Paretic propulsion as a measure of walking performance and functional motor recovery post-stroke: A review

Abstract

Background: Although walking speed is the most common measure of gait performance poststroke, improved walking speed following rehabilitation does not always indicate the recovery of paretic limb function. Over the last decade, the measure paretic propulsion (Pp, defined as the propulsive impulse generated by the paretic leg divided by the sum of the propulsive impulses of both legs) has been established as a measure of paretic limb output and recently targeted in poststroke rehabilitation paradigms. However, the literature lacks a detailed synthesis of how paretic propulsion, walking speed, and other biomechanical and neuromuscular measures collectively relate to post-stroke walking performance and motor recovery. Objective: The aim of this review was to assess factors associated with the ability to generate Pp and identify rehabilitation targets aimed at improving Pp and paretic limb function. Methods: Relevant literature was collected in which paretic propulsion was used to quantify and assess propulsion symmetry and function in hemiparetic gait. Results: Paretic leg extension during terminal stance is strongly associated with Pp. Both paretic leg extension and propulsion are related to step length asymmetry, revealing an interaction between spatiotemporal, kinematic and kinetic metrics that underlies hemiparetic walking performance. The importance of plantarflexor function in producing propulsion is highlighted by the association of an independent plantarflexor excitation module with increased Pp. Furthermore, the literature suggests that although current rehabilitation techniques can improve Pp, these improvements depend on the patient's baseline plantarflexor function. Significance: Pp provides a quantitative measure of propulsion symmetry and should be a primary target of post-stroke gait rehabilitation. The current literature suggests rehabilitation

Persons post-stroke improve step length symmetry by walking asymmetrically

“…Although mechanical work is not related to the cost of transport in all walking conditions 33 , a substantial portion of the cost of transport can be attributed to the mechanical work generated by the legs on the COM during step-to-step transitions 26,[34][35][36] . Persons post-stroke generate more positive work with the nonparetic leg than the paretic leg 4,27,28,31,37 , and this de cit is in uenced by the lack of su cient paretic propulsion during the step-to-step transition occurring during late paretic stance 32,38 . Importantly, this propulsion must also occur at the appropriate timing 39 .…”

“…Either of these factors could result in an elevated cost of transport, and the altered mechanics persisted across both preferred walking and symmetric stepping. Fortunately, many interventions -including fast walking [44][45][46] , functional electrical stimulation of the plantar exors 46 , and split-belt treadmill walking 20,47 -show promise for improving paretic propulsion 38 . These interventions target paretic propulsion through combinations of improving ankle power generation and increasing paretic limb extension during late stance (i.e., trailing limb angle 41,48 ).…”

Persons post-stroke restore step length symmetry by walking asymmetrically

“…A substantial portion of the cost of transport can be attributed to the mechanical work generated by the legs on the COM during step-to-step transitions 26,[33][34][35] . Persons post-stroke generate more positive work with the nonparetic leg than the paretic leg 4,27,28,31,36 , and this deficit is influenced by an inability to generate sufficient paretic propulsion during the step-to-step transition occurring during late paretic stance 32,37 .…”

“…These altered mechanics persisted across both preferred walking and symmetric stepping, with the lone difference being that persons post-stroke generated more positive nonparetic work during single support when symmetric stepping (driven increased vertical COM velocity) to provide additional compensation during paretic swing. Fortunately, many interventionsincluding fast walking [42][43][44] , functional electrical stimulation of the plantarflexors 44 , and split-belt treadmill walking 20,45show promise for improving paretic propulsion 37 . These interventions target paretic propulsion through combinations of improving ankle power generation and increasing paretic limb extension during Symmetric stepping after stroke late stance (i.e., trailing limb angle 39,46 ).…”

Self-perceived functioning and disability after randomized conventional and electromechanically-assisted gait training in subacute stroke: A 6 months follow-up

“…As in most exoskeletons for walking, the HAL has actuators over the hip and knee, but the ankle is left unpowered. In normal gait, the role of the ankle plantar flexors is however essential in contributing to forward propulsion [28,169]. Paretic propulsion, defined as the contribution of the paretic leg in driving the body forward during walking, has recently been suggested as an important measure of walking performance post stroke [169,170].…”