Department of Kinesiology, University of Texas at Austin , Austin, Texas.
Human Research & Engineering Directorate, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland.
J Appl Physiol (1985). 2018 Jun 1;124(6):1438-1446. doi: 10.1152/japplphysiol.00702.2017. Epub 2018 Feb 8.
Weakness of the vastus medialis oblique (VMO) has been proposed to explain the high prevalence of knee pain in female subjects. Clinicians commonly use exercises in an attempt to preferentially activate the VMO. Recently, our group found evidence to support clinical theory that the VMO is neurologically distinct from the vastus medialis (VM). However, the ability to voluntarily activate these muscle subsections is still disputed. The aim of this study was to determine if VM and VMO activation varies between sexes and if control of the two muscles is different between rehabilitation exercises. Thirteen men and 13 women performed isometric straight leg raises in two hip positions, neutral hip rotation and 30 degrees lateral hip rotation. Bipolar intramuscular fine-wire electrodes were inserted into the VM and VMO to obtain motor unit recruitment thresholds and initial firing rates at recruitment. Linear mixed models and Tukey post hoc tests were used to assess significant differences in 654 motor units. Women demonstrated faster motor unit firing rate at recruitment, 1.18 ± 0.56 Hz higher than men. Motor units fired 0.47 ± 0.19 Hz faster during neutral hip rotation compared with lateral hip rotation. The VMO motor units were recruited 2.92 ± 1.28% earlier than the VM. All motor units were recruited 3.74 ± 1.27% earlier during neutral hip rotation than lateral hip rotation. Thus the VM and the VMO can be activated differentially, and their motor unit recruitment properties are affected by sex and hip position. NEW & NOTEWORTHY This is the first study to reveal differential activation of the vastus medialis oblique from the vastus medialis in clinical exercise protocols. Our research group used fine-wire electrodes to examine EMG signals of the vastus medialis oblique and vastus medialis to avoid possible cross talk. We also consider the effect of sex on motor unit firing patterns because of higher prevalence of knee pain in women, and yet few studies evaluating the sex differences in neuromuscular control.
股直肌内侧头（VMO）无力被认为是女性膝关节疼痛高发的原因。临床医生通常采用运动来试图优先激活 VMO。最近，我们的研究小组发现了一些证据，支持了 VMO 在神经上与股直肌（VM）不同的临床理论。然而，人们对是否能主动激活这些肌肉节段仍存在争议。本研究旨在确定 VM 和 VMO 的激活是否存在性别差异，以及在康复运动中，两种肌肉的控制是否不同。13 名男性和 13 名女性分别在中立位和 30°外展位髋关节进行等长直腿抬高，将双极肌内细针电极插入 VM 和 VMO 以获得运动单位募集阈值和募集时的初始放电率。线性混合模型和 Tukey 事后检验用于评估 654 个运动单位的显著性差异。女性在募集时的运动单位放电率更快，比男性高 1.18±0.56 Hz。与外展位髋关节相比，中立位髋关节时运动单位的放电速度快 0.47±0.19 Hz。VMO 运动单位比 VM 早募集 2.92±1.28%。与外展位髋关节相比，中立位髋关节时所有运动单位的募集早 3.74±1.27%。因此，VM 和 VMO 可以被不同地激活，并且它们的运动单位募集特性受性别和髋关节位置的影响。新观点和重要性这是第一项揭示在临床运动方案中股直肌内侧头与股直肌不同激活的研究。我们的研究小组使用细针电极来检查股直肌内侧头和股直肌的肌电图信号，以避免可能的串扰。我们还考虑了性别对运动单位放电模式的影响，因为女性膝关节疼痛的发病率更高，但很少有研究评估神经肌肉控制方面的性别差异。
