Athletes failing to hydrate
Issue: Volume 29 Number 2
As a coach, you will already know how important it is to make sure your athletes have ready access to fluids during a game. But are you really aware of how many players turn up to training or competitions already dehydrated?
In a new research paper published in Applied Physiology, Nutrition, and Metabolism in June, 329 gym-goers' hydration levels were tested before they started their workout. Almost half of the 329 exercisers tested were dehydrated before they even started exercising (Stover et al 2006).
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In-gym study: key findings More than half of the participants thought they were properly hydrated (Stover et al 2006). This is not surprising, as the body does not perceive thirst until dehydration has resulted in losses of about 2 per cent of body weight (Sawker and Pandolf 2001). It has been found that once the body reaches this point of dehydration it is not easy to rehydrate by drinking water (Brake 2001). In fact, exercisers tend to replenish only about 50 per cent of the fluids they lose during a workout when they drink plain water Passe 2001). In the in-gym study, more than two-thirds drink plain water and one-third said they drink nothing during exercise, while nearly 50 percent admitted they struggle to drink enough throughout the day (Stover et al 2006). |
Pre-game dehydration is a challenge faced by many athletes, from elite-level sporting celebrities to children playing Saturday football.
The Gatorade Sports Science Institute has recently tested numerous athletes at the elite level of Australian sport, including the Australian men's cricket team, Australian men's basketball team, netballer Cath Cox, and Ironman Chris Legh to name a few.
Testing on these athletes involves a urine specific gravity test. Essentially, a urine sample is tested to measure the concentration of solutes it contains – the higher the concentration in relation to fluid content, the higher the level of dehydration. A urine specific gravity of greater than 1.020 is considered to signify a dehydrated status.
Of the 29 Australian cricketers and basketball players tested, 20 tested had a urine specific gravity greater than 1.020, indicating that these players were dehydrated at the start of the day.
Professor Louise Burke, Head of Nutrition at the Australian Institute of Sport, who was also involved in the tests, views their results as representative of teams at an elite level and regards testing like this as central to improved awareness of hydration: 'Clearly, it is not helpful to start an exercise session already dehydrated, especially in hot weather.
'The good news is, the more we understand through tests like this, the more we can do to adapt athletes’ hydration practices before, during and after exercise to make sure they stay well hydrated. The results of the cricket testing drew the players’ attention to their day-to-day hydration practices and will help them understand how they need to adapt their fluid strategies to stay on top of their game.'
Research into younger athletes shows that they too commonly turn up to training dehydrated (Walker et al 2004). Among children this is a particularly serious problem. They produce more metabolic heat per kilogram of body weight during exercise, and have a reduced sweating capacity which lessens their ability to lose heat through sweat evaporation (Bar-Or 1989).
But children are certainly not the only ones that should be concerned with the effects of dehydration – there is a clear incentive to make sure all athletes keep thirst at bay. Many studies report that when athletes exercise with fluid deficits of 2 per cent or greater, there is a detectable reduction in performance, endurance or skill (Caldwell, Ahonen and Nouisiainen 1984; Nielsen et al 1981). , This is particularly apparent in hot conditions
The results of pre-training hydration tests make it clear that maintaining proper hydration relies on an effective hydration strategy which starts before players arrive on the field of play. It is also important to ensure these practices do not rely on thirst alone, and incorporate the right fluids to combat dehydration effectively.
Practical tips for athletes
- Encourage each athlete to develop a daily fluid intake plan that is suited to their fluid needs, and altered according to the weather and their exercise activities. This plan should avoid fluid extremes. Just as it is important to avoid dehydration, it is also important not to overhydrate with excessive fluid consumption
- Thirst is a sign of dehydration, and lags behind actual fluid needs. It may also be turned off by drinking small volumes of fluid before full hydration is restored. While it provides some information about fluid needs and the success of a fluid plan, other information should be considered.
- Encourage athletes to keep an eye on the volume and colour of their urine.
- Research has shown that a lightly flavoured beverage with a small amount of sodium, like Gatorade, encourages people to drink greater volumes of fluid and better match their fluid needs (Wilk and Bar-Or 1996).
- To reduce the risk of waking up dehydrated on the day of competition or training, some athletes need to develop special strategies to replace fluid and electrolytes on the previous day. The use of a sports drink may be part of the strategies used to reduce the body’s fluid output and enhance effective rehydration.
Keep an eye out for news of a new hydration tool kit being developed by Gatorade incorporating a hydration protocol developed by the Australian Institute of Sport.
References
Bar-Or O 1989, Temperature regulation during exercise in children and adolescents. In: Gisolfi C, Lamb DR, eds.Perspectives in Exercise and Sports Medicine, Il. Youth, Exercise and Sport. Indianapolis, IN: Benchmark Press; 1989, 335-367.
Brake, D 2001, Fluid consumption, sweat rates and hydration status of thermally stressed underground miners and the implications for heat illness and shortened shifts. Proc 2001 Qld Mining Occ Health and Safety Conf Townsville, 2001.
Caldwell, J, Ahonen, E and Nousiainen, V 1984, 'Differential effects of sauna, diuretic and exercise induced hydration. Journal of Applied Physiology, 57, pp 1018-1023.
Nielsen, N, Kubica, R, Bonnesen, A, Rassmussen, IB, Stokolosa, J and Wilk B 1981, 'Physical work capacity after dehydration and hyperthermia: a comparison of the effect of exercise versus passive heating and sauna and diuretic dehyrdation', Scandinavian Journal of Sports Science, 3, pp. 2-10.
Passe, D. 2001, 'Physiological and psychological determinants of fluid intake', in RS Maughan and R Murray (eds) Sports Drinks: Basic Science and Practical aspects, CRC Press, New York.
Sawka, M.N. and Rudolph, KB 2001, 'Effects of body water loss on physiological function and exercise performance' in C Gisolfi and DR Lamb (eds), Perspectives in Exercise Science and Sports Medicine: Fluid Homeostasis During Exercise, Vol. 3, Cooper Publishing Group, Traverse City Michigan.
Stover, B, Petrie, HJ, Passe, D, Horswill, CA, Murray, B and Wildman R 2006, 'Urine specific gravity in exercisers prior to physical training, Applied Physiology, Nutrition and Metabolism, 31(3), pp. 320-7.
Walker, SM, Casa DJ, Levrault, ML, Psathas, E and Sparrow, SL 2004, 'Children participating in summer soccer camps are chronically dehydrated', Medicine and Science in Sports and Exercise, 36(5) pp.S180-1.
Wilk, B and Bar-Or, O 1996, 'Effect of drink flavour and NaCI on voluntary drinking and hydration in boys exercising in the heat', Journal of Applied Physiology, 80, pp. 1112-7.
