1 capillary blood samples were
taken from the thumb of a pre-warmed hand after they had
been sitting quietly for 15 min. Following this, subjects ingest-
ed either the liquid placebo (P +C and P+ P), or the high carbo-
hydrate meal (M +C). During the 3-hour postprandial period
subjects remained in the laboratory reading and writing, or
were involved with low intensity physical activities (e.g. at-
tending lectures, doing office work etc.) outside the laboratory.
These activities were very similar in all experimental trials. Be-
fore the initiation of exercise, each subject's nude body weight
was recorded. Thereafter. subjects were seated and a venous
blood sample was taken from an antecubital vein as well as an-
other capillary blood sample from a pre-warmed hand. Sub-
jects warmed up for 5 rnin on the treadmill at 60% W,max.
Following this. the speed of the treadmill was increased to
70% m2max and the subjects continued running until exhaus-
tion. They were encouraged to run as long as possible. How-
ever, when they were unable to maintain their prescribed run-
ning speed, and in order to ensure that fatigue had occurred,
the speed was reduced to 60% ~0,max for 2 min. Thereafter.
the speed was returned to the prescribed speed and the sub-
jects were encouraged to continue for as long as possible.
One minute expired air samples and duplicate 2 0 ~ 1
samples were collected at 10min and 20min into exercise
and every 20 min thereafter. Expired air and capillary blood
samples were also collected at the last minute of the run. Also.
each subject's rate of perceived exertion (RPE) was obtained
using the Borg's scale. Furthermore, two additional scales were
used, one to monitor the subject's abdominal discomfort (AD)
and the other was used to assess their sensation of gut fullness
(CF). Both scales ranged from 0 (AD: "Completely comforta-
ble"; GF: "Empty") up to 10 (AD: "Unbearable pain": GF:
"Bloated"). Heart rate was monitored throughout exercise by
short-range telemetry (Polar Electro Sports Tester P E 3000).
Wet sponges were available for the subjects to use ad libitum
throughout each of the runs, Immediately after subjects stop-
ped exercise, a further venous sample was taken while they
were seated: thereafter subjects dried themselves, and post-
exercise nude body weight was recorded.
All trials were conducted under similar laboratory conditions:
temperatures: M + C: 19.8 + 0.8 "C, P + C: 20.3 + 0.6 "C, and P + P:
20.1 ? 0.8 "C; relative humidity: M + C: 59.6 r 2.8 %. P + C:
53.3 r 2.4%, and P+ P: 51.9 &2.3% (mean +SE; n.s.).
Three hours before each run subjects consumed either
10 m x kg-' B W of a liquid placebo (dilute sugar free orange
juice; less than I kcal per 700 ml undiluted) (P+ C. and P + P
trials), or the high carbohydrate meal (M + C) (2.5 g carbohy-
drates per kg BW). The pre-exercise meal (M + C) consisted of
white bread, jam, cornflakes, sugar, skimmed milk and orange
juice which amounted to 86% of energy intake from carbohy-
drate, 11 % from protein and less than 3% from fat. About 88% of
the carbohydrate included in the meal was obtained from food
classified as having a high glycaemic index. whereas the rest
was obtained from food with moderate and low glycaemic in-
dex (11). During exercise in the M + C and P + C trials an isoton-
ic lemon and lime carbohydrate-electrolyte solution was in-
gested, whereas in the P + P trial equivalent amount of a liquid
placebo (dilute sugar free lemon and lime juice) was given. The
carbohydrate-electrolyte solution was a commercially avail-
able sports drink (Lucozade Sport) which contained 6.9% car-
bohydrate (dextrose, maltodextrin and glucose syrup) and four
electrolytes (24 mmol x I- ' sodium. 2.5 mmol x I-' potassium.
