Effects of heat acclimation on hand cooling efficacy following exercise in the heat

ABSTRACT

This study examined the separate and combined effects of heat acclimation and hand cooling on post-exercise cooling rates following bouts of exercise in the heat. Seventeen non-heat acclimated (NHA) males (mean ± SE; age, 23 ± 1 y; mass, 75.30 ± 2.27 kg; maximal oxygen consumption [VO₂ max], 54.1 ± 1.3 ml·kg⁻¹·min⁻¹) completed 2 heat stress tests (HST) when NHA, then 10 days of heat acclimation, then 2 HST once heat acclimated (HA) in an environmental chamber (40°C; 40%RH). HSTs were 2 60-min bouts of treadmill exercise (45% VO₂ max; 2% grade) each followed by 10 min of hand cooling (C) or no cooling (NC). Heat acclimation sessions were 90–240 min of treadmill or stationary bike exercise (60–80% VO₂ max). Repeated measures ANOVA with Fishers LSD post hoc (α < 0.05) identified differences. When NHA, C (0.020 ± 0.003°C·min⁻¹) had a greater cooling rate than NC (0.013 ± 0.003°C·min⁻¹) (mean difference [95%CI]; 0.007°C [0.001,0.013], P = 0.035). Once HA, C (0.021 ± 0.002°C·min⁻¹) was similar to NC (0.025 ± 0.002°C·min⁻¹) (0.004°C [−0.003,0.011], P = 0.216). Hand cooling when HA (0.021 ± 0.002°C·min⁻¹) was similar to when NHA (0.020 ± 0.003°C·min⁻¹) (P = 0.77). In conclusion, when NHA, C provided greater cooling rates than NC. Once HA, C and NC provided similar cooling rates.

KEYWORDS:

• Rectal temperature
• cooling rate
• grip strength
• hyperthermia
• exertional heat illness

Acknowledgments

This study was funded by donations to the Korey Stringer Institute. Authors would like to sincerely thank the many contributing researchers of the Human Performance Laboratory at the University of Connecticut for their outstanding efforts in assisting with data collection.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was supported by donations to the Korey Stringer Institute.