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

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 degrees 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 (T-c) and six skin temperatures for calculation of mean skin temperature (T-s) 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). T-c continued to increase for three and seven minutes post-exercise in 19% RH and 85% RH, respectively and T-s 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, T-c and T-s was higher during post-exercise recovery in 30 degrees C and 85% RH than in 30 degrees C and 19% RH. This study emphasises the importance of including the effect of relative humidity in assessment of both exercise and recovery.