脫氫表雄酮（dehydroepiandrosterone, DHEA）是生殖性荷爾蒙的前驅物，DHEA-S（dehydroepiandrosterone sulfate）濃度隨年齡逐漸下降，該數值已成為人類壽命的重要預測指標。本研究的目的為追蹤年輕女性運動員在一個完整月經週期中血清DHEA-S濃度與肌力的演變。研究過程共有10位年約21歲的年輕女性運動員參與這個追蹤研究。從月經來的第一天起每七天進行一次測量，指標包括月經週（M: Menses week）、排卵週（O: Ovulatory week）、黃體前期週（L1: Luteal phase week 1）、黃體後期週（經前）（L2: Luteal phase week 2）。本研究結果發現全期女性運動員的主觀心情波動不大，但肌力與血清DHEA-S濃度同時在黃體後期（經前）下降，同時血清雌激素與黃體素濃度明顯上升。根據心率變異度的觀察，此時交感神經強度與體溫同時增加。結論：本研究建議女性運動員如尋求最佳成績表現宜避免在黃體後期（經前）參加比賽，另外這時期體能下降的原因可能與身體正專注於利用DHEA製造生殖激素所造成。

Dehydroepiandrosterone (DHEA) is the common precursor of several reproductive hormones. DHEA-sulfate (DHEA-S) declines during adult aging and has been considered as a strong predictor for human longevity. The purpose of the study was to track the evolution of serum DHEA-S concentration and muscle strength during a menstrual cycle for young athletes. Ten female athletes (21 years of age) were enrolled in this longitudinal observation with hormonal and muscle strength assessments for every 7 days since the first day of menses, including Menses (M), Ovulatory (O), Luteal 1 (L1) and Luteal 2 (L2) periods. Despite total mood disturbance was not changed, muscle strength and serum DHEA-S concentrations were declined simultaneously during L2 period with a significant increase of serum estradiol and progesterone concentrations. Furthermore, during L2 period, sympathetic power mirrored by low-frequency heart rate variability (LF-HRV) and body temperature were relatively greater than the rest of the phases. We conclude that physical but not mental capabilities were compromised during premenstrual period for young female athletes. These findings suggest that circumventing athletic event during premenstrual period may be important to maximize the competition outcome for female athletes. This is probably because of increased consumption of endogenous DHEA for the biosynthesis of reproductive hormones during premenstrual phase.