Bambaeichi E, Reilly T, Cable N T, Giacomoni M
Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK
Chronobiol Int. 2004 Jul;21(4-5):645-60. doi: 10.1081/cbi-120039206.
Diurnal variation in muscle performance has been well documented in the past few years, but almost exclusively in the male population. The possible effects of the menstrual cycle on human circadian rhythms have remained equivocal, particularly in the context of muscle strength. The purpose of the study was to analyze the isolated and combined effects of circamensal variation and diurnal changes on muscle strength. Eight eumenorrheic females (age 30 +/- 5 yrs, height 1.63 +/- 0.06m and body mass 66.26 +/- 4.6kg: mean +/- SD) participated in this investigation. Isokinetic peak torque of knee extensors and flexors of the dominant leg were measured at 1.05, 3.14rad.s(-1) (through 90 degrees ROM) at two times-of-day (06:00, 18:00 h) and five time points of the menstrual cycle (menses, mid-follicular, ovulation, mid-luteal, late luteal). In addition, maximum voluntary isometric contraction of knee extensors and flexors and electrically stimulated isometric contraction of the knee extensors were measured at 60 degrees of knee flexion. Rectal temperature was measured during 30min before the tests. There was a significant time-of-day effect on peak torque values for isometric contraction of knee extensors under electrical stimulation (P< 0.05). At 18:00 h, muscle force was 2.6% greater than at 06:00 h. The time-of-day effect was not significant when the tests were performed voluntarily without stimulation: effect size calculations indicated small differences between morning and evening for maximal voluntary isometric contraction and peak torque (at 1.05rad.s(-1) for the knee extensors. A circamensal variation was observed for peak torque of knee flexors at 1.05rad.s(-1), extensors at 3.14rad.s(-1), and also isometric contraction of knee flexors, values being greatest at the ovulation phase. Interaction effects between time-of-day and menstrual cycle phase were not observed in any of the indices of muscle strength studied. The phase of the menstrual cycle seemed to have a greater effect than did the time-of-day on female muscle strength in this group of subjects. The present results suggest that peripheral rather than central mechanisms (e.g., motivation) are implicated in the diurnal variation of maximal isometric strength of women.
在过去几年中，肌肉性能的昼夜变化已有充分记录，但几乎都集中在男性群体中。月经周期对人体昼夜节律的可能影响一直不明确，尤其是在肌肉力量方面。本研究的目的是分析月经周期变化和昼夜变化对肌肉力量的单独及综合影响。八名月经周期正常的女性（年龄30±5岁，身高1.63±0.06米，体重66.26±4.6千克：均值±标准差）参与了本调查。在一天中的两个时间点（06:00、18:00）以及月经周期的五个时间点（月经期、卵泡中期、排卵期、黄体中期、黄体后期），测量优势腿膝伸肌和膝屈肌在1.05、3.14弧度·秒⁻¹（通过90度活动范围）时的等速峰值扭矩。此外，在膝关节屈曲60度时，测量膝伸肌和膝屈肌的最大自主等长收缩以及膝伸肌的电刺激等长收缩。在测试前30分钟测量直肠温度。电刺激下膝伸肌等长收缩的峰值扭矩值存在显著的时间点效应（P<0.05）。在18:00时，肌肉力量比06:00时大2.6%。在无刺激的自主测试中，时间点效应不显著：效应量计算表明，最大自主等长收缩和峰值扭矩（膝伸肌在1.05弧度·秒⁻¹时）在早晨和晚上的差异较小。在1.05弧度·秒⁻¹时膝屈肌的峰值扭矩、3.14弧度·秒⁻¹时膝伸肌的峰值扭矩以及膝屈肌的等长收缩均观察到月经周期变化，在排卵期的值最大。在所研究的任何肌肉力量指标中，均未观察到时间点和月经周期阶段之间的交互作用。在这组受试者中，月经周期阶段对女性肌肉力量的影响似乎比时间点更大。目前的结果表明，女性最大等长力量的昼夜变化涉及外周而非中枢机制（如动机）。
