Neural Control of Balance During Walking

Abstract

Neural control of standing balance has been extensively studied. However, most falls occur during walking rather than standing, and findings from standing balance research do not necessarily carry over to walking. This is primarily due to the constraints of the gait cycle: Body configuration changes dramatically over the gait cycle, necessitating different responses as this configuration changes. Notably, certain responses can only be initiated at specific points in the gait cycle, leading to onset times ranging from 350 to 600 ms, much longer than what is observed during standing (50–200 ms). Here, we investigated the neural control of upright balance during walking. Specifically, how the brain transforms sensory information related to upright balance into corrective motor responses. We used visual disturbances of 20 healthy young subjects walking in a virtual reality cave to induce the perception of a fall to the side and analyzed the muscular responses, changes in ground reaction forces and body kinematics. Our results showed changes in swing leg foot placement and stance leg ankle roll that accelerate the body in the direction opposite of the visually induced fall stimulus, consistent with previous results. Surprisingly, ankle musculature activity changed rapidly in response to the stimulus, suggesting the presence of a direct reflexive pathway from the visual system to the spinal cord, similar to the vestibulospinal pathway. We also observed systematic modulation of the ankle push-off, indicating the discovery of a previously unobserved balance mechanism. Such modulation has implications not only for balance but plays a role in modulation of step width and length as well as cadence. These results indicated a temporally-coordinated series of balance responses over the gait cycle that insures flexible control of upright balance during walking.

Repetitive subconcussive head impacts and changes in sensory processing for balance control

“…[24][25][26] Healthy adults respond to GVS applied during walking using a coordinated series of balance mechanisms. [27,28] Assuming that the perturbation occurs at heel strike, healthy adults sequentially use three mechanisms: lateral ankle roll followed by foot placement change and finally modulation of push off in the trailing leg. [27,28] The lateral ankle mechanism shifts the stance foot center of pressure (CoP) in the direction of the perceived fall by ~2.5 mm.…”

“…[27,28] Assuming that the perturbation occurs at heel strike, healthy adults sequentially use three mechanisms: lateral ankle roll followed by foot placement change and finally modulation of push off in the trailing leg. [27,28] The lateral ankle mechanism shifts the stance foot center of pressure (CoP) in the direction of the perceived fall by ~2.5 mm. [27,28] Foot placement modulation shifts the swing foot of the following step by ~15 mm in the same direction.…”

“…[27,28] The lateral ankle mechanism shifts the stance foot center of pressure (CoP) in the direction of the perceived fall by ~2.5 mm. [27,28] Foot placement modulation shifts the swing foot of the following step by ~15 mm in the same direction. [27,28] Finally, push off modulation adjusts the plantarflexion angle of the trailing leg to move the center of mass (CoM) in the direction opposite of the perceived fall.…”

“…[27,28] Foot placement modulation shifts the swing foot of the following step by ~15 mm in the same direction. [27,28] Finally, push off modulation adjusts the plantarflexion angle of the trailing leg to move the center of mass (CoM) in the direction opposite of the perceived fall. [28] Using these methods, this study aims to examine whether RHI affects sensory processing and subsequent balance control during standing and walking.…”

“…[27,28] Finally, push off modulation adjusts the plantarflexion angle of the trailing leg to move the center of mass (CoM) in the direction opposite of the perceived fall. [28] Using these methods, this study aims to examine whether RHI affects sensory processing and subsequent balance control during standing and walking. We hypothesized immediately following the soccer heading paradigm individuals would have 1) impairments in sensory reweighting during standing and 2) diminished balance responses to GVS during walking.…”