The combined effects of guidance force, bodyweight support and gait speed on muscle activity during able-bodied walking in the Lokomat

• Increasing the level of guidance provided by the Lokomat reduces muscle activity.
• Walking in the Lokomat can induce atypical muscle activity.
• This atypical muscle activity was less prominent at high levels of guidance.
• These guidance effects depend on interactions with speed and bodyweight support.

BackgroundThe ability to provide automated movement guidance is unique for robot assisted gait trainers such as the Lokomat. For the design of training protocols for the Lokomat it is crucial to understand how movement guidance affects the patterning of muscle activity that underlies walking, and how these effects interact with settings for bodyweight support and gait speed.MethodsTen healthy participants walked in the Lokomat, with varying levels of guidance (0, 50 and 100%), bodyweight support (0 or 50% of participants' body weight) and gait speed (0.22, 0.5 or 0.78 m/s). Surface electromyography of Erector Spinae, Gluteus Medius, Vastus Lateralis, Biceps Femoris, Medial Gastrocnemius and Tibialis Anterior were recorded. Group averaged levels of muscle activity were compared between conditions, within specific phases of the gait cycle.FindingsThe provision of guidance reduced the amplitude of activity in muscles associated with stability and propulsion (i.e. Erector Spinae, Gluteus Medius, Biceps Femoris and Medial Gastrocnemius) and normalized abnormally high levels of activity observed in a number of muscles (i.e. Gluteus Medius, Biceps Femoris, and Tibialis anterior). The magnitude of guidance effects depended on both speed and bodyweight support, as reductions in activity were most prominent at low speeds and high levels of bodyweight support.InterpretationThe Lokomat can be effective in eliciting normal patterns of muscle activity, but only under specific settings of its training parameters.