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Anaerobic threshold, muscle volume and hypoxia
R J Shephard1, E Bouhlel, H Vandewalle
1Laboratoire de Physiologie du Travail (CNRS), CHU Pitié-Salpêtrière, Paris, France.
Summary
Exercise intensity, like ventilatory threshold, is not affected by sex or hypoxia. However, mechanical efficiency improves in hypoxia, and local muscle sensations are key for exercise prescription, especially with arm work.
Area of Science:
- Exercise Physiology
- Sports Science
- Human Performance
Background:
- The ventilatory threshold (VT) is a key indicator of exercise intensity.
- Understanding factors affecting VT and exercise efficiency is crucial for training and performance.
Purpose of the Study:
- To investigate the influence of sex, hypoxia, and muscle mass on ventilatory threshold and related physiological parameters.
- To assess mechanical efficiency and oxygen debt repayment across different exercise types and conditions.
- To evaluate the reliability of perceived exertion for exercise prescription at the VT.
Main Methods:
- Eight men and eight women performed four exercise types (2-leg, 1-leg, arm/shoulder, arm) under normoxic and hypoxic conditions.
- Measurements included ventilatory threshold, mechanical efficiency, oxygen debt, heart rate, and perceived exertion.
- Reproducibility of VT was assessed for different muscle group involvements.
Main Results:
- Ventilatory threshold was not significantly affected by sex, hypoxia, or muscle mass volume, but showed poor reproducibility in small muscle tasks.
- Apparent mechanical efficiency increased under hypoxia during 2-leg ergometry.
- Oxygen debt repayment was lower for arm ergometry compared to leg ergometry.
- Heart rate at VT decreased with reduced active muscle volume.
- Perceived exertion was generally light, suggesting local muscular sensations are better for exercise prescription, especially for arm work.
Conclusions:
- Ventilatory threshold is robust across various conditions but less reproducible with smaller muscle groups.
- Hypoxia may enhance mechanical efficiency through anaerobic contribution.
- Exercise prescription, particularly for arm-based activities, should prioritize local muscular sensations over general or respiratory exertion cues.