Soft exosuit boosts runners’ performance

Science Daily gets muscle augmentation away from the whole “real-life Iron Man” thing with news of what looks like a pair of robotic shorts… a hip-helping soft, tethered exosuit that boosts athletes’ speed and energy by more than 5 percent:

A team of scientists in Walsh’s lab led by Wyss Postdoctoral Fellow Giuk Lee, Ph.D. performed the study with an exosuit that incorporated flexible wires connecting apparel anchored to the back of the thigh and waist belt to an external actuation unit. As subjects ran on a treadmill wearing the exosuit, the actuation unit pulled on the wires, which acted as a second pair of hip extensor muscles applying force to the legs with each stride. The metabolic cost was measured by analyzing the subjects’ oxygen consumption and carbon dioxide production while running.

The team tested two different “assistance profiles,” or patterns of wire-pulling: one based on human biology that applied force starting at the point of maximum hip extension observed in normal running, and one based on a simulation of exoskeleton-assisted running from a group at Stanford University that applied force slightly later in the running stride and suggested that the optimal point to provide assistive force might not be the same as the biological norm.

To clarify why applying force later in running stride improved metabolic expenditure so dramatically, the team analyzed what was happening to the subjects’ other joints when their hip joints were being assisted by the actuating wires. They found that the simulation-based profile also affected knee extension and the forces between the foot and the ground, while the biology-based profile did not. “The biological profile only takes into account the amount of torque in the hip joint, but the human body is not a series of independently acting parts — it’s full of muscles that act on multiple joints to coordinate movement,” says Lee. “Applying force to the hip affects the whole body system, and we need to consider that in order to give the best assistance.”

“[I]t will be interesting to see how much more the cost of running can be reduced with further optimization of the system,” says [corresponding author Philippe] Malcolm [of the University of Nebraska, Omaha]. “Our goal is to develop a portable system with a high power-to-weight ratio so that the benefit of using the suit greatly offsets the cost of wearing it. We believe this technology could augment the performance of recreational athletes and/or help with recovery after injury,” adds Lee.

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