Persons with multiple sclerosis (MS) have reduced physical activity (PA) and lower-limb physical function and potentially disordered body composition compared with their peers without MS. The aim of this study was to determine whether PA and body composition were differentially associated with lower-limb physical function in persons with MS compared with controls. Females with MS and age-and body mass index-matched female controls (n = 51; average age 48.1 +/-9.7 yr) were measured for PA with

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... ily step counts, relative fat mass (%Fat), and leg lean mass (LM-LEG) via dual energy X-ray absorptiometry and for lower-limb physical function with objective performance tests. Persons with MS had 12.5% to 53% poorer lower-limb physical function than controls (all p < 0.05). PA, %Fat, and LM-LEG to body mass ratio (LM-LEG/BM) were associated with lower-limb physical function in both persons with MS and controls (all p < 0.05). Based on median splits, higher %Fat, lower LM-LEG/BM, and MS conferred poorer lower-limb physical function (all p < 0.05). PA, %Fat, and LM-LEG/BM were associated with lower-limb physical function, suggesting that body composition, specifically reducing adiposity and increasing lean mass and/or increasing PA levels, may be a potential target for MS interventions. Abbreviations: %Fat = relative fat mass, ANT = anterior, BM = body mass, BMI = BM index, CON = controls, DXA = dual energy X-ray absorptiometry, GLETQ = Godin Leisure Time Exercise Questionnaire, IRB = institutional review board, LLPF = lower-limb physical function, LM-LEG = leg lean mass, LM-LEG/BM = LM-LEG to BM ratio, MED = medial, MS = multiple sclerosis, PA = physical activity, PDDS = Patient Determined Disease Steps, POST = posterior, SD = standard deviation, SEBT = Star Excursion Balance Test, UPGO = timed up-and-go test, WALK = 6-minute walk test.