Int J Sports Med 2004; 25(5): 351-356
DOI: 10.1055/s-2004-820938
Physiology & Biochemistry

© Georg Thieme Verlag KG Stuttgart · New York

Effect of Glycogen Depletion on the Oxygen Uptake Slow Component in Humans

J. Bouckaert1 , A. M. Jones2 , K. Koppo1
  • 1Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
  • 2Department of Exercise and Sport Science, Manchester Metropolitan University, Manchester, UK
Weitere Informationen

Publikationsverlauf

Accepted after revision: October 16, 2003

Publikationsdatum:
15. Juni 2004 (online)

Abstract

Previous studies have indicated that the V·O2 slow component is related to the recruitment of type II muscle fibres. We therefore hypothesised that an exercise and dietary regimen designed to deplete type I muscle fibres of glycogen would result in a greater contribution of type II muscle fibres to the exercise power output and therefore a larger amplitude of the V·O2 slow component. Eight male subjects took part in this study. On day 1, the subjects reported to the laboratory at 8 a.m., and completed a 9 min constant-load cycling test at a work rate equivalent to 85 % V·O2 peak. On day 2 at 12 p.m., the subjects were fed a 4200 kJ meal (60 % protein, 40 % fat); at 6 p.m. they completed a 2 h cycling test at 60 % V·O2 peak. On day 3 at 8 a.m., the subjects performed an exercise test identical to that of day 1. Metabolic and respiratory measurements indicated that our experimental design was effective in reducing the muscle glycogen content. V·O2 was significantly higher (by approximately 140 ml · min-1) throughout exercise following glycogen depletion but no appreciable changes in V·O2 kinetics were found: neither the time constant of the primary response (from 35.4 ± 2.5 to 33.2 ± 4.4 s) nor the amplitude of the slow component (from 404 ± 95 to 376 ± 81 ml · min-1) was significantly altered. Therefore, we suggest that the increased V·O2 throughout exercise and the unaltered V·O2 slow component following glycogen depletion might be explained by a shift towards a greater reliance on fat metabolism in type I muscle fibres with no appreciable change in fibre type recruitment patterns.

References

K. Koppo

Department of Movement and Sports Sciences, Ghent University

Watersportlaan 2

9000 Ghent

Belgium

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