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|Title: ||Carbohydrate intake, muscle metabolism, and enduring running performance in man|
|Authors: ||Chryssanthopoulos, Konstantinos|
|Issue Date: ||1995|
|Publisher: ||© K. Chryssanthopoulos|
|Abstract: ||The purpose of this thesis was to study the effects of a pre-exercise
carbohydrate meal on metabolism, endurance capacity and performance
during prolonged running when carbohydrate was, or was not consumed
The first study (Chapter 4) examined the effects on endurance running
capacity of ingesting a carbohydrate-electrolyte solution during treadmill
exercise to fatigue at 70% V02 max after subjects (10 males) had undergone
an overnight fast (P+C), or when fed with a 2.5 g. kg-1 BW carbohydrate meal
3 hours before exercise (M+C). Exercise time to exhaustion was longer in the
M+C (147.4 ± 9.6 min) and P+C (125.1 ± 7.0 min) trials compared with the
control condition (P+P: 115.1 ± 17.6 min) (p< 0.01 and p< 0.05 respectively).
Also, exercise time was longer in the M+C compared with the P+C trial (p<
0.01). The improvement in endurance capacity in the M+C trial occurred
despite a higher carbohydrate oxidation rate during the first hour of exercise.
The second study (Chapter 5) examined whether a pre-exercise carbohydrate
meal (M+W) can improve endurance capacity, and further examined if the
combination of a pre-exercise meal together with the ingestion of a
carbohydrate-electrolyte solution during exercise (M+C) would be superior to
the carbohydrate meal (M+W) alone. Ten males volunteered in this study.
Although the consumption of the meal increased carbohydrate oxidation
during the first hour of exercise, exercise time to fatigue at 70% V02 max was
longer in the M+C (125.1 + 5.3 min) and M+W (111.9 + 5.6 min) trials
compared with the control trial (P+W : 102.9 ± 7.9 min) (p< 0.01 and p< 0.05
respectively). Also, exercise time was longer (p< 0.05) in the M+C compared
with the M+W trial.
The third study (Chapter 6) investigated whether the high carbohydrate meal
can influence muscle glycogen levels. Eight male subjects participated in the
study. Three hours after the ingestion of the 2.5 g. kg-1 BW carbohydrate meal,
muscle glycogen concentration was 10.6% higher (p< 0.05) in the vastus
lateralis muscle (347.3 + 31.3 mmol. kg dw-1) compared with the muscle
glycogen concentration before feeding (314 ± 33.9 mmol. kg dw-1).
The fourth study (Chapter 7) examined the influence of ingesting a
carbohydrate-electrolyte drink (M+C) on the muscle glycogen utilisation
during 60 min running at 70% V02 max in subjects (8 males) who had
consumed a carbohydrate meal 3 hours before exercise (M+W). Muscle
glycogen concentrations were not different before (M+C : 321.9 ± 27.2 vs
M+W : 338.8 ± 32.8 mmol. kg dw-1), as well as after exercise (M+C : 225.8 ±
26.7 vs M+W: 261 + 40.5 mmol. kg dw-1) between the two experimental
trials. Neither was there any difference in the rate of muscle glycogen
utilisation (M+C : 96.1 ± 22.1 vs M+W: 77.9 ± 11.7 mmol. kg dwl. h-1).
The aim of the last study (Chapter 8) was to investigate whether, after an
overnight fast, the ingestion of a carbohydrate-electrolyte solution during a 30 km self-paced treadmill run (C) would be as effective as the consumption of a
carbohydrate meal (M) (2.0 g. kg-1 BW carbohydrate) 4 hours before exercise.
Ten males volunteered for this study. The overall performance times in the M
and C trials were identical (M: 121.8 ± 3.6 min vs
C: 121.7 ± 4.1 min). No
differences were found between the two trials in running speeds over each
successive 5 km, or even when running speed was analysed every kilometre.
Also, no reduction in the self-selected speeds of subjects was observed
towards the end of the 30 km run in both conditions.
The ingestion of a carbohydrate meal, providing 2.5 g. kg-1 BW carbohydrate,
3 hours before exercise increases muscle glycogen concentration and
improves endurance running capacity, despite an elevated carbohydrate
oxidation rate during the first hour of exercise. It seems that the amount of
carbohydrate given before exercise compensates for the greater carbohydrate
used. Furthermore, the combination of both a pre-exercise carbohydrate meal
and a carbohydrate-electrolyte solution ingested during exercise further
improves endurance capacity.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Sport, Exercise and Health Sciences)|
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