Abstract
BackgroundAppropriate magnitude and directional control of foot-forces is required for successful execution of locomotor tasks. Earlier evidence suggested, following stroke, there is a potential impairment in foot-force control capabilities both during stationary force generation and locomotion. The purpose of this study was to investigate the foot-pedal surface interaction force components, in non-neurologically-impaired and stroke-impaired individuals, in order to determine how fore/aft shear-directed foot/pedal forces are controlled.MethodsSixteen individuals with chronic post-stroke hemiplegia and 10 age-similar non-neurologically-impaired controls performed a foot placement maintenance task under a stationary and a pedaling condition, achieving a target normal pedal force. Electromyography and force profiles were recorded. We expected generation of unduly large magnitude shear pedal forces and reduced participation of multiple muscles that can contribute forces in appropriate directions in individuals post-stroke.ResultsWe found lower force output, inconsistent modulation of muscle activity and reduced ability to change foot force direction in the paretic limbs, but we did not observe unduly large magnitude shear pedal surface forces by the paretic limbs as we hypothesized.ConclusionThese findings suggested the preservation of foot-force control capabilities post-stroke under minimal upright postural control requirements. Further research must be conducted to determine whether inappropriate shear force generation will be revealed under non-seated, postural demanding conditions, where subjects have to actively control for upright body suspension.
Highlights
Appropriate magnitude and directional control of foot-forces is required for successful execution of locomotor tasks
During upright walking, leg muscles must exhibit appropriate coordination that results in adequate footforce amplitude and direction at the end of the stance phase to propel the center of mass forward, at initial contact to brake the forward acceleration of the center of mass, and during mid-stance to support the center of mass and prevent collapse of the stance limb [1]
When pushing on a stationary pedal and during dynamic pedaling, a shift in force path orientation was observed in the paretic limbs, rotating it anteriorly away from the hip, suggesting that the paretic leg had a different preferred direction of force generation compared to the non-paretic leg
Summary
Appropriate magnitude and directional control of foot-forces is required for successful execution of locomotor tasks. When pushing on a stationary pedal and during dynamic pedaling, a shift in force path orientation was observed in the paretic limbs, rotating it anteriorly away from the hip, suggesting that the paretic leg had a different preferred direction of force generation compared to the non-paretic leg. These observations imply a potential impairment in appropriate vector force direction control during locomotion in individuals post-stroke. These studies did not account for the impaired ability of the paretic leg in force output [4,5], making it difficult to derive an appropriate comparison of force vector components
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