Local dynamic stability during long-fatiguing walks in people with multiple sclerosis.

Area of Science:

• Neurology
• Biomechanics
• Rehabilitation Science

Background:

• Altered balance and stability during walking are prevalent in people with multiple sclerosis (PwMS).
• Dynamic gait stability and its relationship with fatigue are understudied in MS.
• The impact of walking-related fatigue on dynamic stability in PwMS remains unclear.

Purpose of the Study:

• To investigate temporal changes in dynamic gait stability during prolonged walking in PwMS versus healthy controls (HC).
• To examine the relationship between changes in dynamic stability and walking performance in PwMS.

Main Methods:

• Twenty-five PwMS and ten HC underwent a six-minute walk test (6MWT) with wireless inertial sensors.
• Local dynamic stability (LDS) was quantified using maximum-finite-time Lyapunov exponents (λS).
• Linear mixed models and Pearson correlation analyzed group differences and stability-performance relationships.

Main Results:

• Significant group*time interaction for LDS: PwMS showed reduced stability compared to HC after minute 4, persisting to minute 6.
• PwMS exhibited shorter walking distances and a greater decline in walking performance (DWI6-1) during the 6MWT.
• A significant correlation was found between the decline in stability (DSI6-1) and walking performance (DWI6-1) in PwMS.

Conclusions:

• Dynamic stability differences between PwMS and HC emerge after approximately 3 minutes of walking.
• Approximately 60% of PwMS experienced decreased stability over time, highlighting the utility of long walks for assessment.
• The correlation between declining stability and reduced walking performance suggests a role for fatigue in balance deterioration during prolonged ambulation in MS.