Stepping onto the unknown: reflexes of the foot and ankle while stepping with perturbed perceptions of terrain
Riddick, RC; Farris, DJ; Cresswell, AG; et al.Kuo, AD; Kelly, LA
Date: 10 March 2021
Article
Journal
Journal of the Royal Society Interface
Publisher
Royal Society
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Abstract
Unanticipated variations in terrain can destabilize the body. The foot is the primary interface with
the ground and we know that cutaneous reflexes provide important sensory feedback. However,
little is known about the contribution of stretch reflexes from the muscles within the foot to upright
stability. We used intramuscular ...
Unanticipated variations in terrain can destabilize the body. The foot is the primary interface with
the ground and we know that cutaneous reflexes provide important sensory feedback. However,
little is known about the contribution of stretch reflexes from the muscles within the foot to upright
stability. We used intramuscular electromyography measurements of the foot muscles flexor
digitorum brevis (FDB) and abductor hallucis (AH) to show for the first time how their short latency
stretch reflex response (SLR) may play an important role in responding to stepping perturbations.
The SLR of FDB and AH was highest for downwards steps and lowest for upwards steps, with the
response amplitude for level and compliant steps in between. When the type of terrain was
unknown or unexpected to the participant, the SLR of AH and the ankle muscle soleus tended to
decrease. We found significant relationships between the contact kinematics and forces of the leg
and the SLR, but a person’s expectation still had significant effects even after accounting for these
relationships. Motor control models of short latency body stabilization should not only include local
muscle dynamics, but also predictions of terrain based on higher-level information such as from
vision or memory.
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