Almost everyone at one time or another has either experienced for themselves, heard of or seen someone else experience what is commonly known as a “side-ache”. It’s certainly well known to many parents who grew up with the same warning they now give their own children, "Wait an hour after eating before you go swimming, so you don’t get a cramp and drown."

I heard that same routine a million times growing up. Thanks Mum!

Also called a “stitch-in-the-side” or simply a “stitch”, this phenomenon is well known to many sporting participants, especially in activities that involve repetitious torso movement, rotation or hypertension, as in running, swimming and horse riding. Runners especially are bothered by the inconvenience of side-stitch because it often forces them to stop, bend over, tighten the abdominal muscles, breathe out through pursed lips and apply direct pressure to the area of pain. These physical techniques are recommended for immediate application.

But what actually causes a side-stitch, and perhaps more importantly, how does one prevent such an annoyance? The medical community recognizes the condition as exercise-related transient abdominal pain (ETAP) and has proposed several causal theories.

Different Strokes for Different Folks

In the ischemic-pain theory, stitch arises when blood flow to the diaphragm or other respiratory muscles is compromised by diversion of blood to the gut for digestion or to the muscles for exercise; hence the advice to avoid physical activity after the immediate consumption of food and drink. In this model, quantity, composition and the caloric density of food are obvious variables.

The ligamentous-pain theory proposes that stitch arises from tugging of the gut on ligaments connecting the gut to the diaphragm. This notion is reinforced by the observation of increased frequency of stitch in motion after the gut is loaded with fluid sufficient to fill it. In controlled trials fluids that differ in carbohydrate form (which influence digestibility and/or absorbability) also affect incidence of stitch. Drinks that contain sucrose or fructose potentiate the greatest incidence of stitch, whereas pure water or drinks containing glucose-polymers (maltodextrin) represent the least risk.

A third explanation associates ETAP with irritation of the parietal peritoneum (PP), suggesting that stitch is a form of exertional peritonitis (inflammation). The peritoneum is a thin layer of connective tissue that lines the abdominal cavity covering most of the viscera (digestive organs & glands). It functions to lubricate and protect the entrails. Irritation of the abdominal portion of the PP can elicit highly localized sharp pain.

To further complicate matters, two separate forms of stitch have been identified. The first and most common form, called “minor annoyance” stitch, is associated with food and drink. The second type is described as “very painful and incapacitating”, is seldom related to food or fluid intake and always occurs on the right side. This more severe type of stitch correlates with missed meals and a state of dehydration caused by inadequate fluid intake.

Sound Advice

From evidence currently available, the Department of Physiology and School of Physical Education, University of Otago, Dunedin, New Zealand, offers the following advice to athletes who want to avoid stitch or reduce its severity:

1. Wait 2-3 hours after a meal or consuming a large volume of fluid before engaging in physical activity, exercise or sport.
2. To reduce the mass of fluid in the stomach, drink small amounts of fluid frequently during the course of exercise, rather than a single large drink.
3. Sports drinks that contain glucose-polymers (Hydrade) are less likely to cause stitch than pure water or soft drinks, especially in exercise lasting several hours in the heat, when the demand for fluid replacement is high.
4. If you experience ETAP frequently, try wearing a light, wide cloth belt with a Velcro fastener around your waist that you can tighten when necessary.

In addition, attention must be given to the importance of pH, electrolyte management and antioxidant intake. First and foremost, the quantity and quality of fluid required by athletes is paramount to understand. As a minimum daily standard, everyone should consume 30-50ml of filtered water per kilogram of bodyweight (2-4 litres).

During strenuous or prolonged physical activity, the water content of all body compartments decreases as a result of fluid loss through sweating and insensible water loss from the lungs, especially at high altitude. Except under resting conditions, thirst is not recognized as a sufficient stimulus for fluid replacement, so smart athletes make hydration before, during and after exercise an absolute priority.

Electrolytes are lost primarily through sweat and urine. Excessive water and electrolyte loss can impair heat tolerance, reduce exercise performance and induce severe cramps, exhaustion and stroke. Modern food is not a reliable source of essential minerals and trace elements, particularly those that control fluid exchange within various fluid compartments, such as potassium, manganese, magnesium and calcium.

Electrolytes allow for a constant, well-regulated exchange of nutrients and waste products between the cell and its external fluid environment. They affect nerve transmission, muscle action, and gland function and also regulate the acid and base qualities of body fluids and blood. Consuming a 6-8% carbohydrate solution reinforced with electrolytes, antioxidants and ascorbic acid can extend exercise capacity and delay muscle fatigue. A 7:1 ratio in favor of potassium over sodium is ideal.

Photo by Andrew Rashotte from Burst

As always, stay well and live free!

Dr.C