New research carried out at Brock University in Ontario refutes the belief that even minor dehydration will hamper sporting performance. Researchers found that even at up to three per cent body mass dehydration, no impairment was seen in exercise in the heat.
Lead researcher Stephen Cheung, a renowned kinesiologist and a long-distance cyclist himself, told The Hamilton Spectator that current guidelines stating that athletes need to keep hydration within two per cent of body mass or suffer hampered performance and health effects weren’t accurate. "We've just proven that it's not so. This also supports why elite marathoners, even in the heat, rarely drink if at all."
The study, published in the Scandinavian Journal of Medicine and Science in Sports, involved 11 trained racing cyclists wearing IV drips while riding stationary bikes under competition-like conditions. While some had IV drips containing a saline solution to replenish fluids, others had fake IV drips that didn’t provide rehydration.
Cheung said it was the first study to separate the conscious awareness of hydration so as to test only hydration status itself. "This includes all the studies used to develop current hydration guidelines,” he said.
"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."
British Cycling refers to existing research when asserting that a two per cent drop in body weight due to sweating ‘will impair performance noticeably’ and that a five per cent drop will see ‘your capacity for work drop by up to 30 per cent’.
It recommends that riders conduct ‘a 60-minute sweat test’ to deduce what they should be drinking during a ride. This simply involves weighing yourself before and after a one-hour ride on which you don’t drink a thing.
Apparently, most riders find that they typically lose 500-1000ml per hour and British Cycling recommends taking in at least 75 per cent of that volume per hour while riding.