Position: On Stomach
Affects lower back, neck, lungs
"Sleeping on your stomach is the worst position for your spine," FitzGordon says. It flattens the natural curve in the lower back and keeps your head turned to one side all night, which distorts the alignment of the spine in your neck. All of this leads to chronic lower back pain, neck pain, and headaches. And because your body weight compresses your lungs, stomach sleeping also impedes your ability to breathe deeply.

Pillow talk 
Kirsch implores her stomach-sleeping patients to change their habits altogether. She recommends investing in a body pillow (go with the long, thin rectangle or cylinder style) to make side sleeping more compelling. It mimics the pressure on the front of the body that sleeping on your stomach offers, she says, but without compressing your organs. "Placing a body pillow between your knees and hugging it with your arms will keep your pelvis, shoulders, and spine balanced," she says.

Fix: side stretch
What it does: Opens the sides of the torso, creating more space for the lungs to expand. Stretches the quadratus lumborum, thus helping to maintain proper lower back curve.

How to do it: Stand tall with abs engaged and hands clasped behind your head. Keeping your spine long, bend to the right as if making a rainbow shape with your torso; go as far as is comfortable. Stay five breaths, breathing naturally, then return to the starting position. Repeat to the left. Stretch each side three times.

Fix: easy bridge pose
What it does: Restores the curve in the lower back, which helps restore your neck's alignment as well. Opens the chest and stretches the diaphragm, improving your ability to breathe deeply.

How to do it: Lie on your back with your knees bent and feet flat, about 12 inches from your hips. To a count of three, reach your arms overhead and lift your hips off the floor; your head, arms, shoulders, and feet remain grounded. Keep your butt soft and core tight as you hold the stretch for a count of three. Now lower your arms and roll your spine, one vertebra at a time, back down to the mat. Repeat five times.