The influence of net ground reaction force orientation on mediolateral stability during walking

• Published in: Gait & posture Vol. 90; pp. 73 - 79
• Main Authors: Rawal, Yash Ramesh, Singer, Jonathan C.
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 01.10.2021
• Subjects: Biomechanical Phenomena; Center of mass; Foot; Gait; Humans; Kinematics; Kinetics; Lateral stability; Postural Balance; Walking; Lateral stability; Kinetics; Gait; Center of mass; Kinematics
• ISSN: 0966-6362; 1879-2219
• DOI: 10.1016/j.gaitpost.2021.08.009

•Mediolateral (ML) stability is an important component of balance during gait.•We examined centre of mass kinematics and kinetic control of mediolateral stability.•ML stability appears to be primarily regulated proactively during gait.•Reactive control may be used when proactive control is insufficient.•Proactive control can offset the necessity for reactive stability control. Previous work has linked the eccentricity of the net ground reaction force (GRFnet) to increased mediolateral instability during single-step voluntary and compensatory stepping responses. The present work sought to understand the extent to which such control mechanisms for mediolateral stability are present during gait. How do gait velocity and step width constraints influence the kinetic control of mediolateral stability control among healthy participants? 25 participants performed three walking conditions – normal walking with self-selected speed and foot-placement, fast walking with self-selected foot-placement, and narrowbase walking – across a 10-meter walkway. Lateral instability was quantified by the mediolateral margin of stability (MoSML). The frontal-plane eccentricity of the GRFnet was calculated as the difference between GRFnet vector orientation and that of a line joining the coordinates of COPnet and COM. Two discrete time-points (P1 and P2) following foot-contact were examined, as they have been suggested to be indicative of proactive and reactive COM control, respectively. Task-related differences in the magnitude and timing of kinematic and kinetic outcome variables were analysed using one-way ANOVAs with repeated-measures. With constraints on step-width in narrow-base walking, participants exhibited reduced stability as evidenced by reduced MoSML, alongside reductions in the peak GRFnet eccentricity (θd) at P1. Participants exhibited no reduction in stability during fast walking, as revealed by the MoSML in part because of a similar onset of P1 within the gait cycle. P2 magnitude was larger in narrow-base walking relative to fast-walking, and occurred at an earlier point in the gait cycle. Findings suggest proactive mechanisms (i.e. P1) may predominantly regulate mediolateral stability during walking. Reactive mechanisms (i.e. P2), however, may be capable of offsetting instability in situations where proactive mechanisms are insufficient.