Fluids for SportBy Jacquie Bird, RD, CDE
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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.
Fluids are required
to replace sweat and respiratory losses (during and after exercise);
strength, endurance and core body temperature. Depending on choices,
provide partial replacement of sodium and potassium as well as
Athletes should be
well hydrated all the time… what does this really mean? The urine
‘lemony-coloured’ and plentiful; conversely, scant volume and darker
dehydration. Of course there is the concern that an athlete may be
large amounts of non-electrolyte fluids, producing copious amounts of
and more than likely will still be dehydrated despite the large volume
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
during and after exercise. Again, it is so important that an athlete
fluid intake during training then use this information to fine-tune for
competition. Research indicates that many athletes replace only 30-70%
lost during exercise. There are many reasons for this; athletes are so
on their training that they can actually forget to drink. Another
that fluid in the mouth, especially plain water actually “turns off”
mechanism, resulting in less fluids being consumed, unless the athlete
paying particular attention and drinking to a ‘plan’.
In the context of
this article it is not possible, nor advisable to give specific
for specific sports, nor for individual athletes, however, these
guidelines, can be used as a starting point:
These drinks are well researched; numerous
been published on sport drinks; they provide fuel (carbohydrates) and
electrolytes, help to prevent fatigue, dehydration, help to maintain a
blood sugar during exercise and assist with rehydration and refueling
exercise. If using powder it is best to follow manufacturers mixing
however depending on the circumstances, powders can be mixed to a
lower concentration of carbohydrates. If the flavor is altered too
voluntary drinking may be decreased and/or the % carbohydrate may be
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.
- sodium: 10-25 mmol/L, improves absorption, flavor and fluid intake
- potassium: 3-5 mmol/L, not required, but many drinks contain potassium
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 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!
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 use energy 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.
Contains fructose and sucrose, (11-15%
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.
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. 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 Review: Research 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.