An integrated thermal sensation scale for estimating thermal strain in water

Acceptable definitions of thermal sensation for cold and hot water immersion do not exist. The use of subjective thermal sensation scales remains unsolved with broad psycho-physiological, and semantic implications. We hypothesize that perception of thermal sensation could be a valid and reliable indicator for thermal strain during exposure in water. We aimed to provide a theoretical background for behavioral thermoregulation and neurocognition to support an integrated thermal sensation scale for estimation of thermal load during head-out water immersion. This research used a mixed methods approach. Domains were identified and items were measured for thermal load to examine the content validity. Thereafter, we formed an integrated scale based on standard 10,551 of International Organization for Standardization (ISO). Finally, we conducted a pilot study for the face validation of the scale based on a 30 min head-out water immersion at 26 degree celsius in healthy adults (females, n = 4; males, n = 4; age: 22.6 +/- 8.0 years; body mass, 67.7 +/- 9.5 kg; height, 169.0 +/- 5.6 cm). We identified three aspects (environment, physiological and behavioral thermoregulation) and a total of 18 items, of whom eight items (water temperature, immersion duration, core temperature, skin temperature, body heat storage, shivering, thermal sensation, and thermal comfort) were acceptable based on terms of scale-level content validity index (SCVI = 92 %). Conditions incorporated into our scale included: icy < 12 degrees C, cold 12-24 degree celsius, cool 24-29 degree celsius, neutral 29-38 degree celsius, warm 38-43 degree celsius, and hot > 43 degree celsius. We found excellent face validity based on a reported homogenous cool feeling and physiological thermoregulatory responses. Our study revealed our model could reasonably characterize body thermal load though whole-body thermal sensation based on well-established thermoregulatory mechanisms during water immersion. Further research is needed to validate the accuracy of our behavioral model in a variety of water temperatures and in a larger sample size.