Effect of 8 days of exercise-heat acclimation on aerobic exercise performance of men in hypobaric hypoxia.

This study assessed whether EHA can alter time-trial performance and/or incidence of acute mountain sickness (AMS) during HH exposure. Thirteen sea level (SL) resident men (SL VO2peak: 3.19 ± 0.43 l·min-1) completed steady-state exercise followed by a 15-min cycle time-trial and assessment of AMS before (HH1; 3,500 m) and after (HH2) an 8-day EHA protocol (120 min; 5 km·hr-1; 2% incline; 40°C and 40% RH). EHA induced lower heart rate (HR) and core temperature, and plasma volume expansion. Time-trial performance was not different between HH1 and HH2 after 2-hr(106.3±23.8 vs 101.4±23.0 kJ, p =0.71) or 24-hrs (107.3±23.4 vs 106.3±20.8 kJ, p>0.9). From HH1 to HH2, HR and oxygen saturation at the end of steady-state exercise and time-trial tests at 2 and 24-hrs was not different (p>0.05). Three of 13 volunteers developed AMS during HH1 but not during HH2, while a fourth volunteer only developed AMS during HH2. Heat shock protein 70 was not different from HH1 to HH2 at SL (1.9±0.7 vs 1.8±0.6 NII, p=0.97) or after 23-hrs (1.8±0.4 vs 1.7±0.5 NII, p=0.78) at HH. Our results indicate that this EHA protocol had little to no effect - neither beneficial nor detrimental - on exercise performance in HH. EHA may reduce AMS in those who initially developed AMS, however, studies at higher elevations having higher incidence rates are needed to confirm our findings. PMID: 32432914 [PubMed - as supplied by publisher]
Source: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology - Category: Physiology Authors: Tags: Am J Physiol Regul Integr Comp Physiol Source Type: research