We will use a longitudinal design that will include three exercise groups. In 20 sessions over 4 weeks, subjects will strengthen their first dorsal interosseus (FDI) muscle of the dominant hand either with voluntary, electrically stimulated, or imagined contractions. The design also includes three control groups, a sham-stimulated group, a repetitive transcranial magnetic stimulation (1HzTMS) group, and a no-intervention group. Before and after the training programs, we will determine the changes in the outcome measures, including voluntary and electrical stimulation evoked force of the trained and the untrained FDI. Measures of excitability of the involved and uninvolved motor cortex, assessed with TMS, and measures of spinal cord excitability, assessed with peripheral nerve stimulation, are the additional outcome measures. The results of these studies will substantially increase our understanding of central nervous system (CNS) control of voluntary movement in health and disease.