What is the recommendation for fluid consumption after exercise?

Before exercise:

All athletes should begin exercise well hydrated. To ensure adequate pre-exercise hydration, athletes should drink 2-2.5 cups (500-600mL) of fluid 2 hours before exercise. If tolerated, drink ½ -1 cup (125-250mL) 10 to 20 minutes before exercise. **Note: There is little performance benefit to being over-hydrated so tailor intakes according to your tolerance.

During exercise:

The goal is to balance fluid intakes with sweat and urine losses. Specific recommendations for individual athletes depend on body mass, sweat rate, environment and tolerance. A guideline to start with is ½ - 1 cup fluid every 20 minutes. In hot conditions, it could go as high as 2 cups every 20 minutes. Aim to drink fluids on a consistent schedule (set a watch timer), do not take an "ad hoc" approach. Do not rely on your thirst sensation.

After exercise:

Re-hydration is critical to recovery. It is recommended that athletes drink 3 cups (750mL) of fluid for every pound of body weight lost during exercise. Re-hydration should be completed within 2 hours of finishing exercise.

Should I drink a sports drink?

Sports drinks have been researched extensively and generally provide an excellent alternative to plain water for hard working athletes. During intense aerobic exercise, the body’s preferred source of fuel is carbohydrate (rather than fat or protein) due to the efficiency of energy transfer to fatigued muscles. The majority of sports drinks are formulated to deliver carbohydrates, electrolytes and fluids in such a way that will minimize stomach upset and maximize intestinal absorption. When compared with water, the flavor of sports drinks typically entices athletes to drink more, thus aiding the hydration process.

Take home message:

• Dehydration will impair physical and mental performance.
• Weigh yourself before and after training to learn how much fluid you typically lose during exercise. This will help you develop a good hydration plan.
• Greater sweat losses occur in warm environments. Athletes should re-hydrate with a fluid that includes salt.

Practical Steps

• Always carry fluid with you or know where to find it (convenience stores, water fountains, public washrooms).
• Drink by schedule (set a watch timer), not by thirst.
• Monitor urine frequency and color (aim for pale yellow).
• Estimate your sweat rate by weighing yourself before & after exercise.
• Put more water in your mouth than over your head.
• Start exercise well hydrated and keep your stomach comfortably full.
• Drink 3 cups of fluid for every pound of body weight loss after exercise

Why is hydration important

• To maintain good blood volume, cardiac output and delivery of oxygen to working muscles
• To generate muscle contractions, decrease risk of muscle cramps
• To regulate core body temperature
• To eliminate waste

How do I know if I am dehydrated?

• Unexplained increase in heart rate
• Increased perceived exertion (exercise feels harder than it should)
• Small amounts of dark yellow urine
• Light-headedness, headaches
• Muscle cramps

Acceptable Fluids Losses

As a general rule, aim to keep losses under 1kg (2.2lb) or < 2% of body weight

1kg (2.2lb) = 1 Litre

Adapted from Nutrition for Cyclists, Grandjean & Ruud, Clinics in Sports Med. Vol 13(1);235-246;1994.

Is it possible to over-hydrate?

Yes, it is possible to drink too much water. An athlete exercising for extended periods in warm temperatures and only replacing sweat losses with water may develop a low serum sodium level. This condition is known as hyponatremia and is very dangerous because it can cause headaches, disorientation and even death. Athletes exercising for extended periods in warm climates should use a sports drink that provides sodium, or talk to a sport dietitian about their hydration practice.

How can I monitor my hydration status?

A simple way to estimate your fluid losses is to compare your body weight before and after exercise. Here is what you do:

1. Weigh yourself before and after training. It is best if you can weigh yourself naked, but if that is not possible, then weigh yourself in the exact same clothing before and after. Empty your bladder before you weigh yourself.

2. Subtract your "after" weight from your "before" weight. If you have lost more than 2 lbs, then you need to drink more fluids during training sessions.

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Possibly the most important nutritional intake substance for athletes is Water. For reference purposes, a reliable report published by the Institute of Medicine (IOM) in 2004 suggests that adult women should consume about 2.7 liters of water each day, while adult men should consume about 3.7 liters per day. Athletes need considerably more water than non-athletes !!!

The American Council on Exercise (ACE) recommends these tips for athletes regarding water and additional fluid intake:

• Drink 17-20 ounces of water two to three hours before the start of exercise
• Drink 8 ounces of fluid 20 to 30 minutes prior to exercise or during warm-up
• Drink 7-10 ounces of fluid every 10 to 20 minutes during exercise
• Drink an additional 8 ounces of fluid within 30 minutes after exercising
• Drink 16-24 ounces of fluid for every pound of body weight lost after exercise

On average, female athletes should consume about 16oz water bottles (~8.25) representing 4.0 liters for women. Male athletes should consume about 16oz water bottles (~11.7) representing 5.7 liters for men. Notably, most of us (athletes and non-athletes) would have a hard time drinking this much water every day. The point is to drink A LOT of water to keep your body hydrated properly; especially for sport.

Methods/tools to monitor daily hydration levels:

• Let thirst be your guide
• Urine should be light yellow, even clear (i.e. should look like lemonade, not orange juice), and urination should occur several times each day, every day 

 For more handy info on hydration, visit the CDC hydration website at: http://www.cdc.gov/healthywater/drinking/nutrition/index.html

Sources:

ACE Report:FitFacts Healthy Hydration, American Council on Exercise

ATTENTION : All content relating to nutrition herein should be considered general, non-clinical information and guidance.  Always consult with your doctor or a professional nutritionist when seeking ANY personalized nutrition advice that may significantly affect your immediate and/or long-term health.

