Answer to O. Jay's Letter to the Editor

Abstract

The authors would like to thank Dr Jay for his insightful and constructive comments on our recently-published manuscript in the International Journal of Sports Medicine [2]. Using the 2-compartment thermometry model of “core” (Tes) and “shell” (Tsk) temperatures to calculate body heat storage (S), we recently postulated that “changes in the pattern” of S may serve as a key signal mediating reductions in self-selected work-rate during moderate duration, high intensity exercise in the heat [2], supporting previous observations [9]. These findings were based upon large differences in S observed between the HOT and COOL conditions during the early stages of exercise, and the tendency for this difference to decline during the later stages of exercise. In light of the inadequacies highlighted by Dr. Jay, when estimating S using the thermometry approach, we agree that “changes in the pattern of S” seem unlikely to serve as the key signal mediating early reduction in work-rate during self-paced exercise in the heat. Indeed, our own calculations (using indirect calorimetry) confirm the author's suggestions that S remained consistently higher in the HOT condition relative to COOL throughout the duration of exercise. Nevertheless, it should be noted that these observations do not detract from the overall message communicated in the manuscript, that a pre-exercise elevation in body heat content leads to an anticipatory reduction in work-rate during self-paced exercise in the heat.