Sleeping on your side is the most common sleeping position, and experts agree that it’s also the healthiest. Chiropractor Kevin Lees, D.C., of The Joint Corp, explains that sleeping on your side relieves back pain and can reduce the risk of breathing problems like sleep apnea, while Park notes that it promotes good circulation. However, the sleeping position also has some potential drawbacks.

The key to restful, restorative sleep is to keep your spine, neck, and shoulders in good shape. But imagine the shape of a person who sleeps on their side: the widest parts of the body, shoulders and hips, will naturally want to sink deeper into the mattress.

If your mattress is too firm and not firm enough, you may wake up with sore or stiff shoulders and hips in the morning. If it’s too soft, your shoulders and hips may sag also deep into the mattress and reset that ever-important alignment that can irritate your joints and ligaments and contribute to lower back pain.

“If you have a mattress that’s too soft, no matter what position you sleep in, it’s like your body is being absorbed by it,” says physical therapist and founder of Aletha Health Christine Cote, PT. “It can be good, but your body should be doing absolutely no work. Without a little muscle contraction to stabilize you, you actually lose some of the support your body needs.”

Experts say side sleepers should have the following sleeping position: