Sweat responses during inactive recovery after high-intensity running in hot, dry and humid conditions

Abstract

This study investigated the relationship between high (85%) and low (19%) relative humidity (RH) and sweat rate during inactive recovery after high-intensity work in a hot environment (30 °C). Ten male subjects performed two 20-minute run trials at 68 ± 4 % of maximal oxygen consumption (VO2max) followed by 36 minutes of inactive recovery in standing position. Regional sweat rate (RSR) was measured on the forearm and mid-central back by technical absorbent pads, and gross sweat loss was estimated from change in body weight. Core temperature (Tc) and six skin temperatures for calculation of mean skin temperature (Ts) were measured continuously together with heart rate (HR) during running and recovery. Results show that RSR was significantly (p<0.05) higher for both arm and back during running and inactive recovery in 85% RH compared to 19% RH. The highest sweat rate was observed on the back during the last five minutes of running in 85% RH (1387 g·m-2·h-1) compared to 19% RH (886 g·m-2·h-1). Gross sweat loss (GSL) was significantly higher in 85% RH (796 ± 414 g·h-1) than 19% RH (489 ± 140 g·h-1) conditions (p=0.010). Tc continued to increase for three and seven minutes post-exercise in 19% RH and 85% RH, respectively and Ts was significantly higher in 85% RH than in 19% RH (p<0.05). HR was 11 bpm higher after running in 85% RH compared to 19% RH (p=0.001). In conclusion, RSR and GSL, as well as HR, Tc and Ts was higher during post-exercise recovery in 30°C and 85% RH than in 30°C and 19% RH. This study emphasises the importance of including the effect of relative humidity in assessment of both exercise and recovery.