How much does balance and muscle strength impact walking in persons with multiple sclerosis? - A cross-sectional study

Introduction: Despite the multitude of rehabilitation interventions targeting gait impairments in persons with multiple sclerosis (PwMS), only little is known about the relative association of muscle strength and balance on different gait outcomes. Aim: To determine the relative association of balance and muscle strength to three gait performance outcomes in PwMS. Method: 90 PwMS were enrolled in this cross-sectional study (72% women; mean age=49.8 +/- 10.5 years; mean EDSS=3.7 +/- 1.3. Spearman correlation and multivariate linear regression analysis were used to determine associations between three (dependent) gait outcomes (six-minute walk test (6MW), Timed 25-Foot Walk (T25FW), and Six Spot Step Test (SSST)). Explanatory variables were maximal muscle strength of the knee extensors, kneeflexors, plantarflexors and dorsiflexors, static balance (postural sway), functional balance (Mini-BESTest) and age and gender. Results: Static balance (r=0.30 to 0.53; p<.05) and muscle strength of the knee extensors, knee flexors, plantarflexors and dorsiflexors (r=0.28 to 0.47; p<.05) were weakly related to all gait performance outcomes, while functional balance showed strong relationships (r=0.70 to 0.83; p<.05). Multivariate regression models including postural sway, muscle strength, and age and gender accounted for 32-39% of the variability in the 6MW, T25FW, and SSST. In 6MW and T25FW, with standardized beta coefficients for postural sway and muscle strength ranging from -0.34 to -0.37 (SE=0.09) and 0.18 to 0.35 (SE=0.10 to 0.12), respectively. For SSST, significant associations were only observed for balance. Conclusions: Balance and muscle strength are significantly associated with gait performance during fast walking, whereas only balance was associated with more complex walking tasks.