The relative contribution of ankle moment and trailing limb angle to propulsive force during gait

Abstract

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.

Symmetry of corticomotor input to plantarflexors influences the propulsive strategy used to increase walking speed post-stroke

“…Information about the symmetry of the corticomotor input to the plantarflexors thus appears to provide information about the capacity to improve the paretic limb’s contribution to propulsion in post-stroke ambulation. Our data suggest that those with greater corticomotor symmetry possess sufficient intact corticomotor pathways to allow for increased paretic plantarflexor recruitment to meet the increased propulsive demands required for faster walking speeds (Hsiao et al 2015a; Hsiao et al 2015b). In contrast, individuals with poor corticomotor symmetry seem to possess weaker corticomotor pathways to the paretic plantarflexors and may have saturated their ability to recruit paretic plantarflexors at slower self-selected gait speeds (Jonkers et al 2009).…”

“…hip flexion moment on ankle joint power or the trailing limb position on anterior ground reaction forces) (Hsiao et al 2015a; Hsiao et al 2015b). Ankle plantarflexion moment symmetry (PF sym ) was calculated for each participant at each speed as the average paretic plantarflexion moment divided by the average nonparetic plantarflexion moment.…”

“…Further, rehabilitation strategies that improved paretic limb propulsion have also improved post-stroke walking function (Awad et al 2014; Bowden et al 2013). The two main contributors to forward propulsion are trailing limb angle and ankle plantarflexion moment (Hsiao et al 2015a; Hsiao et al 2015b). The plantarflexion moment represents the net torque generated by the plantarflexor muscles that cross the ankle joint.…”

“…The plantarflexion moment represents the net torque generated by the plantarflexor muscles that cross the ankle joint. Thus, the ability to activate the plantarflexor muscles plays a critical role in generating propulsion to attain and increase gait speeds in both neurologically-intact (Hsiao et al 2015b) and stroke populations (Olney et al 1994; Hsiao et al 2015a; Peterson et al 2010). …”

A soft robotic exosuit improves walking in patients after stroke

“…GRFs were used to compute PP and non-PP and this study's primary kinetic outcome: interlimb propulsion symmetry. PP was defined as the anterior GRF measured during the paretic limb's stance phase, normalized by body weight (% bw) (65,79,86,(89)(90)(91).…”