Les avantages de la maltodextrine
Orienteering performance and ingestion of glucose and glucose polymers
Br. J. Sp. Med; Vol 23
U.M. Kujala, MD1'2 O.J. Heinonen, MD1 M. Kvist, MD1, O-P. Karkkainen, MSC3 J.
The benefit of glucose polymer ingestion in addition to 2.5
per cent glucose before and during a prolonged orienteering
competition was studied. The final time in the competition
in the group ingesting 2.5 per cent glucose (group G,
n=10) was 113 min 37 s±8 min 11 s, and in the group which
had additionally ingested glucose polymer (group G+GP,
n=8) 107 min 18s±4 min 41 s (NS). One fifth (21 per cent) of
the time difference between the two groups was due to difference
in orienteering errors. Group G+GP orienteered
the last third of the competition faster than group G
(p<0.05). The time ratio between the last third of the
competition and the first third of the competition was lower
in group G+GP than in group G (p<0.05). After the competition,
there was statistially insignificant tendency to
higher serum glucose and lower serum free fatty acid
concentrations in group G+GP, and serum insulin concentration
was higher in group G+GP than in group G
(p<0.05). Three subjects reported that they exhausted during
the competition. These same three subjects had the lowest
serum glucose concentrations after the competition (2.9
mmol.1-', 2.9 mmol.1-', 3.5 mmol.l-') and all of them were
from group G. It is concluded that glucose polymer syrup
ingestion is beneficial for prolonged psychophysical performance.
Introduction
Orienteering is a sport in which the orienteer has to
find his way through unfamiliar terrain from one
control (checkpoint) to another with a map and a
compass. The result of a competition thus, in addition
to physical capacity, also depends on the level of planning
and other orienteering skills as well as on the ability
to maintain the concentration level. In top level
orienteers the 02 consumption and heart rate are quite
even and about 90 per cent of the maximal
capacity during competitions"2. Throughout a long
competition, both the heart rate and the blood lactate
concentration are higher than the anaerobic threshold
determined in laboratory conditions2. The high heart
rate during an orienteering competition may be
explained by central stimuli3 in addition to the loading
of several different muscle groups at the same time
with uneven rhythm when running in difficult terrain.
Dietary carbohydrates and fluids during prolonged
endurance exercise enhance performance. The two
most important factors limiting prolonged, strenuous
exercise are believed to be dehydration and depletion
of muscle glycogen stores. During prolonged exercise
a muscle can increase its net blood borne glucose uptake
10- to 20-fold above the resting value4. Decrease in
blood glucose concentration and simultaneous decrease
in prolonged physical performance level are observed,
although the primary factors limiting performance are
not known exactly5. The effect of lowered blood glucose
levels on performance level in skill sports through
inadequate nutrition of the brain is also discussed6.
Glucose is the major energy source for the brain7. The
brain cannot store this carbohydrate, which means
that the cerebral metabolism is critically dependent
upon freely circulating ambient blood Flucose in order
to maintain normal neuronal function .
Gastric emptying is controlled for example by osmoreceptors
in the duodenum9. Gastric emptying rate
seems to be the primary limiting factor in delivering
water, carbohydrate, and minerals to the body10,
hyperosmolalic solutions being unfavourable. Glucose
polymers appear to be favourable because their osmolality
is low, while high amounts of carbohydrates are
delivered into the intestine.
However, on the basis of recent studies, there is
some disagreement whether carbohydrate feeding
during prolonged exercise enhances performance
by preventing the depletion of muscle glycogen
stores1' 12. The greatest volume of the repeated bolus
and its greatest carbohydrate concentration than can
simultaneously deliver fluid and enhance performance
is not known"3. There is also wide individual
variation in gastric emptying and intestinal transport
Br. J. Sp. Med., Vol. 23, No. 2 105
Correspondence to: DR Urho Kujala, Paavo Nurmi Centre, Sport
Medical Research Unit, Kiinamyllynkatu 10, SF-20520 Turku,
Finland
(© 1989 Butterworth & Co (Publishers) Ltd
0306-3674/89/020105-04 $03.00
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Orienteering performance: U. Kujala et al.
and also in other responses to fluid and substrate administration.
