Physiological responses to short-term high-altitude acclimatization: Insights from predictive modeling approaches

High-altitude (HA) exposure induces cardiovascular, respiratory, and metabolic adjustments that often impair exercise performance. These physiological responses depend on hypoxic severity, exposure duration, and individual susceptibility. Although full acclimatization generally requires about 7 days, early adaptations can emerge within the first 72 h. This study aimed to characterize these early responses and to evaluate the potential of mathematical modeling to predict HA-related exercise performance decline. Nine healthy volunteers (age: 24.4 ± 3.3; weight: 63.7 ± 11.8; height: 169.4 ± 8.4; female: 44%) completed maximal cardiopulmonary exercise tests under three conditions: at sea level (SL), and at 3015 m after 12 h (HA12h) and 60 h (HA60h) of exposure. Although 60 h at HA was insufficient for full acclimatization, significant differences were observed between HA12h and HA60h, indicating partial physiological adaptation. Maximal power output declined at both HA time points. Notably, HA-induced performance deterioration was accurately predicted (R² = 0.81) using SL-derived parameters, particularly maximal oxygen pulse (VO₂/HR_max) and the ventilatory equivalent for carbon dioxide (VE/VCO₂). These findings provide novel insights into early physiological responses to HA and support the development of individualized, model-based tools to anticipate performance loss and optimize training and acclimatization strategies.