Lieber R L, Boakes J L
Department of Surgery, Veterans Administration Medical Center, San Diego, California 92161.
Am J Physiol. 1988 Jun;254(6 Pt 1):C759-68. doi: 10.1152/ajpcell.1988.254.6.C759.
The relationship between semitendinosus muscle force and knee joint kinematics during isometric torque production was examined in the frog (Rana pipiens) hindlimb. Passive muscle sarcomere length was monitored by laser diffraction during knee rotation, and joint center of rotation was determined later using principles of rigid body kinematics. Contractile force at the distal tibia, resulting from semitendinosus contraction, was also measured, and, using the kinematic data, a torque vs. joint angle curve constructed. Muscle sarcomere length varied from 3.6 micron at full knee extension to 2.0 micron at full knee flexion. Effective lever arm varied almost as a sine function, with optimal lever arm at 90 degrees of flexion. Joint torque increased linearly from 0 to 140 degrees of flexion and then sharply decreased to 160 degrees of flexion. Thus the optimal joint angle occurred at an angle (140 degrees) that was neither the angle at which muscle force was maximum (160 degrees) nor the angle at which the effective lever arm was maximum (90 degrees). These data indicate that knee torque production in the frog results from the interaction between muscular and joint properties and not either property alone.
在蛙（豹蛙）后肢等长扭矩产生过程中，研究了半腱肌力量与膝关节运动学之间的关系。在膝关节旋转过程中，通过激光衍射监测被动肌节长度，随后利用刚体运动学原理确定关节旋转中心。还测量了半腱肌收缩产生的胫骨远端收缩力，并利用运动学数据构建了扭矩与关节角度曲线。肌节长度从膝关节完全伸展时的3.6微米变化到膝关节完全屈曲时的2.0微米。有效力臂几乎呈正弦函数变化，在90度屈曲时力臂最佳。关节扭矩从0度到140度屈曲呈线性增加，然后在160度屈曲时急剧下降。因此，最佳关节角度出现在一个角度（140度），该角度既不是肌肉力量最大时的角度（160度），也不是有效力臂最大时的角度（90度）。这些数据表明，蛙膝关节扭矩的产生是肌肉和关节特性相互作用的结果，而非单一特性所致。
