Steve King

Fluids for Sport

By  Jacquie Bird, RD, CDE
Sports Dietitian
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Fluids are a key part of any sports training program. In fact, many sports dietitians state being properly hydrated before, during and after training/competition can have a bigger impact on performance than fuel!Every athlete is unique in that they require a varying amount of fluid on training and non-training days. This is dependant on a number of factors, such as type of sport, genetics, intensity, environmental factors, (temperature, humidity, wind); sweat rate, body size, gender, age and fitness level. No longer are fluid recommendations based on the “ one size fits all” premise.  

Athletes need to determine, during training the amount and type of fluids required, and stay with this plan during competition. After competition it is important to reflect back to see if the plan requires any fine-tuning. 

Fluids are required to replace sweat and respiratory losses (during and after exercise); maintain strength, endurance and core body temperature. Depending on choices, fluids may provide partial replacement of sodium and potassium as well as carbohydrates for fuel. 
Athletes should be well hydrated all the time… what does this really mean? The urine should be ‘lemony-coloured’ and plentiful; conversely, scant volume and darker colour indicates dehydration. Of course there is the concern that an athlete may be consuming large amounts of non-electrolyte fluids, producing copious amounts of urine, and more than likely will still be dehydrated despite the large volume of fluids consumed.

Not all sport scientists agree on the amount of fluid recommended. For example IMMDA, 2006 revised their fluid recommendations for runners and walkers, at which time they stated that athletes “should drink to thirst”. On the other hand, fluid guidelines from the AIS and SDA indicate, “once athletes are thirsty they are already dehydrated”. IMMDA also recommends that fluid intake be based on ‘time’ or a ‘race pace’, so the slower runner/walker should be consuming less fluid that the fast runner, even though the slower athlete will be on the course longer.The joint position paper of the Dietitians of Canada, American College of Sports Medicine and the American Dietetic Association, states that adequate fluid intake before, during and after exercise is necessary for health and optimal performance. No specific recommendations are made for fluid intake prior to and during exercise; however for recovery, the recommendations are to consume approximately 16-24 oz (450-675 ml) for every pound (0.5kg) of body weight lost during exercise. 

Many Registered Sports Dietitians recommend fluid replacement based on body weight, rather than a set amount of fluid before, during and after exercise. Again, it is so important that an athlete practice fluid intake during training then use this information to fine-tune for competition. Research indicates that many athletes replace only 30-70% of sweat lost during exercise. There are many reasons for this; athletes are so focused on their training that they can actually forget to drink. Another concern is that fluid in the mouth, especially plain water actually “turns off” the thirst mechanism, resulting in less fluids being consumed, unless the athlete is paying particular attention and drinking to a ‘plan’. 

In the context of this article it is not possible, nor advisable to give specific recommendations for specific sports, nor for individual athletes, however, these general guidelines, can be used as a starting point:

  • Prior to training: – be well-hydrated – obtain an accurate body weight- 2 to 3 hours prior: 500 – 600 mls – 15 to 20 minutes prior: ‘top-up’ with 200 – 300 mls- sports drinks.
  • During training: 200 – 300 mls every 10 to 20 minutes- sports drinks.
  • Recovery: – weigh again- replace  fluids @1 ½ times weight lost -1 kg weight lost = 1 ½ L fluid required – sports drinks- chocolate milk and liquid meal replacements containboth carbohydrate and protein.

The pros and cons of specific beverages need to be mentioned, including sports drinks, sports water, energy drinks, other caffeine-containing beverages, juice, water and of course alcohol. 

Sports Drinks

These drinks are well researched; numerous articles have been published on sport drinks; they provide fuel (carbohydrates) and electrolytes, help to prevent fatigue, dehydration, help to maintain a stable blood sugar during exercise and assist with rehydration and refueling after exercise. If using powder it is best to follow manufacturers mixing guidelines; however depending on the circumstances, powders can be mixed to a higher or lower concentration of carbohydrates. If the flavor is altered too much, voluntary drinking may be decreased and/or the % carbohydrate may be too high resulting in gastrointestinal upset.

