Taking the plunge: When is best for hot water immersion to complement exercise in heat and hypoxia

This investigation assessed the psycho-physiological and performance effects of hot water immersion (HWI) implemented either before or after a repeated-sprint training in hypoxia (RSH) session conducted in the heat. Ten participants completed three RSH trials (3 x 10 x 5-s sprints), conducted at 40 degrees C and simulated altitude of 3000 m. A 30-min monitoring period preceded and followed all exercise sessions. In PRE, the pre-exercise period was HWI, and the post-exercise period was seated rest in temperate conditions. This combination was reversed in POST. In CON, participants were seated in temperate conditions for both periods. Compared to CON, PRE elicited a reduction in power output during each repeated-sprint set (14.8-16.2%, all p < 0.001), and a significantly higher core temperature (Tc) during the pre-exercise period and throughout the exercise session (p < 0.001 and p = 0.025, respectively). In POST, power output and Tc until the end of exercise were similar to CON, with Tc higher at the conclusion of the post-exercise period (p < 0.001). Time across the entire protocol spent >= 38.5 degrees C Tc was significantly longer in PRE (48.1 +/- 22.5 min) than POST (31.0 +/- 11.3 min, p = 0.05) and CON (15.8 +/- 16.3 min, p < 0.001). Employing HWI following RSH conducted in the heat provides effective outcomes regarding physiological strain and cycling performance when compared to pre-exercise or no HWI.

Automated summary

This study assessed the effects of hot water immersion (HWI) before or after a repeated-sprint training in hypoxia (RSH) session conducted in the heat. Results showed that HWI before the exercise session decreased power output and increased core temperature, while HWI after the exercise session had positive effects on reducing physiological strain and improving cycling performance.