Bilateral differences in leg performance in individuals with Multiple Sclerosis

Abstract

It is well recognized that Multiple Sclerosis (MS) can affect sides of the body asymmetrically, specifically the lower extremities; yet these disparities have not been systematically examined. PUPROSE: To determine whether ambulatory individuals with mild MS would display bilateral differences in physiological and functional measures during exercise and whether these differences contribute to premature muscle fatigue. Methods. Eight individuals with relapsing remitting MS (MS) and seven non-MS individuals (controls), similar in physical characteristics completed three series of unilateral cycling tests. Participant’s legs were categorized into either stronger/less affected or weaker/more affected based on strength testing. To determine interlimb asymmetries, comparisons of submaximal fixed load ride times, VO2peak, and peak workload were performed. Unilateral exercise was performed to determine any pre-post differences in strength, mobility, and foot tap speed. Data were analyzed using paired t-tests for between-leg comparisons and independent t-tests for group differences. RESULTS: Individuals with MS exhibited significant differences (P < 0.05) in: strength (stronger leg: 95.31 ± 27.94 (lbs), weaker leg: 76.98 ± 19.60 (lbs)), submaximal fixed load ride time (stronger leg: 4.83 ± 0.33, weaker leg: 3.44 ± 1.51 min), peak oxygen uptake (stronger leg: 13.7 ± 3.2, weaker leg: 10.6 ± 3.0 ml/kg/min) and workload (watts) (stronger leg: 73.4 ± 22.3, weaker leg: 56.3 ± 26.2 watts) with no differences observed in the control group (P > 0.05). Significant differences (P < 0.05) were observed across groups for stride velocity and strength asymmetry ratios prior to unilateral exercise. Following exercise, the magnitude of asymmetry was reduced in the individuals with MS such that no differences were observed, whereas stride velocity remained slower. CONCLUSION: Ambulatory individuals with MS displayed leg asymmetry not observed in our control participants. Following unilateral exercise the MS group’s strength asymmetry scores were no longer statistically different compared to controls and the MS individuals exhibited significant reductions in stride velocity and foot tap speed. These findings provide possible insight into the consequences of fatigue on lower extremity asymmetry and function and the need for new therapeutic interventions.