A Robotic Assistance With Specialized Timing Improves Motor Performance: Implications for Movement Training.

Robotic devices can expand the repertoire of rehabilitation methods by enabling actions that cannot be replicated by a physical therapist. We previously developed a technique, we term 'rapid assistance,' that can assist movements beginning within the electromechanical delay between muscle activation and muscle contraction. Here, we evaluated the effects of repeated arm extension training with rapid assistance in older adults (n = 18) during a single session. We compared training with rapid assistance to a control group that performed unassisted arm extension training. Participants positively adapted to rapid assistance indicated by quickening reaction times (15.69%, ${t} = -1.79$ , ${p} =0.089$ , ${d} =0.36$ ) and greater extension angular velocities (47.93%, ${t} =3.47$ , ${p} =0.002$ , ${d} =0.56$ ) compared to the control group following training. These motor performance improvements following rapid assistance training may be due to reducing Golgi-tendon inhibition during muscle contraction thereby, introducing an alternate strategy to improve motor performance. This specialized assistive timing may address a trade-off present in rehabilitative practice between assisting a patient or sufficiently challenging them to facilitate functional recovery.