Experimental studies and clinical trials that aim to improve motor function for use of the upper extremity and walking are traditionally separated by the category of neurological disease. This boundary may deter investigators from finding common denominators in the conceptual basis and deployment of rehabilitation interventions, especially across nonprogressive diseases in adults, such as stroke, brain trauma, and spinal cord injury. The results of recent randomized clinical trials for walking by treadmill training and robotic devices and for the upper extremity by constraint-induced therapy, robotics, and brain stimulation suggest that more efficient strategies are needed to devise and prove the value of new therapies. Investigators should consider working across disease platforms to develop and test the most optimal methods for training patients, the most practical trial designs, the best dose-response characteristics of interventions, the most meaningful outcome measures, and the likelihood of transfer of trained performance to real-world settings. Clinicians in the community may be more likely to adopt evidence-based practices drawn from positive trial results if these treatment strategies focus on key motor impairments and related disabilities, rather than on diseases.