Early kinetic responses enhance biomechanical discrimination of falls and recoveries during sudden bilateral slips.

Abstract

Accurately identifying the biomechanical factors that distinguish failed from successful slip recoveries can reveal modifiable targets for fall‑prevention training. However, models for unconstrained slips have largely relied on kinematics alone, and it remains unknown whether early kinetic responses provided additional information to discriminate falls from recovery. We examined whether early kinetic variables enhance classification of falls versus recoveries beyond kinematic measures alone during sudden, unconstrained, bilateral slips. Ten healthy young adults each encountered three unannounced slips induced by a custom wearable apparatus while walking overground. A two-variable kinematic base model that used only vertical center-of-mass acceleration and whole-body angular momentum misclassified one-quarter of the trials. Adding a third kinematic variable, trailing-foot placement, did not improve performance. In contrast, extending the base model with either of two kinetic variables, the mean vertical ground-reaction force or the mean torque about the center of mass measured in the first 100 ms after touchdown of the trailing foot raised cross-validated accuracy from 74% to 85%. Contrary to our expectation, frontal- and sagittal-plane models performed equally well, reflecting that every fall involved a lateral as well as backward loss of balance. The slip-induced falls, which were mainly due to backward loss of balance, show that rapid generation of upward support and forward corrective torque is a distinguishing feature of successful recovery and suggest concrete kinetic targets for perturbation‑based rehabilitation aimed at reducing slip‑related falls.