Hydration

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Drink Responsibly: A Guide to Marathon Safety

                    Dr. Mark Schecker, MD

Despite the growing popularity of participation in marathon events, injury rates of those participating fortunately remain very low. This is largely due to the fact that most entered in these events train properly and are well-educated as to the potential pitfalls of marathon running and walking. Most of the athletes who visit the race aid stations or the finish line medical area at the Myrtle Beach Marathon require only minimal first aid for minor problems like bumps and bruises, strains and sprains, blisters, and nausea. It is well known that both the number of visits to medical aid stations and the severity and types of injuries seen correlate well with environmental conditions, with more casualties occurring on hotter and more humid days.

Some of the more serious injuries that occur in marathoners are directly related to fluid imbalance and an individual’s hydration status. For many years marathon participants were encouraged to drink as much fluid as possible to ward off the effects of dehydration. Dehydration occurs when athletes do not replenish lost fluids (mostly through sweating). Dehydration can hinder maximal performance and increase the likelihood of developing heat associated illness i.e. hypothermia and hyperthermia. Hyperthermia includes a continuum of problems that includes heat cramps, heat exhaustion and the more serious and potentially fatal heat stroke. The basic signs and symptoms of dehydration and heat illness range from irritability and discomfort, to weakness, dizziness, cramps, chills, nausea, vomiting and headache.

Over the past decade it has become evident that drinking too much fluid can be as serious as or even more problematic than drinking too little. Drinking excessive amounts of fluid during prolonged exercise can lead to a condition known as Exercise-Associated Hyponatremia (EAH). EAH occurs when sodium levels in the blood drop to dangerously low levels. The greatest risk of developing EAH appears to be due to drinking large volumes of fluid without adequate sodium intake during exercise lasting 4 hours or longer in which large amounts of sweat and salt is lost. If mild, EAH may cause no symptoms but as sodium levels continue to drop; a progressively worsening headache, bloating, puffiness with swelling of the hands and feet, nausea and vomiting may occur. Later stages may lead to brain swelling (cerebral edema) and if untreated severe EAH can be fatal. Unfortunately the signs and symptoms of EAH and dehydration with heat illness are very similar and it may be a challenge to distinguish one from the other.

Therefore it is also a challenge to strike the right balance between preventing dehydration and exercise-associated hyponatremia. Preventing EAH is accomplished by avoiding excess fluid retention as manifested by weight gain during or after exercise. According to experts this can be accomplished in two major ways: drinking only when thirsty or by an individual calculating their hourly sweat losses during exercise and avoiding drinking in excess of this amount. The easiest way to do this is to weigh yourself nude before you run for 1 hour in the environmental conditions and at the same pace you expect to race. Immediately following the run, towel off and reweigh yourself nude. The difference in weight is equal to your sweat rate per 1 hour. 1 kilogram of weight is equal to 1 liter of fluid (or 1 lb. = 16 fl oz.) and no more than this amount should be consumed in each hour of your race. Alternatively, this should also serve as the best way to prevent dehydration. According to the USATF (USA Track and Field) advisory, ensuring proper pre-exercise hydration requires the consumption of approximately 500 – 600 ml (17-20 fl oz) of water or sports drink 2 – 3 hours before exercise and 300 – 360 ml (10 – 12fl oz) of fluid up to 10 minutes before exercise. Urine color can also be used as a guide to hydration status and should be pale yellow like lemonade rather than dark like apple juice (dehydration) or clear like water (overhydration). Drinking electrolyte fortified sports drinks will not prevent the development of hyponatremia but are probably a better choice than water especially for those at high risk for EAH.

Risks factors for the development of EAH:

Low body weight
Female
4 or more hours exercise duration
Slow pace
Inexperienced participant
Excessive drinking behavior
High availability of fluids
Altered kidney excretory function (including from drugs like ibuprofen, aleve or celebrex ie NSAIDS)
Extremely hot or cold environments

All marathon participants should write their pre-race weight on their race number (bib) before the start of the race. This will assist medical personnel in determining if an injured runner is experiencing the effects of dehydration or hyponatremia.

If you suspect you may be suffering from dehydration, hyponatremia or any other type of injury you should seek medical attention immediately at one of the 12 medical aid stations on the marathon course or at the finish line medical area. The Myrtle Beach Marathon medical team is composed of group of dedicated volunteers including the Emergency Medical Services of Horry County and the city of Myrtle Beach; Emergency Department personnel from Grand Strand Regional Medical Center; and a number of doctors, nurses and other paramedical providers from the community.

So remember drinking responsibly is not only for driving anymore and may be the best way of insuring a fun filled and injury free marathon day.