Question: what causes stitch?

Jacquie Oliwa answered on 13 Jul 2017:

Hi Bosco,
A stitch is a pain in the abdomen (usually on the side) that’s brought on by activity and it’s the bane of many runners’ lives. It can range from sharp or stabbing to mild cramping, aching or pulling, and may involve pain in the shoulder tip too.

Scientists are unsure of the exact cause of stitch. For some time, stitch was thought to be caused by a reduction in blood supply to the diaphragm, a large muscle involved in breathing. It was thought that during exercise, blood was shunted away from the diaphragm and redirected to exercising muscles in the limbs. This theory has now lost favour with scientists. Both the diaphragm and the limb muscles have to work harder during exercise so it is unlikely that an inadequate blood flow would be directed to them.

Another popular theory is that stitch is caused by organs pulling on the ligaments that connect the gut to the diaphragm. Ligaments that support organs such as the stomach, spleen and liver are also attached to the diaphragm. Jolting during exercise may cause these organs to pull on the ligaments and create stress on the diaphragm.

A more recent idea is that stitch is caused by irritation of the parietal peritoneum. Two layers of membrane (peritoneum) line the inside wall of the abdominal cavity. One layer covers the abdominal organs. The other layer (parietal peritoneum) attaches to the abdominal wall. The two layers are separated by lubricating fluid, which allows the two surfaces to move against each other without pain. The parietal peritoneum is attached to a number of nerves. It is thought that the stitch occurs when there is friction between the abdominal contents and the parietal peritoneum. This friction may be caused by a distended (full) stomach or a reduction in the lubricating fluid.

Eating and drinking inappropriately prior to exercise may exacerbate stitch by causing a full stomach or dehydration. Poor fitness, an inadequate warm-up and exercising at high intensity may also be factors. A sudden change in biomechanics such as increased stride length or frequency may increase the risk of stitch by affecting the way that the torso moves.

Best,
Jacquie