A major factor for increasing walking speed is the ability to increase propulsive force. Although propulsive force has been shown to be related to ankle moment and trailing limb angle, the relative contribution of each factor to propulsive force has never been determined. The primary purpose of this study was to quantify the relative contribution of ankle moment and trailing limb angle to propulsive force for able-bodied individuals walking at different speeds. Twenty able-bodied individuals walked at their self-selected and 120% of self-selected walking speed on the treadmill. Kinematic data were collected using an 8-camera motion-capture system. A model describing the relationship between ankle moment, trailing limb angle and propulsive force was obtained through quasi-static analysis. Our main findings were that ankle moment and trailing limb angle each contributes linearly to propulsive force, and that the change in trailing limb angle contributes almost as twice as much as the change in ankle moment to the increase in propulsive force during speed modulation for able-bodied individuals. Able-bodied individuals preferentially modulate trailing limb angle more than ankle moment to increase propulsive force. Future work will determine if this control strategy can be applied to individuals poststroke.

BackgroundPropulsive force generation is critical to walking speed. Trialing limb angle and ankle moment are major contributors to increases in propulsive force during gait. For able-bodied individuals, trailing limb angle contributes twice as much as ankle moment to increases in propulsive force during speed modulation. The aim of this study was to quantify the relative contribution of ankle moment and trailing limb angle to increases in propulsive force for individuals poststroke.MethodsA biomechanical-based model previously developed for able-bodied individuals was evaluated and enhanced for individuals poststroke. Gait analysis was performed as subjects (N = 24) with chronic poststroke hemiparesis walked at their self-selected and fast walking speeds on a treadmill.ResultsBoth trailing limb angle and ankle moment increased during speed modulation. In the paretic limb, the contribution from trailing limb angle versus ankle moment to increases in propulsive force is 74% and 17%. In the non-paretic limb, the contribution from trailing limb angle versus ankle moment to increases in propulsive force is 67% and 22%.ConclusionsIndividuals poststroke increase propulsive force mainly by changing trailing limb angle in both the paretic and non-paretic limbs. This strategy may contribute to the inefficiency in poststroke walking patterns. Future work is needed to examine whether these characteristics can be modified via intervention.

Background Recent rehabilitation efforts after stroke often focus on increasing walking speed because it is associated with quality of life. For individuals poststroke, propulsive force generated from the paretic limb has been shown to be correlated to walking speed. However, little is known about the relative contribution of the paretic versus the non-paretic propulsive forces to changes in walking speed. Objective The primary purpose of this study was to determine the contribution of propulsive force generated from each limb to changes in walking speed during speed modulation within a session and as a result of a 12-week training program. Methods Gait analysis was performed as participants (N=38) with chronic poststroke hemiparesis walked at their self-selected and faster walking speeds on a treadmill before and after a 12-week gait retraining program. Results Prior to training, stroke survivors increased non-paretic propulsive forces as the primary mechanism to change walking speed during speed modulation within a session. Following gait training, the paretic limb played a larger role during speed modulation within a session. In addition, the increases in paretic propulsive forces observed following gait training contributed to the increases in the self-selected walking speeds seen following training. Conclusions Gait retraining in the chronic phase of stroke recovery facilitates paretic limb neuromotor recovery and reduces the reliance on the non-paretic limb’s generation of propulsive force to increase walking speed. These findings support gait rehabilitation efforts directed toward improving the paretic limb’s ability to generate propulsive force.

Current rehabilitation efforts for individuals poststroke focus on increasing walking speed because it is a predictor of community ambulation and participation. Greater propulsive force is required to increase walking speed. Previous studies have identified that trailing limb angle (TLA) and ankle moment are key factors to increases in propulsive force during gait. However, no studies have determined the relative contribution of these two factors to increase propulsive force following intervention. The purpose of this study was to quantify the relative contribution of ankle moment and TLA to increases in propulsive force following 12-weeks of gait training for individuals poststroke. Forty-five participants were assigned to 1 of 3 training groups: training at self-selected speeds (SS), at fastest comfortable speeds (Fast), and Fast with functional electrical stimulation (FastFES). For participants who gained paretic propulsive force following training, a biomechanical-based model previously developed for individuals poststroke was used to calculate the relative contributions of ankle moment and TLA. A two-way, mixed-model design, analysis of covariance adjusted for baseline walking speed was performed to analyze changes in TLA and ankle moment across groups. The model showed that TLA was the major contributor to increases in propulsive force following training. Although the paretic TLA increased from pre-training to post-training, no differences were observed between groups. In contrast, increases in paretic ankle moment were observed only in the FastFES group. Our findings suggested that specific targeting may be needed to increase ankle moment.

No abstract