The sodium and potassium concentrations of most sport drinks will not replace the salt and to a minimal extent the potassium lost in sweat. There are obviously many athletes, who are heavy sweaters, and the concentration of sodium in the sweat may be high; these athletes may want to consider ‘electrolyte replacement supplements. Depending on intensity, sports drinks may be the preferred choice even if the training is less than 1-hour duration. Plain water is appropriate for activities of less than one hour, depending on intensity, environmental conditions, pre workout hydration status and the athletes preferences.
Consider these guidelines when deciding which brand to purchase:

  • carbohydrates: optimal: 6-8 % (6-8 grams/100 ml)
  • carbohydrates: a mix of glucose, glucose polymers, sucrose and fructose, this mix provides better absorption
  • electrolytes:

– sodium: 10-25 mmol/L, improves absorption, flavor and fluid intake

– potassium: 3-5 mmol/L, not required, but many drinks contain potassium              

  • temperature: cool drinks are better tolerated
  • non-carbonated: easier to swallow, therefore more fluid is consumed
  • flavor: fluid intake is significantly increased compared to plain water
  • other ingredients: such as herbs and vitamins, not necessary, increase cost, may interfere with flavor

Sports Water

These drinks are gaining popularity with the “weekend warrior”, or social exerciser.

They are a clear, lightly flavored drink, which contain, additives such as B-vitamins, anti oxidants and electrolytes. So far, research does not show any improvement in performance with the addition of B-complex vitamins or anti-oxidants. Of course, further research may changes this.

The carbohydrate and sodium content are lower than most sports drinks; also the flavor is less pronounced. Due to their lighter flavoring and lower sodium content, they may be good for athletes who want/require more than just plain water but do not want the intense flavor of a sports drink per se. For short duration, less intense exercise or for those athletes wanting to make sure they consume more fluids over the day, these may be beneficial. For moderate to high intensity and longer duration training and practice, sports waters do not provide adequate carbohydrates or sodium.

Caffeine-containing Beverages
Even though caffeine was taken off the WADA list of banned substances in 2004, it remains a controversial topic with athletes, coaches and sport dietitians alike.

Caffeine is a drug that occurs naturally in the leaves, nuts and seeds of a number of plants.

Dietary sources, typically have 30-100 mg caffeine per serving of coffee or tea. Keep in mind, the size and strength of a typical ‘cup’ of coffee has increased dramatically over the last few years. Some prescription and over-the-counter medications have 200-300 mg of caffeine/tablet.Caffeine has numerous actions on various body tissues. Responses vary between individuals and include positive and negative responders as well as non-responders. Some research indicates that caffeine can decrease the perceived rate of exertion for some athletes. Caffeine was also thought to assist in utilization of fat as a fuel source, so that glycogen could be spared; further research showed this was not the case.

Although many of us enjoy a cup of java, and can’t do without that jolt in the morning, we need to remember that excess caffeine can lead to increased heart rate, increased urination, nausea and vomiting, restlessness, sleep deprivation, anxiety, tremors and depression.

For many years, health professionals recommended that caffeine-containing beverages should not be considered as part of the fluid intake, in fact it was considered a ‘dehydrator’; this has changed over the last few years. For some individuals these beverages may provide a significant source of fluids, especially if they are habitual coffee/tea drinkers. Keep in mind though, there is little, if any nutritional value to coffee or tea compared to other fluids such as white or chocolate milk and juice. So keep the use of caffeine-containing beverages to a moderate intake, they should not replace more nutritional fluids.Also of note, coffee and tea are not considered the best source of caffeine for sport due to their unpredictable caffeine content. There is some evidence to suggest there are other compounds in coffee, which may negate the ergogenic effect of the caffeine!

