Biomechanical Comparisons of Active and Unexpected Landings with Changes in Drop Height

The purpose of this study was to determine the differences of kinematics, impact force, soft-tissue vibration, and muscle activity between active (AL) and unexpected landing (UL). Twelve trained male volunteers were requested to land from self-made elevated platform at three heights (30, 45, and 60cm) in AL and UL conditions. During active landing, human body can adjust the landing strategy of musculoskeletal system, mainly through more extended hip and knee joints, which leads to a decrease in peak impact forces / loading rates and relevant soft-tissue vibration, and also an increase in muscle activation. In contrast, during unexpected landing, the lower body was less prepared for the sudden drop landings, which leads to an inadequate postural control, higher impact forces, excessive soft-tissue vibrations, and less muscular activity in lower extremity.