Energy dissipation strategy in backward falls in at-risk older adults: evidence and implications for head injury prevention

Older adults are at elevated risk of sustaining head injuries from head impact during falls. It has been speculated that fall-related head impact stems from insufficient energy dissipation. To address this, this study leveraged a unique dataset of 45 experimentally induced backward falls in 25 at fall-risk older adults (mean age = 72.5 ± 6.1 years) to provide a novel event-based examination of kinematic and energy profile differences between falls with and without head impact. The differences in segment velocities, joint angles, and kinetic energy between falls with and without head impact were analyzed. Falls without head impact exhibited significantly greater trunk forward flexion prior to pelvis contact and reduced peak head vertical velocity throughout the descent compared to falls with head impact. Furthermore, falls resulting in head impact demonstrated a systemic failure in energy management, characterized by higher kinetic energy retention after pelvis and head impact (0.0 J vs. -7.8 J, p < 0.0001 and -41.0 J vs. -84.8 J, p < 0.0001). These results highlight distinct postural and energy dissipation strategies between falls with and without head impact. Greater trunk flexion during descent may facilitate more effective kinetic energy dissipation, offering biomechanical targets for injury prevention in at fall-risk older adults.