In a world filled with adorable athletic gear, gym-friendly underwear gets surprisingly little attention. There are thousands of reviews on Amazon pointing you toward the best sports bras — but how do you pick the right knickers for your morning spin class or lunchtime Pilates sesh? And, heck, do you even need ’em? Surely there’s enough judgment at the gym without adding visible panty lines to the mix.

As it turns out, doctors have their own criteria for determining the best underwear for your workout — and you might want to listen up. We checked in with the experts to learn how your exercise habits can affect your health *down there.*

woman doing yoga

Exercise and vaginal health

Dr. Angela Jones, an OBGYN and Astroglide’s resident sexual health advisor, points out that the sweat and heat generated by your workout can set you up for a slew of unpleasant symptoms. “The key thing to keep in mind regarding vaginitis [inflammation of the vagina, including bacterial vaginosis, yeast infections, and trichomoniasis] is that warm plus moist is a direct setup for vaginitis,” she says. “This is what all women try to avoid.”

That’s because yeast and bacteria thrive in a warm, moist environment, explains Dr. Alyssa Dweck, a New York-based OBGYN who works with urinary, bladder and vaginal health brand AZO. (We apologize for repeating everyone’s least favorite m-word — it won’t happen again.)

Both docs advise getting out of your exercise gear ASAP after a workout. (This rule also applies to swimsuits, so remember to bring a spare if you’re hanging at the beach this summer.)

Picking the right pair

Dr. Dweck and Dr. Jones both suggest picking breathable, lightweight underwear for the gym. “Choose underwear with a cotton crotch,” says Dr. Dweck. “Cotton is absorbent and allows the area to breathe.” Less absorbent materials like nylon, lycra, silk, and lace are best avoided, according to Dr. Jones.

But if breathability is the goal, why not just go commando? “Less is not always more,” says Dr. Jones. “If nothing else, wearing underwear may serve as an extra barrier between your vulva and whatever equipment you happen to be working with.” There’s an exception to this rule, however: “Workout clothes have completely evolved,” Dr. Jones acknowledges. “You may not even have to wear panties, as a lot of them either have built-in wicking material in the crotch or are made of materials that are highly absorbent.”

One final note: if nothing else, definitely skip the Valentine’s Day lingerie. “Thongs are not only uncomfortable, but can be irritating during a workout,” says Dr. Jones. “And [they] may serve as a conduit of spreading bacteria from your ‘hind parts’ to your vagina.” That’s a hard pass from us.

What could go wrong?

1. Bacterial Vaginosis (BV): Women’s health expert Dr. Roshini Raj works with Keep Her Awesome, a resource for understanding BV and other vaginal infections. Raj points out that BV, which develops when you have an imbalance of good and bad bacteria, is the most common gynecologic infection among patients of childbearing age (14–49, give or take). In the US alone, 21 million people with vaginas are afflicted annually; one in three will have at least one occurrence of BV. Since it’s not an STI, you can get it even if you’re not getting it on. It can, however, be passed to partners with vaginas.

To limit your risk of developing BV, Raj also votes for cotton undies during exercise. “Cotton is a comfortable, breathable material that will help limit excess moisture and avoid trapping heat during exercise – both of which create the perfect environment for bacterial growth.” And you’ll want to slip into a fresh pair before you leave the gym.

“BV is not a matter of poor hygiene,” says Dr. Raj. “But it’s important to keep in mind best hygiene practices, especially after exercise, to help avoid a vaginal infection.” That means showering right away — or at least changing out of that sweaty workout gear.

When you do hit the showers, remember that your fave Bath & Body Works products don’t belong *everywhere*: Dr. Raj advises that scented soaps, like douching, can change the pH level of your vagina. “Plain water usually suffices to clean your vulva,” she says, “But if you want to use a soap, make sure it is gentle and unscented.”

2. Urinary Tract Infection (UTI): “There are no good data points to show that clothing can cause a UTI,” says Dr. Dana Rice, a urologist and creator of the UTI Tracker app. “There is not a specific fabric type that is better or worse.” But Rice points out that those sweaty leggings can be a source of bacteria when they’re damp, or if they haven’t been washed properly. “For my patients, I encourage clean undergarments and regular washing of all tight-fitting pants.”

And there’s another important step you should take at the gym to prevent UTIs: “Hydration, both during and after working out, is key to preventing bladder irritation,” says Dr. Rice. She explains that dehydration can alter the pH of your urine and irritate the lining of your bladder. “Many people have cystitis-like symptoms if they are dehydrated,” she says.

If you’re worried about your bladder keeping you up all night, Dr. Rice has a pro tip: “I encourage patients to drink enough water in the morning to keep their urine light yellow or better by lunchtime.” By the time the afternoon rolls around, you can sip a La Croix as needed, or snack on your fave hydrating foods.

Speaking of bladder issues…

Attention, new moms: We see you. There are a lot of complicated feels around exercise post-baby. You might be keen to hit the gym to boost your postpartum mental health or just to get a moment to yourself. Or maybe separation anxiety is too real and you’re hunting for baby-friendly mama workouts you can do from home.

Or — real talk — maybe there’s a little voice in your head wondering if underwear is *enough* to get you through that gym sesh. According to a representative from Poise, one in four women surveyed was hesitant to participate in workout classes, from yoga to Zumba, because of bladder leaks.

Their solution? Wear whatever underwear you like — along with a bladder support device, which you insert like a tampon. Also called an “internal vaginal device,” products like Poise’s Impressa basically help keep your urethra closed when there’s extra pressure on your bladder, like when you’re exercising.

Do you have a fave pair of gym-friendly undies? Tell us where to get ’em @BritandCo!

(Photo via Getty)