In 1986 there were 3151 ranked orienteers in the
male open class in Finland. We have analyzed the fluid
and carbohydrate use of orienteers in the Finnish
Championships and found it to be below the theoretically
optimal level. The aim of this study was to
analyze the benefit of more abundant energy and fluid
ingestion than is commonly used before and during
orienteering competition (prolonged psychophysical
performance) by using glucose polymers.
Subjects and methods
Eighteen male top level orienteers volunteered as subjects
for this study and gave their informed consent
(Table 1). The subjects were ranked between 4 and 157
in the Finnish ranking list, based in success in orienteering
competitions during previous months. The
orienteers were randomly divided into two groups.
Ten orienteers (group G) ingested before and during
their competition a total of 900 ml of 2.5 per cent glucose
according to a given schedule (Table 2). Eight
orienteers (group G+GP) ingested 900 ml of 2.5 per
cent glucose solution and additionally 400 ml of glucose
polymer syrup (Table 2). There was no significant
difference in the mean of the ranking positions between
the groups. Hence it was possible to obtain two groups
of the same performance level for this study. All subjects
orienteered the same course, which was 16 000
metres long when measured from one control to
another. The course had 24 control points and consisted
of three different parts (Figure 1).
From start to control 8 (4200 m), difficult (detailed)
orienteering
From control 8 to control 15 (7000 in), easy (rough)
orienteering
From control 15 to the finish (4800 m), difficult
(detailed) orienteering
Table 1. Age, height, weight and training of the athletes
G (n= 10) G+GP(n=8)
Age (years) 25.1±2.6 26.3±3.2
Height (cm) 181.8±6.5 182.7±4.9
Weight (kg) 69.7±5.7 67.9±5.5
Training 1986 (hours/week) 11.7±4.0 10.8±2.6
G; group ingesting 2.5% glucose solution
G+GP; group ingesting 2.5% glucose solution and glucose polymer
Mean±SD
Table 2. The study schedule
G G+GP
60 min before start blood sample A blood sample A
55 min before start 2.0 dl 2.5% gluc. 2.0 dl 2.5% gluc.
1.0 dl gluc. polym.
30 min before start 2.0 dl 2.5% gluc. 2.0 dl 2.5% gluc.
1.0 dl gluc. polym.
15 min before start 1.0 dl 2.5% gluc. 1.0 dl 2.5% gluc.
Control 8/4.2 km 2.0 dl 2.5% gluc. 2.0 dl 2.5% gluc.
1.0 dl gluc. polym.
Control 15/11.2 km 2.0 dl 2.5% gluc. 2.0 dl 2.5% gluc.
1.0 dl gluc. polym.
Finish/16 km blood sample B blood sample B
J Figure 1. Examples from the different thirds of the orienteering
course a: Detailed orienteering from the first third of the race;
b: Rough orienteering from the second third of the race;
c: Detailed orienteering from the last third of the race
The air temperature varied during the competition
between +5.5°C and +6.9°C and the relative humidity
between 50 per cent and 60 per cent.
The glucose polymer (maltodextrin) consisted of 5-7
glucose units/molecule (MXR; Huhtamaki OY Marli,
Finland). The glucose polymer syrup had 67 g
carbohydrates in 100 ml water and its osmolality was
674 mOsm/kg water. The average temperature of the
liquids ingested was 20°C. The scheme for group
G was chosen to correspond to the normal practice
among Finnish top level orienteers recorded in Finnish
Championships in 1986. When adjusting the
scheme of group G+GP, the practical possibilities in
normal orienteering competition had to be taken into
account.