1.2 mmol x I-
calcium, and 0.8 mmol x 1-
mediately prior to the start of exercise subjects ingested
5 ml x k g BW of the carbohydrate solution (M + C and P + C
trials) or equivalent amount of placebo (P+ P), and 2 ml x kg-'
BW of the assigned fluid every 20min thereafter. The total
amount of carbohydrate ingested in the M+C trial was
259 k 13.8 g (181 ? 9 g as meal and 78 + 6 g during exercise),
whereas in the P + C trial was 70? 4 g.
The method of collection and analysis of expired air samples
was the same as previousfy described (28). Venous blood sam-
ples were collected into lithium heparin and serum tubes.
Blood glucose, blood lactate, haemoglobin, haematocrit, per-
centage changes in plasma volume, plasma FFA, and plasma
Pre-Exercise Carbohydrate Meal and Endurance Running Capacity
glycerol, were measured as previously described (28). Serum
sodium and potassium were anaIysed by flame photometry
(Coming 435 flame photometer). Serum samples were also
stored at - 70°C and analysed at a later date for serum insulin
radioimmunoassay; Coat-A-Count Insulin. DPC kit) using
a gamma counter (Packard. Cobra 5000).
A two-way analysis of variance (ANOVA) for repeated meas-
ures on two factors (treatment by time) was used to compare
cardiovascular changes, blood glucose. and blood lactate re-
sponses between trials. The remaining responses were exam-
ined using a two tailed Student's t-test for dependent samples.
When significant differences were revealed using the ANOVA,
a Tukey post hoc test was performed. The accepted level of sig-
nificance was set at p < 0,05. Data are reported as mean f SE.
Exercise time was longer in the M + C (147.4 + 9.6 rnin; n =9)
and P + C (125.3 + 7.0 min: n = 10) trials compared with the
P+ P (115.1 r7.6 min; n= 10) trial (p < 0.01 and p< 0.05 respec-
tively). Also, exercise time was longer in the M +C compared
with the P + C trial (p < 0.07 ). No difference was found. how-
ever, when exercise time to exhaustion was analysed by order
(TI : 126.3 + 10.8 min vs T2: 129.8 29.3 min vs T3: 130.0f
6.5 min; n.s.).
Oxygen uptake ( ~ 0 ~ ) .
averaged 41.1 r 1.6 ml x k g x min-I (2.9 f 0.2 1 x min- I). 41.5 ?
1.2 ml x k g x min-I (2.9 f 0.2 I x min- I), and 41.8 * 1.7 rnl x
trjals respectively (n.s.). The average% ~ 0 ~ m a x
ing the McC, P+C, and P+P trials were 69.8 k0.6%.
70.5? 0.6%. and 71.0 +0.8%, respectively (n.s.).
was similar between the three trials and
in the M+C. P+C. and P+P
Respiratory exchange ratio (RER), was higher (p < 0.01) in the
M + C trial compared with the P + C, and P+ P trials during the
first hour of exercise (Fig.l), reflecting a higher carbohydrate
oxidation rate (Fig. 2) (p < 0.01).
