Recovery from sagittal-plane whole body angular momentum perturbations during walking

Area of Science:

• Biomechanics
• Human locomotion
• Gait stability

Background:

• Whole body angular momentum (WBAM) regulation is critical for maintaining balance during walking.
• Understanding how healthy individuals recover from WBAM perturbations is essential for insights into gait stability.

Purpose of the Study:

• To investigate the mechanisms by which healthy individuals recover whole body angular momentum (WBAM) in the sagittal plane following external perturbations.
• To determine the roles of centre of pressure (CoP) modulation and ground reaction force (GRF) direction adjustments in WBAM recovery.

Main Methods:

• Participants walked on a treadmill while experiencing simultaneous, opposing perturbations to the pelvis and upper body to perturb WBAM without affecting whole body linear momentum (WBLM).
• Perturbations varied in magnitude (4-16% body weight) and duration (150ms), applied at toe-off.
• Kinematic and kinetic data were analyzed to assess WBAM recovery and identify contributing factors.

Main Results:

• Individuals rapidly recovered WBAM post-perturbation by adjusting the GRF moment arm relative to the centre of mass (CoM).
• The stance leg's hip joint was identified as a key contributor to WBAM recovery.
• Recovery was primarily driven by changes in GRF direction, specifically horizontal GRF alterations, rather than CoP modulation.

Conclusions:

• Healthy individuals prioritize whole body angular momentum (WBAM) regulation over whole body linear momentum (WBLM) during the initial phase of recovery from perturbations.
• The study highlights the importance of GRF vector adjustments, particularly via hip joint action, in maintaining gait stability.