Heat acclimation enhances the cold-induced vasodilation response

Urša Ciuha,Tinkara Mlinar,Joshua T Royal,Igor B Mekjavic,Alexandros Sotiridis,Ola Eiken

doi:10.1007/s00421-021-04761-x

Abstract

PurposeIt has been reported that the cold-induced vasodilation (CIVD) response can be trained using either regular local cold stimulation or exercise training. The present study investigated whether repeated exposure to environmental stressors, known to improve aerobic performance (heat and/or hypoxia), could also provide benefit to the CIVD response.MethodsForty male participants undertook three 10-day acclimation protocols including daily exercise training: heat acclimation (HeA; daily exercise training at an ambient temperature, Ta = 35 °C), combined heat and hypoxic acclimation (HeA/HypA; daily exercise training at Ta = 35 °C, while confined to a simulated altitude of ~ 4000 m) and exercise training in normoxic thermoneutral conditions (NorEx; no environmental stressors). To observe potential effects of the local acclimation on the CIVD response, participants additionally immersed their hand in warm water (35 °C) daily during the HeA/HypA and NorEx. Before and after the acclimation protocols, participants completed hand immersions in cold water (8 °C) for 30 min, followed by 15-min recovery phases. The temperature was measured in each finger.ResultsFollowing the HeA protocol, the average temperature of all five fingers was higher during immersion (from 13.9 ± 2.4 to 15.5 ± 2.5 °C; p = 0.04) and recovery (from 22.2 ± 4.0 to 25.9 ± 4.9 °C; p = 0.02). The HeA/HypA and NorEx protocols did not enhance the CIVD response.ConclusionWhole-body heat acclimation increased the finger vasodilatory response during cold-water immersion, and enhanced the rewarming rate of the hand, thus potentially contributing to improved local cold tolerance. Daily hand immersion in warm water for 10 days during HeA/Hyp and NorEx, did not contribute to any changes in the CIVD response.

Highlights

The possibility that an optimal cold-induced vasodilation (CIVD) response may offer protection against local cold injury has provided the impetus for studies investigating the manner in which the CIVD response could be trained
The hands of cold-acclimatised individuals exhibit increased blood flow, resulting in higher skin temperature, and earlier onset of the CIVD response. This local adaptation to a cold stimulus is greatly dependent on the thermal state of the body as a whole (Daanen 2003), with the CIVD response more pronounced when the body core and skin temperatures are elevated during local cooling (Daanen and Ducharme 1999; Daanen et al 1997)
Baseline measurements of the finger temperatures during the first 3 min of the trial did not differ before and after each of the 10-day intervention (HeA p: = 0.14; heat acclimation (HeA)/HypA: p = 0.4; normoxic thermoneutral exercise training (NorEx): p = 0.3), confirming that the CIVD trials were initiated at similar finger temperatures before and after each protocol

Summary

Introduction

The possibility that an optimal cold-induced vasodilation (CIVD) response may offer protection against local cold injury has provided the impetus for studies investigating the manner in which the CIVD response could be trained. Whole-body cold exposure, observed in Korean female divers wearing only thin cotton bathing suits, has been shown to induce insulative acclimatisation, evident in reduced heat loss during cold stress, rather than vasomotor acclimatisation, manifested in decreased susceptibility to cold pain or cold injury in the extremities (Lee et al 2017). Their CIVD response during hand immersion was weaker (Paik et al 1972) than that observed in Arctic fishermen (Krog et al 1960). This suggests that the resultant higher core temperature during the dives augmented the CIVD response

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Conclusion