Good nutrition and hydration are essential to help you perform at your best when exercising. For anyone who will be exercising for an extended period, it is important to plan what you eat and drink before, during and after exercise. This is especially important for anyone involved in sport where optimal nutrition and hydration can make a significant difference to your performance. For anyone participating in exercise at a more moderate level, a healthy diet that includes plenty of fruit, vegetables and water will usually suffice.

Fuel for exercise

The body’s main sources of fuel during exercise are fat and carbohydrate, and the one you need to focus on is carbohydrate. This is because we all have ample stores of fat to undertake even the longest bouts of exercise (unless in a state of starvation). However, our carbohydrate stores (in the form of muscle glycogen) are more limited and can become significantly depleted during vigorous exercise in excess of 90 minutes or moderate exercise of a longer duration (several hours).

Carbohydrate stores can also become depleted over the course of several exercise sessions, if not replenished through appropriate nutrition between times. Depleted muscle glycogen will impair your capacity to exercise, limiting how fast you can run, cycle or swim. This is clearly evident in some people at the end of a marathon, in which their muscles have become depleted of glycogen and they struggle to maintain a speed faster than a slow jog.

Fluid for exercise

Maintaining your body in a fully hydrated state is essential for both your health and performance when exercising. If you are dehydrated you will have a reduced blood volume and less fluid available to form sweat. Dehydration will reduce your capacity to deliver oxygen to your muscles and your ability to prevent your body from overheating, both of which will adversely affect your exercise performance. So it’s important to be fully hydrated when you start exercising, and to maintain a regular intake of fluids while exercising to prevent dehydration.

Food and fluid before exercise

In most circumstances, most of us will have enough stored fat and carbohydrate to fuel our next exercise session without needing to make special arrangements (as exemplified by those who walk or jog before breakfast). However, if you are undertaking a more prolonged or vigorous bout of exercise, you may wish to maximise your glycogen stores before you exercise, and you can do this by eating a meal between one and 4 hours beforehand. This allows enough time for the meal to be digested. Ideally, you should eat a small amount of food that is low in fibre for easy digestion.

To increase your body’s fuel supply, the meal should be predominantly carbohydrate — approximately 2 to 5 grams of carbohydrate per kilogram of bodyweight. Meals based around rice, pasta, bread or potatoes are often advocated by sports dietitians, and you’ll need to try different ones to see what suits you best. The meal should also be low in fat and protein, to minimise any gastrointestinal discomfort.

For most sports and types of exercise, it is recommended that you drink 400-600 mL of fluid one to 2 hours before the activity, and another 200-400 mL 15 minutes before exercising. Water is usually a suitable choice of fluid to drink before exercising.

Food and fluid during exercise

Fluid loss can impair performance and can affect your body’s ability to control its own temperature. If you are exercising for less than 60 minutes, you should drink approximately 200 mL of fluid every 15-20 minutes. Water is appropriate in this situation. In longer duration activities where there is a risk of glycogen depletion, such as more than 60 minutes of vigorous exercise, a sports drink containing glucose and electrolytes can be most effective. And for activities lasting several hours these sports drinks can be supplemented with energy bars.

Post-exercise food and fluid

After exercise it is important to restore your body’s fuel and fluid stores to normal levels. For most people this is easily achieved by following a healthy diet that includes plenty of fruit and vegetables, and plenty of non-alcoholic, non-caffeinated fluids.

Replacing fluid stores largely depends on how much fluid was lost during exercise. This can be calculated by comparing your pre- and post-exercise bodyweight. A simpler method is to check your urine. You need to drink sufficient fluid until you are passing clear, dilute urine.

The amount of fluid that you'll need to drink will depend upon how much you’ve sweated and the temperature of the environment. So on hot days after a vigorous bout of exercise, you may need to drink several litres. In doing so, be wary of consuming it in the form of sugary drinks, as you may take in more calories than you’ve burned off during the exercise. This may not be a problem if you are a highly trained sports person with a good body composition, but will be contrary to your goals if you are trying to lose weight.

To replenish your glycogen stores after exercising vigorously, you need to eat 1-1.5 grams of carbohydrate per kilogram of bodyweight within the first couple of hours after exercise. Ideally, this should be in the form of high GI foods, such as sports drinks, muffins or white bread. Over the 24 hours after exercise, a total of 7 to 10 grams of carbohydrate per kilogram of bodyweight should be ingested to maximise the glycogen stores again, thereby preparing you for your next bout of exercise.

Note of caution

People with diabetes, people with metabolic disorders and those on special diets should consult their specialist and dietician for advice on how to modify food and fluid intake in accordance with exercise.

1. Australian Institute of Sport [website]. Fluid: who needs it? (updated 2009, July). Available at: http://www.ausport.gov.au/ais/nutrition/factsheets/hydration2/fluid_-_who_needs_it (accessed 2010, Feb 9)2. Australian Institute of Sport [website]. Eating before exercise (updated 2009, July). Available at: http://www.ausport.gov.au/ais/nutrition/factsheets/competition_and_training2/eating_before_exercise (accessed 2010, Feb 15)

3. Australian Institute of Sport [website]. Recovery nutrition (updated 2009, July). Available at: http://www.ausport.gov.au/ais/nutrition/factsheets/competition_and_training2/recovery_nutrition (accessed 2010, Feb 15)