On using methods from robotics to study human task dependent balance during whole-body pointing and drawing movements

The human body is capable of a complex variety of movements and the redundant nature of the anthropomorphic structure makes it an interesting system to study from a robotics point of view. In this paper we study the strategies used by humans to balance during whole body pointing and drawing movements as a function of several simultaneously executed tasks. We record the motion of participants using motion capture, force-plates and electromyography. Joint kinematics, motion of center of pressure and center of gravity and joint torques are then estimated using a complex musculoskeletal model. The effects of executing secondary tasks (balancing on one foot, or holding a cup in place) were studied by analyzing the accuracy of movement, the center of mass and center of pressure displacement, the coordination of the lower and upper body, and the modulation of muscle activity. Our results show that the nominal motion rules can be modified by the addition of a secondary objective. The approach used in this study is an interesting extension to conventional human movement studies and provides an alternative way to understand human movements using methodologies from robotics.