The 19th century pioneers of motor physiology - Helmholtz, Hering, Fick and others - used the mathematics of motion, known as kinematics, to describe the laws of human movement and to deduce the neural control principles underlying these laws. After long neglect - partly due to limitations in stimulation and recording techniques - the kinematic approach is now resurging, fortified with modern computers and electrophysiology. New developments in recording techniques, as well as an improved understanding of the complex control properties of three-dimensional movements, have led to a flood of...