Changes in the Electromyographic Activity and Joint Moments due to the Self-reinnervation of the Lateral Gastrocnemius and Soleus Muscles
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Peripheral nerve injuries can cause serious health problems and result in lifelong disabilities. Although researchers have been studying peripheral nerve injuries, patients may not regain complete function of their muscles even after surgeries to repair their nerves are performed. However, animal studies have shown that after peripheral nerve cut and repair (muscle self-reinnervation), stretch-reflex in the affected muscles does not recover, which may affect the muscle electromyographic (EMG) activity of all muscle synergists, as well as joint kinematics. The aim of this study is to determine the effects of the self-reinnervation of the lateral gastrocnemius (LG) and soleus (SO) muscles in the hind limb of felines on the mean EMG activity of the intact synergist medial gastrocnemius (MG), as well as the moments at the knee and ankle joints during different walking conditions: level (0%), downslope (-50%), and upslope (+50%). The EMG activity and joint kinematics were recorded on the three different walking conditions before and 12 weeks after the self-reinnervation of LG and SO when these muscles recovered their activity. The self-reinnervation of the two muscles caused the MG EMG activity to increase for all walking conditions. However, the changes in the knee and ankle moments differed depending on the three different walking conditions. It was concluded that the changes in EMG and joint moments after self-reinnervation could be caused by the absence of stretch-reflex in the affected muscles and/or changes in physiological properties of muscles.