Researchers at the Wyss Institute and John A. Paulson School of Engineering and Applied Sciences at Harvard University have developed a robotic exosuit that they say may represent an ideal platform for assisted running.
According to the researchers, the tethered soft exosuit may be able to reduce the metabolic cost of running on a treadmill by 5.4% compared to not wearing the exosuit. This could lead to new wearable technologies for athletes and consumers in the future.
“Homo sapiens has evolved to become very good at distance running, but our results show that further improvements to this already extremely efficient system are possible,” Philippe Malcolm, PhD, corresponding author of the study, which appears in Science Robotics.
A team of researchers led by Wyss Postdoctoral Fellow Giuk Lee, PhD, performed the study in the lab of Wyss Core Faculty member Conor Walsh, PhD, using 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, explains a media release from Wyss Institute for Biologically Inspired Engineering at Harvard.
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.
Confirming this suspicion, the researchers found that the simulation-based profile outperformed the biology-based profile in reducing metabolic cost by about a factor of two.
“Our finding supports a paradigm shift toward the concept that mimicking our current understanding of biology is not necessarily always optimal,” they write, per the release.
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,” Lee says, in the release. “Applying force to the hip affects the whole body system, and we need to consider that in order to give the best assistance.”
While the study’s results suggest that the increased biomechanical involvement of the simulation-based assistance profile is responsible for the reduction in metabolic cost, further biomechanical analyses are needed to confirm its findings.
“We only tested two actuation profiles in this study, so it will be interesting to see how much more the cost of running can be reduced with further optimization of the system,” says Malcolm, former Postdoctoral Research Fellow at the Wyss Institute and SEAS, and now Assistant Professor at the University of Nebraska, Omaha, where he continues to collaborate on this work, per the release.
“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,” Lee adds.
This study is a great example of how our team can quickly leverage its experience and expertise in wearable technology and biomechanics to demonstrate how human performance can be improved in new application areas,” Walsh concludes.
[Source(s): Wyss Institute for Biologically Inspired Engineering at Harvard, Science Daily]