Strength and work parameters in people with multiple sclerosis and in healthy individuals: A responsiveness study of the ankle dorsiflexors

BACKGROUND: The high variability in muscle performance, especially in muscle strength, typical of people with multiple sclerosis (PwMS) implies that in order for strength variations to be clinically interpretable, the extent of variability should be properly quantified. OBJECTIVE: To establish the responsiveness of maximal isokinetic strength measurements obtained from the ankle dorsiflexors of PwMS and of a cohort of matched healthy controls. METHODS: Twenty PwMS and 20 healthy controls participated in this study. All subjects underwent a dedicated familiarization session and then three isokinetic testing sessions (Test 1; 1-day retest; 1-week retest) in which the peak moment (PM) and maximal work (MW) were recorded in the more affected side. RESULTS: PwMS proved significantly weaker than controls (p < 0.00005). The test-retest consistency of the measurements proved high for both groups (all intraclass correlation coefficients > 0.9). Importantly, the smallest real difference (SRD) scores ranged 11.4-19.8% for PwMS and 9.2-14.4% for controls. CONCLUSIONS: The responsiveness of the strength and work findings in this cohort indicates that isokinetic measurements of dorsiflexion performance in PwMS may effectively be employed for detecting the efficiency of an intervention in spite of the fluctuating nature of this disease.