Resistance training for muscle weakness in multiple sclerosis: direct versus contralateral approach in individuals with ankle dorsiflexors' disparity in strength

OBJECTIVE: To compare effects of contralateral strength training (CST) versus direct strength training (DST) of the more-affected ankle dorsiflexors on muscle performance and clinical-functional outcomes in people with multiple sclerosis (MS) exhibiting inter-limb strength asymmetry. DESIGN: Randomized controlled trial PARTICIPANTS: Individuals with relapsing-remitting MS and mild-to-moderate disability (EDSS≤6) presenting with ankle dorsiflexors' strength disparity. INTERVENTION: Participants were randomly assigned to a CST (n=15) or DST (n=15) group performing a 6-week maximal-intensity strength training of the less- or more-affected dorsiflexors, respectively. MAIN OUTCOME MEASURES: Maximal strength, endurance to fatigue and mobility outcomes were assessed before (PRE), at the intervention end (POST) and at 12-week follow-up. Strength and fatigue parameters were measured after 3 weeks of training (mid-intervention). RESULTS: In the more-affected limb of both groups, PRE-to-POST significant increases in maximal strength (p≤0.006) and fatigue endurance (p≤0.04) were detected along with consistent retention of these improvements at follow-up (p≤0.04). At mid-intervention the DST group showed significant improvements (p≤0.002), with no further increase at the POST, despite training continuation. Conversely, the CST group showed non-significant strength gains, increasing to significance at the POST (p≤0.003). In both groups, significant PRE-to-POST improvements in mobility outcomes (p≤0.03), not retained at follow-up, were observed. CONCLUSIONS: After 6 weeks of training, CST proved as effective as DST in enhancing performance of the more-affected limb with a different time-course, which may have practical implications in management of severely weakened limbs where DST is not initially possible.