Why the study?
The study investigated thermoregulatory and cardiovascular responses during cycling in temperate and warm environments with and without cutaneous capsaicin application, hypothesizing it would attenuate exercise-induced increases in rectal temperature and blood pressure.
Does capsaicin application on the skin alter thermoregulatory and cardiovascular responses during dynamic exercise in temperate and warm conditions in males?
Does capsaicin application on the skin alter thermoregulatory and cardiovascular responses during dynamic exercise in temperate and warm conditions in males?
Topical capsaicin application during exercise enhances heat loss mechanisms via increased sweating and skin vasodilation without altering cardiovascular responses.
Capsaicin may blunt core temperature rise during exercise without affecting BP; hypothesis-generating for heat mitigation, pending clinical trials.
Thermoregulatory and cardiovascular responses during cycling in temperate and warm environments without and with application of capsaicin on the skin were investigated. We hypothesized that regardless of environmental temperature, capsaicin application would activate heat loss mechanisms attenuating exercise-induced rectal temperature (Tre) and blood pressure increase. Eight males cycled at 55% of their maximal aerobic power so long as to reach 38.2°C Tre at 20.8 ± 1.0°C and at 30.6 ± 1.1°C ambient temperatures twice: without (NCA) and with (CA) application of capsaicin patches (12 × 18 cm, 4.8 mg). Patches were applied on pectoralis major, trapezius and vastus lateralis muscles. Thermoregulatory (Tre, proximal-distal skin temperature gradient, sweating rate), cardiovascular variables and oxygen uptake were continuously recorded. In both ambient conditions, during the first 14 min of exercise, the local vasoconstrictive tone as a function of the relative change in Tre was lower in CA than NCA (p < .05, d = 0.84-1.15). Further, sweating rate was higher and occurred at a lower Tre increase in CA compared to NCA (p = .03, d = 0.6) resulting in extended time to reach 38.2°C Tre (p = .03, d = 0.9). Moreover, oxygen consumption was higher in CA than in NCA (p < .001, d = 0.8). Mean arterial pressure was lower during cycling in warm compared to temperate environment, but was unaffected by capsaicin. We conclude that activation of thermal sensors by capsaicin results in lower Tre rise during exercise, which is mediated through greater skin vasodilation along with higher rate and earlier onset of sweating. Nonetheless, capsaicin application has no extra effect on exercise cardiovascular responses.
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Botonis et al. (2019) studied this question.
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