Introduction Short term heat acclimation (STHA) is a preferred regime for athletes since it is easier to adopt when sustaining quality training and tapering performance in the weeks before competition. Females have been reported to respond to STHA; however they required long term HA to establish cardiovascular and thermoregulatory adaptation (Mee et al., In Press a). The current study assessed the effectiveness of five days HA combined with a restricted sweat evaporation exposure, to elicit thermoregulatory, cardiovascular and sudomotor adaptation. Method Nine females performed two running heat tolerance tests (Mee et al., In Press b), separated by five controlled hyperthermia HA sessions. Before HA, participants were exposed to a hot environment (50°C, 30% RH), whilst wearing a 100% Vinyl sauna suit (HAsauna) or a temperate environment (HA) for 20 minutes. Trials were performed in a randomised order and separated by ~7 weeks. Testing was completed during the follicular phase of the menstrual cycle or the pill free phase of oral contraception use; confirmed by plasma concentrations of 17β-estradiol and progesterone. Results In HAsauna, resting rectal temperature (Trrest) (-0.28 ± 0.15°C), resting heart rate (HRrest) (-9 ± 4 beats.min-1), peak rectal temperature (Trpeak) (-0.42 ± 0.22°C), peak heart rate (HRpeak) (-12 ± 7 beats.min-1) peak skin temperature (Tskinpeak) (-0.89 ± 0.86°C) and sweat ion concentration (-16 ± 10 mmol.L-1) reduced, sweat-onset Tr (-0.26 ± 0.15°C), sweat rate (SR) (565 ± 197 g.hr-1) and forearm SR (SRforearm) (+0.15 ± 0.14 mg.cm2/min) (p ≤ 0.05) increased. In HA, HRpeak (-4 ± 5 beats.min-1) and sweat ion concentration (-8 ± 4 mmol.L-1) reduced; and SR increased (+462 ± 399 g.hr-1) (p ≤ 0.05); while no differences were observed in Trrest, Trpeak, HRrest, Tskinpeak, SRforearm and sweat-onset Tr. Plasma volume expansion was greater following HAsauna (9.3 ± 7.6% vs 1.3 ± 5.0%; p ≤ 0.05). Discussion HAsauna trial was effective in attenuating thermoregulatory and cardiovascular strain; this was not achieved following the HA trial alone. Exercise was matched for metabolic heat production thus; the reduced thermoregulatory strain was potentially due to an increased evaporative heat loss, resulting in a reduction in heat storage as a result of altered afferent neural activity from the peripheral or central thermos-receptors. Conclusions Findings suggest thermoregulatory, cardiovascular and sudomotor adaptations can be achieved following short term HA in females, when HA is preceded by a period of restricted sweat evaporation. References J.A. Mee, J. Doust & N.S Maxwell. Repeatability of a running heat tolerance test. The Journal of Thermal Biology. (In Press). J.A. Mee, O.R. Gibson, J. Doust & N.S. Maxwell. A comparison of males and females’ temporal patterning to short and long term heat acclimation. Scandinavian Journal of Medicine Science in Sports. Training and competing in the heat special edition. (In Press).
|Publication status||Published - 2015|