A team of Iranian biomedical engineers has made an unpowered exoskeleton that reduces metabolic rate while running. The news is a major milestone in the science of human augmentation, where researchers have long been unable to craft a lightweight wearable device that improves on human metabolic rate during exercise.
Even powered exoskeletons have had difficulty improving on metabolic rate. In the mid and late 2000s, researchers from Ekso Bionics, one of the pioneers in the field of robot-assisted walking, had difficulty creating a robot that was light enough to wear but assistive enough to increase metabolic endurance. That the challenge has been so difficult to crack is a testament to the efficiency of the human body.
A number of unpowered exoskeleton devices are now on the market, including models from Noonee, Spring Loaded Technology, Cyberdyne, and Ekso Bionics. But those devices, while offering additional support or strength assistance, don't reduce metabolic rate.
The unpowered exoskeleton developed by the Iranian researchers reduces metabolic rate by 8 percent during running. It works by the recycling motion from the runner's "scissor kick."
"The reciprocal motion of the body recycles that energy, thereby allowing us to create an unpowered exoskeleton. No external battery is required, making the device lightweight and unobtrusive," said lead researcher Rezvan Nasiri. "Users do not need to run at a constant speed to achieve metabolic rate reduction."
Instead of motors or sensors, the lightweight device relies on a rotational spring system.
"The team in Iran has found a way to remap the structure of the musculoskeletal system with little more than a spring, essentially giving runners the equivalent of a new body part and an alternative pathway for exchanging energy, said Dr. Greg Sawicki, an Associate Professor of Mechanical Engineering and Biological Sciences at Georgia Tech, and head of the Human Physiology of Wearable Robotics Lab. "Their research has tremendous implications for our field, and I'm excited to see what develops as a result of this trailblazing work."
The research is especially tantalizing because it passively improves on a mechanical system that nature has already optimized.
"It has been incredibly hard to reduce energy costs of a physically intact human by adding a device to their legs," said Dr. Rodger Kram, Associate Professor Emeritus of Integrative Physiology at the University of Colorado, Boulder. "Achieving this is a tremendous breakthrough in the field of human augmentation because humans are so incredibly good at minimizing metabolic energy cost during locomotion. Until now, no one has been able to add a device to humans that could reduce that metabolic energy expenditure for running."
The results of the research were published this month in the journal IEEE Transactions on Neural Systems and Rehabilitation Engineering (TNSRE). Though the work is academic in nature, the commercial appeal of a device like the one created by the researchers is evident.
The global sports equipment market was valued at around $66 billion in 2016.