Adaptability of human movement in unknown dynamical environments

This paper investigates how a human learns to adapt to his/her unknown dynamical environment during performing a required task. We focus on a specific task of turning a crank. The crank´s size and its center are unknown and can be adjusted. An AC motor was equipped to change the crank´s dynamics. A camera was used to monitor the task, and a monitor provides the subjects with various visual information that may coincide or not with the real crank. We find that, in contrast to Shadmehr and Mussa-Ivaldi´s conclusion (1994) that there was a kinematic plan independent of dynamical conditions, even after sufficient training, human movements exhibit different performance with respect to different environmental dynamic conditions. We suggest that the human movement is generated not by reducing the environmental disturbances but through adapting to the environmental dynamics