Stitches in the side mostly occur while running. The actual cause of this is unclear even today. Theories range from an over stimulation of neural pathways and incorrect body posture to a swelling of the spleen caused by increased circulation and activity, which then presses on the abdominal cavity. The most popular and most widely known theory states that stitches in the side are caused by excessively burdening the diaphragm, coupled with a lack of oxygen. A full stomach – which is never conducive to physical activity – may also increase the pressure and thus stitches in the side.
Researchers agree on one thing: stiches are not dangerous and proper breathing as well as regular exercise reduce the risk of stitches enormously. Torso and abdominal muscles are strengthened and endurance is improved, so that the oxygen from the lungs can be used more effectively and no holding of your breath or gasping respiration is necessary.
Since the cause is still not clearly determined, it is recommended to respond to stitches in the side by pausing, then walking a few relaxing steps while taking deep, slow and concentrated breaths until they stop – be it during a workout or while running. It also may be helpful to stretch your arms over your head, thus reducing the pressure on the chest and abdominal cavities. Then you can start again full speed ahead – as long as you pay attention to proper breathing!