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May 12/15 10:30 am - Brock Study Debunks Dehydration Performance Impairment Myth

Posted by Editoress on 05/12/15

New research by scientists at Brock University has debunked the widely-held belief that dehydration saps the strength of athletes performing in hot conditions.

It is common to see distance runners or cyclists gulp water and other drinks during long races, trying to replenish fluids and avoid the loss of strength that has long been accepted as a consequence of dehydration.

But the Brock study, published this month in the Scandinavian Journal of Medicine and Science in Sports, concludes there is no such impairment.

Lead researcher Stephen Cheung, a renowned kinesiologist whose research subjects have ranged from Olympic athletes to offshore oil workers, said his team's findings refute the long-unquestioned tenet that water loss hinders a competitor's performance.

This particular research involved 11 trained racing cyclists who wore IV drips while riding stationary bikes under competition-like conditions. Some cyclists had IV drips containing a saline solution to replenish fluids lost through sweat, but others had IV drips that were shams, providing no rehydration at all.

The cyclists were not told which type of IV drip they were wearing, and the researchers found there was virtually no difference in their performances.

Cheung, himself a long-distance cyclist, is the Canada Research Chair in environmental ergonomics. His research team took an unprecedented approach in gauging the impacts of hydration on human resilience.

"We're the first study to separate the conscious awareness of hydration status to truly test that by itself," said Cheung. "This includes all the studies used to develop current hydration guidelines."

"All existing studies manipulate hydration by giving or not giving water, so that manipulates both the physical state of hydration and also the perception of drinking and thirst. In other words, 'I'm thirsty or upset that I don't get to drink, so I'm not going to ride as hard'."

"What we've found was really novel. Even at up to three per cent body mass dehydration, no impairment was seen in exercise in the heat."

Cheung said current guidelines repeatedly emphasize that athletes need to keep hydration within two per cent of body mass, or pay the price in terms of performance and health effects.

"We've just proven that it's not so. This also supports why elite marathoners, even in the heat, rarely drink if at all."


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