Functional roles of stepping-leg joint torques in body deceleration during the post-trip landing phase in gait

Tripping during walking alters the whole-body linear momentum (WBLM) and angular momentum (WBAM). Inadequate regulation of these changes affects normal gait, potentially resulting in falls and injuries. To avoid these incidents, it is necessary to exert joint torques to generate ground reaction forces (GRFs) that will serve to mitigate WBLM and WBAM changes. However, it remains unclear which joint torques and how they contribute to generating the post-trip GRF.

How is the GRF generated to control the WBLMs and WBAM during the post-trip landing phase in gait?

Twelve young adults completed 150 walking trials on a walkway, with tripping induced in 60 of them. They were required to recover to normal walking after tripping. Body landmark coordinates and GRF data were obtained using a motion capture system and a force platform, respectively. Joint torques, WBLM, WBAM, and the contribution of each torque to the GRF were calculated.

The upward GRF was primarily generated by the ankle-plantarflexion torque of the stepping leg, supported by the knee- and hip-extension torques (contributions to vertical GRF: ankle-plantarflexion, 64.4 ± 7.8 %; knee flexion-extension, 16.3 ± 6.1 %; hip flexion-extension, 8.8 ± 4.3 %). The posterior GRF was mainly generated by the knee- and hip-extension torques (contributions to anterior-posterior GRF: knee flexion-extension, 40.2 ± 8.2 %; hip flexion-extension, 12.9 ± 5.6 %). Additionally, the ankle-plantarflexion torque contributed to the backward GRF moment immediately after post-trip stepping-foot contact (contribution to forward-backward GRF moment: 41.7 ± 4.1 %).

The findings of this study enhance the understanding of the kinetics of a body's deceleration to prevent falls during the post-trip landing phase and can serve as normative data for fall-prevention programs in rehabilitation settings and the development of powered exoskeletons.