You’ve heard of string theory – the scientific framework that explains the origin of the universe, now meet shoestring theory – the scientific reason behind why pesky shoelaces come undone.

The conundrum that has tripped up runners, paused important conversations and caused general inconvenience and annoyance for centuries (the first shoes laces date back to 3,500BC), was unravelled by hardworking mechanical engineers at UC Berkeley (University of California, Berkeley) through a series of experiments using slow-motion cameras.

Here’s what they found: when we run our feet strike the ground at seven times the force of gravity and the knot stretches, relaxes and loosens in response to that force – remember Newton’s ‘every action has an equal and opposite reaction’? Then the swinging action of our legs acts like an invisible hand, tugging the ends out from the loose night finally making it completely unknot.

While the study answers a whimsical headscratcher that has bothered humankind for years, there’s a serious scientific reason why it was undertaken: ‘when you talk about knotted structures, if you can start to understand the shoelace, then you can apply it to other things, like DNA or microstructures, that fail under dynamic forces,’ said Christopher Daily-Diamond, study co-author and a graduate student at Berkeley. (UC Berkeley News)

The research involved Christine Gregg, a co-author in the study and a runner, jog on a treadmill in a pair of laced-up running shoes while her colleagues filmed what happens to her shoes.

The study which was published on April 11 in the journal Proceedings of the Royal Society A, aims to understand knots from a mechanical perspective and the kind of pressure and load that causes them to fail.

So are there any fail proof knots, then, like the square knot that sailors swear by?

The researchers conducted tests on both the trusted square knot and the regular bow-tie knot, but both came to the same sorry end. While some materials of laces are better for tying knots, the all eventually came undone because of the same reasons, scientists explained.

The good news is, there’s always Velcro.