The relationship between upper leg muscle strength and walking capacity in persons with multiple sclerosis

Abstract

Background: In persons with multiple sclerosis (PwMS) resistance training improves muscle strength but effects on walking capacity are inconsistent. Objective: The objective was to determine the relation between different types of upper leg muscle strength measurements and walking capacity in PwMS. Methods: An observational cross-sectional study design was applied. Upper leg muscle strength of 52 PwMS (Expanded Disability Status Scale, EDSS range 1.5-6.5) was measured using isometric (knee extensors and flexors) and isokinetic (knee extensors) dynamometry. Walking capacity was assessed using the Timed 25-Foot Walk, Timed Up and Go and Two Minute Walk Test. Subgroups with mild (EDSS 1.5-4.0, n=31) and moderate (EDSS 4.5-6.5, n=21) ambulatory dysfunction were distinguished, and results were hypothesized to differ depending on multiple sclerosis (MS)-related disability status. Correlation and regression analyses were performed on the data of the most affected leg. Results: Greatest (r:0.2-0.7) and significant Pearson correlation coefficients were found in the moderate compared to mild MS subgroup. Within knee extensor measurements, it was found that isokinetic endurance strength related best to walking capacity. When comparing maximal isometric strength measurements, knee flexors (r:0.5-0.7) related better to walking capacity than knee extensors (r:0.1-0.4). Regression analyses confirmed endurance knee extensor strength (similar to 25 %) and isometric knee flexor strength (similar to 40%) as main predictors for walking capacity. Conclusion: Resistance training protocols may consider inclusion of exercises focusing on endurance knee extensor and isometric knee flexor strength when aiming to enhance walking capacity in persons with moderate ambulatory dysfunction.