Americans suffer three-quarters of a million strokes every year. For those who survive, recovery can be long and arduous. It doesn't help that rehabilitation techniques are, for the most part, still remarkably low-tech. Therapists typically exercise patients' impaired limbs using repetitive hands-on maneuvers and mark improvements on clipboards. Because it's labor-intensive, the process is also expensive. Indeed, the annual price tag for the U.S. economy of stroke treatment is $30 billion and will likely escalate as Baby Boomers reach the peak stroke ages and drugs improve survival rates.

One solution: robots to boost the effectiveness and productivity of rehab. Systems designed by Neville Hogan and Hermano I. Krebs of MIT simultaneously deliver therapy and measure recovery of limb control. Playing specifically designed video games, the patient maneuvers the robot's mechanical arm horizontally, moving it like an oversized computer mouse to work the wrists, elbows and forearms at graded levels of resistance. A computer records the robot arm's position, velocity and the force the patient exerts.