A comparison of galvanic skin conductance and skin wettedness as indicators of thermal discomfort during moderate and high metabolic rates

The relationship between local thermal comfort, local skin wettedness (w) and local galvanic skin conductance (GSC) in four body segments during two different exercise intensities was compared in 10 males. In a balanced order, participants walked at 35% VO for 45min (WALK) (29.0±1.9°C, 29.8±3.6% RH, no wind) in one test and in a separate test ran at 70% VO for 45min (RUN) (26.2±2.1°C, 31.1±7.0% RH, no wind). During both tests, participants wore a loose fitting 100% polyester long sleeve top and trouser ensemble with a low resistance to heat and vapour transfer (total thermal resistance of 0.154mKW and total water vapour resistance of 35.9mPaW). w, change from baseline in GSC (δGSC) and local thermal comfort were recorded every 5min. The results suggest that both w and δGSC are strong predictors of thermal comfort during the WALK when sweat production is low and thermal discomfort minimal (r>0.78 and r>0.71, respectively). Interestingly, during the RUN w plateaued at ~0.6 to 0.8 due to the high sweat production, whilst δGSC gradually increased throughout the experiment. δGSC had a similar relationship with thermal comfort to w during the RUN (r>0.95 and r>0.94, respectively). Despite the strength of these relationships, the ability of w to predict local thermal comfort accurately dramatically reduces in the exponential part of the curve. In a situation of uncompensated heat stress such as high metabolic rate in hot climate, where sweat production is high, δGSC shows to be a better predictor of local thermal comfort than w. The w data shows regional differences in the threshold which triggers local discomfort during the WALK than RUN; lower values are found for upper arms (0.22±0.03 and 0.28 ±0.22) and upper legs (0.22±0.11 and 0.22±0.10), higher values for upper back (0.30±0.12 and 0.36 ±0.10) and chest (0.27±0.10 and 0.39 ±0.32), respectively. However, no regional differences in the threshold of discomfort are found in the {increment}GSC data. Instead, the data suggests that the degree of discomfort experienced appears to be related to the amount of sweat within and around the skin (as indirectly measured by δGSC) at each body site. © 2013 Elsevier Ltd.