Sneakers, gym shoes, tennis shoes, trainers — whatever you call them, those athletically-inclined shoes on your feet can probably be washed in the washing machine. Really. But almost no one I know does it.
Rather, most of my peers wear shoes until they get unacceptably dingy, then buy new shoes, on the mistaken belief that dirty shoes are “worn out.” But they’re probably not. They’re just dirty. So wash them.
First, take out the laces. You’ll wash the laces in the same load. They’ll get twisted and tangled no matter what you do. But they’ll get clean.
Take out the foam inserts. They won’t get clean, and might fall apart. Consider replacing them with new insoles.
Use half the normal amount of detergent. You won’t need more, because you’ll also…
Add one scoop of an oxygen bleach, like Oxy-Clean. This is the secret ingredient that makes them look new-ish.
Wash them on a normal cycle, warm water, with a towel to dampen some of the banging.
Let them air-dry, unless you have a special rack for your dryer.
I’ve had success with every pair of shoes I’ve washed, but can’t guarantee you’ll have the same luck. Leather, suede and such variants might dry out or crack. The worst-case scenario is that washing the shoes will cause them to fall apart or become unwearable. But considering they were more-or-less unwearable when you put them in the machine, that’s not such a loss.
Real running shoes — the kind you take out on the road — do have an expiration date, a point at which the the foam and shock-absorbing features break down. So keep in mind that washing these shoes could hasten their demise, or at least mask the signs. But once retired from “real” running, these shoes are probably fine for normal wear.
When your shoes finally pass into a zone where you just don’t want to wear them anymore, make sure to donate them to charity. Shoes that most Americans would consider worn-out are always needed in poorer parts of the world.