Some things are better after they’re broken in (jeans, shoes, husbands). But once a sports bra has broken down, it should be tossed out. If it’s consistently air-dried (hot tumble dry-ing ruins Lycra), a sports bra should last about 100 wearings.

Not keeping tally? Here’s how to know when it’s time to send your old jog bra the way of those Jazzercise videos.

Perform a stretch test. Gently tug the elastic straps and band. If you don’t feel any resistance, buy a new bra.

Compare the old and the new. Stack a new sports bra on top of a similarly styled old one. If the old bra has a wider band and longer straps, throw it out.

Go with your gut. “When a sports bra loses its oomph, you risk developing motion-related sagging,” says LaJean Lawson, an exercise-science researcher at Oregon State University, in Corvallis. A sports bra provides almost twice the support of a regular bra. For a quick test, jog in place wearing a normal bra, then a sports bra. If your breasts don’t feel significantly more secure, get a new one.