Author(s): KELLY, M., SNOW, R.J., BROWN, H.A., CONDO, D., GUY, J.H., CHALMERS, S., BROATCH, J.R., ROBERTS, S.R., PÉRIARD, J.D., BOWE, S.J., CARR, A.J., Institution: DEAKIN UNIVERSITY, Country: AUSTRALIA, Abstract-ID: 1224

INTRODUCTION:
The exercise employed within a heat acclimation (HA) protocol is recommended to be similar to the sporting demands of the competition in the heat [1,2]. It remains unclear however, if the magnitude of adaptations transfers to different patterns of exercise after high intensity intermittent heat acclimation. The aim of this study was to determine whether thermophysiological and perceptual adaptations from high intensity intermittent heat acclimation transfer differently when females perform continuous versus intermittent heat response tests.
METHODS:
Eleven non-heat acclimatised females (mean ± SEM: age 27±2 y; body mass 69.63±2.64 kg; V̇O2peak 39.70±1.05 mL.kg-1.min-1; body surface area 1.78±0.04 m2) of recreationally active to highly trained status [3], completed six, 60-min sessions of intermittent (Int) cycling (repeated 30 s intervals) in the heat (~ 40°C, ~ 40% relative humidity) over seven days in the follicular phase of the menstrual cycle. In a randomised and balanced design, participants completed a 60 min Continuous (Con) and Int heat stress test (HST) both before HA (~ 33-34 ± 7 days) and after HA (2- and 4-days). All exercise sessions (HA and HST) were matched for mean external work-rate and designed to elicit ~ 60% V̇O2peak. Key outcome measures included delta change in rectal temperature (ΔTre), skin temperature (ΔTsk), heart rate (ΔHR), as well as rating of perceived exertion (ΔRPE), and thermal discomfort (ΔTD) for pre- and post- Int and Con HST only. Linear mixed models with Bonferroni post-hoc procedures were used to identify differences, with results considered statistically significant when p<0.05, and presented as mean ± 95% confidence intervals (CI).
RESULTS:
Following Int HA, ΔHR was 12 beats.min-1 [95%CI: 2, 21; p=0.015) lower during Int HST (pre-post: -15 beats.min-1) compared to Con HST (pre-post; -3 beats.min-1). A HA main effect for a reduction in ΔTre (-0.2°C [95%CI: -0.3, 0.0]; p=0.010), ΔTsk (-1.0°C [95%CI: -1.4, -0.6]; p<0.001), ΔRPE (-1.8 AU [95%CI: -2, -1]; p<0.001) and ΔTD (-163 mm [95%CI: -252, -76]; p<0.001) was identified and irrespective of HST.
CONCLUSION:
Following the Int HA protocol in females, there was a greater extent of transfer for mean HR only during the Int HST. All other thermophysiological and perceptual adaptations induced with Int HA transferred similarly to both Int and Con HST.

1. Racinais et al. (2015) Scan J Med Sci Sport, 2. Casadio et al. (2017) Sports Med., 3 McKay et al. (2022) IJSPP.