Reappraisal of hydration guidelines

December 2, 2013 by Camilo Mejia Giraldo, Science Network WA
Reappraisal of hydration guidelines
Dr Wall says although the research does not seek to replace official hydration guidelines, it questions past studies. Image: The Pug Father

Surprising results of a study on dehydration and athletic performance will encourage greater analysis of the subject among the science community, according to researchers involved.

Conducted at Edith Cowan University, the study sought to better understand the precise level where dehydration begins to have a detrimental effect on —commonly perceived to occur when the body experiences less than two per cent loss of

Using a time trial method, the study analysed the performance of 10 well-trained cyclists at different stages of dehydration and found no differences in the athlete's physical performance, heart rate, or perceptual responses.

"There is a large perceptual component, and we have been able to remove that placebo effect," says Dr Bradley Wall, lead author and lecturer at Murdoch University who says a psychological barrier was removed by blinding the participant to their hydration status.

"Everyone has told me previously that if I'm dehydrated then I'm going to go slower; subconsciously you know that," he says.

The 25km time trial required participants to cycle in a chamber that mimicked real-world conditions – including wind speed and temperature – while being intravenously kept at particular dehydration levels.

"By infusing [saline-based solution] directly into the bloodstream it not only blinded the participants on how much rehydration they were actually receiving, but also reduced some of the effects of rehydration, like gastric emptying," Dr Wall says.

By analysing rectal temperatures and heart rates during the trial, and samples of blood to measure concentrations of electrolytes, levels of chloride, sodium and potassium after the trial, the study was able to show the effects of differing levels of dehydration and rule out any possible variables.

Contrary to the hypothesis of the researchers, the time trial showed near equal results among the participants in all areas.

"We know that if people lose a significant amount of body mass there is going to be a performance decrement, but we've shown that up to less than three per cent [body mass loss] there was no decrement," Dr Wall says.

The results have already drawn criticism on their apparent challenge of hydration guidelines.

Dr Wall says although the research does not seek to replace official hydration guidelines, it questions past studies.

"You read magazine articles that say that two per cent dehydration can impair performance by 10 per cent.

"When you go searching for the literature you find that the studies are not really conducted in real world conditions.

"We are not saying that isn't bad … we are saying that the studies which the guidelines have been based on probably need to be readdressed," he says.

Explore further: Athletes not slowed by dehydration, study finds

Related Stories

Athletes not slowed by dehydration, study finds

October 1, 2013
(Medical Xpress)—New research led by Murdoch University and Edith Cowan University has shed new light on a long-held belief that dehydration causes a decrease in high-level athletic performance.

Milk better than water to rehydrate kids: study

August 17, 2011
Active children need to be watered with milk. It's a more effective way of countering dehydration than a sports drink or water itself, say researchers at McMaster University.

Dehydration likely among young athletes, research finds

August 1, 2013
(Medical Xpress)—Even when young players have water available while practicing soccer, they still became dehydrated, a University of Arkansas researcher found in a field study in Greece. Stavros Kavouras, an assistant professor ...

Parenteral hydration no benefit for cancer care in hospices

November 28, 2012
(HealthDay)—For patients with advanced cancer in hospices, providing parenteral saline (1 liter per day) does not improve symptoms associated with dehydration, quality of life, or overall survival compared with placebo, ...

Cranky today? Even mild dehydration can alter our moods

February 17, 2012
Most people only think about drinking water when they are thirsty; but by then it may already be too late.

Recommended for you

Sleep better, lose weight?

January 17, 2018
(HealthDay)—Sleeplessness could cost you when it's time to stand on your bathroom scale, a new British study suggests.

Who uses phone apps to track sleep habits? Mostly the healthy and wealthy in US

January 16, 2018
The profile of most Americans who use popular mobile phone apps that track sleep habits is that they are relatively affluent, claim to eat well, and say they are in good health, even if some of them tend to smoke.

Improvements in mortality rates are slowed by rise in obesity in the United States

January 15, 2018
With countless medical advances and efforts to curb smoking, one might expect that life expectancy in the United States would improve. Yet according to recent studies, there's been a reduction in the rate of improvement in ...

Teens likely to crave junk food after watching TV ads

January 15, 2018
Teenagers who watch more than three hours of commercial TV a day are more likely to eat hundreds of extra junk food snacks, according to a report by Cancer Research UK.

Can muesli help against arthritis?

January 15, 2018
It is well known that healthy eating increases a general sense of wellbeing. Researchers at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have now discovered that a fibre-rich diet can have a positive influence ...

Your dishwasher is not as sterile as you think

January 13, 2018
(HealthDay)—Your dishwasher may get those plates spotless, but it is also probably teeming with bacteria and fungus, a new study suggests.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.