Be prepared when breaking in new running shoes.

For over two years, I was devoted to my Adidas Ultraboost shoes. I ran my first two marathons in the first-generation, uncaged version and swore by their lightweight, knit uppers and cushioned foam soles. Then I ran my third marathon in New Balance Fresh Foam 1080s, which felt even more supportive without adding any bulk—I continued running in them for almost a year.

But recently, while training for a half marathon in the 1080s, I decided I didn’t need so much support and switched back to my Ultraboosts for a quick 5K. But the shoe that I used to swear by suddenly murdered my feet.

My shoes are my lifeline in the sport, so the possibility that my favourite running shoes wouldn’t work for me anymore made me start to panic.

But as it turns out, there’s a right way to transition sneakers.

As much as any runner loves their tried-and-true shoes, they’re eventually going to have to replace them. That’s because, “over time, and depending on what surfaces you run on and how hard you are on your feet, your shoes will break down,” says running coach John Honerkamp. It used to be that companies recommended replacing running shoes after 500 kilometres. Now, materials have gotten more advanced and more durable, so they can handle even more wear and tear.

“Once you break in most newer shoes—which only takes about 10 kilometres —they’re stable for at least 650 to 800 kilometres,” says biomechanist Martyn Shorten, Ph.D. Other shoes can last even longer.

If you’re replacing your old pair with the exact same shoe, “sneaker technology has evolved enough that you don’t need to spend as much time breaking them in,” Robinson says. “You’ll be able to wear those kicks fresh out of the box.” Sure, the shoe might feel a little stiffer than your broken-down pair, but your feet will already be used to the particular specs of that style.

But if you want to shake things up—maybe you want more support, you want to try a new brand your speedy friend recommended, you’re just sick of your old shoes, or a company discontinued your favourite style—it’s less about breaking in the shoe and more about breaking in your body, Shorten says.

“Your body can and does adapt to different shoes over time, but the key is to avoid sudden changes,” he says. “I wouldn’t recommend throwing out your old pair and immediately jumping into your new pair—make that transition over a period of a couple of weeks.”

That means you shouldn’t just toss your old shoes for a new pair as soon as you feel them breaking down (when you notice heavy wear on the soles or your toes poking through the uppers, or that you’re feeling more aches and pains or soreness in your feet, shins, or knees), Honerkamp says. As soon as you see or feel any of those telltale signs, though, that’s when you should start shopping. Once you find the right pair, keep running in your old shoes for another four to six weeks and start working in your new ones.

Don’t go too hard on your first few runs in those shiny new kicks either. “Start with an easy paced five to ten kilometre run,” Robinson says. “Give yourself time to understand what’s going on with the relationship between the shoe and the sweat and the legs.” Then, as your feet adjust, you can slowly build up your mileage until things feel A-OK.

If you’re not swapping your old shoes for a fresh version of the same style, be smart about the shoes you switch to. Good running shoes don’t come cheap, so it’s important to seek out a pair that really works for you—not just the pair someone swears will take three minutes off your PR.

And make sure you test them out first. “I’ve noticed that we’re really in a moment where we’re going on feeling—a lot of brands are shifting the focus to how the shoe feels versus certain features, promises, or even aesthetics,” Robinson says. Because this is a case where first impressions really matter, “most running specialty stores will allow you to run in the store or even outside the store to test a pair,” Honerkamp adds.

“Base your decision on how comfortable you feel in the shoes,” Shorten says. “If you put it on your foot and it doesn’t feel right, that’s a good indicator of whether or not it will work for you.” And when you do buy a pair, Honerkamp recommends doing your first run on a treadmill so that you can return them if they don’t work well after a few kilometres.

Treadmill trial run or not, you need to ease into your new shoes. That’s because when your foot is used to a certain level of support, stiffness, or flexibility, changes at the ground level can have serious effects all the way up your body. Picture this: If you get a new shoe with a lot more cushion than your old shoe, that sole is going to be thicker, which means you’re probably going to have to pick your foot up a little higher than you’re used to—otherwise, you’ll trip. It might take a run or two to get your bearings.

“A lot of these shoes have so many features that there might be something going on in the shoe that’s working against your stride in a subtle way, so you need to feel it out,” Robinson says.

Whatever running shoes you choose, your body will adapt. You just need to be smart about the process and patient enough to let your feet catch up to your fancy new kicks.

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