Determinant factors of the decrease in aerobic performance in moderate acute hypoxia in women endurance athletes

Area of Science:

• Sports Medicine
• Exercise Physiology
• Altitude Physiology

Background:

• Maximal aerobic performance is crucial for endurance athletes.
• Altitude exposure presents physiological challenges to oxygen transport and utilization.
• Understanding limiting factors in hypoxia is key for training and performance optimization.

Purpose of the Study:

• To investigate the factors limiting maximal aerobic performance in endurance-trained (TW) versus untrained (UW) women.
• To assess the impact of varying altitudes on physiological responses during incremental exercise.

Main Methods:

• Subjects (TW and UW) underwent incremental cycle ergometer tests at sea level and simulated altitudes (1000m, 2500m, 4500m).
• Measurements included maximal oxygen uptake (VO2 max), heart rate, ventilation, cardiac output, oxygen saturation (Sa'O2 max), and oxygen transport (QaO2 max).

Main Results:

• Maximal oxygen uptake decrement (Delta VO2 max) was greater in TW at all altitudes.
• Maximal oxygen transport (QaO2 max) decreased from 1000m in both groups, with no difference at 4500m.
• Oxygen extraction (O2ERmax) was higher in TW, while mixed venous O2 pressure (PvO2 max) was lower at altitude.

Conclusions:

• Reduced maximal oxygen transport is the primary determinant of VO2 max decrement in moderate acute hypoxia for both trained and untrained women.
• Tissue oxygen extraction capacity cannot fully compensate for the reduced oxygen delivery at altitude.
• These findings highlight the critical role of oxygen transport in limiting aerobic performance under hypoxic conditions.