1Department of Kinesiology, University of Texas at Austin, Austin, TX; 2Human Research and Engineering Directorate, U.S. Army Research Laboratory, Aberdeen Proving Ground, MD; and 3Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, Chapel Hill, NC.
Med Sci Sports Exerc. 2013 Nov;45(11):2151-7. doi: 10.1249/MSS.0b013e318299a69d.
Sports medicine professionals commonly describe two functionally different units of the vastus medialis (VM), the VM, and the vastus medialis oblique (VMO), but the anatomical support is equivocal. The functional difference of the VMO is principle to rehabilitation programs designed to alleviate anterior knee pain, a pathology that is known to have a greater occurrence in women. The purpose of this study was to determine whether the motor units of the VM and VMO are differentially recruited and if this recruitment pattern has an effect of sex or menstrual cycle phase.
Single motor unit recordings from the VM and VMO were obtained for men and women during an isometric ramp knee extension. Eleven men were tested once. Seven women were tested during five different phases of the menstrual cycle, determined by basal body temperature mapping. The recruitment threshold and the initial firing rate at recruitment were determined from 510 motor unit recordings.
The initial firing rate was lower in the VMO than that in the VM in women (P < 0.001) but not in men. There was no difference in recruitment thresholds for the VM and VMO in either sex or across the menstrual cycle. There was a main effect of menstrual phase on initial firing rate, showing increases from the early follicular to late luteal phase (P = 0.003). The initial firing rate in the VMO was lower than that in the VM during ovulatory (P = 0.009) and midluteal (P = 0.009) phases.
The relative control of the VM and VMO changes across the menstrual cycle. This could influence patellar pathologies that have a higher incidence in women.
运动医学专业人员通常将股四头肌的两个功能不同的单位（股直肌和股内斜肌）描述为股直肌和股内斜肌，但解剖学上的支持是有争议的。股内斜肌的功能差异是设计旨在缓解前膝痛的康复计划的基础，这种病理学在女性中更为常见。本研究的目的是确定股直肌和股内斜肌的运动单位是否有差异募集，如果这种募集模式对性别或月经周期阶段有影响。
对男性和女性进行等长斜坡膝关节伸展时，从股直肌和股内斜肌中获得单个运动单位记录。11 名男性进行了一次测试。7 名女性在通过基础体温绘图确定的五个不同月经周期阶段进行了测试。从 510 个运动单位记录中确定募集阈值和募集时的初始放电率。
女性的股内斜肌的初始放电率低于股直肌（P<0.001），但男性则不然。无论性别或月经周期如何，股直肌和股内斜肌的募集阈值均无差异。月经周期阶段对初始放电率有主要影响，从早期卵泡期到晚期黄体期逐渐增加（P=0.003）。在排卵（P=0.009）和中期黄体（P=0.009）阶段，股内斜肌的初始放电率低于股直肌。
股直肌和股内斜肌的相对控制在月经周期中发生变化。这可能会影响在女性中发病率较高的髌股疾病。
