Impairment and disability in persons with MS: do functional performance or functional limitations matter?

Persons with multiple sclerosis (MS) often demonstrate impairment in cardiorespiratory and musculoskeletal systems that may be associated with functional performance, functional limitations, and disability limitations. This study examined such relationships in persons with MS using Nagi's disablement model and its subsequent conceptual modifications. The sample included 63 persons with MS (75% relapsing-remitting MS, median EDSS = 4.0, and mean MS duration = 13.1 years) who underwent measurements of aerobic fitness and muscular strength (i.e. impairment), functional performance, functional limitations, and disability limitations. The data were primarily examined using path analysis in Mplus 7.0. Our final model provided an excellent fit for the data (χ² = 0.67, df = 3, p = 0.88, SRMR = 0.01, and CFI = 1.00). The final model indicated that aerobic fitness and muscular strength were indirectly associated with disability limitations in persons with MS through a pathway that included functional limitations (indirect path coefficients of 0.29 and 0.20, respectively), but not functional performance. Aerobic fitness and muscular strength may be the important targets of exercise training interventions for improving perceived functional limitations and disability limitations in persons with MS.