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Muscle energetics during prolonged cycling after exercise hypervolemia
H J Green1, L L Jones, M E Houston
1Department of Kinesiology, University of Waterloo, Ontario, Canada.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|February 1, 1989
Summary
Exercise-induced hypervolemia, or increased plasma volume, did not alter muscle energy homeostasis in untrained males. Muscle glycogen utilization decreased with training, potentially due to increased blood glucose use or reduced anaerobic glycolysis.
Area of Science:
- Exercise Physiology
- Sports Science
- Human Metabolism
Background:
- Plasma volume expansion (hypervolemia) through exercise is a known adaptation.
- The impact of exercise-induced hypervolemia on muscle substrate utilization and bioenergetics during prolonged exercise remains unclear.
Purpose of the Study:
- To investigate the effects of exercise-induced hypervolemia on muscle substrate utilization and bioenergetics.
- To determine if increased plasma volume influences energy metabolism during sustained heavy exercise.
Main Methods:
- Six untrained males underwent a 3-day cycling protocol to induce hypervolemia.
- Muscle biopsies and blood samples were analyzed at rest and during prolonged exercise before and after the intervention.
- Measurements included high-energy phosphates, glycolytic intermediates, substrate concentrations, and hormonal responses.
Main Results:
- Hypervolemia was confirmed by a 21.2% increase in plasma volume.
- No significant differences in muscle high-energy phosphate metabolism or key glycolytic intermediates were observed.
- Muscle glucose and glycogen concentrations increased post-intervention, with blunted epinephrine and norepinephrine responses during exercise.
Conclusions:
- Exercise-induced hypervolemia does not appear to alter muscle energy homeostasis during prolonged heavy exercise.
- Reduced muscle glycogen utilization is an early training adaptation, possibly mediated by altered glucose metabolism or glycolysis.
- Further research is needed to elucidate the precise mechanisms behind these metabolic adaptations.