Understanding of human movements in crank rotation

Deals with a crank rotation task. The task requires coordinated movements of arm links without developing excessive internal forces. This research is directed, mainly, to the understanding of comfortable human movements constrained by the external environment. To get a deeper insight into the crank rotation task, we develop a mathematical model and analyze a weighted minimum norm muscle force distribution scheme that can be used in the resolution of the force redundancy. Analysis of experimental data shows that in comfortable motions a human is likely to modulate the rotational stiffness of the crank. This gives an additional constraint that can be used in the resolution of the force redundancy by optimization techniques.