Sternum drop as a kinematic measure of trip recovery performance

Deficient trip recovery kinematics have been implicated in many trip-induced falls. Three key requisites for successful trip recovery include limiting trunk flexion, maintaining adequate hip height to enable repeated stepping, and completing recovery steps to extend the base of support. The purpose of this study was to evaluate sternum drop as a new measure of trip recovery performance. Sternum drop may be a more robust than other measures of trip recovery performance because, unlike other common trip recovery measures, it is sensitive to two of the three trip recovery requisites. Thirty community-dwelling older adults were exposed to two laboratory-induced trips while walking on a walkway. Sternum drop was determined using two separate methods: from optoelectronic motion capture and an inertial measurement unit. For comparison sternum drop, trunk angle and hip height, both at touchdown of the first recovery step, were also determined. Sternum drop from optoelectronic motion capture exhibited strong correlation with trunk angle at touchdown (repeated-measures correlation coefficient (r_rm) = 0.94; p < 0.001), strong correlation with hip height at touchdown (r_rm = -0.90; p < 0.001), and strong correlation with sternum drop from IMU (r_rm = 0.95; p < 0.001). In addition, sternum drop from optoelectronic motion capture (p < 0.001) and sternum drop from inertial measurement unit (p = 0.001) differed between falls and recoveries, with the former exhibiting the largest effect size (partial eta² = 0.36) between falls and recoveries. These results support sternum drop as a valid kinematic measure of trip recovery performance.