The study has two experiments. Both experiments use a within-subjects design. The purpose of the first experiment is to determine whether learning to accurately perform an alternating wrist flexion and extension movement task is associated with reduced co-contraction of wrist flexor and extensor muscles. Subjects will practice making accurate wrist flexions and extensions to keep a cursor on a target for fifteen-minute sessions every weekday until they are able to obtain 95% accuracy. Activity of the arm muscles will be monitored during the sessions with surface electrodes on the arm muscles. The first experiment will also determine the best training parameters for learning the task. In the second experiment, a second group of subjects will learn the task using the best training parameters. The strength of the reflex for reciprocal inhibition will be measured before, during and after training. Reciprocal inhibition will also be measured after the movement has become highly learned.