Impact of carbohydrate supplementation during endurance training on glycogen storage and performance.
OBJECTIVE
Glucose ingestion may improve exercise endurance, but it apparently also influences the transcription rate of several metabolic genes and it alters muscle metabolism during an acute exercise bout. Therefore, we investigated how chronic training responses are affected by glucose ingestion.


METHODS
In previously untrained males performance and various muscular adaptations were evaluated before and after 8 weeks of supervised endurance training conducted either with (n = 8; CHO group) or without (n = 7; placebo) glucose supplementation.


RESULTS
The two groups achieved similar improvements in maximal oxygen uptake and peak power output during incremental cycling (both parameters elevated by 17% on average) and both groups lost approximately 3 kg of fat mass during the 8 weeks of training. An equal reduction in respiratory exchange ratio (0.02 units) during submaximal exercise was observed in both groups. Beta-hydroxyacyl-CoA-dehydrogenase activity was increased in both groups, however, to a larger extent in the placebo group (45 +/- 11%) than CHO (23 +/- 9%, P < 0.05). GLUT-4 protein expression increased by 74 +/- 14% in the placebo group and 45 +/- 14% in CHO (both P < 0.05), while resting muscle glycogen increased (P < 0.05) to a larger extent in the placebo group (96 +/- 4%) than CHO (33 +/- 2%).


CONCLUSIONS
These results show that carbohydrate supplementation consumed during exercise training influences various muscular training adaptations, but improvements in cardiorespiratory fitness and reductions in fat mass are not affected.
Nybo
L
L
Institute of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark. lnnielsen@aki.ku.dk
Pedersen
K
K
Christensen
B
B
Aagaard
P
P
Brandt
N
N
Kiens
B
B
D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000378:metabolism; D000222:Adaptation, Physiological; D000328:Adult; D004040:Dietary Carbohydrates; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology; D005947:Glucose / Q000008:administration & dosage / Q000378:metabolism*; D006003:Glycogen; D006801:Humans; D008055:Lipids / Q000097:blood; D008297:Male; D016555:Matched-Pair Analysis; D018482:Muscle, Skeletal / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology*; D012016:Reference Values; D014280:Triglycerides / Q000378:metabolism
D004040:Dietary Carbohydrates; D008055:Lipids; D014280:Triglycerides; D006003:Glycogen; D015094:3-Hydroxyacyl CoA Dehydrogenases; C021388:3-hydroxybutyryl-CoA dehydrogenase; D005947:Glucose