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Objective: We examined the effects of twitch contraction induced by lumbar spinal root magnetic stimulation on immobilization-induced limited range of motion and skeletal muscle fibrosis in rat soleus muscle. Design: The groups included male Wistar rats (controls), rats with both bilateral ankle joints immobilized with plaster casts for 4 wks (immobilization [IM]), and rats in which twitch contraction of the soleus muscle was induced by lumbar magnetic stimulation for 4 wks of immobilization (twitch contraction [TC]). Group differences in ankle dorsiflexion range of motion, collagen content as determined by hydroxyproline assay, and the expression of fibrosis-related genes as determined by reverse transcription-polymerase chain reaction (hypoxia inducible factor 1α, α-smooth muscle actin, and types I and III collagen) in the soleus muscle were examined after the 4-wk-long experiment. Results: Range of motion in the TC group was significantly greater than that in the IM group. The hydroxyproline content and the expressions of fibrosis-related genes decreased significantly in the TC group compared with those in the IM group. No significant differences were seen in the expression of transforming growth factor β mRNA. Conclusions: These results suggest that twitch contraction induced by lumbar spinal root magnetic stimulation may reduce immobilization induced limited range of motion and skeletal muscle fibrosis. [ABSTRACT FROM AUTHOR]