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Spinal cord epidural stimulation can promote the recovery of motor function in individuals with severe spinal cord injury (SCI) by enabling the spinal circuitry to interpret sensory information and generate related neuromuscular responses. This approach enables the spinal cord to generate lower limb extension patterns during weight bearing, allowing individuals with SCI to achieve upright standing. We have shown that the human spinal cord can generate some standing postural responses during self-initiated body weight shifting. In this study, we investigated the ability of individuals with motor complete SCI receiving epidural stimulation to generate standing reactive postural responses after external perturbations were applied at the trunk. A cable-driven robotic device was used to provide constant assistance for pelvic control and to deliver precise trunk perturbations while participants used their hands to grasp onto handlebars for self-balance support (hands-on) as well as when participants were without support (free-hands). Five individuals with motor complete SCI receiving lumbosacral spinal cord epidural stimulation parameters specific for standing (Stand-scES) participated in this study. Trunk perturbations (average magnitude: 17 ± 3% body weight) were delivered randomly in the four cardinal directions. Participants attempted to control each perturbation such that upright standing was maintained and no additional external assistance was needed. Lower limb postural responses were generally more frequent, larger in magnitude, and appropriately modulated during the free-hands condition. This was associated with trunk displacement and lower limb loading modulation that were larger in the free-hands condition. Further, we observed discernible lower limb muscle synergies that were similar between the two perturbed standing conditions. These findings suggest that the human spinal circuitry involved in postural control retains the ability to generate meaningful lower limb postural responses after SCI when its excitability is properly modulated. Moreover, lower limb postural responses appear enhanced by a standing environment without upper limb stabilization that promotes afferent inputs associated with a larger modulation of ground reaction forces and trunk kinematics. These findings should be considered when developing future experimental frameworks aimed at studying upright postural control and activity-based recovery training protocols aimed at promoting neural plasticity and sensory-motor recovery. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the effects of step length and foot strike pattern along with their interaction on tibiofemoral joint (TFJ) and medial compartment TFJ kinetics during running. Nineteen participants ran with a rear foot strike pattern at their preferred speed using a short (−10%), preferred, and long (+10%) step length. These step length conditions were then repeated using a forefoot strike pattern. Regardless of foot strike pattern, a 10% shorter step length resulted in decreased peak contact force, force impulse per step, force impulse per kilometre, and average loading rate at the TFJ and medial compartment, while a 10% increased step length had the opposite effects (allP < 0.05). A forefoot strike pattern significantly lowered TFJ and medial compartment TFJ average loading rates compared with a rear foot strike pattern (both <0.05) but did not change TFJ or medial compartment peak force, force impulse per step, or force impulse per km. The combination of a shorter step length and forefoot strike pattern produced the greatest reduction in peak medial compartment contact force (P < 0.05). Knowledge of these running modification effects may be relevant to the management or prevention of TFJ injury or pathology among runners. [ABSTRACT FROM AUTHOR]

Objective: Powered ankle exoskeletons with biofeedback systems have proven effective at improving ankle plantar flexor muscle recruitment and push-off power in individuals with cerebral palsy (CP). However, their clinical translation and feasibility for at-home training remain limited. This study sought to design an unpowered wearable ankle device with spring resistance combined with a gamified ankle power biofeedback system. Our primary goal was to validate the device's ability to increase plantar flexor muscle recruitment and push-off power relative to baseline, and ensure that these improvements were comparable to those achieved with motorized resistance., Methods: Seven ambulatory individuals with CP completed walking sessions with (1) a powered ankle exoskeleton with motorized resistance, (2) our novel ankle device with spring resistance, and (3) shoes only (baseline); Both devices utilized the same biofeedback system., Results: Relative to baseline, both the motorized and spring resistance increased peak (48%, p<0.05) and mean (43-45%, p<0.05) soleus activation and mean (37-39%, p<0.05) medial gastrocnemius activation. No differences in muscle recruitment between spring and motorized devices were observed. Walking with spring resistance increased average ankle push-off positive power by 22% (p = 0.003) compared to motorized resistance and by 23% (p = 0.013) compared to baseline., Conclusion: An ankle device providing targeted spring resistance with ankle power biofeedback can effectively improve push-off muscle recruitment and power in individuals with CP., Significance: This supports future research studying outcomes following training with spring-based ankle resistance devices that lower barriers for clinical translation.

Objective: This pilot study investigated the feasibility and efficacy of using autonomous ankle exoskeletons in community settings among individuals with cerebral palsy (CP). Five participants completed two structured community walking protocols: a week-long ankle exoskeleton acclimation and training intervention, and a dose-matched Sham intervention of unassisted walking. Results: Results demonstrated significant improvements in acclimatized walking performance with the ankle exoskeleton, including increased speed and stride length. Participants also reported increased enjoyment and perceived benefits of using the exoskeleton. While ankle exoskeleton training did not lead to significant improvements in unassisted walking, this study demonstrates the feasibility of using ankle exoskeletons in the real world by people with CP. Conclusions: This study highlights the potential of wearable exoskeletons to augment community walking performance in CP, laying a foundation for further exploration in real-world environments., Competing Interests: ZL is a co-founder with shareholder interest in Biomotum, Inc., a spinoff company from his laboratory that is seeking to commercialize the device used in this study. He also has intellectual property inventorship rights covering aspects of the design and control of the device used in this study., (© 2024 The Authors.)