Customized passive-dynamic ankle-foot orthoses can improve walking economy and speed for many individuals post-stroke.

BACKGROUND: Passive-dynamic ankle-foot orthoses (PD-AFOs) are often prescribed to address plantar flexor weakness during gait, which is commonly observed after stroke. However, limited evidence is available to inform the prescription guidelines of PD-AFO bending stiffness. This study assessed the extent to which PD-AFOs customized to match an individual's level of plantar flexor weakness influence walking function, as compared to No AFO and their standard of care (SOC) AFO. METHODS: Mechanical cost-of-transport, self-selected walking speed, and key biomechanical variables were measured while individuals greater than six months post-stroke walked with No AFO, with their SOC AFO, and with a stiffness-customized PD-AFO. Outcomes were compared across these conditions using a repeated measures ANOVA or Friedman test (depending on normality) for group-level analysis and simulation modeling analysis for individual-level analysis. RESULTS: Twenty participants completed study activities. Mechanical cost-of-transport and self-selected walking speed improved with the stiffness-customized PD-AFOs compared to No AFO and SOC AFO. However, this did not result in a consistent improvement in other biomechanical variables toward typical values. In line with the heterogeneous nature of the post-stroke population, the response to the PD-AFO was highly variable. CONCLUSIONS: Stiffness-customized PD-AFOs can improve the mechanical cost-of-transport and self-selected walking speed in many individuals post-stroke, as compared to No AFO and participants' standard of care AFO. This work provides initial efficacy data for stiffness-customized PD-AFOs in individuals post-stroke and lays the foundation for future studies to enable consistently effective prescription of PD-AFOs for patients post-stroke in clinical practice. TRIAL REGISTRATION: NCT04619043.

Shifts of the point-of-change can be attributed to a lower mechanical cost of motor execution.

In a previous study on hand selection in a sequential reaching task, the authors showed a shift of the point-of-change (POC) to the left of the midline. This implies that participants conducted a number of contralateral reaches with their dominant, right hand. Contralateral movements have longer planning and execution times and a lower precision. In the current study, we asked whether lower mechanical costs of motor execution or lower cognitive costs of motor planning compensated for these disadvantages. Theories on hemispheric differences postulate lower mechanical costs in the dominant hemisphere and lower cognitive costs in the left hemisphere (independent of handedness). In right-handed participants, both factors act agonistically to reduce the total cost of right-handed reaches. To distinguish between the cost factors, we had left- and right-hand-dominant participants execute a sequential, unimanual reaching task. Results showed a left-shift of the POC in the right-handed and a right-shift in the left-handed group. Both shifts were similar in magnitude. These findings indicate that only the mechanical cost of motor execution compensates for the disadvantages of the contralateral reaches, while the cognitive cost of motor planning is irrelevant for the POC shift.

A comparative collision-based analysis of human gait.

This study compares human walking and running, and places them within the context of other mammalian gaits. We use a collision-based approach to analyse the fundamental dynamics of the centre of mass (CoM) according to three angles derived from the instantaneous force and velocity vectors. These dimensionless angles permit comparisons across gait, species and size. The collision angle Φ, which is equivalent to the dimensionless mechanical cost of transport CoTmech, is found to be three times greater during running than walking of humans. This threefold difference is consistent with previous studies of walking versus trotting of quadrupeds, albeit tends to be greater in the gaits of humans and hopping bipeds than in quadrupeds. Plotting the collision angle Φ together with the angles of the CoM force vector Θ and velocity vector Λ results in the functional grouping of bipedal and quadrupedal gaits according to their CoM dynamics-walking, galloping and ambling are distinguished as separate gaits that employ collision reduction, whereas trotting, running and hopping employ little collision reduction and represent more of a continuum that is influenced by dimensionless speed. Comparable with quadrupedal mammals, collision fraction (the ratio of actual to potential collision) is 0.51 during walking and 0.89 during running, indicating substantial collision reduction during walking, but not running, of humans.