Stochastic resonance as a tool to improve walking deficits and biomechanical alterations in adults
Date
2025
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
There has been a significant increase in emergency room visits because of fall injuries as well as deaths from unintentional falls. Literature reported these incidents across different populations treated in most clinical settings, including neurological, musculoskeletal, and in and out-patient units. Apart from musculoskeletal impairments, fall incidents are also related to postural instabilities due to overlooked sensory deficits. Therefore, clinicians need to be able to screen, assess, and identify sensory deficits, especially after fall and fracture incidents, for the best instability rehabilitation outcomes. One of the possible deficits is a scarcity of somatosensory inputs and compromised sensory integration at the ankle joint. This deficit leads to extensive use of the hip joints over ankle joints to recover from a fall, which is another possible instability-related factor. The use of lower extremity joints to regain balance after a potential fall is associated with the reactive postural control mechanism. This mechanism involves strategies resembling an ascending hierarchy of musculature activation, distal to proximal, when the balance is probed with small to large perturbations, respectively. ☐ People with movement disorders, such as Parkinson disease (PD), present with somatosensory deficits and musculoskeletal problems, such as feet and postural deformities. One or a combination of both, somatosensory and musculoskeletal issues, might be related to their instability. Likewise, people with functional chronic ankle instability (CAI) show sensory impairments that could be related to anatomical structural changes found in their ankles after the initial onset of injury, such as ligamentous scarring and adhesions. Multiple sensory-centric approaches have been developed to address affected sensory systems. Stochastic resonance stimulation (SR) is one such method, which has showed a beneficial impact on balance by overcoming somatosensory deficits in different populations. Sub-sensory noise is applied to enhance the detection of weak signals within a targeted body system. However, its effect on people with PD (PwPD) and those with CAI during visually perturbed walking is still unknown. This project will implement an individualized SR stimulation applied to lower extremities during walking to enhance the sensory deficits in both populations. ☐ In Aim 1, we investigated the immediate effects of SR stimulation in reducing the body sway during a visually perturbed walking in PwPD. We found that the response to visual perturbations was significantly higher with SR compared to the no-SR condition in the more affected side. This suggests that SR stimulation may add additional noise to the somatosensory system in the PD population in what we defined as the more affected side, based on motor symptoms. We found that identifying and applying SR to an affected side with sensory deficits will yield noticeable postural improvements. ☐ In Aim 2, we explored whether SR stimulation enhances the use of distal over proximal balance mechanisms to recover from a potential fall that is induced by visual perturbations. We found that SR stimulation did not affect the lower limbs’ response. We suggest that unexplored balance contributors may be involved in the change of the body sway seen in Aim 1. Moreover, we propose that there may be a delay in achieving stability using the distal strategies, which could be related to the poor processing rate in PwPD. ☐ To study the SR effects in a population with a more defined laterality, less overall complexity, and who present with sensory-related disabilities, we investigated the impact of SR stimulation in people with CAI, who show persistent sensorimotor integration deficits. In Aim 3, we analyzed the immediate effect of the SR stimulation in improving dynamic postural stability during walking in a visually perturbed environment. We found that the body sway response to visual perturbations was significantly lower with SR compared to no-SR condition in the affected limb of individuals with CAI. We propose that SR stimulation selectively affects the impaired neural pathways with no or adverse impact on the intact pathways, represented by the unaffected limb. ☐ In Aim 4, we investigated if SR stimulation alters the biomechanical strategies used in reactive postural control in response to visual perturbations. We found that SR stimulation did not affect the way participants use their lower extremities, proximal versus distal, to recover from a potential fall. Unexplored balance-related factors other than the strategies used by lower extremities may be a reason for the insignificant finding. Giving the multifaceted nature of the CAI condition, we suggest that SR could have an impact on higher-order sensorimotor integration rather than direct influence on peripheral motor outputs. ☐ Overall, these findings will contribute to our understanding of the role of sensory inputs in controlling dynamic balance during walking in a challenging setting. This understanding facilitates the design of more tailored sensory-centric interventions, particularly when gait and balance training are important components of a treatment plan in individuals with PD and those with CAI.
Description
Keywords
Adults, Electrical stimulation, Pathological conditions, Postural control, Sensory deficits, Virtual reality