The Effect of Predictability of the Perturbation Magnitude on Anticipatory and Compensatory Postural Adjustments during a Bimanual Load-Lifting Task

Background: To minimize the potential postural disturbance induced by external or self-initiated perturbations, humans generate anticipatory postural adjustments based on their perceived consequences of the body disturbance. Lifting is a common activity that induces a self-initiated perturbation that can compromise balance control. Aim: To assess anticipatory (APAs) and compensatory (CPAs) postural adjustments generated in response to a self-initiated perturbation induced by lifting objects of uncertain mass. Methods: Ten young adults lifted the tray with either light or heavy object placed in it. Electromyographic activity of eight trunk and leg muscles, and center-of-pressure (COP) displacements were recorded and analyzed during the APAs and CPAs phases. Results: When the object mass changed unpredictably, the participants generated APAs based on the most recent experience of lifting and needed three trials of lifting to generate optimal APAs and CPAs. Conclusions: Young adults were able to predict the perturbation magnitude during self-initiated perturbations induced by lifting objects. The outcome provides a foundation for future studies focusing on the role of predictability of perturbation consequences in postural control of older adults and individuals with balance deficit.