Runners learn to cope with being dehydrated, says expert

'You are not going to crash from dehydration on an average workout,' says sports professor

Mild dehydration will not hinder exercise (Rex)

The human body is adept at coping with being mildly dehydrated and runners shouldn't be too obsessed with sports drinks and constantly topping up with water, according to an expert.

John Brewer, professor of applied sport science at St Mary’s University and former director of Lucozade’s sports science institute, says that the reduction in body weight associated with water loss can have a beneficial impact on some endurance runners.

As a result, athletes can train themselves to cope with mild dehydration.

“Each litre of fluid lost equates to approximately 1kg of body weight. Carrying around less weight has a positive impact on endurance performance, so people train their bodies to cope with dehydration, rather than fighting to prevent it," he told the Times.

“The body is actually incredibly adept at withstanding fluid losses. You are not going to crash from dehydration on an average workout,” he said.

Professor Brewer also said the sugar added to sports drinks to increase the body’s absorption of fluid were “only necessary in lengthy endurance events” and that water was sufficient for exercise for anything up to the equivalent of a 10-mile run.

“Run 5km and you might burn 340 calories. Take a sports drink and you offset 130 of those immediately,” said Professor Brewer.

Dr Mitchell Rosner, a kidney specialist from the University of Virginia school of medicine, highlighted the issue of over-hydration causing Exercise-Associated Hyponatremia (EAH), which can be fatal.

He recommended drinking when thirsty to avoid hyponatremia and significant dehydration.