Lower limb joint moments on the fast belt contribute to a reduction of step length asymmetry over ground after split-belt treadmill training in stroke: A pilot study

The main goal was to investigate changes in muscle activity and joint moments related to step length (SL) symmetry improvements in individuals poststroke following repeated split-belt treadmill (SBT) walking. Twelve individuals with a first unilateral cerebral stroke presenting initial SL asymmetry (ratio = 1.10-2.05), and mean time post stroke 23 (SD 24.7 months) were included. Participants were trained during six sessions of SBT walking using an error-augmentation protocol. The training resulted in a reduction in SL asymmetry during walking over ground retained over 1-month post-training (p = 0.002). Significant increases in SL and joint moments (plantarflexors: 20-60%, knee flexors: 20-60% and hip extensors: 0-20% of the gait cycle) were observed on the side trained on the fast belt (effect size from 0.41 to 0.60). The improvement in SL symmetry was observed with an increase in plantarflexion joint moment symmetry. Changes in muscle activity varied among participants. In contrast to previous findings with a single exposure to SBT-training, our results showed no negative effects on paretic plantarflexors when walking over ground after repeated exposure to SBT walking. These findings justify larger trials to gain more solid information on the current protocol which appears as an efficient training for long-term recovery on SL asymmetry and on affected plantarflexors.