Shoelaces.They're great for keeping shoes on our feet, and yet seem to come undone usually without warning at the most inconvenient of times.
Most children are taught to tie their shoelaces in two stages, the starting knot followed by the finishing bow.
The direction that you carry out these two stages results in two different types of knot.
The easiest way to tell which knot you use it to tug the sides of the shoe apart and look at how the bow sits.
If the bows are crooked and lie more in line with the toe and heel then it's likely that you use a granny knot.
However, if the bows on your tied laces sit horizontally across the shoe and look more balanced, then you probably use a square knot.
This and other fascinating shoelace tying information came from a new paper published in the proceedings of the Royal Society called The roles of impact and inertia in the failure of a shoelace knot.
The study focused on the phenomenon where a securely tied shoe suddenly transforms into a trip threatening, flapping lace shoe.
It found that the probability of this happening increased if you tied a granny knot as standard and if you participated in activities such walking around the office or running for the bus.
In the study, researchers set up a series of experiments where a runner was instructed to tie her shoes either using a Granny knot or square knot.
Although they look the same, the composition of the two knots is subtly different.
Square knots are tied by crossing the lace in your right hand in front of the one in your left hand and then threading it under the left one.
For the bow you repeat the process, but crossing the end that's now in your right hand behind the one in your left with added loops to make the bow.
Granny knots have the same overhand motion which is repeated for the knot and bow.
After tying her shoes, a high-speed camera was used to film the runner as she walked and ran on a treadmill.
Once the biomechanics of her human gait were determined, a mechanical leg designed to swing and stomp like the runner was used to measure which movements and forces were required to indirectly untie a shoelace.
From their experiments, they found that shoelaces need to be exposed to foot stomping and swinging to become untied, both of which are experienced when walking and running.
They also found that the act of just swinging your legs without stomping, such as when swinging legs under a chair did not untie the shoelace.
Video evidence showed that the force generated from stomping the foot on the ground when taking a step gradually loosened the knot while the swinging motion of the foot required to take the next step created forces that tugged the ends of the laces.
Once the knot was loosened and the ends had started to slide, the frictional forces were reduced, which accelerated the loosening, and the knot unravelled.
The study concluded that shoelace knots tied with a granny knot only take a few seconds to untie and involve just two to three strides.
Granny knots were also found to be more likely to untie by a factor of five when compared to the square knot tied laces.
So, the next time you tie your shoelaces and want to keep them more secure using science, just remember to use this rhyme: Right over left, left over right, makes a knot both tidy and tight.