Graduate School of Health and Sport Science, Nippon Sport Science University , Tokyo, Japan ; Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo , Tokyo, Japan.
J Sports Sci Med. 2007 Dec 1;6(4):543-8. eCollection 2007.
The sensation of joint stiffness is frequently observed after eccentric contractions (ECs) in human, but the joint stiffness of animals after ECs has not been examined previously. This study tested whether a bout of ECs affects rat ankle joint stiffness. We also evaluate muscle passive tension in the rat hindlimb to examine the relationships of ankle joint stiffness with muscle passive tension. Anesthetized male Wistar rats (n = 23) were firmly secured on a platform in the prone position. A bout of ECs was performed on the gastrocnemius muscle with a combination of electrically induced tetanic contractions via a skin electrode and simultaneous forced dorsiflexion of the ankle joint (velocity, 15°/s; from 0°to 45°). Passive resistive torque (PRT) of the ankle joint was measured to evaluate joint stiffness. Passive tension of the exposed gastrocnemius muscle was also measured when the maximum value of joint stiffness was obtained. The PRT on days 2, 3, and 4 was significantly higher than the pre-treatment value (days 2 and 4; p < 0.001, days 3; p < 0.01). The passive tension on day 4 was significantly higher than that of the sham-operated group. The muscle wet mass was identical in both groups, suggesting the absence of edema. We conclude PRT increases after ECs in rat ankle joint. We also show the possibility that it is associated with muscle passive tension, independent of edema formation. Key pointsWe confirmed that ECs raise joint PRT and are associated with reduction of muscle passive tension.The changes in joint stiffness and muscle passive tension after ECs have been examined independently and the direct relationships have not been examined previously.We experimentally showed that ECs increased both joint PRT and muscle passive tension and these two parameters were significantly correlated.
在人类中，经常观察到离心收缩（ECs）后关节僵硬，但之前没有检查过 ECs 后动物的关节僵硬。本研究测试了一阵 ECs 是否会影响大鼠踝关节刚度。我们还评估了大鼠后肢肌肉的被动张力，以检查踝关节刚度与肌肉被动张力的关系。将麻醉的雄性 Wistar 大鼠（n = 23）牢固地固定在俯卧位的平台上。通过皮肤电极进行电诱发强直收缩，并同时强制背屈踝关节（速度为 15°/s；从 0°到 45°），对腓肠肌进行一阵 ECs。测量踝关节的被动阻力扭矩（PRT）以评估关节刚度。当获得最大关节刚度值时，还测量了暴露的腓肠肌的被动张力。第 2、3 和 4 天的 PRT 明显高于治疗前值（第 2 和 4 天；p <0.001，第 3 天；p <0.01）。第 4 天的被动张力明显高于假手术组。两组的肌肉湿重相同，表明无水肿。我们得出结论，大鼠踝关节 ECs 后 PRT 增加。我们还表明，它与肌肉被动张力有关，与水肿形成无关。关键点我们证实 ECs 会增加关节 PRT，并与肌肉被动张力的降低有关。我们独立检查了 ECs 后关节刚度和肌肉被动张力的变化，并且以前没有检查过它们之间的直接关系。我们通过实验表明，ECs 增加了关节 PRT 和肌肉被动张力，这两个参数之间存在显著相关性。
