Conference Calls for Monitoring of Hydration for Optimum Athletic Performance   

A study to be presented at the British Nutrition Foundation's conference, Hydration and Health, in London on 11th November, calls for sports coaches to ensure adequate provision of fluids and access to weighing scales at training and competition venues, to help cut down the number of athletes competing while dehydrated.  

The study¹, by Dr Karen Reid of University of Wales, Trinity St David, is the first large scale study in the UK to investigate hydration knowledge, attitudes and practices of athletes and sportspeople, participating at a national level in both team and individual sports.  It shows that 46% of athletes rely on their coaches for hydration information but only 6.3% of athletes ‘often’ use simple and effective weighing measurements, before and after exercise, to estimate their fluid requirements.  

It is widely acknowledged in the sports world that dehydration increases cardiovascular strain, thermal strain, glycogen utilisation (in turn depleting valuable stores in the body), muscle lactate production (contributing to muscle fatigue) and the perceived rate of exertion.  Yet, research being presented at the conference, will show that many athletes still compete dehydrated and that their knowledge about hydration and practices for monitoring hydration levels is limited.

Dr Karen Reid commented: “There is a substantial body of previously published research² indicating that many athletes compete in a dehydrated state and there appears to be no correlation between sweat loss and fluid intake during exercise.  This suggests that athletes are not drinking at a rate that relates to their individual sweat rates.”

A second paper³, by Dr Ricardo Costa of Coventry University, also being presented at the British Nutrition Foundation conference, will report on the hydration status of runners competing in a multi-stage ultra-marathon, set in a hot ambient environment.  The study shows that while ultra-marathon runners are reported to be consuming sufficient fluid for their daily activity levels, in doing so they are more likely to be at risk of over-drinking than dehydration. Over-drinking can lead to hyponaetremia (low levels of sodium in the blood) and its associated health consequences (e.g. hyponaetremic encephalopathy – swelling of the brain), and also reductions in exercise performance.  

Bridget Benelam, nutrition scientist at the British Nutrition Foundation (BNF) comments: “Clearly the hydration issues for athletes differ, which confirms the need for coaches and sportsmen alike to pay more attention to simple measurement techniques.”

“For the enthusiastic amateurs among us, who want to enjoy running or taking part in individual or team sports, the principles still apply.  If you want to keep your body working to its optimum level, it’s advisable to keep a check on your hydration level.”

To help amateur and professional sportspeople alike stay in top condition, the BNF has put together the following simply hydration measurement tips:*

Before Exercise    

•    Drink about 500mls of fluid 2 hours before exercising to allow time for any excess to be lost in urine
•    Then drink a further 125-250mls immediately before exercise
•    Weigh yourself (see After Exercise below).
During Exercise  

 •    Drink small amounts regularly, aiming for 125-250mls every 10-20 minutes. You can maintain optimal performance by replacing at least 80% of sweat loss during performance.
After Exercise    

•    You need to consume 150% of the amount of fluid lost during exercise to allow for the fluid that is naturally lost from the body via urine.  For example, if you have lost 1L of fluid, you need to drink 1.5L.
•    The easiest way to calculate your fluid loss is to weigh yourself before and after training. 1kg of weight loss resulting from exercise, is roughly equivalent to 1L of fluid loss.
•    Weight loss in kilos then needs to be multiplied by 1.5 to calculate the amount of fluid to consume
•    This does not need to be consumed all at once, immediately after exercise. Aim for 500ml immediately after training, then consume the remainder at intervals afterwards.

*Note. These tips are for general use and do not constitute specific advice for individuals.

For further information, interviews and images contact:

Bridget Benelam
Tel: 0207 4046504/07966 032293. Email:  

Dr Emma Williams
Tel: 0207 4046504. Email

¹‘Knowledge, Attitudes and Practices of Athletes and Sportspeople with Respect to Their Hydration’

² American College of Sports Medicine. Position stand: Exercise and fluid replacement. Med. Sci. Sports Exerc. 2007; 39:377-390
Burke, L.M. Fluid balance during team sports. J. Sports Sci. 1997; 15: 287-295
Maughan, R.J. Merson, S.J., Broad, N.P., Shirreffs, S.M. Fluid and electrolyte intake and loss in elite soccer players during training. Int. J. Sport. Nutr. Metab. 2004; 14: 333-346
Maughan, R.J., Shirreffs, S.M., Merson, S.J. and Horswill C.A. Fluid and electrolyte balance in elite male football (soccer) players training in a cool environment. J. Sports Sci. 2005; 23: 73-79
Maughan, R.J., Watson, P., Evans, G.H., Broad, N.P., Shirreffs, S.M. Water balance and salt losses in competitive football. Int. J. Sport. Nutr. Metab. 2007; 17:583-594

³’The use of bioelectrical impedance analysis in assessing hydration status of runners competing in a multi-stage ultra-marathon conducted in a hot ambient environment’

Notes for Editors:
1.    The British Nutrition Foundation (BNF) conference Hydration and health is being held in London on the 11th November 2010.
2.    BNF offers an expert nutrition information service for journalists and media. Tel: 02074046504. Email:
3.    BNF was established over 40 years ago and exists to deliver authoritative, evidence-based information on food and nutrition in the context of health and lifestyle. The Foundation’s work is conducted and communicated through a unique blend of nutrition science, education and media activities. BNF’s strong governance is broad-based but weighted towards the academic community.  BNF is a registered charity that attracts funding from a variety of sources, including contracts with the European Commission, national government departments and agencies; food producers and manufacturers, retailers and food service companies; grant providing bodies, trusts and other charities. Further details about our work, governance and funding can be found on our website ( and in our Annual Reports.
4.    The Foundation thanks  the European Hydration Institute for financial support that has enabled the cost of this event to delegates to be subsidised  

Last reviewed November 2010. Next review due December 2013.