Simulating Real-World Slips: Enhanced Kinematic and Neuromuscular Responses to Experimental Slips in the Early vs. Late Stance Phase in Young and Older Adults

Slips are a leading cause of injury and hospitalization among at-risk individuals. Replicating real-world slips by experimental, mechanical perturbations is essential for characterizing reactive balance mechanisms activated during near-fall situations and for training these mechanisms in fall prevention programs. This study compared treadmill-based, slip-like perturbations targeting the early (early perturbations, EP) vs. late stance phase (late perturbations, LP) in 22 young and 21 older adults. Biomechanical and neuromuscular responses were assessed using full-body kinematics and surface electromyography (EMG). Additionally, participants provided subjective rating of perturbation intensity and inconvenience. EP elicited stronger reactive balance responses than LP, characterized by greater deviations in leg joint and trunk kinematics, as well as shorter EMG onset latencies and enhanced EMG peak amplitudes. Gait parameters required longer to recover to baseline following EP than LP. Subjectively, EP were rated as more intense and inconvenient, and were perceived to more closely mimic real-world slips. Older adults showed delayed and attenuated reactive balance responses compared to younger adults. These findings highlight the importance of targeting the vulnerable early stance phase to accurately simulate real-world slip events. Such perturbation paradigms may support the development of more effective, task-specific perturbation-based training programs aimed at reducing falls in at-risk populations.