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Advice > Health > Medical advice

Medical advice for  runners

By Dr Laurence POLETTI.

Here are the replies to the medical questions most often asked about taking part in the Ultra-Trail du Mont-Blanc®. We hope they will enable you to prepare well for this event and we remain available for any information information.

This information does not in any case replace the recommendations that you will be able to obtain from your general practitioner.


Is there an age limit ?

- No

What are the cardiac risks run ?

- The main cardiac risk is of a heart attack arriving following the rupture of an atheromic plate in a coronary artery. This accident is unpredictable, cannot be preventively detected by an effort test, but is fortunately very rare. This risk can be increased by: tough climatic conditions, maximum effort, dehydration.

- Coronary risks (reached by the arteries of the heart) are minimal for well-trained sportspeople and do not present a cardio-vascular risk factor.

- On the contrary, if you have already shown a cardiac problem or if you have cardio-vascular risk factors (smoking, hypertension, excess of cholesterol, diabetes, overweight, hereditary, serious stress), it's strongly advised to take medical advice and to take an effort test. It is possible that you will be advised against taking part in an ultra-endurance race

Must one take an effort test before the race ?

 - No, if you have no cardio-vascular risk factor.

 What is the syndrome of cardiac fatigue ?

 - It's about fatigue of the cardiac muscle, the myocardium, observed by a scan after ultra events with the most achieving runners. This syndrome is benign, and recovers spontaneously and complete in about 8h.

Can one take part in this race if one is:

  • Diabetic ?

- Yes, if it concerns a slight or recent diabetes, while taking account of the hypoglycaemic risks linked to a long-lasting physical exercise (medical advice for adaptation to your treatment, very regular consumption of slow sugars, and always with you the means to re-sugar rapidly)

- In the case of more serious and insulin-dependant diabetes, the practising of ultra-endurance is not recommended. In fact, the adaptation of doses of insulin (or of oral treatments often combined) to the realisation of an ultra-endurance effort is a very difficult exercise, and the consequences of an inbalance can be very serious.

- In all cases, if you are diabetic, it is imperative to have a very good experience of ultra and of the management of your diabetes during the effort.

  • Hypertension?

- Yes, but only if your hypertension is well under control by the treatment.

  • Hypercholesterolemic?

- Yes; if this excess of cholesterol is not accompanied by an increased risk of cardiac or vascular illness (through association with other risk factors, or if you have already shown a cardio-vascular problem such as an angina pectoris, heart attack, arthritis, cerebral accident)

- You must know that the hypolipemiant treatements which aim to reduce the rate of cholersterol can have a harmful effect on the muscles and notably on the muscles while exercising. From this fact, they can aggravate a problem arriving during or after the race: rhabdomyolysis (see below).

  • Asthmatic ?

- Yes, if you asthma is slight and well treated. Be vigilant despite this in relation to climatic factors and to dehydration which can aggravate this illness (just like the effort)

- A severe asthma badly controlled by the treatment is a contra-indication to ultra-endurance.

In a general manner, people having resumed a sporting activity belatedly, after many years of inactivity, has a risk profile. Personalised medical advise is recommended.


Dehydration and hyponatremy (lack of salt)

- This concerns a fairly frequent problem when the race is taking places in a hot and humid atmosphere. Dehydration can be accompanied in severe forms by a serious drop in arterial pressure by hypervolemy (drop in blood volume)

- To avoid this, it's important to rehydrate yourself regularly, and best of all to take salt with your drinks. In fact, the losses also concern salt, and this is indispensible for the good regulation of water in the organism.

- The concentration of salt in your drinks must be close to that of the blood so that its absorption is at a maximum on the intestinal level. On the practical level, you can add a pinch of salt in each drink (the salty tast my be just noticeable). Avoid salt tablets which all at once contribute too much salt and block intestinal absorption.

Digestive troubles

- This concerns problems most often encountered by the runners. Intestinal absorption is reduced during the race, and for as long as this goes on. This is translated by various troubles, such as diarrhoea and wind.

- In the case of digestive difficulties, it's preferable to limit and space out food intake by using food of high nutritional value (eg. energy bars). It is important not to overload the digestive system by continuing to take food and drink at the same rhythm: you then risk a blocking of intestinal absorption and a hypoglycaemia.


- This concerns a reduction of the sugar level in the blood, provoked by long-lasting exercise. In fact, even if you are feeding normally, the reserves of glycogen are diminishing all along the race and you can present a "fuel breakdown". This breakdown can be increased by digestive problems, limiting the absorption of sugars.

Hypoglycaemia can lead to a great fatigue, sweating, vomiting, a loss of clear-headedness.

