Is Drinking to Thirst Optimum?

Backgrounds/Aims: Prior to 1969, athletes were advised to avoid drinking during exercise. At least 4 subsequent events led to the adoption of a radically different approach. By 1996, all exercisers were advised to drink ‘as much as tolerable’ in order to insure that they did not lose any weight during exercise – the ‘zero percent dehydration’ doctrine. This advice requires that athletes drink enough to ‘stay ahead of thirst’. The act of drinking is a basic survival instinct that has been regulated by complex, unconscious controls ever since the first fish-like creatures moved onto land and should not require conscious adjustment. Methods: Literature survey of all studies comparing the effects of drinking to thirst (ad libitum) and drinking to prevent any weight loss during exercise – the ‘zero percent dehydration’ doctrine. Result: No study found that drinking more than ad libitum during exercise produced any biological advantage, but it could cause exercise-associated hyponatremia. Conclusion: Drinking ad libitum appears to optimize performance and safety during exercise in many situations. The presence of thirst, not of waPublished online: February 22, 2011 Prof. T.D. Noakes Department of Human Biology, Sports Science Institute of South Africa Boundary Road Newlands, 7925 (South Africa) Tel. +27 21 650 4557, Fax +27 21 686 7530, E-Mail timothy.noakes @ uct.ac.za © 2011 S. Karger AG, Basel 0250–6807/10/0576–0009$26.00/0 Accessible online at: www.karger.com/anm D ow nl oa de d by : 54 .1 91 .4 0. 80 4 /6 /2 01 7 3: 07 :5 0 A M