How do cushy running shoes cause stress fractures in the foot? Well, that is a great question and that is what we’re talking about today on the Doc On The Run Podcast.
If you have a high arched foot that is prone to getting stress fractures, a podiatrist may have told you that you need cushy running shoes, and I got a question from someone who was given that advice. She said, “I am so confused, I thought stress fractures were from pounding. I got a stress fracture, and my doc said it was my cushy shoes. I do not understand how this is true.”
Okay, cushioning is supposed to protect you from axial loading. How does it do that? Well, it does that the same way that an airbag in a car decreases injuries when you have an accident. When you get in an accident, if you’re not wearing a seat belt and you suddenly stop, the car stops moving. You become a human projectile, and you continue moving and then slam into the steering column or the dashboard or the windshield or whatever is in front of you. That causes injury.
It causes injury because when you hit something hard like a steering column or dashboard or windshield, you come to a very sudden stop. The same reason that stuntmen can jump off of buildings and land on a huge airbag is because it takes time for them to decelerate over the length of that airbag. Same is true when you hit the inside of an airbag, in a car, in an accident. Same is true when you land running on your running shoes. The cushy shoes absorb impact over a longer distance than if you landed barefoot on concrete, that is a very short distance.
The amount of force is the same but the time that it occurs over is decreased when you have a very short distance and when you increase the time that you land in a soft cushy surface, it decreases the overall load because of the time that it’s applied. What increases though is something else. When you land on cushy shoes, if you have an unstable foot type or your foot moves, wobbles, wiggles, whatever in the shoe because it’s cushy and squishy, especially if it’s worn out and it wobbles even more once it’s worn out, then in that case you might be over pronating or actually trying to fight that pronation and that movement by holding everything really still. That could cause stress fractures two different ways.
One of them is if you make your foot rigid by holding it still, you can get a stress fracture the same way that somebody with a more rigid foot type would get it. The other way is that stress fractures are not just caused by landing on a surface and banging it over and over and over. They also can be caused by the muscles that stabilize the bone pulling what we call contractile forces where obviously if you do biceps curls, if you grab weight, you pull it up, the muscle contracts.
The muscle contracts by pulling on one bone where it attaches and the other bone where it originates. So, it’s pulling on both places where the muscle starts and ends and all the little muscles in the foot that are trying to stabilize those bones can pull and tug so much that it causes inflammation in the bone that leads to a stress reaction and subsequently a stress fracture. That is why if you have an unstable flexible foot, you don’t really want cushiony shoes because you will then flex and move and stretch things more and your foot has to work harder with those muscles pulling on the bones that could lead to a stress reaction or a stress fracture.
Great question and sorry to have this issue but it’s important you understand the difference between those shoes. Also, super important you understand the severity of the injury. If you have a crack in the bone, that is a stress fracture. If you don’t have a crack, that is a stress reaction. Got to know the difference. If you don’t know the severity of your injury, you’re never going to get better as fast as possible.
If you want to do a deep dive into stress fractures and stress reactions in the foot in runners, I put a thing together for you. It’s only for runners. If you’re not a runner, don’t show up. You’re wasting your time, it’s only for runners. It’s the stress fracture masterclass and you can come join me for free in that training. It’s almost an hour long at www.docontherun.com/stressfracturemasterclass. So, come check it out and I’ll see you in the training.
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