Every runner has experienced the dreaded side stitch, a sudden sharp pain in the side of the upper abdomen at the base of the ribs. The pain is caused by a spasm of the diaphragm, the muscle that controls your breathing. A stitch will usually go away quickly after slowing down or stopping, but even on the run, you can often make it go away by bringing your breathing into careful control.

Concentrate on belly breathing, pushing your belly out when you breathe in and relaxing it as you breathe out. Take deep breaths on the intake, and exhale suddenly, even noisily. To get the diaphragm to contract in rhythm with your steps, try to inhale and exhale as you land on your left foot.