Objective: Current treatments for falls in people with multiple sclerosis (PwMS) are incompletely effective. Reactive balance can prevent falls after a loss of balance and is negatively impacted by MS. Perturbation training may improve reactive balance. However, the effects of extended training and its impacts on falls are poorly understood in PwMS.

Methods: We conducted a task-specific, multi-baseline, in-place reactive balance training program. Over 2 weeks and 6 sessions, participants were exposed to approximately 192 support-surface perturbations in four directions (forward, backward, leftward, and rightward). Reactive stepping was assessed twice before training (Baseline-1 & Baseline-2; [B1, B2], 2-weeks apart), and twice after training (Post-1 & Post-2 [P1, P2], immediately and 2 months after training). Linear mixed models assessed exposure effects (B1-B2), immediate improvement (B2-P1), and retained improvement (B2-P2). Falls were prospectively assessed for 2 months before and after training. Primary outcomes were margin of stability (MOS), latency, and length of the first reactive step after a backwards loss of balance.

Results: Twenty-seven PwMS at risk of falls completed the study through P1 (immediate improvement), with 96.9 % session attendance, and minimal reported adverse events. Of these, 20 participants completed P2 (2-month retention) testing. For backward losses of balance, no significant changes were observed from exposure (B1-B2; p's ≥ 0.603). There were statistically significant immediate improvements in MOS and step latency (B2-P1; p = 0.036 & p = 0.012, respectively) and retained improvement in step latency (B2-P2; p = 0.033). For forward losses of balance, participants exhibited immediate improvement in MOS (p = 0.042) and step latency (p = 0.042). Fall counts were not lower after training compared to pre-training (p = 0.266). No adverse events were observed.

Conclusions: PwMS exhibited immediate and retained improvements in reactive stepping after 2-weeks of perturbation training, particularly in reactive step latency. This single-group, non-randomized clinical trial shows feasibility of reactive balance in PwMS and provides preliminary evidence of effectiveness of this intervention.