The effect of acute hot water immersion on cutaneous peripheral microvascular responses in males of White-European, Black-African and South-Asian descent

Cardiovascular disease is more prevalent in individuals of Black-African (BA) and South-Asian (SA) descent than White-European (WE) counterparts, with vascular dysfunction identified as contributing to this disparity. Chronic heat therapy can elicit positive vascular adaptations, potentially underpinned by the repeated cardiovascular strain experienced during acute heat exposures. This study examined the cutaneous peripheral microvascular responses following acute hot (HWI) and thermoneutral (CON) water immersion between males of WE, BA, and SA descent. Thirty-one young, healthy WE (n = 10), BA (n = 10), SA (n = 11) males completed 60 minutes of HWI (39°C) and CON (36°C) with thermoregulatory, cardiovascular, and perceptual responses measured throughout. Following 60 minutes of thermoneutral rest, forearm and Great toe cutaneous vascular conductance (CVC) were recorded during cutaneous post-occlusive reactive hyperemia (PORH) and local heating (LH). Baseline CVC was similar between groups (p ≥ 0.08). During PORH, BA had lower peak forearm and Great toe CVC than WE and SA, and a reduced CVC area under the curve compared to WE (p ≤ 0.01). Furthermore, BA Great toe CVC was blunted compared to WE and SA during both 42°C (p ≤ 0.033) and 44°C (p ≤ 0.02) LH, respectively. Great toe CVC was acutely increased following HWI in responses to 44°C LH compared to CON (p ≤ 0.039), with no race × condition interaction effects. In conclusion, despite blunted microvascular responses in BA, acute HWI did not elicit distinct effects between males of WE, BA, and SA descent, although microvascular responses to LH were greater following HWI.