Just do it — the right way
Researchers reveal how to keep laces tied
Scientists, who have studied most things, have now studied why shoelaces come untied.
A two-year project at UC Berkeley also has found that a lot of people don’t know the best way to tie their shoes, including the scientist who performed the study.
“I’d been doing it wrong,” said study co-author Christine Gregg, a mechanical
engineering student. “This could be the most useful thing I learned in grad school.”
Gregg, a recreational runner, had become curious about why her sneaker laces kept coming undone. So, for two years, she and fellow student Christopher Daily-Diamond photographed their shoelaces, filmed their shoelaces, videotaped their shoelaces, and got down on their hands and knees to study every last little thing about their shoelaces. They ran on treadmills and ran down the university hallways and tied and retied their shoes countless times.
“We spent hours and hours,” she said.
Gregg found that shoelaces come undone because a shoe strikes the ground at seven times the force of gravity, stretching and relaxing the knot. The loosened knot is further undone when “the swinging leg applies an inertial force on the free ends of the laces,” according to the research.
“To untie my knots, I pull on the free end of a bow tie,” Gregg said. “The shoelace knot comes untied due to the same sort of motion — the inertial forces of the leg swinging back and forth while the knot is loosened from the shoe repeatedly striking the ground.”
Gregg, 26, a fourthyear doctoral student from Wilmington, Del., whose earlier research involved typing a letter by blowing on a flute, said her findings could lead to great things. Perhaps surgeons could use her knot research to improve the way they tie sutures during an appendectomy. Perhaps geneticists could better understand how DNA strands become entwined.
“We’re just at the beginning of understanding what this means,” she said.
On a practical level, however, there was one key finding for all shoelace users. Gregg found that there is a strong shoelace knot and a weak shoelace knot. Many people tie the weak knot because they don’t know any better.
To tie the strong knot, hold an end of the shoelace in each hand. Wrap the left end over the right end and pull it through. Make a loop with the right end, hold it in your right hand and wrap the left end around it clockwise, not counterclockwise, before pulling it through to finish the knot.
The resulting knot should align along the width of the shoe. That’s a stronger knot, Gregg said, than one that aligns along the length of the shoe — the kind of knot that Gregg used to make before she did the study.
“It may seem frivolous, but I think it’s important,” Gregg said. “It’s basic science. No one really understands how entangled structures interact. This is a first step toward a greater awareness.”
Professor Oliver O’Reilly, whose lab conducted the research, said he sought nothing less than “understanding knots from a mechanics perspective.” But even after two years, he said he did not understand why the clockwise-wrapped knot was stronger than the counterclockwise one.
“We still do not understand why there’s a fundamental mechanical difference between those two knots,” O’Reilly said.
The study was published Tuesday in the journal Proceedings of the Royal Society A of London alongside articles about airbags, tsunamis and the Japanese art of paper folding.
“This is a first step toward a greater awareness.” Christine Gregg, UC Berkeley researcher