Implications of maximal muscle strength and aerobic capacity for lower extremity physical function in people with multiple sclerosis: a cross-sectional study

Background: Multiple sclerosis (MS) is characterized by impairment of physical function that is often linked to neuromuscular and cardiovascular deficits. However, the specific contributions of muscle strength and aerobic capacity to physical function in MS are not fully understood. Objective: This study aimed to investigate the independent roles of maximal muscle strength (MVC) and aerobic capacity (VO₂peak) on lower extremity physical function, as measured by the 6-minute walk test (6MWT) and five-time sit-to-stand test (5STS) in people with MS (pwMS). Methods: In a cross-sectional study, 150 pwMS underwent assessment of VO₂peak, maximal voluntary contraction (MVC), and physical function (6MWT and 5STS). Regression analyses were conducted to explore the associations between physiological parameters and physical function. Results: MVC and VO₂peak were moderately associated with (i.e., explained) 6MWT (R² = 0.40, p < 0.001), yet with VO₂peak (β = 7.9, std. β = 0.45, p < 0.001) having a preferential influence compared to MVC (β = 48.2, std. β = 0.26, p < 0.001). MVC and VO₂peak were weakly associated with (i.e., explained) 5STS (R² = 0.14, p < 0.001), yet with MVC (β = 0.06, std. β = 0.28, p = 0.004) having a preferential influence compared to VO₂peak (β = 0.00, std. β = 0.16, p = 0.101). Conclusion: Both maximal muscle strength and aerobic capacity to physical function in pwMS. Maximal muscle strength was preferentially linked to performance in the 5STS test, whereas aerobic capacity was preferentially linked to performance in the 6MWT. These findings support the need for tailored exercise interventions to target specific physiological deficits during MS rehabilitation.