Sitting all day long is about as fun as it is good for our health. In fact, a new study suggests that the more total time we spend sitting and the longer we sit at a time—especially as we get older—the greater our mortality risk.

Scary long-term impacts aside, though, sitting too much can have a very noticeable effect on how our bodies feel every single day. Not only does it mess with our posture, but it can also be a literal pain the butt.

If you wriggle around in your chair at work all day trying to kick that dull aching feeling in your butt (no, you’re not the only one!), get this: That pain in your behind may be a legit—and fairly common—condition called ‘piriformis syndrome.’

Hold up: A piriformis is, what, exactly? Basically, beneath the bigger glute muscles in your butt is your piriformis, a muscle that runs from the very bottom of your spine out to your hip joint. This muscle also passes by the sciatic nerve, which runs down your spine, through your butt, and continues down each of your legs. In some people, the sciatic nerve actually runs through the piriformis muscle, according to research published in The Journal of the American Osteopathic Association. (It’s unusual, but it puts you at greater risk for piriformis syndrome.)

When your piriformis muscle tightens up or spasms, it puts pressure on the sciatic nerve, potentially leaving you with pain, tingling, and numbness in your butt and even down your leg, explains Gary Guerriero, P.T., co-owner of U.S. Athletic Training Center in New York City. Experts call this ‘piriformis syndrome’ and it feels a lot like sciatica, a condition typically caused by back injuries that affect the sciatic nerve and lead to pain, tingling, and loss of feeling in the lower-back, butt, and leg.

While piriformis syndrome can result from lots of glutes-heavy exercise (like walking, hiking, or running), it can also pop up just because you sit on your behind all day, Guerriero says. Look out for pain when sitting for more than 15 minutes, trouble rotating your foot inward, discomfort when walking (especially up stairs) and squatting, and tingling or numbness anywhere from your glutes to your foot.

If your crazy-tight piriformis continues to press on your sciatic nerve long-term, it can affect the nerve’s ability to signal the muscles throughout your glute and leg, says Guerriero. And if the muscles throughout your leg don’t get the proper signals from the nerve, they can’t respond as well during daily movements and exercise, leaving them less able to grow stronger and putting you at greater risk for injury.

Related: 6 Possible Reasons Why You’re Not Building Muscle

If all this just made a light bulb go off in your head, you have a couple orders of business to take care of. One: If you sit all day, set a timer on your phone to make sure you get up and walk around for a few minutes at least every hour, says Guerriero. Two: See a physical therapist.

If you’re just feeling tight, a P.T. will start by applying heat to relax the muscle so it can be stretched—but if you’re in pain, they’ll start with ice. Then they’ll stretch and lengthen the piriformis to help relieve the pressure on the sciatic nerve, Guerriero says. Check out two of his go-to stretches:

Lying Piriformis Stretch: Lie on your back and raise your left knee to your chest. Then, put your left hand on your left knee and your right hand on your left ankle. Draw your knee to your right shoulder until you feel moderate tension in your left glutes. Hold for 30 seconds and repeat on the opposite side.

Chair Glute Stretch: Sit upright in a chair and cross your left ankle over your right thigh. Place your right hand on your left ankle and your left hand around your left knee. Gently pull your leg up towards you until you feel moderate tension in your glutes. Hold for 30 seconds and repeat on the opposite side. Repeat for four or five rounds.

From there, a P.T. can help you strengthen your piriformis and other glutes muscles to keep piriformis syndrome issues from coming back, Guerriero says. (Expect exercises like squats and lunges.) You’ll also need to get ample rest in order to bounce back. Depending on your initial level of pain—and whether your piriformis syndrome is related to exercise and overuse—you’ll probably have to lay off your usual workout routine until your pain is below a four on a scale of one-to-10, he says.

Related: Training equipment (like a yoga mat) can help you stretch and strengthen at home.