Finally: The Real Reason Your Shoelaces Always Come Untied

You’re not so bad at tying your shoelaces after all. A new study conducted at UC Berkeley proves that shoelaces come untied because of an inevitable force of nature. It’s not your speedy looping or lazy bunny ears.

The researchers used a slow-motion camera and a series of experiments involving a grad student running on a treadmill to prove that shoelace knot failure happens in a matter of seconds, “triggered by a complex interaction of forces,” says the study.

The stomping and whipping forces of your leg moving and foot hitting the ground are the reasons you have to keep bending over to tie that pesky shoe in the most untimely circumstances — like on the steps going up from the subway. “The forces act like an invisible hand, loosening the knot and then tugging on the free ends of your laces until the whole thing unravels,” the researchers explain.

 

“When running, your foot strikes the ground at seven times the force of gravity,” says the study. This causes the knot to stretch and then relax. Relaxing leads to loosening, and add the swinging leg, which causes a pulling force on the loose ends of the laces, and the laces can come undone in as few as two strides. This explains why when walking to the park, your shoelace knots seem completely intact, but of course as soon as you start running, when it really counts, they inconveniently come undone.

We know what you’re thinking: But that happens only sometimes. Certain knots are stronger than others. In tying, when not using the bunny-ear method, only one loop, the strength of the resulting knot depends on the direction in which you loop, swoop and pull. If the looping lace continues around the loop in the direction is it already going, the knot will last longer. If it goes under or over the loop, it’s weaker. It’s much easier to understand if you just try it on a pair of shoes. So go ahead and retie your shoes. We’ll wait.

In conclusion, certain knots are certainly stronger than others — the double knots we’ve been implementing since childhood are not (or knot, pun intended) for nothing. As are certain laces. However, the study proves that physics will untie all knots eventually. The important thing to know is, it’s not your fault.

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