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Abstract
Recent evidence suggests that skeletal muscle dysfunction may be involved in the progression of physical disability in persons with Multiple Sclerosis (MS). However, the relationship between declines in muscle function and the development of walking impairments in persons with MS remains unclear. Furthermore, studies have shown that exercise can improve mobility in persons MS, but the effects of exercise training on muscle oxidative capacity and endurance in persons with MS is unknown. The present studies aimed to identify the relationships between skeletal muscle dysfunction and walking impairment in persons with MS and evaluate the effect of exercise training on muscle plasticity in persons with MS who have moderate to severe disability. Muscle function, walking function, and perceptions of walking impairments were evaluated in twenty women with MS in a cross sectional study. Muscle oxidative capacity and muscle endurance were significantly lower (p<0.01) in persons moderate to severe disability (EDSS5.0) compared to persons with mild disability (EDDS4.5). Both muscle oxidative capacity (R2=0.71; p<0.01) and muscle endurance (R2=0.78; p<0.01) were correlated with walking function. Muscle strength was weakly correlated to walking function (R2=0.21; p=0.02). In addition, muscle oxidative capacity correlated with muscle endurance (R2=0.74; p<0.01). Further studies were performed to evaluate the effect of body weight-supported treadmill (BWSTT) training on muscle oxidative capacity and muscle endurance, and walking function in 6 persons with MS who have severe disability (EDSS6.0). Muscle oxidative capacity increased 68.2% and muscle endurance increased an average of 56%.2 in the medial gastrocnemius. There were no significant improvements in tibialis anterior endurance or walking endurance. These findings suggest that reductions in muscle oxidative capacity and muscle endurance are related to declines in walking function in persons with MS. In addition, we demonstrated improved muscle oxidative capacity and endurance with endurance exercise training in person with MS, even in the presence of severe disability (EDSS=6.0-6.5).