Falls are one of the most common types of jobsite injuries in the United States and many of them involve the same simple element: a ladder. In fact, among construction workers, an estimated 81% of fall injuries treated in hospital emergency rooms involve a ladder, according to the Centers for Disease Control.
Despite the fact that they are often involved in accidents, there is little research on what constitutes a safe ladder.
To learn more, the National Institute for Occupational Safety and Health (NIOSH) recently selected a University of Pittsburgh professor for a $1.8 million grant to develop safer ladder designs and explore individual risk factors for ladder falls. The work, led by Kurt Beschorner, associate professor of bioengineering at Pitt’s Swanson School of Engineering, will focus on measuring friction and its role in influencing slip and fall risks on ladders.
If friction is too low between the ladder rung and the shoe or boot, then the foot can slip off of the ladder, leading to a fall, Beschorner said.
“A slip happens when there is insufficient friction between the shoe surface and ladder rung, but little is known about how ladder design or an individual’s body affects slip and fall risk,” said Beschorner.
The study will consist of human participant testing and mechanical testing. The human participant testing will look at different ladder climber populations (male versus female, obesity groups, height groups). The mechanical testing will enable researchers to determine how rung design influences friction. The team will combine human participant data and mechanics data to predict when a slip will occur.
“The available friction is the amount that occurs between a shoe and rung,” Beschorner explained. “When that value is less than the amount of friction that is required to complete a task, there is a risk of a slip-and-fall event.”
To measure the required friction, the research group will install force plate technology onto rungs and build a ladder around it. They will combine force data with motion data to better understand how various factors affect slips and falls.
For the available friction, they will use a device that simulates a slip under controlled conditions and measure how much friction is generated. They will create a slippery rung scenario with a harnessed participant to test whether an individual slips under these specific conditions.
Previous work from students in Pitt's Human Movement & Balance Laboratory found that groups at increased risk of ladder falls are older adults, inexperienced climbers and people with less body strength. The new study will build on these preliminary findings and will also extend the lab’s prior work on friction between shoes and walking surfaces to ladder slipping.
The past research has shown that the angle of the ladder influences the risk of slipping.
"Specifically, more friction was needed to prevent a slip for a completely vertical ladder compared to a ladder that it is at an angle," Beschorner said.
Researchers also found that fall risk after a simulated foot slip was higher for females than males, an effect that is explained by differences in upper-body strength. These preliminary results suggest that ladder design influences fall risk and that current ladders may be inappropriately designed for certain groups of ladder users, he said.