Chou TH, et al. - Hyperthermia is well known to lower stroke volume (SV) during prolonged exercise of moderate intensity, but the underlying mechanism is inconclusive, especially when the skin temperature (Tsk) is hot (≥ 38°C). In this research, a low dose of β1-blockade (βB) independently reduced heart rate (HR) to examine its impact on SV during exercise when the skin is hot. Also studied was the effect of rapid cooling of the skin on reversing cardiovascular responses. During heating and cooling, forearm venous volume (FVV) was not different between trials. According to findings, the increase in HR instead of an increase in cutaneous blood flow or FVV was responsible for the reduction in SV during moderate intensity exercise when Tsk was held at 38°C.