Facial fanning reduces heart rate but not tolerance to a simulated hemorrhagic challenge following exercise heat stress in young healthy humans

Am J Physiol Regul Integr Comp Physiol. 2023 Dec 18. doi: 10.1152/ajpregu.00180.2023. Online ahead of print.ABSTRACTWe investigated whether reducing face skin temperature alters arterial blood pressure control and lower body negative pressure (LBNP) tolerance after exercise heat stress. Eight subjects (1 female; age, 27 ± 9 years) exercised at ~63% VO2max until core temperature had increased ~1.5°C before undergoing LBNP to pre syncope either with fanning to return face skin temperature to baseline (∆-5°C, Fan trial) or without (No Fan trial). LBNP tolerance was quantified as cumulative stress index (CSI; mmHg*min). Prior to LBNP whole body and face skin temperatures were elevated from baseline in both trials (38.0 ± 0.5°C and 36.3 ± 0.5°C, respectively, both P < 0.001). During LBNP, face skin temperature decreased in the Fan trial (30.9 ± 1.0°C) but was unchanged in the No Fan trial (36.1 ± 0.6°C, between trials P < 0.001). Mean arterial pressure was not different between trials (P = 0.237) and was similarly reduced at pre syncope in both trials (from:82 ± 7 to: 67 ± 8mmHg, P < 0.001). During LBNP, heart rate was attenuated in the Fan trial at Mid LBNP (146 ± 16 vs. 158 ± 12 bpm, P = 0.036) and at peak heart rate (158 ± 15 vs. 170 ± 15 bpm; P < 0.001). LBNP tolerance was not different between trials (321 ± 248 vs. 328 ± 115 mmHg*min, P = 0.851). In exercise heat stressed individuals, lowering face skin temperature to normothermic values suppr...
Source: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology - Category: Physiology Authors: Source Type: research