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Mechanical engineers from the University of California Berkeley found out the reason why a shoelace knot becomes untied in a series of experiments that used ultra slow-motion cameras to capture the mechanism how the shoelaces unravel.

The research aims to shed more light into knotted structures and why they fail, much like DNA and why a shoelace knot becomes untied. Christine Griggs, the co-author of this study, donned her running shoes while the research team filmed her shoes as she ran on the treadmill using slow-motion cameras. They found out that when running, the foot strikes the ground with a force that is seven times the force of gravity. As this force stretches the knot on the shoelace, the swinging motion of the leg applies a force on the free ends of the shoelace much like a hand pulling on the ends of the shoelace, BBC reported.

Study co-author Christopher Daily-Diamond that for the shoelaces to unravel, you would need the impulsive force at the base of the knot and the pulling force of the free ends of the shoelace.

The researcher team tested their theory with different types of shoelaces to test knot mechanics to delve deeper as to why a shoelace knot becomes untied. They also used weights at the ends of the shoelaces that swung from a knot and found out that knots failed faster as the inertial forces on the free ends increase, Berkeley News reported.

The engineers believe that studying knots from a mechanics perspective will be the basis of future research as to why similar structures have different structural integrities. The same kind of baseline has been developed in understanding the failure of knotted structures under sustained loads. They will then be able to show how knotted structures fail under dynamic pressures of changing forces and loads and translate it to microstructures like the DNA.