Data from: Neural control of balance during walking

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 600ms, much longer than what is observed during
standing (50–200ms). 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.