Summer might be finished here in Australia but staying hydrated on the bike is as important as ever. In fact, for years we’ve been bombarded with messages about hydration and performance – “lose more than 2% of your body weight and your performance will decline by x%”, or words to this effect. It’s become burnt into the minds of cyclists the world over. But it’s surprisingly rare that anyone thinks to question this message. Where did it come from? What science is it based on? And can aggressive hydration actually make that much difference? Alan McCubbin investigates.