Abstract
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.
Highlights
It is well-documented that heat-sensitive and cold-sensitive temperature receptor potential (TRP) channels significantly contribute to mammals’ temperature regulation (Caterina, 2007; Romanovsky et al, 2009)
We investigated the effects of capsaicin application on the skin (5% of the skin surface area) during dynamic wholebody exercise on thermoregulatory and cardiovascular responses at temperate and warm conditions
The principal findings of the present study were: (a) regardless of ambient temperature, capsaicin application before the initiation of exercise reduced heat gain during exercise due toa greater heat loss indicated by a lower estimated vasoconstrictive tone of the skin as well as to an earlier onset and higher rate of sweating; in turn, both these responses ended in a slower rise of rectal temperature during exercise, and (b) the higher heat dissipation observed after application of capsaicin was not accompanied by lessened blood pressure increase during exercise, as it was anticipated based on previous data at rest
Summary
It is well-documented that heat-sensitive and cold-sensitive temperature receptor potential (TRP) channels significantly contribute to mammals’ temperature regulation (Caterina, 2007; Romanovsky et al, 2009). A recent study in humans (Botonis et al, 2019), confirming previous observations in animals (Donnerer & Lembeck, 1983; Jansco-Cabor, Szolcsanyi, & Jancso, 1970), demonstrated a significant rectal temperature decline during resting conditionas a result of capsaicin application on subjects’ skin. Along these lines, studies conducted in vivo have shown that TRPV1 channels contribute to thermal hyperaemia (Wong & Fieger, 2010) accompanied by cutaneous active vasodilation (Wong & Fieger, 2012). Notwithstanding the increasing accumulation of research underlining the cardioprotective effects of TRPV1 activation (Mc Carty et al, 2015) and its influence on blood pressure at rest and during static exercise, the cardiovascular effects of TRPV1 stimulation through capsaicin application during dynamic whole-body exercise have never been determined
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