Antecubital venous blood samples were taken one
hour before the competition (sample A) and 60-120 s
after the competition (sample B) (Table 2). Serum was
separated and stored in -20° until analysis. Immunoreactive
serum insulin (S-Ins) was determined by the
commercial RIA-method (Novo, Denmark), and
serum free fatty acids (S-FFA) were determined by enzymatic
colorimetric method (Nefa C, Wako Chemicals
GmbH, West Germany). A Transcon 102 FN
analyzer (Orion Analytica, Finland) was utilized for
combined enzymatic determination of serum glucose
(S-Gluc)14.
After the competition, the subjects answered a
structured questionnaire including data on previous
training and other background information, and comments
on aspects such as orienteering errors made and
gastrointestinal symptoms experienced during the
study competition. They also marked the exact route
that they had used on the maps. On the basis of this information
the time lost due to orienteering errors was
calculated. To evaluate the number of errors, the sum
score of orienteering errors was formed as follows:
1 point; small error; time loss 30 s - 2 min 30 s
2 points; moderate error; 2 min 30 s - 5 min
3 points; major error; more than 5 min
During the days preceding the study competition,
the subjects had a normal Finnish mixed diet; none of
the subjects underwent special carbohydrate loading.
106 Br. J. Sp. Med., Vol. 23, No. 2
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Orienteering performance: U. Kujala et al.
In the morning before the competition, the subjects
had a normal mixed light breakfast according to their
own habits, but including no more than 500 ml of
fluids.
Statistical differences were tested using the Mann-
Whitney U test and X2 test.
Results
One subject from both groups suffered from gastrointestinal
symptoms which lowered his performance.
On the basis of subjective opinions, three subjects in
group G and none in group G+GP reported feeling
exhausted during the competition.
There was no time difference between the groups in
the first third of the competition, but group G+GP ran
the last third in a shorter time than the control group G
(p<0.05), (Table 3). About one fifth (21 per cent) of the
total time difference between the groups was due to
difference in orienteering errors observed (Table 3).
The sum score of the errors during the last third of the
competition was 1.8±2.1 in group G and 1.4±1.3 in
group G+GP (NS). The time ratio between the last
third of the competition and the first third of the competition
was lower in group G+GP than in group G
(p<0.05), (Table 3).
After the competition, the serum insulin concentration
was higher in group G+GP than in group G
(p<0.05), (Figure 2). An insignificant trend to higher
serum glucose and lower serum free fatty acid concentrations
were correspondingly observed (Figures 3
and 4).
The lowest glucose concentration after the competition
in group G+GP was 4.8 mmol.l-', while in group
G there were two subjects with a glucose concentration
of 2.9 mmol.lP and one subject of 3.5 mmol.l'.
These three subjects orienteered the last third of the
competition proportionally more slowly than the
mean of group G, and they were also the same subjects
who reported that they had become exhausted during
the competition.
Discussion
Our study scheme was not assessed to be theoretically
optimal with reference to fluid and energy ingestion,
but the practical possibilities in an orienteering competition
has to be taken into account. For example, the
ingestion of carbohydrates 45-15 minutes before exercise,
which is common in orienteers, is not recommended
because it can cause hyperinsulinemia followed
Table 3. The time during the different thirds of the competition,
the time ratio between the last and first third of the competition,
the elapsed time and the estimated time lost due to orienteering
errors during different thirds of the competition in groups G and
G+GP (mean±SD) (*P<0.05, difference between the groups)
G (n= 10) G+GP(n=8)
Time I Start to control 8 (min.s) 31.07±1.48 30.52±1.39
Time II Control 8 to control 15 (min.s) 42.05±2.10 41.27±2.43
Time III Control 15 to finish (min.s) 40.25±6.40 34.59±1.59*
Time III/time I 1.30±0.21 1.14±0.08*
Total time (min.s) 113.37±8.11 107.18±4.41
Time lost due to errors 1 (min.s) 2.27±2.00 2.11 ± 1.33
Time lost due to errors 2 (min.s) 0.36±0.56 0.23±0.45
Time lost due to errors 3 (min.s) 1.56±2.50 1.05±1.15
20
_ 15
E
.3
0)
._c
Ce I0
5
Before
i-- P< 0.05
Figure 2. Serum insulin (S-Ins) concentration (mean±SEM)
60 min before and immediately after the competition
8
E
E
)
8~
4 Before After
2 .
