At Nagasaki University in Nagasaki-City, Japan, mechanical engineer Shunji Moromugi straps on a pair of what he calls “power pants” and gets to work. Holding a 16-kilogram barbell on his shoulders, he does 90 squats in 90 seconds without breaking a sweat. That’s because the pants contain computerized sensors that detect what his legs are doing-deep knee bends-and tubelike artificial muscles, mounted on both sides of the knee, that expand and contract with flows of compressed air. The artificial muscles are attached to a steel brace that spans the thigh and calf; when they lengthen, they extend Moromugi’s knee and help him stand more easily.

These power pants might just be the closest thing yet to a realization of long-held visions of mechanical systems that improve the mobility of the elderly and disabled or boost the strength of soldiers and rescue workers. Where previous wearable robots proved cumbersome and hard to control, this latest version-a collaboration between Nagasaki University, the University of Electro-Communications in Tokyo, Japan, and the University of California, Irvine-is smarter and more practical. Robotics experts say it’s an important step toward building machines that people will actually use. “This is novel because it’s sensing over the entire soft-tissue interface of the body,” says Ephrahim Garcia, a mechanical and aerospace engineer at Cornell University and a former program manager at the U.S. Defense Advanced Research Projects Agency. “You need intense amounts of computation to pull it off,” he adds.

Indeed, the system’s tiny sensors are distributed over the legs and hips to measure signals that muscles give off when they contract. Every few milliseconds, strain gauges and ultrasonic disk-shaped sensors in cuffs around the user’s legs measure the stiffness and density of the underlying tissues and communicate wirelessly with a computer that makes sense of the signals-predicting the user’s intended movements on the basis of experimental data and mathematical models. Then, like a diligent weight-room spotter, the computer controls the artificial muscles. “We’re trying to reduce fatigue and eventually help disabled people,” says Maria Feng, a civil engineer at UC Irvine and a collaborator on the project.

The robotic pants are being tested at Nagasaki University for use as a physical-therapy tool for patients confined to bed. The researchers are also testing a mechanical glove that allows a user to pick up a coffee cup just by tensing muscles in his or her upper arm-important for, say, a person who has lost fine motor control due to a spinal injury or cerebral palsy. In the next two years, says Feng, the researchers will work out the remaining bugs and begin widespread testing of the devices in clinics and with patients.

If all goes well, such human-assist machines might hit the market in five to ten years. That’s because dozens of robotics researchers are working on related projects, with tens of millions of dollars of funding from DARPA alone. At the University of California, Berkeley, mechanical engineers have built robotic “exoskeletons” that connect to people’s legs to help them balance, walk, and run with less effort. The researchers are currently developing a prototype lower-body suit, powered by rocket fuel, that could allow soldiers to move more easily over uneven terrain while carrying heavy equipment.

So who will be the first to actually use such devices? The consensus among the researchers is that physical therapy and rehabilitation will be the initial commercial applications. But that will require streamlining the technology to make it as safe and reliable as possible. It’s still too early to say whether the real impact will be felt on the battlefield or in the home. But if the research and development is successful-and wearable robots prove to be good for your health-they may become fashionable to boot.