Error variability affects the after effects following motor learning of lateral balance control during walking in people with spinal cord injury

Abstract

People with incomplete spinal cord injury (iSCI) usually show impairments in lateral balance control during walking. Effective interventions for improving balance control are still lacking, probably due to limited understanding of motor learning mechanisms. The objective of this study was to determine how error size and error variability impact the motor learning of lateral balance control during walking in people with iSCI. Fifteen people with iSCI were recruited. A controlled assistance force was applied to the pelvis in the medial‐lateral direction using a customized cable‐driven robotic system. Participants were tested using 3 conditions, including abrupt, gradual, and varied forces. In each condition, participants walked on a treadmill with no force for 1 min (baseline), with force for 9 min (adaptation), and then with no force for additional 2 min (post‐adaptation). The margin of stability at heel contact (MoS_HC) and minimum value moment (MoS_Min) were calculated to compare the learning effect across different conditions. Electromyogram signals from the weaker leg were also collected. Participants showed an increase in MoS_Min (after effect) following force release during the post‐adaptation period for all three conditions. Participants showed a faster adaptation and a shorter lasting of after effect in MoS_Min for the varied condition in comparison with the gradual and abrupt force conditions. Increased error variability may facilitate motor learning in lateral balance control during walking in people with iSCI, although a faster learning may induce a shorter lasting of after effect. Error size did not show an impact on the lasting of after effect.

Increased motor variability facilitates motor learning in weight shift toward the paretic side during walking in individuals post‐stroke

“…Results from previous animal studies showed that reducing motor variability during locomotor training can be detrimental to motor learning (Cai et al., 2006; Ziegler et al., 2010). In line with this, results from an earlier study in people with spinal cord injury indicated that increased error variability may facilitate motor learning in lateral balance control during walking (Lin et al., 2019a). Also, a clinical study in individuals post‐stroke indicated that variable practice was beneficial to the improvement in functional gains (Hornby et al., 2019).…”

Direct biomechanical manipulation of human gait stability: A systematic review

“…19 papers involved force application on pelvis manipulation, describing five device types. The most frequently investigated device type contains ML forces applied to the pelvis (P1), for which moderate and indicative evidence was found, respectively, for non-impaired [ 16 , 56 , 58 , 60 , 65 , 73 – 80 ] and impaired [ 60 , 62 , 73 , 75 , 78 , 80 – 82 ] subjects. Other studies described BWS forces to the pelvis (P2), pelvis restriction devices (P3 and P4), and the effect of handrail combined with pelvis stabilisation (P5), providing insufficient evidence.…”