Momentum analysis of sitback failures in sit-to-stand trials

The authors characterize successful sit-to-stand maneuvers and compare these to sitback and step failures, using whole body (WE) and upper body (HAT) linear and angular momentum parameters. Controls consisted of 11 normal elders. Six failed sit-to-stand maneuvers in which sitbacks occurred were extracted from archived tests of patients; primarily patients with vestibular pathology. Whole body (WB) momentum and upper body or HAT momentum parameters were calculated. Sitback failures were associated with lower HAT AP linear momentum at the time of maximum ground reaction force (GRF); i.e., just after liftoff. The sitback failures were also associated with lower knee torques at the time of maximum GRF and lower values of the maximum GRF. Thus, sitback failures appear to be due lack of adequate momentum and torque generation. These findings improve one´s understanding of the biomechanics of sit-to-stand and the mechanism of loss of balance during this demanding activity