Endurance sport hits the stomach

7. March 2018

If you have ever completed a marathon or a longer triathlon, you often hear stories of stomach problems during the competition or have had troubles of your own. “I had constant cramps” or “I hit a wall”, you might hear, or something similar. Many consider this phenomenon to be part of the trials and tribulations of competition, but most often it is no coincidence when your stomach rebels during a competition.

Physical intensity and digestion don’t go well together. The faster you run and push your personal limit, the more the body switches to “competition mode” and prioritises those processes that are responsible for high speed. The available oxygen is then used primarily for supplying energy to the muscles, while all other systems, such as digestion, are reduced to a minimum and in extreme cases even switched to emergency operation. For example, during a fast kilometre run, it is practically impossible to drink even a sip, let alone consume solid food.

Caution with medications

Digestive problems during long sporting activities therefore depend critically on the intensity of the exercise, as well as what type of food is consumed and when. Athletic strain and unfamiliar food throws the stomach’s micro-climate into disorder. This can manifest itself through various symptoms, such as burping, heartburn, chest pains, nausea, and vomiting.

General nausea occurs among long-distance runners most often during or shortly after the end of the race. One particularity about this is that athletes who have drunk fluids immediately prior to the competition run a much higher risk of encountering troubles in their upper digestive track. A key reason for this is the delayed gastric emptying that has been observed at elevated running intensities. Also, athletes who drink too little and are dehydrated exhibit delayed gastric emptying. Dehydration thus also increases the risk of gastro-intestinal discomfort when we run, which can lead to nausea and vomiting. Other contributing factors for stomach problems include intense heat and long distances. High outdoor temperatures can inhibit gastric emptying by reducing blood flow to the intestines and therefore reducing their mobility.

Also, don't forget: Regular administration of certain medications such as anti-inflammatories or cortisone may also trigger of stomach troubles. And nicotine, caffeine and alcohol as well as large quantities of protein-rich food can also be contributing factors.




The art of balance

The art of endurance sport lies in striking the optimal balance between the intensity of exercise – finding a level at which it is just barely still possible to fuel the body with the amount of energy it requires – and an appropriate diet to which the stomach is accustomed. The optimal intensity is first and foremost a question of feeling and experience, but it also depends on how ambitious athletes are or how much risk they wish to take.

When athletes are pushing their limits to achieve their best running or riding times, their stomachs may rebel even with the slightest fluid intake (at the Ironman Hawaii, for example, with its hot weather conditions, digestive problems are a widespread phenomenon).

If, to the contrary, athletes conserve energy and follow a good – and perhaps even tasty – diet, then they may in fact get through the race without physical problems and even with reserves to spare at the end, but to achieve this they cannot operate at their maximum performance level. Thus the “perfect race” is also always a quest for the “perfect” pace, combined with the necessary diet.

How to avoid stomach problems during competitions

In an “emergency”, take the pace down a notch

  • In the pre-competition phase, give preference to refined products such as white bread, cornflakes, porridge, or white pastas and do not consume whole foods.
  • Avoid difficult-to-digest foods such as beans, onions, garlic, chillies, leek, leaf salad, dried fruit, or fried or breaded foods, as well as “au gratin” dishes. Vegetables and foods containing protein should also be steered away from immediately before a competition.
  • Dairy products are to be consumed only if you are used to them, and with caution.
  • Foods rich in dietary fibres such as pulses or whole grain cereal are ill-advised.
  • In the run-up to exercise, avoid nicotine and consume caffeinated and alcoholic beverages only in extreme moderation.
  • Painkillers such as Aspirin and Ibuprofen should not be taken. 
  • In the event of physical activity lasting more than one hour, you should also eat carbohydrates in addition to fluids from the very beginning.
  • From two hours of exercise and up, additional sodium intake is advisable. This can be done by mixing a bit of cooking salt into a drink (about 2 grams per litre).
  • Hypertonic beverages (e.g. cola or other sweet drinks) should be avoided or diluted due to the consequent delay of gastric emptying (approximately 1:3; at least one part water, maximum 3 parts juice).
  • Try to avoid ice-cold and carbonated drinks, as well as those with too many ingredients.
  • With regard to tolerance, individual preferences vary greatly, so test products in advance during training in terms of how well they are tolerated and consume them – and particularly gels – with sufficient fluid. When faced with unfamiliar products on site, take along your own food and drink.
  • A food journal is advisable. What do I need each hour and how much? A precise intake interval helps with monitoring, e.g. based on time (every 20 min.) or running distance (every 4 km).
  • If your stomach rebels, the first thing to do is: take your pace down a notch!