Effects of asymmetrical support on lower limb muscle activity during Lokomat guided gait in persons with a chronic stroke: an explorative study.

Background: The Lokomat, one of the most popular robotic exoskeletons, can take the asymmetry in the gait pattern of unilaterally affected patients into account with its opportunity to provide unequal levels of movement support (or 'guidance') to each of the legs. This asymmetrical guidance may be used to selectively unburden limbs with impaired voluntary control and/or to exploit the interlimb couplings for training purposes. However, there is a need to explore and understand these specific device opportunities more broadly before implementing them in training.

Aim: The aim of this study was to explore the effects of (a)symmetrical guidance settings on lower limb muscle activity in persons with post stroke hemiparesis, during Lokomat guided gait.

Design: A single group, dependent factorial design.

Setting: Rehabilitation center; a single session of Lokomat guided walking.

Population: A group of ten persons with post stroke hemiparesis.

Methods: Participants walked in the Lokomat in eight conditions, consisting of symmetrical and asymmetrical guidance situations, at both 0.28 m/s and 0.56 m/s. During symmetrical conditions, both legs received 30% or 100% guidance, while during asymmetrical conditions one leg received 30% and the other leg 100% guidance. Surface electromyography was bilaterally measured from: Biceps Femoris, Rectus Femoris, Vastus Medialis, Medial Gastrocnemius and Tibialis Anterior. Statistical effects were assessed using Statistical Parametric Mapping.

Results: The provision of assymetrical guidance did not affect the level of lower limb muscle activity. In addition, no effect (except for Vastus Medialis in the affected leg during 1.5-2.4% of the gait cycle) of symmetrical guidance on muscle amplitude could be observed.

Conclusions: The results show no evidence that either symmetrical or asymmetrical guidance settings provided by the Lokomat can be used to manipulate activity of lower limb musculature in persons with post stroke hemiparesis.

Clinical Rehabilitation Impact: This study provides insights for the use of specific opportunities provided by the Lokomat for training purposes post stroke.