Influence of an unexpected perturbation on adaptive gait behavior

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.

The impact of mobile phone use on where we look and how we walk when negotiating floor based obstacles

“…Therefore, the following variables were not assigned to each (left or right) limb, rather ‘lead’ and ‘trail’ limb to reflect the first and second foot stepping up onto the surface height change. The following variables were analysed as they are considered important to assess the kinematics of gait and changes in such variables have been shown to increase the risk of tripping / falling [33];…”

Visuomotor Transformation for the Lead Leg Affects Trail Leg Trajectories During Visually Guided Crossing Over a Virtual Obstacle in Humans

“…The obstacle was 89 cm wide with a depth of 3.5 cm and a height of 22 cm. The size of obstacle was within the range of that used in the previous studies (width: 57-100 cm; depth: 0.3-10 cm; height: 1-30 cm; Patla and Vickers, 1997;Mohagheghi et al, 2004;Rhea and Rietdyk, 2011;Lajoie et al, 2012;Kim et al, 2018). At the beginning of a trial, subjects were instructed to stand rigidly with their toes precisely on a start line drawn on the floor.…”

“…Generally, in the studies using visuomotor perturbation, the perturbation was applied more consistently throughout a lot of trials Krakauer et al, 2000). In the number of consecutive obstacle clearance trials, however, the toe height gradually decreases potentially due to fatigue or the process to search the optimal strategy (Rhea and Rietdyk, 2011). These factors will make it complex to identify whether the change of toe height is owing to the corrective response against the perturbation or the other factors.…”

“…Previous studies on obstacle avoidance in humans have debated the relationship of limb elevation control between the lead and trail legs. Rhea and Rietdyk (2011) demonstrated that obstacle contact with the trail leg results in changes in toe elevation and clearance in that leg but not in the lead leg in subsequent trials (Rhea and Rietdyk, 2011). The removal of all vision during the last portion close to an obstacle and during obstacle crossing increased the toe elevation height only in the lead leg (Mohagheghi et al, 2004).…”

“…Accordingly, lead and trail limb trajectories are considered to be determined based on independent controllers. This knowledge, however, should be revalidated, because the visual information in the affected leg was not available to the other leg movement in the previous studies (Mohagheghi et al, 2004;Rhea and Rietdyk, 2011). The influence of the change of visuomotor transformation in one leg on that in the other leg has not been fully elucidated despite the importance of vision in crossing an obstacle.…”