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Oxygen consumption, lactate accumulation, and sympathetic response during prolonged exercise under hypoxia
P Bouissou1, C Y Guezennec, G Defer
1Laboratoire de Physiologie, Faculté de médecine, Creteil, France.
International Journal of Sports Medicine
|August 1, 1987
Summary
Hypoxia at 3000m altitude increases blood lactate accumulation during prolonged exercise, despite similar cardiorespiratory responses. This suggests impaired lactate removal, not increased glycolysis, contributes to higher lactate levels.
Area of Science:
- Exercise Physiology
- Altitude Physiology
Background:
- Understanding physiological responses to exercise at altitude is crucial for athletes and military personnel.
- Hypoxia at simulated 3000m altitude affects exercise intensity and oxygen uptake.
Purpose of the Study:
- To investigate the effects of simulated altitude on cardiorespiratory, metabolic, and hormonal responses during prolonged exercise.
- To determine if hypoxia alters blood lactate accumulation and removal during submaximal exercise.
Main Methods:
- Six healthy men performed 1-hour ergocycle exercise at 60% VO2 max at sea level (normoxia) and simulated 3000m altitude (hypoxia).
- Measurements included oxygen uptake (VO2), ventilation (VE), respiratory exchange ratio (R), heart rate (Hr), blood lactate, and catecholamines.
Main Results:
- Hypoxia resulted in lower absolute workload despite similar relative intensity.
- Oxygen uptake (VO2) was lower in hypoxia, with no significant changes in ventilation (VE), respiratory exchange ratio (R), or heart rate (Hr).
- Blood lactate concentration remained elevated throughout exercise at altitude and was significantly higher at the end of exercise compared to normoxia.
Conclusions:
- Hypoxia does not significantly alter cardiorespiratory and sympathetic responses during prolonged relative workload exercise.
- Hypoxia tends to increase blood lactate accumulation, likely due to impaired lactate removal rather than increased glycolytic flux.
- These findings have implications for exercise performance and training strategies at altitude.