No differences were found in the heart rate responses between
trials (Mean: M + C: 155 & 5 b x min- ' vs P+ C: 158 f 5 bx min- '
vs P + P: 158 2 5 b x min I ) . However, heart rates were higher
(p <0.01) in all trials at exhaustion compared with the heart
rates during the first hour of exercise. Rate of perceived exer-
tion increased from 10.7k 0.4 at lOmin of exercise to
17.7 + 0.4 at exhaustion in all trials (p< 0.01). At 80 min of exer-
cise RPE was lower in the M+C (12.7f0.6) and P+C
(13.1 k0.7) trials compared with P+P (14.350.7) trial
(p < 0.01 and p < 0.05 respectively). No difference was ob-
served, however, in the GF and AD responses between the
The volume of fluid consumed during exercise was
1137 k 90 ml, 1015 + 60 ml, and 968 ? 70 ml in the M +C. P + C,
and P + P trials respectively. These values were significantly
different only between the M +C and P+ P trials ( p i 0.05;
n = 9). The average decrease in body mass, as a result of exer-
cise, was 3.31 k 0.27 kg. 2.82 k 0.25 kg, and 2.60 50.25 kg in
M + C, P + C. and P + P trials respectively. These values were cor-
rected for the fluid ingested during running. These decreases
Int.]. Sports Med. 18 (1997)
Fig.1 Respiratory exchange ratio (RER) during the M + C, P + C. and
P + P trials (mean f SE; n = 9)
pc0.01 fromP+Cand P t P ; " p<0.05fromM+C
- b P I C
M a t
Flg. 2 Carbohydrate oxidation rate (g x min-') during the M + C, P + C,
and P + P trials (mean? SE; n = 9)
p<0.01 fromP+CandP+P;" p<0.01 frornP+P
represented body weight changes of 4.7 ? 0.4%. 3.9 a 0.3%. and
3.6?0.4% respectively. The decrease in body weight as
expressed both in kg and percent change (%) of body weight,
was higher in the M+C trial compared with the P+C
(p < 0.05, n = 9). and P + P (p < 0.01. n = 9) trials. However. no
difference was observed between the three trials in the mean
change of plasma volume (M +C: - 8.3 r 1.9% vs P+ C: - 7.5 ?
1.1 % vs P+ P: - 9.3 k 1.8%).
Blood glucose concentration (Fig. 3) was higher at exhaustion
in the M + C trial compared with the P+ P trial ( p i 0.05). How-
ever, in the P+ P trial blood glucose concentration at exhaus-
tion (4.2 kO.2 mmol x 1- I ) was not different from the blood glu-
cose concentration at the start of exercise (Omin: 4.62
0.1 mmol x I- I). Also, blood glucose concentrarion tended to
be higher (p = 0.05) in the P + C trial at 10 min, at 60 min of
exercise compared with the P+ P and M + C, and P+ P trials,
Blood lactate concentrations were similar between trials
throughout exercise and averaged 3.2 * 0.3 mmol x I-',
Int. 1. Sports Med. 18 (1997)
C. Chryssonthopoulos, C . Williams
Table 1 Serum insulin (mu x I-'), plasma FFA, plasma glycerol, serum sodium and serum potassium concentrations (mmol x I-') before and after
exercise in the M + C. P + C, and P + P trials (mean ? SE; n = 9)
P + C
P + C
M + C
0.1 lCf 0.01
1 42d k 0.5
4.2d * 0.1
4.3a-c + 0.5
0.36aJ + 0.04
0.08b.c ir 0.01
2.7 f 0.6
0.67 f 0.1 1
0.38 f 0.06
143 k 0.6
1.9 ? 0.3
0.58b f 0.07
142 + 0.6
a: p<0.01 from M + C: b: p c 0.05 from M +C; c: pc0.01 from post exercise; d: pc0.05 from port exercise: e: p c 0.05 from P+ P
4 0 '
(M + C) compared with the ingestion of the carbohydrate-elec-
trolyte solution (P + C) alone. Furthermore. the 6.9% carbohy-
drate-electrolyte drink (P + C) produced a smaller (9%) but sig-
nificant improvement in endurance capacity compared to con-
trol conditions (P + P). However. the biggest improvement
(28 %) over control (P + P), was achieved when the pre-exercise
meal was combined with the ingestion of the carbohydrate-
electrolyte solution (M + C) during exercise.
Various studies have shown an improved endurance capacity
during cycling (6.8.29). and running (16,20,25,26), as a result
of carbohydrate ingestion during exercise. It has been suggest-
ed that the main contribution of exogenous carbohydrate is to
maintain blood glucose concentrations and a high rate of car-
bohydrate oxidation by the working muscle during endurance
cycling exercise (6,8). This is because during cycling, fatigue in
the fasted state has been associated with a decline in blood
glucose concentration, and the rate of carbohydrate oxidation
(4,6,29). In the present study the respiratory exchange ratios,
reflecting the rate of carbohydrate oxidation, were not signifi-
cantly reduced wjth time in the control trial (P+ P), although
the non ~tah'Sti~a1ly significant decline observed towards the
end of exercise (Fig. 2) may hold some physiological significance.
