Study on change of rat soleus extensibility caused by reduction in joint movement with unweighting of the hind limbs

[Purpose] The purpose of this study was to investigate the change in soleus extensibility from a joint contracture caused by a reduction in joint movement with unweighted lower limbs and to interpret the results to aid in the treatment of human joint contractures. [Subjects and Methods] The subjects of this study were twenty-one 10-weeks-old male Wistar rats. Twenty-one rats were divided into one control (C) and two experimental groups. The first experimental group included fixed right ankle joints in full plantar flexion (F). The second experimental group's hind limbs were suspended and the right ankle joints were fixed in full plantar flexion (FS). The period of this study was one week. On the first and last day of this study, all of the rats' ankle dorsiflexion angles were measured. On the last day of this study, all of the rats' soleus extensibilities were measured. [Results] On the last day of this study, the ankle dorsiflexion angles and the soleus extensibility in the FS group were significantly more decreased than those of the F group. [Conclusion] It was shown that the skeletal muscle extensibility from joint contracture caused by reduction of joint movement with unweighted lower limbs was more markedly decreased than that from joint contracture caused by reduction of joint movement.