To avoid this, have a very regular intake of sugars. If you have digestive difficulties, take foods of a high nutritional value (see above) and momentarily reduce your racing speed so as to diminish your energy expenditure during the time that your digestive comfort is improving.

- In the case of hypoglycaemia, it's vital to take a complete rest, and to re-sugar yourself, with rapid sugars first of all (that you leave to melt under your tongue) and then slower absorption sugars to make sure of a minimum of glycogen restocking before going off again.

The heat-stroke from exercising

- This is a relatively rare accident but can have serious consequences. A more benign form is hyper-thermic exhaustion, with a rapid recovery.

The causal circumstances are: a high surrounding temperature, strong sunshine, serious humidity, absence of wind, clothing stopping the evaporation of sweat, dehydration, poor training..

- How to avoid it? By a good hydration in shady and airy places as soon as possible, while progessively acclimatising yourself to efforts in hot surroundings during your training, by avoid at all costs drug sustances and alcohol, by not running if you have a fever, by not trying to excel yourself (which can have serious consequences on your organism).

Muscular problems

- Cramps are often related to hyponatremia accompanying certain states of dehydration. You must therefore take in water and salt.

- There are also postural muscular pains, linked to the fact of staying standing while running for a long time. These contractions have pre-existing problems of posture and an osteopath's advice can be useful.

Rhabdomyolysis and acute renal insufficiency

- Often enough, ultra-endurance races are accompanied by a benign muscular attack with small muscular destruction and falling of myoglobin (component of the muscular cell). This is translated by pains after the race and dark urine. Recovery is rapid and complete.

- Much more rarely, this destruction can be much more serious; it concerns rhabdomyolysis, which is an acute muscular destruction, touching the muscles enabling movements and can be caused, among other things, by a long-lasting sports exercise. Rhabdomyolysis involves the freeing in the blood of myoglobin, which has a toxic action on the kidneys (as much weakened by a possible dehydration). Acute renal insufficiency can thus complicate rhabdomyolysis. These problems can go on up for to 24 hours after the race. Treated in time, healing is total.

- The eccentric work of the muscles ( eg: the quadriceps during a descent) and the duration of the race are factors causing this pathology, as well as a hot and humid atmosphere, a viral problem, taking certain medicines (see below).

- What are its symptoms? Taut, very painful muscles, swellings, dark red urine but sometimes moderated pains and a simply tiredness. Renal insufficiency causes a drop or a stopping of urinary output, a torpor. The symptoms are sometimes not many, and one must not hesitate in consulting (the diagnosis is done by a blood test) if you are not feeling well, if your recovery is abnormal.

- How to avoid it? By a good hydration (regularly take alkaline drinks type Vichy to limited the acidity of the urine and facilitate the work of the kidneys, not forgetting the salt!), by avoiding aspirin and anti-inflammatory products, by taking advantage of soft and superficial massaging (aggressive massaging only aggravates muscular destruction)

Traumatological risks

- Acute traumatology (sprain, fracture): the risks of accidents depend a great deal on the paths taken and the climatic conditions: be wise!

- Micro-traumatology is dominated by fractures from foot or pelvis fatigue, as well as Achilles heels or knees. The ultra-trail being an event with gentle slopes, these pathologies, linked to the multiplication of shocks and above all their force, are somewhat less serious than on other shorter and more rapid events.

- Be attentive to your footwear and do not take the Start if you have an unsolved problem, which will only deteriorate with the race.

What are the medicines to avoid during the race ?

It is preferable to avoid taking aspirin and anti-inflammatory products which can be toxic at kidney level, this organ being already strongly taxed by the often frequent liberation of myoglobin during ultra-endurance races

Aspirin, and hypocholesterolemiant medicines can have a harmful direction action on the muscles ( and notably on the muscles being exercised); these substances are to be avoided.

In case of pains, prefer rather the taking of paracetamol (except in a medical problem such as heat-stroke or rhabdomyolysis where it is contra-indicated because of its hepatic toxicity).

Generally speaking, do not try at any price to overcome pains which are the warning signs of your organism and must be respected .

What are the risks linked to the absorption of drugs ?

- The taking of drugs can only aggravate or set off numerous problems such as exercise heat-strokes, tendinous or muscular rupture, fatigue fracture, cardiac pathology...etc.

- Generally speaking, the drug makes to you take medical risks, sometimes serioius, and it is strongly advised against. It is, in additiona, completely against the spirit of trailing. 


Advice written up with the valuable help of Doctors Armand TOMASZEWSKI and Eric PAGE.


and scientific research





& Nutrition