Multiple variables explain the variability in the decrement in VO2max during acute hypobaric hypoxia

Area of Science:

• Exercise Physiology
• Environmental Physiology
• Altitude Training

Background:

• Understanding VO2max decrements in hypobaric hypoxia (HH) is crucial for athletes and military personnel operating at altitude.
• Individual variability in VO2max response to HH necessitates identifying predictive factors.

Purpose of the Study:

• To determine the relationships between decrements in sea level (SL) VO2max during HH and related physiological and anthropometric variables.
• To identify predictors of VO2max reduction under simulated high-altitude conditions.

Main Methods:

• Multiple regression analyses were used to assess relationships between VO2max decrement and independent variables.
• Subjects (N=28) underwent cycle ergometry tests at various hypobaric hypoxia (HH) conditions (682, 632, 566 Torr).
• Measured variables included SL-VO2max, SL lactate threshold (SL-LT), delta SaO2max, lean body mass (LBM), and gender.

Main Results:

• VO2max significantly decreased with increasing altitude (e.g., from 3.5 to 3.4 L.min-1 at 682 Torr).
• The relative VO2max decrement during HH was -9.2%/100 mm Hg, with a predicted decrease below 705 Torr.
• SL-VO2max, SL-LT, delta SaO2max, LBM, and gender collectively explained 89.03% of the variance in VO2max decrement (760-566 Torr).

Conclusions:

• Individuals with higher SL-VO2max, lower SL-LT, greater SaO2max reduction, higher LBM, and males experience the largest VO2max decrements in HH.
• SL-LT, LBM, and gender uniquely contribute to explaining between-subject variability in VO2max response to HH.
• Oxygen diffusion within skeletal muscle may play a role in VO2max variability during hypobaric hypoxia.