The Heat Exposure Schedule On Vascular Inflammation Responses To Heat Acclimation

Understanding thermoregulatory acclimation during work challenges in both females and males remains an active area of environmental physiology research. Myriad body-wide adaptive responses are frequently influenced by a milieu of circulating factors, including blood markers of vascular inflammation. How these markers respond to variations in acute and repeated challenges of exercise+heat may influence heat acclimation outcomes. PURPOSE: To quantify circulating markers of vascular inflammation following either sustained (1x 90 minutes) or intermittent (3x 30 Minutes) exercise+heat exposure protocols. METHODS: Females and males (n = 30 each) were randomized to receive a week of low intensity exercise performed during one of two identically timed (90 minute) heat exposures. Gender-based groups (n = 15 each) performed either sustained (90 minutes) or intermittent (3x 30 minutes, 3-hour separation) heat exposure (38 °C, 60% RH) while walking on a treadmill (1.6 m·s-1, 5% grade). Blood samples drawn Pre and Post the first 30 minutes of exercise on days 1 and 7 were examined for vascular inflammation markers, including bFGF, Fit-1, ICAM, INF-y, IL-10, 1 L-12p40, IL-15, IL-16, IL-17b, IL-17c, IL1Ra, IL-6, IL-7, IL-8, PGIF, Tie-2, VEGF, VEGFa, VEGFc, VEGFd, and CRP. RESULTS: Pre-Post increases were present on day 1 and day 7 for 12/20 markers (bFGF, Fit-1, ICAM, IL-16, IL-17b, IL-6, IL-7, IL-8, PGIF, VEGFa, VEGFc, VEGFd; p < 0.05). Interestingly, females had robust responses in VEGFa, VEGFc and VEGFd for all treatments, while males did not. CONCLUSIONS: Low intensity exercise results in a comparable elevation of circulating markers of vascular inflammation for sustained and intermittent heating protocols. Moreover, females - but not males - expressed an increase in several VEGF isoforms, a finding that suggests that heat acclimation differences between males and females may be linked to circulating factors associated with vascular inflammation. Supported by: Supported by the United States Department of Defense, Department of the Air Force (FA8650-19-C6124).