Avoid gastric disorders during a snowy trail

How to avoid gastric disorders on a snowy trail?

Haunted by the trailer, gastric disorders nevertheless affect most runners from a certain duration of effort. They are feared and rightly so, since they often lead to saying goodbye to their objectives or simply to abandonment. What are the causes of this? How do they manifest themselves? How can they be prevented? Should we change our eating habits on a snowy trail like the one at Sancy Hivernal? Answers in this article.

Gastric disorders, causes and symptoms

The majority of runners have already heard about it or have simply been confronted with it. During endurance efforts and more particularly ultra-endurance, gastric or digestive disorders affect 30 to 90% of competitors. Most of the time, these disorders can be minor and the symptoms transient, but they often become very disabling to the point of significantly reducing performance and leading to abandonment.

  • To fully understand the phenomenon of digestive disorders, it is important to understand the causes. Here is a list of the main factors that increase the risk of gastric pain:
  • If you start at the beginning, digestive disorders can be the result of poor general nutrition and especially in the days before the race. A high-calorie diet, too high in fat and/or fiber or a too short time between the last meal and the beginning of the effort are all aggravating factors.
  • Over-consumption of energy products before and during the race, or simply the use of inappropriate dietary supplements: hypertonic energy drinks (too high in carbohydrates), energy gels taken pure and often too concentrated, energy drinks are all examples of products to ban. Too much fluid intake will also affect gastric comfort.
  • Intestinal ischemia. This is the decrease in the flow of blood to the digestive system in favor of redistribution of blood to the muscles. It is a mechanical consequence of the effort and it is very difficult to act on it. The effort requiring massive blood circulation in the muscles, the blood flow in the intestine will be decreased (at 70% VO2max, it is reduced by 80%!) and the digestive system will find itself in debt of oxygen causing abdominal pain, vomiting or diarrhea.
  • Dehydration will also contribute to the onset and manifestation of gastric pain by increasing intestinal ischemia.
  • The mechanical effect created by shocks, vibrations and bounces directly related to running. This phenomenon is accentuated during the descending parts.

As you will have understood, the causes of digestive problems are multiple. Some are purely disciplinary and require regular training in the same way as physical training, the digestive system also trains.

For others, they are the result of poor eating habits, poor reflexes or the use of inappropriate products.

Gastric disorders, good reflexes

Nutritional preparation for a trail begins well before the start of the event. And this one is on your plates. A varied, balanced diet adapted to the upcoming event is the first step towards a race that will go smoothly. Choose a variety of carbohydrate sources (pasta, rice, leguminous plant, etc.), fresh and seasonal fruits, vegetables low in fiber. This diet should be perfectly normal without being too hyperglucidic. Fat-rich ingredients must be reduced, as must dairy products, which are often difficult to digest during exercise. It is also important to hydrate very regularly during race week (1.5 to 2L of fluids per day). Beware of coffee or tea. These are elements that increase dehydration, another cause of gastric pain. Finally, traditional “cures of malto ” are the main causes of gastric pain. By trying to saturate the energy reserves in an “artificial” way, many runners encounter the catastrophic effects of these cures on the digestive tract. A balanced and adapted diet fulfils the role of saturator of the reserves in a natural way.

During exercise, simple rules must be applied to limit the appearance of gastric disorders. The first is to hydrate very regularly (500mL per hour of effort). This will help to prevent dehydration and dilute the contents of the digestive tract. The second is to use drinks, gels or solid products that suit you. It is obviously forbidden not to have tested your sports nutrition before going on a trail. Once you are sure that it is suitable for you and that you assimilate it correctly, you must calibrate the contributions properly. It is important to keep in mind that the body is able to oxidize 60g of energy substrate per hour of effort. It is therefore necessary to forget all the super-concentrated energy drinks or gels. A drink or gel containing between 30 and 50g of carbohydrates, combined with vitamins from the B group as well as essential minerals (sodium, potassium, magnesium in particular) allows optimal assimilation. The supply of antioxidants in drinks and gels should be closely monitored because when they are overdosed, antioxidants turn into pro-oxidants and can cause gastric, muscle and cramping pain. The use of pure energy gels should be immediately followed by water ingestion to avoid an excessive influx of carbohydrates into the digestive system. Finally, it is interesting to vary energy sources by using solid foods from time to time that will use other energy sources. Bars and fruit jellies are very useful in this respect.

To finish on the right reflexes to adopt, it is also wise to know how to sort during refueling. These are often very varied and constitute a “nice reward” for the kilometers covered, but beware of the foods that can be found there. Of course, each of us has our own digestive tolerance. Some people will be able to enjoy delicatessen, cheese or other “tempting” foods without too much risk, for others, it will be necessary to be more judicious in the selection (dried fruits, fresh fruits, soups…).

Impact of winter trails

With the cold, and this is a human reflex, we tend to be less hydrated. Indeed, the figures show that the sensation of thirst is reduced by 40% in cold weather (1). This bad habit must be corrected, and it is necessary to adopt the reflex to drink even without the feeling of thirst. Let us not forget that thirst is only a warning signal, dehydration is already well established when the signal is perceived. Moreover, let us immediately twist the neck to the false idea that athletes do not sweat or less in winter. So certainly, sweat is less felt and less visible than in hot weather because it is eliminated much more quickly.

with cold, but it is well present and all the more concentrated in mineral salts (2,3). We even talk about “delayed sweating” in winter because it takes longer for the body to warm up than in summer. The energy expenditure is thus increased in order to fight against the cold (4).

Thus, it is even more important to be very vigilant about hydration and nutrition during snowy trails. Moisturizing regularly, every 10 to 15 minutes and having a regular energy supply is just as important or even more important than in mild or hot weather. A slightly higher concentration of carbohydrates (about 50g per hour of effort) even seems relevant.

In addition, the last trick to get in top shape during winter months is to fill up with vitamin D and iron. The vast majority of the population is deficient in vitamin D and iron in winter and even more so for women. And yet, these two elements play crucial roles in injury prevention, muscle contraction and recovery. A balanced diet and food supplements help to combat this seasonal deficiency. And some sports nutrition products are even designed for this purpose!


J.RAOUX , Labs Nutrition

(1) Meyer N.L., Manore M.M., Helle C. (2011). « Nutrition for Winter Sport. » J Sports Sci 29 (1):S127-36.
(2) Kenefick, R. W., M. P. Hazzard, et al. (2004). « Thirst sensations and AVP responses at rest and during exercise-cold exposure. » Med Sci Sports Exerc 36 (9): 1528-1534.
(3) Castellani J.W., Young A.J., Ducharme M.B., Giesbrecht G.G., Glickman E., Sallis R.E. (2006). « American College of Sports Medicine Position stand: prevention of cold injuries during exercise.” Med Sci Sports Exerc 38 (11):2012–2029.
(4) Kuhn F., Daniel H. (2012). « Nutrition de l’endurance »