Medically speaking, the "side stitches" that you experience are called "exercise-related transient abdominal pains" or ETAPs. These stitches are very common and not serious, although they can be painful and can put a crimp in your exercise session. (People who exercise are much more likely than couch potatoes to experience ETAPs.)
Stitches are cramps or spasms in the diaphragm, the muscle that separates your abdominal organs from your chest and lungs. When you inhale, your diaphragm drops down; when you exhale, it expands upwards. But vigorous movement can jerk the diaphragm down when it is expanding upward, leading to a "stitch." You may have noticed that stitches usually occur on your right side - this is because the diaphragm is attached to the liver, which is on the right.
To prevent stitches, you can try the following tricks:
- Breathe evenly and deeply, not shallowly, using your diaphragm. You're breathing correctly for exercise if you can see or feel your belly expand when you inhale.
- Avoid running downhill (it increases the force on your body, making stitches more likely to occur).
- Avoid big meals for three hours prior to exercise.
- Cut back a bit on the fluids you drink before and during exercise to see if this helps.
- Purse your lips when you exhale and inhale. This can both relieve and prevent stitches.
- Stretch your diaphragm muscles before exercise. Just raise your right arm overhead and bend to the left. Hold the stretch for 30 seconds and then repeat on the other side.
- Slow your pace - stitches may not occur as frequently.
- Watch your breathing to make sure you're not always inhaling as the same foot hits the ground. Try to alternate breathing in and out on opposite feet.
When you get a stitch, bend forward slightly and massage the area. (Most people do this naturally to ease the pain.)
Andrew Weil, M.D.