Repeatability of a Running Heat Tolerance Test

At present there is no standardised heat tolerance test (HTT) procedure adopting a running mode of exercise. Current HTTs may misdiagnose a runner's susceptibility to a hyperthermic state due to differences in exercise intensity. The current study aimed to establish the repeatability of a practical running test to evaluate individual's ability to tolerate exercise heat stress. Sixteen (8M, 8F) participants performed the running HTT (RHTT) (30min, 9kmh−1, 2% elevation) on two separate occasions in a hot environment (40°C and 40% relative humidity). There were no differences in peak rectal temperature (RHTT1: 38.82±0.47°C, RHTT2: 38.86±0.49°C, Intra-class correlation coefficient (ICC)=0.93, typical error of measure (TEM)=0.13°C), peak skin temperature (RHTT1: 38.12±0.45, RHTT2: 38.11±0.45°C, ICC=0.79, TEM=0.30°C), peak heart rate (RHTT1: 182±15 beatsmin−1, RHTT2: 183±15 beatsmin−1, ICC=0.99, TEM=2 beatsmin−1), nor sweat rate (1721±675gh−1, 1716±745gh−1, ICC=0.95, TEM=162gh−1) between RHTT1 and RHTT2 (p>0.05). Results demonstrate good agreement, strong correlations and small differences between repeated trials, and the TEM values suggest low within-participant variability. The RHTT was effective in differentiating between individuals physiological responses; supporting a heat tolerance continuum. The findings suggest the RHTT is a repeatable measure of physiological strain in the heat and may be used to assess the effectiveness of acute and chronic heat alleviating procedures.