The acute effect of heat exposure on forearm macro‐ and microvascular function: Impact of measurement timing, heating modality and biological sex

Abstract

New Findings What is the central question of this study?Do measurement timing, heating modality and biological sex modulate the acute effect of heat exposure on brachial artery flow‐mediated dilatation and postocclusion reactive hyperaemia? What is the main finding and its importance?The acute effect of heat exposure on brachial artery flow‐mediated dilatation and postocclusion reactive hyperaemia is: (1) transient and short lasting; (2) different between forearm and whole‐body heating; (3) unaffected by forearm heating during whole‐body heating; and (4) not different but not always equivalent between males and females. These findings provide a useful basis for future studies to investigate the acute effect of heat exposure on vascular function. Abstract The aim of this study was to gain a better understanding of the acute effect of heat exposure on brachial artery flow‐mediated dilatation (FMD) and postocclusion reactive hyperaemia (PORH) by: characterizing the time course of changes post‐heating; comparing forearm and whole‐body heating; determining the impact of forearm heating during whole‐body heating; and comparing males and females. Twenty adults (11 males and nine females; 28 ± 6 years of age) underwent two forearm [10 min electric blanket (EB) or 30 min hot water immersion (WI)] and two whole‐body [60 min water‐perfused suit with forearm covered (WBH‐C) or uncovered (WBH‐U)] heating modalities. The FMD and PORH were measured before and after (≤5, 30, 60, 90 and 120 min) heating. The FMD increased from baseline 30 min after EB, and 30 and 90 min after WI. In contrast, FMD decreased from baseline immediately after both WBH modalities. Peak PORH increased immediately after WI and both WBH modalities. Total PORH did not differ after WI, whereas it decreased immediately after both WBH modalities. Covering the forearm during WBH did not alter acute changes in FMD or PORH. Changes in FMD and PORH did not differ statistically between males and females during each heating modality, although the observed differences could not always be considered equivalent. These results demonstrate that the acute effect of heat exposure on brachial artery FMD and PORH is: (1) transient and short lasting; (2) different between forearm heating and WBH; (3) unaffected by direct forearm heating during WBH; and (4) not different but not always equivalent between males and females.

The importance of microvascular inflammation in ageing and age-related diseases: a position paper from the ESH working group on small arteries, section of microvascular inflammation

“…Unhealthy dietary and eating patterns [56], as well as nutrient overload [57], cause an imbalance in the oxygen supply/demand ratio, activating hypoxia-inducible factor 1a (HIF-1a) and promoting impaired angiogenesis [58]. Additional environment determinants, including environment pollutants, temperature, seasonal changes, circadian rhythm and infections have demonstrated significant role in regulating microvascular inflammation and cardiovascular (CV) diseases [59][60][61][62][63][64][65][66][67][68] The final effector through which all these stressors promote microvascular ageing [69][70][71] is the immune-inflammatory response [60]. Ultimately, they create a lowgrade pro-oxidant pro-inflammatory environment [72] that leads to MD [73,74].…”

“…Unhealthy dietary and eating patterns [56], as well as nutrient overload [57], cause an imbalance in the oxygen supply/demand ratio, activating hypoxia-inducible factor 1α (HIF-1α) and promoting impaired angiogenesis [58]. Additional environment determinants, including environment pollutants, temperature, seasonal changes, circadian rhythm and infections have demonstrated significant role in regulating microvascular inflammation and cardiovascular (CV) diseases [59–68]…”