Abstract
During locomotion over uneven terrain, gait must be adapted to avoid a trip. In the event of a foot-obstacle contact, the body reactively responds to the perturbation. However, it is unknown if any proactive adjustments are made in subsequent strides to reduce the likelihood of another contact, and how long any proactive adaptations persist. This study examined gait behavior while stepping over a 10cm obstacle placed in the middle of an 8m walkway. The four obstacle crossings that preceded a spontaneous obstacle contact were compared to the eight obstacle crossings subsequent to the contact. Foot position before the obstacle was not modified following the obstacle contact. However, toe clearance and peak toe elevation increased in the limb that was tripped; the unperturbed limb showed no differences. These findings demonstrate that the sensory information of the perturbed limb proactively influenced the ipsilateral but not the contralateral limb, supporting the idea that the lead and trail limb are controlled independently during obstacle crossing. The proactive adaptation lasted for at least eight trials, suggesting that an unexpected perturbation influences the control of adafptive gait well after obstacle contact.
Highlights
Functional mobility requires that gait is adapted to accommodate or avoid obstacles in the environment
A subject may modify the position of the foot placement in front of the obstacle and/or raise their toe higher when stepping over the obstacle in subsequent trials to proactively reduce the likelihood of future obstacle contacts
Dependent variables not affected by the trial group were: lead and trail limb horizontal distance, lead limb toe clearance, and lead limb peak toe elevation (p > 0.09)
Summary
Functional mobility requires that gait is adapted to accommodate or avoid obstacles in the environment. To gain insight into the manner in which a trip is avoided, researchers have reported lower limb kinematics when approaching and clearing an obstacle [3] and [4]. If enough contacts are observed, further insight into adaptive locomotor control can be gained. It is conceivable that obstacle contact may proactively change the behavior used to clear the obstacle in subsequent trials. A subject may modify the position of the foot placement in front of the obstacle (termed ‘horizontal distance’) and/or raise their toe higher (termed ‘toe clearance’ and ‘peak toe elevation’) when stepping over the obstacle in subsequent trials to proactively reduce the likelihood of future obstacle contacts. If gait is proactively modulated following obstacle contact, the magnitude and persistence of the modulation is unknown. If the control of each limb is independent, as has been suggested [7], [8] and [9], the changes should be limited to the perturbed limb
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