A homogeneous group of persons with multiple sclerosis seem to use different net joint power strategies to increase gait speed - a pilot study

Background: Major symptoms associated with multiple sclerosis are muscle weakness, fatique and loss of limb coordination, all of which contribute to an unsafe gait. To improve gait function in persons with multiple sclerosis (PwMS) it is essential to determine which problems underlie gait dysfunction. Aims: This pilot study examined changes in net joint power generated or absorbed by hip flexors (H2-S, H3-S), hip extensors (H1-S), hip abductors (H1-F, H2-F, H3-F) knee extensors (K1-S, K2-S, K3-S) and ankle plantar flexors (A1-S, A2-S) bilaterally, when gait speed increased. Methods: Fourteen PwMS with an EDSS score median at 2.5 (Inter quartile range=1) participated. The gait patterns were analysed using 3D motion analysis at self-selected and maximum gait speed. The net joint power peaks were measured for H1-S, H2-S, H3-S, H1-F, H2-F, H3-F, K1-S, K2-S, K3-S, A1-S and A2-S in the affected and least affected limb, and both intra- and inter-limb comparisons and associations were made, using non-parametric statistics. Results: Except from the eccentric work by A1-S in both limbs, net joint power increased in hip flexors, hip extensors, knee extensors and plantar flexors in affected and least affected limb (from 31% to 135%;p<=0.05) when gait speed increased (median=0.36 m/s;p<=0.001). In the frontal plane, only H1-F and H3-F in the affected limb increased significantly, and no differences were found in net joint power changes between limbs. Even so, there was a trend towards larger joint powers in the least affected limb. Moderate to strong correlations (p<=0.05) were estimated between changes in gait speed and changes in concentric A2-S (r=0.54), eccentric H2-S (r=0.61) and K3-S (r=0.75) in the affected limb. In least affected limb, correlations (p<=0.05) were found between changes in gait speed and changes in concentric H3-S (r=0.66) and eccentric H2-S (r=0.61), K3-S (r=0.75) and H1-F (r=0.58). Intra-limb correlations (r=0.56-0.72;p<0.05) between changes in A2-S, H3-S and K3-S existed in the affected limb but not in the least affected limb. Conclusions: A homogeneous group of PwMS seems to improve gait speed using different net joint power strategies. Even so, trends indicated that hip abductor power increased in the affected limb, net joint power in sagittal plan increased bilaterally, and intra-limb net joint power synergies between plantar flexors (A2-S), hip flexors (H3-S) and knee extensors (K3-S) existed in the affected limb only. Hip extensors power in the least affected limb (H1-S) might assist this synergy to improve gait speed.