Effect of rehabilitation protocols on muscle function and morphology following hindlimb disuse in weanling rats

Abstract

Background: Primary or secondary disorders in developing skeletal muscles are prevalent in physical therapy practice. Assessment of gait functional changes and morphological aspects of hindlimb muscles of weanling rats have not been reported simultaneously in the literature. Rehabilitation by active (eccentric training) and passive (stretching) exercises after hypomobility needs to be investigated. Methods: After ten days of immobilisation in a plantar flexion-shortened position, animals underwent eccentric training on treadmills, intermittent (a single series of ten exercises of 30 seconds each, with a 30-s interval) or continuous stretching protocols for 40 minutes, or had free cage activity for three days. Analysis of gait variables and muscle morphology (immunohistochemical staining of soleus and plantar muscles for fibronectin and types I and III collagen and immunofluorescence staining for dystrophin, laminin, Pax-7, and CD68) were performed. Results: On the third day, the rehabilitated animals touched the ground surface with their toes, except for the group undergoing continuous stretching. The total amount of extracellular macrophages was higher in the rehabilitated animals. The number of satellite cells was not significantly different between groups. Conclusion: Three days of active training (eccentric exercise) showed greater effectiveness compared to the other rehabilitation programs. Weanling rats seem to respond differently to external stimuli such as disuse and remobilisation.