A methodology to assess the effect of sweat on infrared thermography data after running: preliminary study

Abstract The aim of this technical report is to present a preliminary study carried out to define the methodology to be employed for further research on assessing the effect of sweating on infrared thermography and thermal contact sensors after moderate intensity running. Nine recreational runners participated in this preliminary study. Participants ran for 35 min (5 min warm-up and 30 min at a rate of perceived exertion rate of 12 points on the 6-20 points Borg scale). Skin temperature (infrared thermography, Flir E60bx; four thermal contact sensors, IButton DS1923 Hygrochron) and relative humidity (thermal contact sensors) were measured on the anterior thigh on both lower limbs before and after running. Two thermal contact sensors were located on each lower limb, one being attached throughout the complete protocol (fixed) and the other just 5 min before each data acquisition (non-fixed). The fixed sensor presented a higher skin temperature after running than infrared thermography (33.9 ±1.3 vs. 33.2 ±1.4°C). The skin temperature of the non-fixed sensor was lower than the other methods, before (28.3 ±3.3 vs. 31.8 ±1.4 [thermography] vs. 31.3 ±1.3°C[fixed]) and after running (31.8 ±1.8 vs 33.2 ±1.4 [thermography] vs. 33.9 ±1.3 °C[fixed]). The fixed sensor presented higher relative humidity after exercise than the non-fixed sensor (101 ±2 vs. 83 ±16.2%). The mean relative humidity of the fixed sensor suggests sweat saturation caused by the method of attaching the sensor. After this preliminary study, some modifications were proposed for future research, the most important being attaching the non-fixed sensors 10 minutes before acquiring the data.