Errors in the ankle plantarflexor force production are related to the gait deficits of individuals with multiple sclerosis

• Ankle control was quantified and its relationship to gait deficits was explored.
• Subjects with MS had greater errors in their ankle force production than controls.
• Subjects with MS had altered spatiotemporal kinematics and reduced ankle moments.
• Greater errors in ankle control were related to gait deficits and weaker muscles.
• Walking limitations of people with MS may party be due to poor ankle motor control.

BackgroundIndividuals with multiple sclerosis (MS) often have limited mobility that is thought to be due to the neuromuscular impairments of the ankle. Greater isometric motor control of the ankle has been associated with better standing postural balance but its relationship to mobility is less understood. The objectives of this investigation were to quantify the motor control of the ankle plantarflexors of individuals with MS during a dynamic isometric motor task, and explore the relationship between the ankle force control and gait alterations.MethodsFifteen individuals with MS and 15 healthy adults participated in both a dynamic isometric ankle plantarflexion force matching task and a biomechanical gait analysis.FindingsOur results displayed that the subjects with MS had a greater amount of error in their dynamic isometric force production, were weaker, walked with altered spatiotemporal kinematics, and had reduced maximal ankle moment at toe-off than the control group. The greater amount of error in the dynamic force production was related to the decreases in strength, step length, walking velocity, and maximal ankle moment during walking.InterpretationAltogether these results imply that errors in the ankle plantarflexion force production may be a limiting factor in the mobility of individuals with MS.