Sagittal-plane motions accompany recovery from frontal-plane pelvis perturbations during staggered stance

Research output: Contribution to conferencePosterAcademic


Background and aim: A staggered stance posture can be adopted in many scenarios during daily life. For example, during very slow walking a relatively long part of the gait cycle is spent in double support [1]. While standing in staggered stance, the recovery options in the frontal-plane without stepping are limited. This is due to the narrow base of support (BoS) compared to the larger BoS in the sagittal-plane. However, walking simulations showed that sagittal-plane ankle torques can also support in frontal-plane recovery [2]. We aimed to identify how healthy subjects make use of sagittal-plane motions when balance is perturbed in the frontal-plane while standing in staggered stance.

Methods: Ten healthy subjects stood in staggered stance, with the right foot leading, the left foot trailing and the centre of mass (CoM) in the middle. They received pelvis perturbations in medial (leftward) and lateral (rightward) directions (figure 1), with a magnitude of 9% of the subject’s body weight and a duration of 150 ms. Data was recorded with a Qualisys motion capture system, Delsys EMG sensors and two Motekforce Link force plates. Body kinematics and dynamics were acquired via OpenSim [3]. The analysed outcome variables were the centre of pressure (CoP), CoM, extrapolated CoM (XCoM), muscle activities and joint torques.

Results: Initially, the mediolateral (ML) perturbations predominantly induced ML motion of the CoM with an accompanying weight shift in the direction of the perturbation. However, also motions in the sagittal-plane were involved in the recovery, figure 1. After medial perturbations, plantarflexion of both ankles was seen, shifting the CoP to the front. However, the CoM was also brought forward due to extension of both knees and a forward lean of the torso. This reduced the load on the trailing leg, which had initially increased due to the medial perturbation. An opposite strategy was seen after the lateral perturbations. Dorsiflexion of the ankles resulted in a backward shift of the CoP, while the CoM was brought backward due to flexion of the knees. This reduced the load on the leading leg, which was initially increased due to the lateral perturbation. These responses contribute in returning to the original weight distribution between the left and right leg, without directly opposing the perturbation direction in order to return to the initial condition.

Conclusions: Strategies in the sagittal-plane accompany balance recovery after perturbations in the frontal-plane. These contributions could be explained by the strong plantar-dorsiflexion muscles and their large ability to modulate the CoP in the AP direction and restore weight bearing.

Original languageEnglish
Publication statusPublished - 7 Jul 2022
EventISPGR World congress 2022 - Hotel Bonaventure, Montreal, Canada
Duration: 3 Jul 20227 Jul 2022


ConferenceISPGR World congress 2022
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