TSS High School High School Engineering

Why Do Shoelaces Untie Themselves?

Even though there are so many different ways to tie your shoelaces, most knots tend to undo themselves only in a matter of time.

Shoelaces are one of the most exasperating and troublesome objects people deal with in their daily lives. From Sawtooth to Loop Back to Zipper, there are tons of different methods to tie shoelaces. Even though there are so many different ways to tie your shoelaces, most knots tend to undo themselves only in a matter of time.


In order to find out why even the best knots fail to stay tied, a research team mechanical engineers at the University of California, Berkeley gathered a volunteer to run on a treadmill. By allowing the runner to run on the treadmill, acceleration, or G-Force, was measured by putting accelerometers on the runner’s shoes. The researchers also used a slow-motion video to capture the moments in which the knots came undone. they were able to conclude that there were two key steps in which the shoelaces unraveled. The first was a gradual process of “slipping” as the knot came undone, and the other key step was a “catastrophic failure” in which the knots came undone completely. The researchers also concluded that surprisingly, the G-force that the shoelaces experienced was higher than that of a rollercoaster.


In order to measure the time and rate of how fast the shoelaces became undone, the team borrowed some of the lab equipment in order to design an experiment. The researchers designed a mechanical pendulum in which the pendulum would portray a human’s leg also the impact it has when the feet touches the ground. The researchers were also able to calculate for the speed at which the runner’s run by adding weights on the shoelaces. This experiment helped the researchers see which knot would be sturdier: the Granny know or the Square knot. In the end, the researchers were able to conclude that the “Pendulum experiment” id support the first experiment as the shoelaces came undone at a gradual rate. However, both key factors were required as the laces eventually came undone more rapidly at a faster rate.

Although the scientists were able to conclude on how the shoelaces became undone, it is still unsure about why one know is more sturdier than the other. Most believe it is due to the higher tension that is created when the knot is tied. However, this research has been a key factor in the medical field as the research will be used for future DNA knots and other microscopic knots that will help change the technology of the future.


1. Weisberger, Mindy. “Why Do Shoelaces Come Untied? Science Explains.” LiveScience, Purch, 11 Apr. 2017, https://www.livescience.com/58649-why-shoelaces-untie.html

2. Israel, Brett. “Shoe-String Theory: Science Shows Why Shoelaces Come Untied.” Berkeley News, 28 Feb. 2018, http://news.berkeley.edu/2017/04/11/shoe-string-theory-science-shows-why-shoelaces-come-untied/

3. Hersher, Rebecca. “Untangling The Mystery Of Why Shoelaces Come Untied.” NPR, NPR, 17 Apr. 2017, https://www.npr.org/sections/health-shots/2017/04/17/523636317/untangling-the-mystery-of-why-shoelaces-come-untied

4. ChrobakApr, Ula, et al. “Why Do Shoelaces Untie Themselves? This Team May Have the Answer.” Science | AAAS, American Association for the Advancement of Science, 19 Dec. 2017, http://www.sciencemag.org/news/2017/04/why-do-shoelaces-untie-themselves-team-may-have-answer

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