Furthermore, there was no significant reduction in blood glu-
cose concentration at exhaustion compared with the start of
exercise (0 min: 4.6 mmol x I-' vs Exh: 4.2 mmol x I- I). When
running is the mode of exercise blood glucose concentrations
and carbohydrate oxidation rates do not decrease with time
to the same extent as during cycling (19.24-26).
Fig. 3 Blood glucose concentration
and P + P trials (mean i:SE: n = 9)
a p=O.OSfromM+Cand P+P;
p = 0.05 from P + P;
D < 0.05 from M + C
3.4 k0.5 mmol x I-', and 3.1 f0.5 mmol r I-' in the M + C, P + C,
and P + P trials respectively.
At the start of exercise serum insulin concentration (Table 1) in
the M + C trial was about 3.2 fold and 4.4fold higher compared
with the P + C and P + P trials respectively (p < 0.01).
Plasma FFA concentrations (Table I) were lower (p<0.01) at
the beginning of exercise in the M + C trial compared with the
P + C and P + P trials. In addition, post-exercise plasma FFA con-
centrations were lower (p < 0.05) when carbohydrates were in-
gested during exercise (M + C, and P + C) compared with place-
bo ingestion (P + P). Plasma glycerol concentrations (Table 1)
were also lower in the M + C condition compared with the
P+ C (p < 0.05) and P t P (p c 0.01) conditions. Finally, pre-exer-
cise serum sodium concentration was found to be higher
(p<0.05) three hours after the consumption of the meal
(m + C), whereas serum potassium concentration was not dif-
ferent between the three conditions (Table 1).
The main finding of this study was an 18% improvement in en-
durance running capacity as a result of combining the carbo-
hydrate meal with the carbohydrate-electrolyte solution
Nevertheless, some authors have suggested that carbohydrate
intake during exercise may reduce the rate of muscle glycogen
utilisation and spare the limited muscle glycogen stores (9.23.
24). Recent studies have shown a reduced rate of glycogen
breakdown in Type I muscle fibers when carbohydrates are in-
gested during exercise compared with either water (23) or pla-
cebo (24) ingestion. Furthermore, the ingestion of carbohy-
drates during exercise may markedly reduce the hepatic glu-
cose production at 70% ~0,rnax (13).
The improvement in endurance capacity in the M + C trial is
consistent with other studies in which pre-exercise carbohy-
drate feedings were combined with carbohydrate ingestion
during exercise. These improvements in endurance capacity
were greater than the improvements when carbohydrate was
ingested only during exercise (1,15,29). A possible influence
on running capacity in the M + C trial could have been a higher
liver (17), and/or muscle carbohydrate stores (7) before the
Pre-Exercise Carbohydrate Meal and Endurance Running Capacity Int. 1. Sports Med. 18 (1997)
start of exercise. We have shown that this carbohydrate meal
increases glycogen concentration of the vastus lateralis muscle
by 11 % (2). However. the possibility that some portion of the
meal was still in the stomach or small intestine when exercise
begun, continuing to provide some substrate to the working
muscles during exercise, cannot be excluded. This suggestion
is supported by the higher plasma insulin levels before exer-
cise in the M + C trial compared to the P + C and P + P trials. This
observation seems to suggest that three hours after the inges-
tion of rhe meal (M + C) the process of digestionlabsorption
was still in progress.
