Whether you’re hitting your stride during your daily jog, getting your groove on doing Zumba or taking a spinning class, you should have a good-fitting sports bra. “Breasts that aren’t fully supported can move up and down a couple of inches during a workout,” says Jené Luciani, author of The Bra Book. Too much movement upfront can lead to back problems and saggy boobs—no one wants that. Follow this advice to find the best fit for you.
Know your size. An estimated 80 percent of women wear the wrong bra size. Not just sports bras, but everyday bras, too. To find our your correct measurements, go to a department or lingerie store where trained sales staff will measure you to get you in the right width and cup size. It's the size to look for in a sports bra. While you can get sports bras at regular department stores, you'll find a much better selection get at a sporting goods store. Some sports bras are sold in small, medium and large, so check the tags for correlating cup sizes.
Pick the best style for you. Compression bras press your breasts close to your chest. “You usually pull these over your head,” says Leanne Hand, an Atlanta bra fitter with more than 10 years of experience. “They work great for smaller cup women, but can give a uniboob appearance.” Larger-busted women need encapsulation bras—they look like traditional bras—that have two defined cups that compress and support each breast individually just. You can find them with and without underwire.
Look for good straps. You’ll get more support the closer the straps are to the center of your back (like a racerback). Width also counts—wider straps are more supportive than thin ones.
Consider your sport. High-impact sports like running and kickboxing require more support than lower-impact ones like biking and yoga. Encapsulation bras always provide greater support, but you can find compression bras designed for high-impact sports.
Try it on. You’ve got the right size and style, now you need to test it out before you buy it. Put it on and jump up and down or run around the dressing room for and do a couple of jumping jacks (Come on! Nobody is watching!). The elastic band on the bottom of the bra should stay snug around your rib cage, but it shouldn’t be so tight that it restricts your breathing. “You want your breast tissue to stay close to your chest wall, so when your rib cage goes up or down, your breasts go up or down too,” says Hand. “You don’t want any independent up-and-down or side-to-side movement.”
Get the right fabric. Always go for moisture-wicking material like CoolMax or polyester (not cotton) that absorbs sweat away from your body stretches and moves comfortably with you without chafing.
Replace your sports bra at least once a year. “Definitely toss it when the elastic band is super stretchy, the material is pilling, or the hook-and-eye clasp has too much give,” says Hand. Your sports bras will last longer if you wash them in a closable lingerie bag in the gentle cycle and hang to air dry.
A version of this story originally appeared on iVillage.