This Ankle Exoskeleton Was Designed to Make Running Easier
Photo: Stanford UniversityRunning is one of the most affordable forms of exercise, but it’s also one that people love to groan about—and for good reason. It’s a high-impact sport that can be hard on the body, and that’s without factoring in however you might feel about your individual athleticism. But Stanford engineers have found a wearable exoskeleton that you can strap onto your ankle to help you run more easily, according to a study published in Science Robotics. The device was made to strap around your shin and attaches to a running shoe with a rope under the heel and a carbon fiber plate in the sole near the toe. To test its effectiveness, the engineers experimented with two types of running assistance: one that was motor-powered and another was that was spring-powered. Test subjects then ran on a treadmill with the rig turned off, with the motor-powered assistance, and then with spring-like assistance. The way the two modes work targeted different parts of the leg. The spring mode, like the name implies, works as if there was a spring parallel to a runner’s calf. That would save energy at the beginning of your step so you could unload it when you push off your toes. The powered mode works more like a bicycle brake cable, in that the motors tug a cable running at the back of the rig from the heel to the calf. What you end up with is better ankle extension at the end of a running step. Unsurprisingly, the researchers found that the motor-powered exoskeleton, once switched on, reduced the energy cost of running by 15 percent compared to running without it. They also found the powered exoskeleton could boost speed by as much as 10 percent. However, the study’s authors were surprised to find that the spring mode actually increased energy demand by 11 percent. “When people run, their legs behave a lot like a spring, so we were very surprised that spring-like assistance was not effective,” Steve Collins, a senior author on the study and an associate professor of mechanical engineering at Stanford, said in a press statement. “We all have an intuition about how we run or walk, but even leading scientists don’t really understand how people perform these activities.”Smart shoes, foot pods, and smartwatches comprise the bulk of running-focused wearables right now. The latter two don’t necessarily improve your speed just by wearing them, but they do give you metrics like stride and cadence that you can use to gauge your progress over time. Shoes are a different matter. A ton of research goes into their design, and small tweaks actually do make a difference. You only have to look at how Nike’s Vaporfly shoes shook the entire running world to see how technology can completely upend norms.But looking at this particular rig, you’d be forgiven for wondering who on earth might actually sign up to wear one of these things—even if it does make running easier and faster. After all, an exoskeleton isn’t exactly light, and researchers found running with it switched off was 13 percent more energy-intensive than just running in a pair of shoes. Future iterations would have to be much lighter to become viable beyond a research lab. And while many elite and hardcore runners will do anything to shave off a few seconds, you probably won’t see them donning exoskeletons at a race starting line anytime soon. That said, the researchers envision the exoskeleton as a way to help people get into running recreationally. According to Statista, only a quarter of Americans between 18 and 29 years old went for at least one run or jog in a 12-month period. That number dropped to 20 percent for adults between 30 and 49 years old.“These are the largest improvements in energy economy that we’ve seen with any device used to assist running,” Collins said.The exoskeleton won’t help people qualify for a marathon, Collins said, but it could help beginners keep up with more experienced friends. In the study, the potential effect was likened to electric-assist bicycles, which help beginning cyclists power up hills. The researchers also noted the device could be used to take make running easier for people like emergency responders who have to run for work.