Award-winning study finds exoskeletons help forestry workers, but with stipulations

A new study has found that back-support exoskeletons could help forestry workers reduce back injury risks, but their effectiveness depends on the exoskeleton’s design and the posture required for the task.

The study, supported by the U.S. Department of Commerce and published in Applied Ergonomics, was among the first to focus on forestry workers. It received the Human Factors and Ergonomics Society’s best experimental paper award, given for innovative research on emerging topics in occupational ergonomics.

“We were interested in finding out if these devices can actually reduce work-related injuries or if the physical demands of forestry work—such as awkward cutting angles and the vibrations of a chainsaw—make them impractical for these workers,” said lead author Seobin Choi, PhD, a postdoctoral researcher in the Texas A&M University School of Public Health when the research was conducted.

For example, she said passive exoskeleton support engages only when the user’s body reaches a certain angle, and because forestry work requires cutting at different heights and using different postures, a device that helps while cutting at waist height might not be effective for cutting near the ground.

“In other words, exoskeletons don’t work for all working conditions,” said Choi, who is now an assistant professor at South Korea’s Incheon National University. “They may sometimes cause new problems with balance, muscle strain and freedom of movement and can also simply shift physical stress from the lower back to the legs or shoulders.”

For the study, the team tested how three commercially-available passive back-support exoskeletons—the Ottobock Back, HeroWear Apex and Laevo FLEX—affected loggers’ muscle strain and balance during simulated tree-cutting tasks.

The Ottobock Back and Laevo FLEX are rigid, with hard frames and mechanical joints, while the textile-based HeroWear Apex is soft and flexible, but all three are considered passive because they provide support through springs and elastic bands instead of batteries or motors. This also makes them lighter, more portable and more affordable.

Participants were 20 healthy, adult males. On average, they were 29 years old, 5 feet 10 inches tall and weighed 177 pounds. They were tested using each of the exoskeletons and without an exoskeleton on a secured mock-up tree that had cuts 4.72 inches deep and 10.6, 18.5 and 31 inches from the ground.

The researchers focused on three key areas: back strain (by measuring electromyographic activity in the muscles), effort (how hard the users thought the task was) and balance.

Their analyses yielded four general findings:

• Exoskeletons were most effective for chainsaw cutting at the middle height (18.5 inches). This is the only height that caused participants to bend their backs enough to trigger the device’s support mechanism.

• Rigid exoskeletons reduced muscle strain. At that middle height, rigid exoskeletons significantly lowered the amount of lower back strain and reduced how much the workers had to bend their trunks. The rigid Ottobock and Laevo models reduced muscle activity by roughly 18-35%, while the soft model provided less support.

• All exoskeletons relieved tiredness. Across the board, workers reported that the tasks felt less physically exhausting for their whole body and their lower back when they used the support.
• For balance, there was a trade-off. While the devices helped with back strain, they didn’t always make the workers more stable. Instead, they changed how the workers balanced themselves. The exoskeletons improved steadiness in side-to-side movements at the middle cutting height, but actually reduced steadiness in front-to-back movements at the same height.

“The exoskeletons did provide support in some cases during our simulated timber felling tasks, but they require a cautious approach when navigating the numerous obstacles and uneven, slippery ground in a real-world forest,” said the corresponding author and project principal investigator, Jeong Ho “Jay” Kim, PhD, an associate professor at the Texas A&M School of Public Health.

He said more testing in real-world forests is needed to address the issue of balance before exoskeletons become standard gear for forestry workers.

Others involved in the research were four colleagues from Oregon State University, including doctoral students Mina Salehi and Allen Chan, who were visiting research assistants at Texas A&M at the time of the study.