Ventilatory Changes After Active Heat Acclimation for Multiday Ultramarathon Races in the Sahara Desert

Abstract

To determine the effect of active heat acclimation (HA) on ventilatory responses, 4 endurance‐trained athletes (42.0 ± 5.7 y, mean ± SD) underwent 10 day of activity in 35–40°C and ~15% RH conditions to prepare for multiday ultramarathon races in the Sahara desert. Exercise during HA included 1 h/day of running at ≥50% maximal oxygen consumption (VO2max). Physiological assessments included pre‐ and post‐HA VO2max, heart rate (HR), esophageal (Tes), rectal (Tre), and skin temperatures (4 sites). Pre‐ and post‐HA VO2max values were not significantly different (52.8 ± 4.0 vs 52.0 ± 4.6 mL·kg−1·min−1, p = 0.35). Attainment of HA was confirmed by a significant reduction in exercise HR (p < 0.01) and trends (p=0.12) for reductions in both Thermal Comfort ratings and Borg Ratings of Perceived Exertion over the 10‐d HA period. During incremental exercise, from pre‐ to post‐HA, the ventilatory equivalent for O2 (VE/VO2) increased from 28.6 ± 1.0 to 30.2 ± 1.0 (p = 0.06), whereas the ventilatory equivalent for CO2 (VE/VCO2) showed no change (29.6 ± 0.8 vs 29.8 ± 2.0, p = 0.37). These preliminary data suggest that active HA increases ventilatory responses independently of an exercise training effect.Supported by NSERC, Canadian Foundation for Innovation.