Postural change during hyperthermia modifies thermal perception in men

Abstract

Increase in skin and esophageal temperature (Tsk and Tes) enhances heat dissipative responses and induces behavioral thermoregulatory responses with the perception of both temperatures. We assessed whether the perception of both temperatures was modified with postural change from supine (SUP) to sitting (SIT) during hyperthermia (HT) which attenuates heat dissipative responses.MethodsEleven healthy young men underwent measurement of noticeable increase/decrease (± 0.1°C/sec) of skin temperature (warm/cold threshold) at forearm and chest by using a thermode(6.25 cm2), and of subjective thermal sensation (visual analogue scale) in SUP and SIT in normothermia (NT, Tes; 36.6 ± 0.2°C) and HT (Tes; 37.3 ± 0.1°C, lower legs immersion in 42°C water). Tes, Tsk, cutaneous vascular conductance (CVC) and sweat rate (SR) at forearm and chest were measured continuously.ResultsCold threshold at both sites were decreased and subjective thermal sensation, CVC and SR were increased in HT compared with NT (P < 0.05). In HT, cold threshold at forearm was decreased and subjective thermal sensation was increased while CVC at forearm was decreased in SIT compared with SUP (P < 0.05). Warm threshold at both sites remained unchanged.ConclusionsPostural change from SUP to SIT during hyperthermia attenuates cold threshold and enhances subjective thermal sensation which is accompanied by attenuated heat dissipative responses.