Figure 3. Serum glucose (S-Gluc) concentration (mean±SEM)
60 min before and immediately after the competition
by hypoglycemia'5. In our study, pre-exercise carbohydrate
ingestion did not cause significant decrease
of endurance capacity in group G+GP when compared
to group F (Table 3). The group G+GP was
drinking 200 ml of a 2.5 per cent glucose solution and
100 ml of a 67 per cent carbohydrate solution at each
time point except for one. This effectively gives 300 ml
of a carbohydrate solution with a carbohydrate content
of 24 gm/100 ml. On the basis of laboratory experiments,
such a solution should be emptied reasonably
rapidly from the stomach and should be reasonably
well absorbed by the small intestine'.
There seems to be a more significant difference
between the groups in the final results of the orienteering
competition than in similar studies demanding
only physical performance capacity'2, although a dif-
Br. J. Sp. Med., Vol. 23, No. 2 107
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Br. J. Sp. Med., Vol. 23, No. 2
1.4
1 .2 ^ I~~~oT -1.0
E
E 0.8 -
cz 0.6 - After
0.4-
0.2 -
Before
Figure 4. Serum free fatty acids (S-FFA) concentration
(mean±SEM) 60 min before and immediately after the competition
ference in physical performance level has been noted
during exercise exceeding 90 min exercise also earlier5.
There is always a problem in attempting to compare
the performance of two different subjects.
Because we can also compare the results of the last
and the first thirds of the competition within both
groups, we can exclude the possibility that the time
differences between the groups are solely due to
groups selection. The number of orienteering errors
did not significantly differ between the groups, and
the group difference in the time lost due to orienteering
errors accounted for only one fifth of the total time
difference between the two groups. We suggest that
top level orienteers can concentrate and avoid making
serious errors even when the brain is working on
limited glucose. Thus one possible explanation for the
significant difference between the results can be attributed
to better nutrition of the brain. This is also in
agreement with the fact that those subjects whose
blood glucose concentrations were lowest at the finish
subjectively became exhausted and objectively had
longer elapsed times during the last third of the competition.
This theory also agrees with other earlier
studies in skill sports but more studies are required6.
It has been suggested that, when the initial glycogen
levels are elevated, carbohydrate ingestion during
exercise does not result in a significant saving of muscle
glycogen or performance improvement during a
two-hour exercise period". We suggest that adequate
carbohydrate ingestion using glucose polymers during
long competitions is beneficial. In addition to increasing
performance level, the use of glucose polymers
might also hasten recovery, which is supported by a
smaller decrease in S-Ins concentration, and also by a
smaller increase in the plasma vasopressin concentration
in group G+GP than in group G (p<O.OO1), which
was recorded in the association with this study'6. We
did not measure muscle glycogen concentration,
because taking the samples would have significantly
disturbed the performance of the subjects in our study
schedule, a fact we discovered in our pilot study.
We conclude that the ingestion of glucose polymer
with 2.5 per cent glucose solution as one alternative in
carbohydrate feeding during high level prolonged
psychophysical performance is well tolerated and
beneficial. On the basis of our study we recommend
that more refreshment controls be provided in orienteering
competitions.
Acknowledgements
The authors thank the Finnish Central Sports Federation
and the Finnish Orienteering Association for their
financial support. Our acknowledgement is also due
to Erkki Alanen for the statistical work in the study.
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