You have to drink to perform at your best, however there are more and more studies showing that drinking too much to avoid dehydration during long training sessions and sports events is in fact unnecessary and in some cases even fatal.
Nowadays few people go jogging, never mind racing, without a bottle of water or sports drink. The fear of dehydration is ill-founded and even dangerous, since constant over-drinking may cause potentially fatal exercise-associated hyponatraemia (EAH). This is caused by consuming abnormally huge volumes of fluid during training.
EAH was first reported in 1985 by a research group led by Professor Timothy Noakes of the Sports Institute of South Africa, University of Cape Town. The total of documented fatalities from EAH was at least 14; with 1600 recorded near-fatalities around the world. In contrast, no athlete has ever died of dehydration during or after a race. So why do people have such fear of dehydration?
Dehydration, by as little as two per cent of body mass (1.4kg for a 70 kg person), can decrease both mental (focus, concentration, reaction time) and physical (endurance) performance. The negative impacts of dehydration on endurance performance are proven with a wealth of scientific evidence. According to the published scientific evidence, it’s agreed by experts avoiding dehydration greater than 2% of body mass loss during endurance exercise should be considered to avoid impairments to endurance performance.
However, there is also scientific evidence that’s contrary to this, for instance that by Professor Tim Noakes in his book Waterlogged: The Serious Problem of Overhydration in Endurance Sports (2012) and that by a research team led by Professor Paul Laursen of New Zealand’s Sport Performance Research Institute. The latter’s study, in the British Journal of Sports Medicine is entitled: Current hydration guidelines are erroneous: dehydration does not impair exercise performance in the heat. They studied well-trained cyclists in a laboratory setting. Crucially the cyclists didn’t know their hydration status and were exposed to wind speeds that were similar to weather conditions outdoor. They discovered that, in contrast with a well-established dogma, dehydration of more than 2% of body weight increases perceived effort and decreases aerobic performance, especially in warm-hot conditions.
It was long believed that being dehydrated leads to poor performance, but recent evidence has not proven a reduction in performance but has shown that drinking too much liquid can actually be a problem. So make sure you get reasonably hydrated before a race or a training session, without going overboard. During a race or training drink to thirst. If you are thirsty, drink, if you aren’t then you don’t need to. This is the key.