Kinematic analysis of video-captured falls experienced by older adults in long-term care.

Falls cause 95% of hip and wrist fractures and 60% of head injuries in older adults. Risk for such injuries depends in part on velocity at contact, and the time available during the fall to generate protective responses. However, we have no information on the impact velocities and durations of falls in older adults. We addressed this barrier through kinematic analysis of 25 real-life falls (experienced by 23 individuals of mean age 80 years (SD=9.8)) captured on video in two long-term facilities. All 25 falls involved impact to the pelvis, 12 involved head impact, and 21 involved hand impact. We determined time-varying positions by digitizing each video, using direct linear transformations calibrated for each fall, and impact velocities through differentiation. The vertical impact velocity averaged 2.14 m/s (SD=0.63) for the pelvis, 2.91 m/s (SD=0.86) for the head, and 2.87 m/s (SD=1.60) for the hand. These values are 38%, 28%, and 4% lower, respectively, than predictions from an inverted pendulum model. Furthermore, the average pelvis impact velocity was 16% lower than values reported previously for young individuals in laboratory falling experiments. The average fall duration was 1271 ms (SD=648) from the initiation of imbalance to pelvis impact, and 583 ms (SD=255) from the start of descent to pelvis impact. These first measures of the kinematics of falls in older adults can inform the design and testing of fall injury prevention interventions (e.g., hip protectors, helmets, and flooring).