Abstract: BACKGROUND: Spinal cord injury leads to varying degrees of muscle atrophy. While there are multiple treatment options available for muscle atrophy after spinal cord injury, few studies have compared the efficacy of different rehabilitative strategies in addressing muscle atrophy resulting from spinal cord injury.
OBJECTIVE: To investigate the effects of neuromuscular electrical stimulation, repetitive peripheral magnetic stimulation and treadmill training on gastrocnemius muscle function in rats after spinal cord injury.
METHODS: Thirty female Sprague-Dawley rats were randomly divided into five groups, including the sham-operated group, the model group, the electrical stimulation group, the magnetic stimulation group, and the treadmill training group. The rats in the sham-operated group only underwent spinous process and laminar dissection without spinal cord injury, while rats in the other groups were subjected to a modified Allen’s method to establish a T10 incomplete moderate spinal cord injury model. After modeling, the sham-operated group and the model group received no intervention, whereas the remaining groups underwent corresponding bilateral gastrocnemius neuromuscular electrical stimulation, repetitive peripheral magnetic stimulation, or treadmill exercise training. The Basso, Beattie and Bresnahan locomotor scale and inclined plate test were used to assess the hind limb motor function of the rats before and 0, 3, 7, and 14 days after modeling. The gastrocnemius muscle tissues were collected on the 14th day after surgery, and the muscle atrophy was assessed by relative wet weight ratio of the gastrocnemius muscle. The cross-sectional area of muscle fibers of the gastrocnemius muscle was detected by hematoxylin-eosin staining. The distribution and activity of acetylcholinesterase at the neuromuscular junction of the gastrocnemius muscle were detected by acetylcholinesterase staining. The expression of Atrogin-1 and MuRF1 protein in gastrocnemius muscle was detected by western blot assay. 
RESULTS AND CONCLUSION: (1) Compared with the sham-operated group, the Basso, Beattie and Bresnahan score, inclined angle of the inclined plate test, relative wet weight ratio of the gastrocnemius muscle, muscle fiber cross-sectional area, and average absorbance value of acetylcholinesterase in the gastrocnemius muscle were significantly decreased in the model group (P < 0.05), and the expression of Atrogin-1 and MuRF1 protein was significantly increased (P < 0.05). (2) Compared with the model group, the Basso, Beattie and Bresnahan score, inclined angle of the inclined plate test, relative wet weight ratio of the gastrocnemius muscle, muscle fiber cross-sectional area, and average absorbance value of acetylcholinesterase in the gastrocnemius muscle were significantly increased in the electrical stimulation, magnetic stimulation, and treadmill training groups (P < 0.05). Moreover, the above indicators in the treadmill training group were significantly higher than those in the magnetic stimulation group, while the Basso, Beattie and Bresnahan score, inclined angle of the inclined plate test, relative wet weight ratio of the gastrocnemius muscle, and average absorbance value of acetylcholinesterase in the gastrocnemius muscle in the treadmill training group were significantly higher those in the electrical stimulation group (P < 0.05). (3) In addition, the expression level of Atrogin-1 protein was significantly lower in the electrical stimulation, magnetic stimulation, and treadmill training groups than in the model group, while the expression level of Atrogin-1 protein in the treadmill training group was significantly lower than that in the magnetic stimulation group (P < 0.05). The expression level of MuRF1 protein was significantly lower in the electrical stimulation group and the treadmill training group than in the model group (P < 0.05), while there was no significant difference in the protein expression of MuRF1 between the magnetic stimulation group and the model group (P > 0.05). To conclude, neuromuscular electrical stimulation, repetitive peripheral magnetic stimulation and treadmill training can all improve gastrocnemius muscle function and reduce muscle atrophy in rats with spinal cord injury, with treadmill training showing the best effects.

Key words: spinal cord injury, muscular atrophy, neuromuscular electrical stimulation, repetitive peripheral magnetic stimulation, treadmill training, gastrocnemius muscle