Trajectory formation in sequential arm movements: A critical investigation of optimization approach to human movement control

Sequential movements are characterized by the partially defined states of dynamical systems. A mathematical model for the control of human sequential movements is formulated by defining an objective function, using the same strategy as the previous investigations on simple point-to-point motion and locomotion. The problem of indeterminacy is solved using the dynamical optimization theory. In moving from an initial to a final position in a given time, the objective function is in the form of a quadratic integral whose integrand is a weighted sum of two terms. The first term is the square of the change in torque, and the second is the square of the angular velocity. The model predicts the measured trajectories in planar, multijoint arm movements, leading us to a conclusion that in sequential movements, both the "energy" consumption of the muscles and the motion of the musculoskeletal system are approximately optimum. The optimization approach is discussed on the basis of the previous studies on point-to-point movements and the present study on sequential movements.