Modulation of elbow joint stiffness and co-contraction of agonist-antagonist muscles during human rhythmic movement.

本研究旨在探讨人体节律性运动中关节僵硬的调节机制。为了评估肘关节的力学性能，在运动过程中，每个受试者的前臂都受到了电磁力矩马达系统的外部扰动。关节刚度呈显著的二次曲线趋势，最小值接近器械-肢体系统的固有频率。这一结果表明：1)调节关节刚度的机制可能随固有频率和运动频率之间的关系而变化；2)协同收缩机制在慢动作时对保持关节刚度的作用不如在快动作时重要。

The purpose of this study is to investigate the modulation mechanism of joint stiffness during human rhythmic movement. To estimate the mechanical properties of the elbow joint, external perturbations were applied by an electromagnetic torque motor system to the forearm of each subject during the movement. Joint stiffness showed a significant quadratic trend with a minimum close to the natural frequency of the apparatus-limb system. This results suggested that 1) the mechanism by which joint stiffness is modulated may change according to the relation between natural frequency and movement frequency, and 2) the co-contraction mechanism is less important for maintaining joint stiffness during slow movement than during fast movement.