During exercise, more sodium is lost in sweat than is usually replaced by food and fluids. Your body can tolerate a degree of imbalance for a short period of time. If the imbalance continues for too long, sodium in the bloodstream is diluted and hyponatraemia (low concentration of sodium in the blood) results. Long runs and races carry a greater risk of hyponatraemia because of the total amount of sweat lost. Adequate hydration and sodium intake – either via sports drinks or food – becomes vitally important during long races (or long training runs).
Symptoms of hyponatraemia can range from mild to severe and can include nausea, muscle cramps, disorientation, slurred speech, confusion, and inappropriate behaviourr. As it progresses, seizures or coma may result. Severe hyponatraemia is a true medical emergency.
Minor symptoms, such as nausea and mild muscle cramps, can be treated by eating salty foods and hydrating with a sodium containing sports drink. More severe symptoms require treatment by qualified medical personnel. If you think you are suffering from hyponatraemia or are unsure, seek medical attention immediately.
Some authorities recommend drinking less water to rebalance sodium and water intake. However, given the risk of dehydration and heat injury, this is not a practical recommendation. Increasing salt intake seems more prudent. By ingesting more sodium, hydration with water is balanced and dilution of blood sodium does not occur.
Rehearse your hydration, feeding, and salt strategy during your training sessions. There are so many variations between individuals that there is no single right answer. Know what your body’s’ needs are.
It is best if you strive to get your sodium from both sports drinks and salty foods – as opposed to salt tablets – for two reasons. Salty foods stimulate thirst, and it is possible to ingest too much salt with tablets but very difficult with food. One litre of sports drink contains approximately 500mg of sodium, half your hourly requirement. The remainder may come from food sources such as half a vegemite sandwich.
If you don’t think that your food and sports drink is providing enough sodium, then consider salt tablets. But make sure you know how much you are taking, and only do so under medical supervision.
Some practical pointers for you to remember include:
· Drink frequently to attempt to stay hydrated.
· During a long, hot race, aim for a total sodium intake of approximately 1 gram per hour. Please note that this may not be appropriate for everyone.
· During training, heat acclimatisation, and for several days leading up to a big race make sure sodium intake is not too low.
· Sodium is also important for recovery.
· Anti-inflammatories, diuretics, narcotics, and certain psychiatric medications should be avoided during exercise, but especially during a race as they interfere with kidney function and may contribute to the development of hyponatraemia in athletes.
· Check with your doctor if you have any health problems.