Multiple sclerosis influences the precision of the ankle plantarflexon muscular force production

•Individuals with MS had greater variability in the ankle plantarflexion torque.•Individuals with MS had weaker ankle plantarflexors.•Individuals with MS walked slower and had altered spatiotemporal gait kinematics.•Ankle torque variability was related to altered spatiotemporal kinematics.•Weaker plantarflexors was related to altered spatiotemporal kinematics.

ObjectiveTo quantify the precision of the steady-state isometric control of the ankle plantarflexors musculature of individuals with multiple sclerosis (MS), and to evaluate if the precision is related to the mobility impairments.MethodsIndividuals with MS and healthy adults performed a submaximal steady-state isometric contraction with the ankle plantarflexors. The coefficient of variation was used to assess the amount of variability or error in the precision of the torques generated by the ankle plantarflexor musculature. The participants also walked across a digital mat at their preferred and fast-as-possible walking speeds, which recorded their spatiotemporal gait kinematics.ResultsThe individuals with MS: (1) had reduced maximal voluntary torques at the ankle, (2) a greater amount of variability in the precision of the isometric ankle torques, (3) altered and more variable spatiotemporal gait kinematics, and (4) a greater amount of variability in the isometric ankle torques were related to a slower walking speed and cadence, shorter step length and a greater amount of gait variability.ConclusionsThese results further fuels the impression that a reduction in control of the ankle joint musculature may be a key factor in the mobility and balance impairments seen in individuals with MS.