Although insulin concentrations decrease rapidly when subjects
start to exercise its efict onfuel utilisation remains during the
exercise period (7). Elevated insulin concentrations at the start
of exercise may reduce the availability of FFA to the working
muscles, and increase the rate of muscle glycogen utilisation
(5), which may lead to premature fatigue (10). Nevertheless,
despite the elevated carbohydrate metabolism in the M+C
trial endurance capacity was improved compared to P + C and
P + P trials. It seems that in the M +C trial the meal increased
the pre-exercise insulin concentration, facilitating in this way
the uptake of the carbohydrate from the carbohydrate-electro-
lyte drink by the exercising muscle. The availability of this exo-
genous carbohydrate source to the muscle probably off-set the
elevated rate of carbohydrate oxidation.
During thefirst hour ofexercise the subjects oxidised about 46g
of carbohydra te more in the M + C trial compared to the carbohy-
drates oxidised following an overnight fast (PtC, P+P). This
amount is only equivalent to about 25%ojthe total carbohydrate
load consumed (about 180g) in the pre-exercise meal (M + C).
Therefore, it can be argued that the total pre-exercise carbohy-
drate load was more advantageous than the metabolic disad-
vantage of an occelemted carbohydmte oxidation rate.
The post-exercise FFA concentrations were lower when the
carbohydrate drink was ingested during exercise (P+C) com-
pared with the ingestion of placebo (P+ P). This is a common
observation which suggests a depression of F A mobilisation
when carbohydrates are ingested during exercise (3). However.
since the rates of fat oxidation were similar between the P+C
and P + P trials, as reflected by the RER values, it can be argued
that either the possible depression o j FFA mobiiisation in the
P+ C was not strong enough to deny this substrate to the working
muscle. or an alternative source of fat, such as intramuscular
triglycerides, was probably used (12).
In summary, the result of this study confirmed theobservation
of many investigators that a carbohydrate-electrolyte solution
ingested during exercise can improve endurance running ca-
pacity (16.20.24-26). Furthermore, the combination of both
a pre-exercise carbohydrate meal, providing 2.5g carbohy-
drate per I<g BW, and a carbohydrate-electrolyte solution in-
gested during exercise further improves endurance running
capacity. despite an elevated carbohydrate oxidation rate dur-
ing the first hour of exercise.
The authors wish to thank Dr. Alan Nevill, Department of
Sports Sciences. Liverpool John Moores University, England,
for his assistance in the statistical analyses of the results, and
Mrs. Maria Nute for her help during the experimental trials.
This study was supported by SmithKlineBeecham.
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23Tsintzas 0. K., Williams C., Boobis L. Greenhaff P.: Carbohydrate
ingestion and glycogen utilization in different muscle fibre types
in man. j Physiof 489: 243 - 250,1995.
0. K.. Williams C., Boobis L. Greenhaff P.: Carbohydrate
ingestion and single muscle fibre glycogen metabolism during
prolonged running in men.JAppl Physiof 81: 801 -809.1996.
K., Williams C., Wilson W.. Burrin J.: Influence of car-
bohydrate supplementation early in exercise on endurance run-
ning capacity. Med Sci Sports Exerc Vol 28, No 11: 1373 - 1379,
26Wilber R. L . . Moffatt R.].: Influence of carbohydrate ingestion on
blood glucose and performance in runners. 1ntJ Sports Nutr 2:
27 Willcutts K. F.. Wilcox A. R, Grunewald K. K.: Energy metabolism
dur~ng exercise at different time intervals following a meal. hrJ
Sports Med 9: 204 - 243.1988.
Williams C., Nute M. G.. Broadbank L. Vinall S.: Influence of fluid
intake on endurance running performance. A comparison be-
tween water. glucose and fructose solutions. Eur j Appl Physiof
29 Wright D. A,, Sherman W. M.. Dernbach A. R: Carbohydrate feed-
ing~ before, dunng or in combination improve cycling endurance
performance.]Appl Physiol71: 1082- 1088.1991.
C. Chrvssan thopoo/os. C. Williams
Professor Clyde Williams PhD
Department of Physical Education
Sports Science and Recreation Management
Leicestershire, LEI13 TU
Telephone (office): +01509-228186
Telephone (home): +01509-214151