You're doing sit-ups to strengthen and flatten your belly, but you're getting the opposite result; instead, your belly seems to stick out more as you crunch up.
This is usually because you have a benign, but cosmetically annoying, condition known as diastasis recti, or ab separation. It often occurs after pregnancy, but can also be experienced by men who've been lifting heavy weights or gained a lot of weight. You may not even notice the separation and resulting bulge until you strain, such as during sit-ups.
What is Diastasis Recti?
Your abs are divided into a left and right side. The linea alba connects these two sides, and when under stress, it thins and widens the gap resulting in a protruding belly. Diastasis recti can make you look pregnant long after having your baby. It also shows up as a football-shaped dome right in the middle of your stomach when you're doing sit-ups and other ab exercises.
Identifying Diastasis Recti
Getting a doctor's confirmation that you have diastasis recti and not a hernia is always a good idea, but you can perform a self-test easily.
Lie on your back with your knees bent and your feet planted on the floor. Place one hand on your belly and put your finger right at your navel. Press your fingers down and lift just your head and neck up as if you were starting a crunch. Feel for for a space between the two sides of your rectus abdominis, the front abdominal muscle.
You likely have the separation if you feel a finger or more distance between the two sides of the muscle.
Diastasis recti is a benign condition, meaning it doesn't immediately affect your health. It is, however, cosmetically unattractive to have a ridge run down your midsection. In rare cases, surgery is required to repair the gap, but usually you can pull the muscle back together with deliberate exercises.
Some exercises, including sit-ups, make the gap worse, so do these instead:
Squat with a ball: Place an inflated mini exercise ball -- about the size of a soccer ball -- between your thighs and squeeze as you squat.
Bracing: Sit in a comfortable position and place your hands on your abs. Breathe normally as you pull the ab muscles in toward your spine. Hold for 30 seconds.
Bridging: Lie on your back and bend your knees with your feet planted hip-distance apart. Squeeze your abs in as you lift your hips up to create a line from your knees to your shoulders.
Leg slides: Lie on your back with your knees bent and feet planted. Draw your navel in toward your spine as you slide your right leg out straight on the mat. Use control to pull it back in and repeat with the left leg. Alternate for the desired number of repetitions.
In many cases, diastasis recti heals on its own and needs no specific intervention.
If you're postpartum, get clearance from your doctor before starting an exercise program.