Hydration status, sweating rate, heart rate and perceived exertion after running sessions in different relative humidity conditions: a randomized controlled trial

Abstract

The purpose of this study was to analyze the impact of running in normal relative humidity (RH = 53%) and very high RH (94%) on hydration status (HS), sweating rate (SR), heart rate (HR), and rating of perceived exertion (RPE). Fourteen men (25.2 ± 6.6 yrs) performed two sessions of treadmill running. Body mass (normal RH:-1.35%, very high RH:-1.65%) HS (normal RH:-14.8%; very high RH:-20.8%) were reduced while RPE (normal RH: +26%; very high RH: +28%) and HR were increased (very high RH: +5.8%: 20-40 min, +3.1%: 40-60 min, +3%: 20-40 min; +2.3%: 40-60 min for normal RH). As expected, SR was significantly greater during very high RH (-20/8%) compared to normal RH (-14.8%). Running in very high RH at moderate temperature has a greater negative impact on SR, HS, body mass, HR, RPE in men than running in normal RH at the same temperature, which places the runner in greater danger of heat illnesses such as heat exhaustion or heat stroke.

Dehydration, Wellness, and Training Demands of Professional Soccer Players during Preseason

“…The present study demonstrated a positive correlation between the percentage of change of dehydration and the percentage of change of RPE. This result is in line with previous studies showing that lower hydration status or higher fluid loss (dehydration) harmed RPE and generally triggered higher RPE values [ 38 , 44 – 47 ]. Similarly, a recent study on professional soccer players reported that the percentage of dehydration was higher in exercises performed at RPE = 6-8 than RPE = 2-4 [ 47 ].…”

“…For instance, the higher the environmental temperature, the greater the sweating rate. Conversely, as relative humidity increases, less sweat evaporates, which raises the athlete's body temperature; in turn, the rate of sweating increases the RPE [ 44 ].…”

Recovery of Heart Rate Variability After Exercise Under Hot Conditions: The Effect of Relative Humidity

“…Additionally, hot environments have a direct effect on frequency domain variables, such as LF and HF power, 23 –26 total power (TP), and very low frequency power, 22 –24 showing that higher temperatures provoke a decrease in cardiac variability. Higher relative humidity (RH) shows increments in body, skin, and rectal temperature and HR during exercise under hot and neutral conditions 27,28 but not in the rate of perceived exertion. 28 The effect of RH on HRV has not been analyzed before; thus, it might be important to describe the effect RH may have on HRV.…”

“…Higher relative humidity (RH) shows increments in body, skin, and rectal temperature and HR during exercise under hot and neutral conditions 27,28 but not in the rate of perceived exertion. 28 The effect of RH on HRV has not been analyzed before; thus, it might be important to describe the effect RH may have on HRV.…”