Hirata Kosuke, Miyamoto-Mikami Eri, Kanehisa Hiroaki, Miyamoto Naokazu
National Institute of Fitness and Sports in Kanoya, 1 Shiromizu, Kanoya, Kagoshima, 891-2311, Japan.
Japan Society for the Promotion of Science, Tokyo, Japan.
Eur J Appl Physiol. 2016 May;116(5):911-8. doi: 10.1007/s00421-016-3349-3. Epub 2016 Mar 5.
It remains unclear whether the acute effect of stretching on passive muscle stiffness differs among the synergists. We examined the muscle stiffness responses of the medial (MG) and lateral gastrocnemii (LG), and soleus (Sol) during passive dorsiflexion before and after a static stretching by using ultrasound shear wave elastography.
Before and after a 5-min static stretching by passive dorsiflexion, shear modulus of the triceps surae and the Achilles tendon (AT) during passive dorsiflexion in the knee extended position were measured in 12 healthy subjects.
Before the static stretching, shear modulus was the greatest in MG and smallest in Sol. The stretching induced significant reductions in shear modulus of MG, but not in shear modulus of LG and Sol. The slack angle was observed at more plantar flexed position in the following order: AT, MG, LG, and Sol. After the stretching, the slack angles of each muscle and AT were significantly shifted to more dorsiflexed positions with a similar extent. When considering the shift in slack angle, the change in MG shear modulus became smaller.
The present study indicates that passive muscle stiffness differs among the triceps surae, and that the acute effect of a static stretching is observed only in the stiff muscle. However, a large part of the reduction of passive muscle stiffness at a given joint angle could be due to an increase in the slack length.
尚不清楚拉伸对被动肌肉僵硬度的急性影响在协同肌之间是否存在差异。我们使用超声剪切波弹性成像技术，研究了静态拉伸前后，在被动背屈过程中腓肠肌内侧头（MG）、外侧头（LG）和比目鱼肌（Sol）的肌肉僵硬度反应。
在12名健康受试者中，测量了在膝关节伸直位被动背屈过程中，5分钟被动背屈静态拉伸前后小腿三头肌和跟腱（AT）的剪切模量。
在静态拉伸前，MG的剪切模量最大，Sol的最小。拉伸导致MG的剪切模量显著降低，但LG和Sol的剪切模量没有降低。松弛角在跖屈位置的观察顺序如下：AT、MG、LG和Sol。拉伸后，各肌肉和AT的松弛角均显著向背屈位置移动，且移动程度相似。考虑到松弛角的变化，MG剪切模量的变化变小。
本研究表明，小腿三头肌的被动肌肉僵硬度存在差异，并且静态拉伸的急性效应仅在僵硬的肌肉中观察到。然而，在给定关节角度下，被动肌肉僵硬度的降低很大一部分可能是由于松弛长度的增加。
