School of Sport, Exercise and Nutrition, Massey University, Palmerston North, New Zealand.
School of Physical Education, Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand.
J Physiol. 2019 Jan;597(1):71-88. doi: 10.1113/JP276233. Epub 2018 Nov 22.
One in two female athletes chronically take a combined, monophasic oral contraceptive pill (OCP). Previous thermoregulatory investigations proposed that an endogenous rhythm of the menstrual cycle still occurs with OCP usage. Forthcoming large international sporting events will expose female athletes to hot environments differing in their thermal profile, yet few data exist on how trained women will respond from both a thermoregulatory and performance stand-point. In the present study, we have demonstrated that a small endogenous rhythm of the menstrual cycle still affects T and also that chronic OCP use attenuates the sweating response, whereas behavioural thermoregulation is maintained. Furthermore, humid heat affects both performance and thermoregulatory responses to a greater extent than OCP usage and the menstrual cycle does.
We studied thermoregulatory responses of ten well-trained ( , 57 ± 7 mL min kg ) women taking a combined, monophasic oral contraceptive pill (OCP) (≥12 months) during exercise in dry and humid heat, across their active OCP cycle. They completed four trials, each of resting and cycling at fixed intensities (125 and 150 W), aiming to assess autonomic regulation, and then a self-paced intensity (30-min work trial) to assess behavioural regulation. Trials were conducted in quasi-follicular (qF) and quasi-luteal (qL) phases in dry (DRY) and humid (HUM) heat matched for wet bulb globe temperature (WBGT) (27°C). During rest and exercise at 125 W, rectal temperature was 0.15°C higher in qL than qF (P = 0.05) independent of environment (P = 0.17). The onset threshold and thermosensitivity of local sweat rate and forearm blood flow relative to mean body temperature was unaffected by the OCP cycle (both P > 0.30). Exercise performance did not differ between quasi-phases (qF: 268 ± 31 kJ, qL: 263 ± 26 kJ, P = 0.31) but was 5 ± 7% higher during DRY than during HUM (273 ± 29 kJ, 258 ± 28 kJ; P = 0.03). Compared to matched eumenorrhoeic athletes, chronic OCP use impaired the sweating onset threshold and thermosensitivity (both P < 0.01). In well-trained, OCP-using women exercising in the heat: (i) a performance-thermoregulatory trade-off occurred that required behavioural adjustment; (ii) humidity impaired performance as a result of reduced evaporative power despite matched WBGT; and (iii) the sudomotor but not behavioural thermoregulatory responses were impaired compared to matched eumenorrhoeic athletes.
有二分之一的女运动员长期服用复方单相口服避孕药（OCP）。先前的体温调节研究表明，即使使用 OCP，月经周期仍存在内在节律。即将到来的大型国际体育赛事将使女运动员置身于热环境中，这些环境在热特性方面存在差异，但关于训练有素的女性将如何从体温调节和表现两个方面做出反应的数据很少。在本研究中，我们已经证明，月经周期的小内在节律仍然会影响 T 值，并且长期服用 OCP 会减弱出汗反应，而行为性体温调节则保持不变。此外，与 OCP 使用和月经周期相比，湿热对运动表现和体温调节反应的影响更大。
我们研究了在干燥和湿热环境中，十名服用复方单相口服避孕药（OCP）（≥12 个月）的训练有素的女性（ ，57±7mL·min -1 ·kg -1 ）在运动过程中的体温调节反应，跨越她们的活跃 OCP 周期。她们完成了四项试验，每项试验均包括在固定强度（125 和 150 W）下的休息和骑行，旨在评估自主调节，然后进行自我调节强度（30 分钟工作试验）以评估行为调节。试验在干燥（DRY）和湿热（HUM）环境中，在湿球黑球温度（WBGT）（27°C）匹配的情况下，在卵泡期（qF）和黄体期（qL）进行。在休息和 125 W 运动时，qL 期的直肠温度比 qF 期高 0.15°C（P=0.05），与环境无关（P=0.17）。局部排汗率和前臂血流量相对于平均体温的起始阈值和热敏性不受 OCP 周期的影响（均 P>0.30）。在 qF 和 qL 时，运动表现没有差异（qF：268±31 kJ，qL：263±26 kJ，P=0.31），但在 DRY 时比 HUM 时高 5%±7%（273±29 kJ，258±28 kJ；P=0.03）。与匹配的月经正常的运动员相比，长期服用 OCP 会损害出汗起始阈值和热敏性（均 P<0.01）。在进行热环境运动的训练有素、服用 OCP 的女性中：（i）出现了性能-体温调节的权衡，需要进行行为调整；（ii）尽管 WBGT 匹配，但湿度降低了蒸发能力，从而降低了运动表现；（iii）与匹配的月经正常的运动员相比，出汗的自主调节反应而不是行为性体温调节反应受损。
