Effects Of treadmill training on hindlimb muscles of spinal cord–injured mice

INTRODUCTION Treadmill training is known to prevent muscle atrophy after spinal cord injury (SCI), but the training duration required to optimize recovery has not been investigated. METHODS Hemisected mice were randomized to 3, 6, or 9 weeks of training or no training. Muscle fiber type composition and fiber cross-sectional area (CSA) of medial gastrocnemius (MG), soleus (SOL), and tibialis anterior (TA) were assessed using ATPase histochemistry. RESULTS Muscle fiber type composition of SCI animals did not change with training. However, 9 weeks of training increased the CSA of type IIB and IIX fibers in TA and MG muscles. CONCLUSIONS Nine weeks of training after incomplete SCI was effective in preventing atrophy of fast-twitch muscles, but there were limited effects on slow-twitch muscles and muscle fiber type composition. These data provide important evidence of the benefits of exercising paralyzed limbs after SCI. Muscle Nerve, 2016 Muscle Nerve 55: 232-242, 2017.