Heat adaptation in humans with controlled heart rate heat acclimation

We read with interest the recent review by Taylor et al. (2020) discussing heat acclimation (HA) in the context of controlled and regulated physiological variables to compare the controlled heart rate (HR) and controlled hyperthermia protocols. The authors concluded that controlling HR and similar variables are “experimental simplifications with clear, and sometimes unanticipated and undesirable consequences” (Taylor et al. 2020). The choice of HA protocol is certainly important and should be based on specific aims. HA protocols include exercising at a constant or self-selected work rate, controlling core temperature, immersing in hot water after exercising in cool conditions, or simply resting in the heat. All of these approaches have advantages and shortcomings, whether in their implementation (logistical or equipment constraints), the nature of the stimulus provided (adaptation impulse), or in the transfer of adaptation to different environmental and exercise conditions (adaptation specificity).