The cost of imbalance: how balance problems drive energy cost of walking in persons with multiple sclerosis

INTRODUCTION: People with multiple sclerosis have difficulties walking and show a high energy cost of walking. Balance problems may contribute. AIM: To investigate the relationship between dynamic balance and energy cost of walking in people with multiple sclerosis, and whether walking speed affects this relationship. METHODS: In a cross-sectional cohort, 20 people with multiple sclerosis walked on an instrumented treadmill at a comfortable and fast walking speed. The energy cost of walking was derived from oxygen consumption. Dynamic balance was approximated as the medio-lateral margin of stability and using balance board testing. Linear mixed models were used, with walking speed as effect modifier. RESULTS: The mean energy cost of walking was 4.99 J/kg/m at a comfortable and 4.84 J/kg/m at a fast walking speed. The medio-lateral margin of stability was significantly associated with energy cost of walking, with walking speed a significant effect modifier (β = -27.07, 95% CI: -49.32; -4.83). At lower speeds this association was stronger, attenuating at higher speeds. DISCUSSION: Poorer dynamic balance was associated with higher energy cost of walking, predominantly at lower walking speeds. Jointly improving walking speed and dynamic balance may reduce the energetic burden of walking in this population.