Designing “Smart Underwear” to Prevent Workplace Back Injury

New “smart underwear” developed at Vanderbilt University Medical Center may reduce load and fatigue on the back.
New wearable device combines proven assistive technology and digital innovation.

Wearable devices are seeing massive growth at the same time as back pain is on the rise—complicated by the risk of opioid reliance in treatment. Recognizing an opportunity in the wearables movement, Karl Zelik, Ph.D., assistant professor of physical medicine and rehabilitation at Vanderbilt University Medical Center, set out to design a new solution for back injury prevention during heavy lifting.

“The vision for this device is that it seamlessly integrates into your life so you can wear it comfortably and only engage it when you need the assistance,” Zelik said. Based on the simple concept of recruiting stored energy in a spring, Zelik designed a device dubbed “smart underwear” that is light and comfortable, and can be controlled easily by the wearer to assist in lifting.

“The goal is to reduce the risk of injuring the back in the first place,” said Aaron Yang, M.D., medical director of outpatient services at Vanderbilt Stallworth Rehabilitation Hospital and co-investigator on the device. “I see people in certain occupations that are more susceptible to back injuries from prolonged or repetitive movements, such as health care professionals who stand or lean for long periods of time. For these people, this device may have preventative implications.”

The Problem with the Back

Back injuries account for 20 percent of all workplace injuries, forming the single largest category of worker’s compensation injury. Previous efforts to spare the back through various interventions and devices have made little headway. As long ago as 1996, the National Institute of Occupational Safety and Health (NIOSH) declared that the ubiquitous lumbar back belts employers have relied upon for decades showed no evidence of preventing back injury. A larger retail study in 2000 arrived at the same conclusion, though the news seems to have had little impact on employers with scarce alternatives.

For fatigue reduction and injury prevention, a worker could wear an exoskeletal suit, which is made from metal struts and has built-in motors or springs for offloading weight on the lower back. However, exoskeletons are often heavy, bulky, and protrude out from the body. Because they are impractical to wear through normal daily activities like sitting down, the main adopters to date have been automotive manufacturers whose workers do repetitive tasks while standing in one spot.

How “Smart Underwear” Works

Zelik’s smart underwear, in contrast, is wearable throughout the day and wherever the worker goes without interference. The device works through two springs, attached in series and embedded in clothing, starting in a form-fitting vest, going down through a panel along the back, into pant legs that resemble boxer briefs. A thin, weak spring that extends from the shoulders to the mid-back enables normal movement when the device is not engaged. This spring connects to a stiffer spring extending from the mid-back down to the upper thighs that provides support assistance.

The wearer can engage assistance by either turning a dial, tapping the vest or using an app that activates the clutch set between the two springs. This clutch forces the wearer’s movement through the stiff spring only. “The device redirects some of the force through the clothes, so there is both redistribution and reduction in the force on the user’s back,” Zelik said.

Based on laboratory experiments using muscle activity sensors, the prototype offsets between 14 and 43 percent of the load on the lower back, depending on the task. The device was put to the test in loading, unloading and holding tasks, offering the most support when the wearer is leaning and lifting.

“You can think of reducing load on the back as being most related to injury risks, whereas reducing fatigue is more related to long-term productivity and the well-being of the work force.”

Zelik’s team also has a new study under peer review showing the device can reduce the rate at which lower back muscles fatigue by up to 80 percent. “You can think of reducing load on the back as being most related to injury risks, whereas reducing fatigue is more related to long-term productivity and the well-being of the work force,” Zelik said.

Next Steps

Zelik and Yang look forward to field tests soon with partners in the retail, automotive, manufacturing, logistics and healthcare industries. “These industries are full of people with physically demanding jobs—nurses, package handlers, people in factories and warehouses who do a lot of lifting and leaning,” Zelik said. The potential savings to employers are enormous. “There are the medical bills, the missed work and the impact that losing trained people has on employers.”

The personal cost is, of course, tremendous as well. “Back pain changes everything – whether you go home and play with your kids, socialize or not, work around the house. Chronic back pain is a vicious disability,” Zelik said.

For their next design, Zelik’s team is funded through an NIH R01 grant to integrate embedded sensors that activate the device’s resistance autonomously. The sensors also will accumulate data and issue warnings when the wearer is overexerting.