Relationships Among Physical Inactivity, Deconditioning, and Walking Impairment in Persons With Multiple Sclerosis

Background and Purpose: We have previously proposed a conceptual model of physical inactivity, physiological deconditioning, and walking impairment in persons with multiple sclerosis (MS) that suggests engaging in physical activity and improving physiological conditioning may lead to improvements in walking performance. This cross-sectional study examined the nature of associations among physical activity, aerobic capacity, and walking performance in persons with MS and healthy controls. Methods: The sample included 31 persons with MS and 31 controls matched by age, sex, height, and weight. Participants completed the 6-minute walk (6MW), wore an ActiGraph model GT3X accelerometer for 7 days as an objective measure of physical activity (expressed as time spent in moderate-to-vigorous physical activity [MVPA]), and completed an incremental exercise test on a cycle ergometer as a measure of aerobic capacity (VO2peak). Results: Hierarchical linear regression analyses indicated that MVPA and VO2peak partially explained group differences in 6MW performance (R-2 = 0.782), although group remained a significant predictor of 6MW performance (beta = 0.304; P < 0.001). Path analysis indicated that group had both statistically significant direct and indirect effects on 6MW performance, and the indirect effect operated through pathways involving MVPA and VO2peak. Discussion and Conclusions: These results provide direct preliminary evidence that physiological deconditioning, perhaps occurring as a result of physical inactivity, may explain variability in walking impairment in persons with MS. These findings support the design and implementation of targeted interventions for improving walking impairment in this population. Video Abstract available for more insights from the authors (see Supplemental Digital Content 1, http://links.lww.com/JNPT/A93).