Lei Tze-Huan, Stannard Stephen R, Perry Blake G, Schlader Zachary J, Cotter James D, Mündel Toby
School of Sport and Exercise, Massey University, Palmerston North, New Zealand.
Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA.
J Physiol. 2017 May 1;595(9):2823-2837. doi: 10.1113/JP273176. Epub 2017 Jan 4.
Despite an attenuated fluctuation in ovarian hormone concentrations in well-trained women, one in two of such women believe their menstrual cycle negatively impacts training and performance. Forthcoming large international events will expose female athletes to hot environments, and studies evaluating aerobic exercise performance in such environments across the menstrual cycle are sparse, with mixed findings. We have identified that autonomic heat loss responses at rest and during fixed-intensity exercise in well-trained women are not affected by menstrual cycle phase, but differ between dry and humid heat. Furthermore, exercise performance is not different across the menstrual cycle, yet is lower in humid heat, in conjunction with reduced evaporative cooling. Menstrual cycle phase does not appear to affect exercise performance in the heat in well-trained women, but humidity impairs performance, probably due to reduced evaporative power.
We studied thermoregulatory responses of ten well-trained [V̇O2 max , 57 (7) ml min kg ] eumenorrheic women exercising in dry and humid heat, across their menstrual cycle. They completed four trials, each of resting and cycling at fixed intensities (125 and 150 W), to assess autonomic regulation, then self-paced intensity (30 min work trial), to assess behavioural regulation. Trials were in early-follicular (EF) and mid-luteal (ML) phases in dry (DRY) and humid (HUM) heat matched for wet bulb globe temperature (WBGT, 27°C). During rest and fixed-intensity exercise, rectal temperature was ∼0.2°C higher in ML than EF (P < 0.01) independent of environment (P = 0.66). Mean skin temperature did not differ between menstrual phases (P ≥ 0.13) but was higher in DRY than HUM (P < 0.01). Local sweat rate and/or forearm blood flow differed as a function of menstrual phase and environment (interaction: P ≤ 0.01). Exercise performance did not differ between phases [EF: 257 (37), ML: 255 (43) kJ, P = 0.62], but was 7 (9)% higher in DRY than HUM [263 (39), 248 (40) kJ; P < 0.01] in conjunction with equivalent autonomic regulation and thermal strain but higher evaporative cooling [16 (6) W m ; P < 0.01]. In well-trained women exercising in the heat: (1) menstrual phase did not affect performance, (2) humidity impaired performance due to reduced evaporative cooling despite matched WBGT and (3) behavioural responses nullified thermodynamic and autonomic differences associated with menstrual phase and dry vs. humid heat.
尽管训练有素的女性卵巢激素浓度波动减弱，但其中每两人中就有一人认为她们的月经周期会对训练和表现产生负面影响。即将到来的大型国际赛事将使女运动员暴露在炎热环境中，而评估月经周期中女性在这种环境下有氧运动表现的研究很少，且结果不一。我们已经确定，训练有素的女性在休息和进行固定强度运动时的自主散热反应不受月经周期阶段的影响，但在干热和湿热环境下有所不同。此外，运动表现在月经周期中并无差异，但在湿热环境中较低，同时蒸发散热减少。月经周期阶段似乎不会影响训练有素的女性在炎热环境中的运动表现，但湿度会损害表现，可能是由于蒸发能力降低。
我们研究了10名月经周期正常、训练有素（最大摄氧量为57（7）ml·min⁻¹·kg⁻¹）的女性在月经周期中于干热和湿热环境下运动时的体温调节反应。她们完成了四项试验，每项试验包括休息和以固定强度（125瓦和150瓦）骑行，以评估自主调节，然后是自定强度（30分钟工作试验）以评估行为调节。试验在干热（DRY）和湿热（HUM）环境下的卵泡早期（EF）和黄体中期（ML）阶段进行，湿球黑球温度（WBGT，27°C）匹配。在休息和固定强度运动期间，无论环境如何（P = 0.66），黄体中期的直肠温度比卵泡早期高约0.2°C（P < 0.01）。月经周期各阶段的平均皮肤温度无差异（P ≥ 0.13），但干热环境下高于湿热环境（P < 0.01）。局部出汗率和/或前臂血流量因月经周期阶段和环境而异（交互作用：P ≤ 0.01）。各阶段的运动表现无差异[卵泡早期：257（37）kJ，黄体中期：255（43）kJ，P = 0.62]，但在干热环境下比湿热环境高7（9）%[263（39）kJ，248（40）kJ；P < 0.01]，同时自主调节和热应激相当，但蒸发散热更高[16（6）W·m⁻²；P < 0.01]。对于在炎热环境中运动的训练有素的女性：（1）月经周期阶段不影响表现，（2）尽管WBGT匹配，但湿度因蒸发散热减少而损害表现，（3）行为反应消除了与月经周期阶段以及干热和湿热环境相关的热力学和自主差异。
