Wakahara Taku, Kanehisa Hiroaki, Kawakami Yasuo, Fukunaga Tetsuo
Graduate School of Human Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, Japan.
J Electromyogr Kinesiol. 2009 Oct;19(5):980-7. doi: 10.1016/j.jelekin.2008.05.008. Epub 2008 Jul 22.
The present study aimed to clarify the effects of knee joint angle on the behavior of the medial gastrocnemius muscle (MG) fascicles during eccentric plantar flexions. Eight male subjects performed maximal eccentric plantar flexions at two knee positions [fully extended (K0) and 90 degrees flexed (K90)]. The eccentric actions were preceded by static plantar flexion at a 30 degrees plantar flexed position and then the ankle joint was forcibly dorsiflexed to 15 degrees of dorsiflexion with an isokinetic dynamometer at 30 degrees /s and 150 degrees /s. Tendon force was calculated by dividing the plantar flexion torque by the estimated moment arm of the Achilles tendon. The MG fascicle length was determined with ultrasonography. The tendon forces during eccentric plantar flexions were influenced by the knee joint angle, but not by the angular velocity. The MG fascicle lengths were elongated as the ankle was dorsiflexed in K0, but in K90 they were almost constant despite the identical range of ankle joint motion. These results suggested that MG fascicle behavior during eccentric actions was markedly affected by the knee joint angle. The difference in the fascicle behavior between K0 and K90 could be attributed to the non-linear force-length relations and/or to the slackness of tendinous tissues.
本研究旨在阐明膝关节角度对离心性跖屈过程中腓肠肌内侧头（MG）肌束行为的影响。八名男性受试者在两个膝关节位置[完全伸展（K0）和屈曲90度（K90）]进行最大离心性跖屈。在离心动作之前，先在跖屈30度位置进行静态跖屈，然后用等速测力计以30度/秒和150度/秒的速度将踝关节强行背屈至背屈15度。通过将跖屈扭矩除以跟腱估计力臂来计算肌腱力。用超声检查确定MG肌束长度。离心性跖屈过程中的肌腱力受膝关节角度影响，但不受角速度影响。在K0中，随着踝关节背屈，MG肌束长度延长，但在K90中，尽管踝关节运动范围相同，其肌束长度几乎保持不变。这些结果表明，离心动作过程中MG肌束行为受膝关节角度显著影响。K0和K90之间肌束行为的差异可能归因于非线性力-长度关系和/或肌腱组织的松弛。
