Ito M, Akima H, Fukunaga T
Graduate School of Health and Sport Science, Nippon Sport Science University, Setagaya, Tokyo, Japan.
J Biomech. 2000 Feb;33(2):215-8. doi: 10.1016/s0021-9290(99)00154-2.
The tendon excursion of the tibialis anterior (TA) muscle was measured in vivo using B-mode ultrasonography in seven subjects under three force levels (0, 30 and 60% maximal voluntary contraction, MVC). For each force level, the TA moment arm (m) was determined by calculating the derivative of the tendon excursion relative to the ankle angle (a). A dynamometer controlled the ankle angle while force levels were monitored. The parametric model proposed by Miller and Dennis (1996), m = R sin(a + delta), where R is the largest moment arm and delta represents the offset angle of R from 90 degrees, was used in a least-squares fit of the relationship between moment arm and ankle angle. The R values at 0% MVC were significantly smaller than those at 30 and 60% MVC. The values of calculated moment arm at 0% MVC were not considered adequate estimates of the TA moment arm because of the possible confounding effect of the slackness of the relaxed muscle-tendon unit in more dorsiflexed positions. The moment arm values at 30 and 60% MVC were believed to provide reliable estimates of those of TA since the application of tension probably reduced the effects of the slackness of the muscle-tendon unit and tendon elongation on tendon excursion measurement at these force levels. Since the ultrasonographic technique is an in vivo application of the tendon excursion technique and therefore takes the functional meaning into consideration, it can yield more significant moment arms than other in vivo or cadaver techniques.
在七名受试者中，使用B型超声在三种力水平（0、30%和60%最大自主收缩，MVC）下对胫骨前肌（TA）的肌腱偏移进行了体内测量。对于每个力水平，通过计算肌腱偏移相对于踝关节角度（a）的导数来确定TA力臂（m）。在监测力水平的同时，用测力计控制踝关节角度。采用Miller和Dennis（1996）提出的参数模型m = R sin（a + δ），其中R是最大力臂，δ表示R相对于90度的偏移角度，对力臂与踝关节角度之间的关系进行最小二乘拟合。0%MVC时的R值显著小于30%和60%MVC时的R值。由于在更背屈位置放松的肌腱单位松弛可能产生混杂效应，0%MVC时计算的力臂值被认为不足以估计TA力臂。30%和60%MVC时的力臂值被认为能够可靠地估计TA的力臂，因为在这些力水平下施加张力可能减少了肌腱单位松弛和肌腱伸长对肌腱偏移测量的影响。由于超声技术是肌腱偏移技术的体内应用，因此考虑了功能意义，它可以产生比其他体内或尸体技术更显著的力臂。