Soda Drinks
If using, remember to de-fizz; the carbonation may actually decrease fluid intake (a sore throat may result if trying to swallow quickly). The bubbles in soda also can give a false sense of fullness, resulting in less fluid being consumed. Soda drinks contains less sodium than most sport drinks. The high fructose content (11%) may lead to gastrointestinal upsets. However, soda does provide a nice ‘flavor change’ from sports drinks. Test these out in training before attempting to use in competition.

Energy Drinks

Energy drinks are advertised as soft drinks with energy ‘boosters’. This kick comes from the addition of many caffeine-containing ingredients, such as guarana, yerba mate, and kola nuts and the high sugar content (almost double that of a soda pop). The higher concentration of carbohydrate and carbonation may lead to gastrointestinal upsets and dehydration. Other ingredients such as taurine, herbs (ginseng, ginkgo biloba) and vitamins do not improve performance. 

Health concerns related to energy drinks: increased heart rate, increased anxiety, nervousness, heart palpitations and gastric upset.

Young athletes (less than 18 years), women who are pregnant or breast-feeding, those with diabetes or heart disease should not useenergy drinks.

Use caution if using energy drinks; the side effects far outweigh any performance enhancing benefits; always discuss their use with a Registered Sports Dietitian or a Doctor specializing in Sports Medicine.

If you need an energy boost, use “real” foods, grab a healthy snack such as a piece of fruit, low fat yoghurt, chocolate or white milk. Being dehydrated can cause fatigue, not getting enough sleep can cause fatigue, so make sure you are well-hydrated and get plenty of rest.Fruit Juice

Contains fructose and sucrose, (11-15% carbohydrate); this concentration increases the risk of gastrointestinal upsets.

Juice may be beneficial as an every-day source of fluids, carbohydrates and some vitamins, however juice is not recommended before or during training and/or competition.


Last but not least, the use of alcohol in sport!

Even though alcohol and some sports, especially some team sports are closely associated, alcohol is not a sports-performance enhancer. It is in fact detrimental to training, competition and the recovery process. Some research indicates that alcohol has a detrimental effect on concentration, reaction time and co-ordination. Other negatives to alcohol use include impaired digestion, decreased nutrient absorption and compromised fuel metabolism.

Athletes need to consider the impact of excessive alcoholic consumption on their sport performance, including increased urine losses, inadequate post-exercise rehydration, decreased glycogen replacement, swelling of blood vessels, worsening of certain injuries, poor judgment, increase in fat stores and weight gain.

Not to mention the hangover the next morning, which again may lead to decreased fuel and fluid intake, compromising recovery, performance and tissue repair/resynthesis.

Word of advice, avoid alcohol consumption before, during and after training.

Final considerations for fluid intake and sport:

  1. Have a drink bottle with you: water, sports water or sports drink
  2. Be well hydrated before starting an activity
  3. Always ‘top up’, this improves absorption in the gut
  4. Do not over hydrate
  5. Practice in training, fine tune for competition
  6. Weigh before and after training, know your weight loss, replace accordingly with appropriate fluids
  7. More than 2% body weight loss will result in impaired performance


1. Australia Institute of Sport, Fact Sheets, Department of Sports Nutrition, 2009.

2. Health Canada: Safe Use of Energy Drinks, 2005.

3. International Marathon Medical Director’s Association, Revised Fluid Recommendations for Runners and Walkers, 2006.

4. International Society Sports Nutrition: Exercise and Sport Nutrition ReviewResearch and Recommendations, 2004.

5. Joint Position Paper of the Canadian Dietetic Association, American College of Sports Medicine and the American Dietetic Association, Nutrition and Athletic Performance, 2008.

6. National Athletic Trainers Association Position Statement: Fluid Replacement for Athletes, 2000.

7.Practical Sports Nutrition, Louis Burke, 2007.

8. Sports Dietitians of Australia, Fact Sheets, 2009.

9. World Anti-Doping Agency, 2010.

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