When is visual information used to control locomotion when descending a kerb?

Area of Science:

• Biomechanics
• Neuroscience
• Human Locomotion

Background:

• Descending curbs requires precise foot placement and body lowering.
• Vision, particularly from the lower visual field (LVF), aids in adaptive gait.
• The role of LVF in online gait control during curb negotiation is not fully understood.

Purpose of the Study:

• To investigate the timing of LVF information usage for controlling locomotion when stepping down a curb.
• To determine when LVF input is critical for planning foot clearance and kinematic adjustments.

Main Methods:

• 12 participants stepped down a curb while LVF was unpredictably occluded.
• Occlusion occurred at different time points: final step contact or penultimate step contact.
• Measurements included foot placement, foot clearance, and kinematic parameters.

Main Results:

• LVF occlusion during the final step had no significant effect on gait variables.
• Occluding LVF during the penultimate step significantly altered foot clearance and kinematics.
• Participants showed uncertainty in judging the kerb's horizontal location when LVF was occluded earlier.

Conclusions:

• Concurrent feedback from the limb or immediate ground is not used for curb stepping.
• LVF information from the penultimate step is essential for planning heel clearance and kinematics.
• Foot placement information acquired during the penultimate step is most critical for curb negotiation.