Leg Joint Stiffness Affects Dynamics of Backward Falling From Standing Height: A Simulation Work

Area of Science:

• Biomechanics
• Gerontology
• Injury Prevention

Background:

• Backward falls are a major cause of injury in older adults, often linked to loss of consciousness.
• Understanding backward fall dynamics, including duration and impact severity, is crucial for injury prevention.
• The role of lower limb joint stiffness in backward fall mechanics remains under-investigated.

Purpose of the Study:

• To investigate how individual leg joint stiffness influences backward fall dynamics after loss of consciousness.
• To quantify the effects of ankle, knee, and hip joint stiffness on falling duration and impact velocities.

Main Methods:

• A 15-segment human body model was utilized for backward fall simulations.
• Simulations involved systematically varying ankle, knee, and hip joint stiffness parameters.
• Joint stiffness ranged from 0 to 8.73 N·m·deg-1 (500 N·m·rad-1).

Main Results:

• Falling duration ranged from 0.27 to 0.63 seconds.
• Impact speeds for the head and hip varied between 2.65–7.88 m·s-1 and 0.35–3.36 m·s-1, respectively.
• Hip and knee joint stiffness had comparable effects on fall dynamics; ankle stiffness had minimal impact.

Conclusions:

• Hip and knee joint stiffness are key factors influencing backward fall dynamics.
• Ankle joint stiffness has a negligible effect on backward fall duration and impact.
• Findings can inform the design of advanced protective devices to mitigate fall-related injuries in older adults.