In a potential breakthrough for the treatment of spinal-cord injuries, a man paralyzed below the chest has regained some ability to move and stand through the use of electrical stimulation coupled with intense physical rehabilitation—a combination previously shown to work only in animals.

This is the first such success in humans, so researchers on the case—from the University of Louisville, the University of California, Los Angeles, and the California Institute of Technology—remain cautious. They say findings must be replicated...