Perturbation practice in multiple sclerosis: Assessing generalization from support surface translations to tether-release tasks

Objective: To determine whether improvements in protective stepping experienced after repeated support surface translations generalize to a different balance challenge in people with multiple sclerosis (PwMS) Background: MS affects almost 1 million people in the United States and impairs balance and mobility. Perturbation practice can improve aspects of protective stepping in PwMS, but whether these improvements generalize is unknown. Methods: Fourteen PwMS completed two visits, 24hrs apart. The balance tasks included tether-release trials and support surface translations on a treadmill eliciting backward protective stepping. Margin of stability, step length, and step latency were calculated. Generalization was assessed via multilevel mediation models (MLMM) with bootstrapping to produce percentile and bias corrected confidence intervals Results: There were no mediated effects for margin of stability or step latency; however, mediation was observed for step length, indicating that participants increased step length throughout the treadmill trials, and this generalized to tether-release trials Discussion: MLMM may be useful for evaluating generalization of motor training to novel balance situations, particularly in small sample sizes. Using these analyses, we observed PwMS generalized improvements in step length, suggesting that aspects of protective step training may translate to improvements in other reactive balance tasks in PwMS.