Energetic cost of walking and spasticity in persons with multiple sclerosis with moderate disability

BACKGROUND: The energetic cost of walking (C-w) is elevated in persons with multiple sclerosis (MS). This may be explained by spasticity and spatiotemporal parameters of gait. OBJECTIVE: To examine the associations among C-w, spasticity of ankle plantarflexors, and spatiotemporal gait parameters in persons with MS who had moderate disability. METHODS: The sample included 44 persons with MS who had moderate disability. C-w was measured over-ground during the 6-Minute Walk using indirect calorimetry and was calculated based on net oxygen consumption and walking speed (i.e., expressed ml.kg(-1).m(-1)). Participants underwent the Modified Ashworth Scale as a measurement of spasticity and performed 4 trials of walking on a GAITRite electronic walkway for measurement of spatiotemporal gait parameters. RESULTS: Spasticity was positively correlated with C-w (r = 0.52, p < 0.05) and inversely correlated with cadence (r = -.45, p < 0.05) and step length (r = -0.40, p < 0.05). Cadence (r = -0.59, p < 0.05) and step length (r = -0.56, p < 0.05) were inversely correlated with C-w. The regression analysis indicated that spasticity explained significant variance in C-w, and cadence and step length accounted for the association. CONCLUSIONS: These results suggest that worse spasticity of the ankle plantarflexors and slower cadence and shorter step length, in turn, are responsible for elevated C-w among persons with MS with moderate disability. This supports the development of therapeutic, rehabilitation interventions delivered by clinicians for managing spasticity and the resulting C-w that may interfere with activities of daily living.