Most runners tie a shoelace bow that comes undone twice as often as the strong version; the fix is to wrap the second loop the other way.
the5krunner’s take: Look at your bow on the next run: if it sits along the shoe rather than across it, you are tying the weak knot, and switching is a 2-second habit to learn that could save you 30 seconds in a race. Or you could buy elastic laces!
- Mechanical engineers at UC Berkeley filmed a runner’s laces on a treadmill at 900 frames per second to see why knots fail.
- Each footstrike hits the knot at about seven times the force of gravity, stretching and relaxing it. At the same time, the swinging leg whips the loose ends and pulls on them.
- It takes both together. Stomping without swinging, or swinging without stomping, leaves the knot tied.
- Nothing happens for a long time, then the knot fails in seconds. Once it starts to loosen, the laces can be fully undone in two more strides.
- The weak bow, based on a granny knot, twists and points along the shoe. The strong bow, based on a square knot, lies flat across it. In a 15-minute run, the weak bow failed twice as often.
- To tie the strong one, cross left over right as usual, make the first loop with your right hand, then wrap the other lace clockwise around it before pulling through. Most people wrap anticlockwise. If you start right over left, reverse the wrap.
For runners: a loose lace is a potential race-day disaster
In training, a lace that comes undone costs a stop and a few seconds. In a race, it costs the time to retie, and on a busy course a dragging lace is a trip hazard. Even the strong bow fails eventually, so for racing add a double knot or a heel lock, which also takes some of the pull off the bow. Triathletes and duathletes sidestep the whole problem with elastic laces, which is why they rarely tie anything in transition.
Quick answers
Why do my shoelaces keep coming undone when I run?
Each footstrike loosens the knot while the swinging leg pulls on the loose ends. Once it starts to slip, it can fail within two strides.
How do I know if I tie the weak shoelace knot?
Look at the finished bow. If it twists and points along the shoe, it is the weak version. The strong version lies flat across the shoe.
Related: running shoe lacing that fixes heel slip and black toes and top 10 triathlon race tips.
Source and original research by: the5krunner and UC Berkeley.
If you enjoyed this quick read, here are three more in the series:
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- Huawei Sense G1 – Continuous Blood Glucose (Invasive)
- Runna caps seven-day plans to cut injuries
Last Updated on 14 November 2026 by tfk the5krunner
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tfk is the founder and author of the5krunner, an independent endurance sports technology publication. With 20 years of hands-on testing of GPS watches and wearables, and competing in triathlons at an international age-group level, tfk provides in-depth expert analysis of fitness technology for serious athletes and endurance sport competitors. See the gear tfk uses. ID
