Back-saving Underwear And The Magic Of Assistive Fabric

The word "exosuit" conjures images of Tony Stark or any of a growing number of powered exoskeleton products from companies like Ekso Bionics and Sarcos. I'm bullish on the future of such devices in applications like construction, but it's another kind of exosuit, one that doesn't rely on power, that's likelier to enter the market in a significant way. 

These exosuits are unpowered and low-profile, relying on elastics and biomechanics to ease to strain in lightweight, low-cost assistive devices that (unlike the copper-infused garbage peddled on infomercials) actually work. 

A new article in the Nature journal Scientific Reports describes one such device designed to be worn under the clothes and promising reduced fatigue in lower back muscles on the order of 29-47 percent. The article, "Low-Profile Elastic Exosuit Reduces Back Muscle Fatigue," comes from researchers at Vanderbilt University. Led by Assistant Professor of Mechanical Engineering Karl Zelik and recent Ph.D. graduate and primary author Erik Lamers, the researchers employed surface electromyography to measure changes in low back muscle fatigue in male and female participants to arrive at their findings.

"These findings show how exosuits could provide valuable back relief to frontline and essential workers who have been taking a physical toll and supporting all of us throughout this pandemic. What we learned has the potential to shape the biomechanical and industrial standards of future wearable technologies," said Zelik, who holds secondary appointments in biomedical engineering and in physical medicine and rehabilitation.

The low-profile exosuit employs elastic to provide assistive forces in coordination with the extensor muscles of the lower back, which are subject to strain and pain during repetitive use. The device also relieves strain on the spine, greatly reducing the risk of inury. In one finding, a the act of holding a 35-pound weight (about the size of my increasingly-hard-to-hoist son) was made less tiring than holding a 24-pound weight (coincidentally, about the size of my much more packable daughter). 

"Wearables are going to change the way we work and live, and we want to improve safety, health and well-being for everyone. One of the critical challenges moving forward will be to ensure that all wearable technology is developed to serve and protect both women and men. We are thrilled that this research helped lead to the first commercial exosuit or exoskeleton designed with both male- and female-fits," said, himself a former long jump and triple jump athlete.

The fascinating takeaway here is that the suit relies not on sophisticated sensing equipment and actuated joints, but a simple elastic band and a deeper understanding of how muscles like the lats, which manipulate the shoulder joint, are called on to take some of the strain when the main back extensor muscles tire. The suit's elastic band kicks in during lifting in the same way.

"The lats act sort of like an exosuit. When a person's low back muscles become over-strained and fatigued, they summon extra assistance from their lats to relieve this back strain and fatigue. The elastic bands in our exosuit work the same way to help sustain endurance and strength," said Lamers, a National Science Foundation Graduate Research Fellow who worked in Vanderbilt's Center for Rehabilitation Engineering and Assistive Technology.

Zelik, a former collegiate athlete who competed in the long jump and triple jump, knows firsthand how intensive physical activity can fatigue the body. He also understands the importance of ensuring that the exosuit and its utility are built with inclusive design practices. "Wearables are going to change the way we work and live, and we want to improve safety, health and well-being for everyone. One of the critical challenges moving forward will be to ensure that all wearable technology is developed to serve and protect both women and men. We are thrilled that this research helped lead to the first commercial exosuit or exoskeleton designed with both male- and female-fits," Zelik said.

The research, which may yield a pair of back-saving underwear in the future, was supported by Lamers' NSF Graduate Research Fellowship and a Vanderbilt University Discovery Grant. Researchers Aaron Yang, an assistant professor of physical medicine and rehabilitation at Vanderbilt University Medical Center, and two Vanderbilt undergraduates, Juliana Soltys and Keaton Scherpereel, collaborated on this study.