“They found that when walking, the combined impact and acceleration on a shoelace totals a whopping 7 gs—
“It took the interlaced effects of the two forces [impact and swinging side-to-side] to undo the knot: the repeated impacts loosened it while the changes of direction pulled on the laces.”
Now you know.
https://www.scientificamerican.com/article/unravelling-why-shoelace-knots-fail/
Tucking the laces in works pretty well, too, much better than the double-knot:

