Wednesday, June 8, 2011

Hydrate to Win: Hydration and Performance

By Anne Guzman, Peaks Coaching Group Nutritionist

Athletes must be fully hydrated before they train or compete because the body cannot adapt to dehydration. Training quality will suffer if we allow ourselves to become dehydrated during training. The same goes for competition. In fact, as little dehydration as 2% can have a significant negative impact on performance. The sensation of thirst rarely occurs before the loss of 1.5 to 2 liters of water (approximately 2% of body weight) due to plasma osmolarity.

According to the American College of Sports Medicine, thirst is not a good indicator of when to drink. This is even more important with age, as our thirst mechanism decreases with age. With many hours on the trainer and rollers indoors, it’s easy to let dehydration sneak up on you. Before you know it, you feel weak and can’t seem to find that energy you had weeks before. Dehydration is one of the number one causes of fatigue.

In this article I will cover what you should be drinking during training rides and easy rides, as well as post-exercise rehydration strategies. A simple way to check if you are hydrated is to look at your urine color. It should be pale in color, although if you’re taking supplements this can be unreliable, as B vitamins add a yellow color. A more precise method would be to purchase an osmometer, which measures urine osmolarity. An osmolarity over 900m osmol/kg indicates that the athlete is relatively dehydrated; values of 100 to 300m osmol/kg indicate that the athlete is well hydrated. You can purchase an osmometer for under $300.

Another test is body weight upon rising and before urinating. A drop in body mass from day to day is likely to indicate dehydration. Ideally athletes should consume enough liquid during activity to make body weight remain fairly stable before and after exercise. Weigh yourself before and after your training sessions. A general rule of thumb is to drink 500 ml of fluid (2 cups) for every pound lost.

Although there are no specific guidelines from the American or Canadian Dietetic Associations regarding how much to drink (largely due to the variance in individual sweat rates), there are some guidelines in place. The American College of Sports Medicine on Fluid Intake for Exercise and the Position Stand on Exercise and Fluid Replacement (2007), for example, recommend the following: Drink 6-8ml of fluid per kg of body weight about 2 hours before exercise. Drinking beverages with sodium or eating snacks with salt can stimulate thirst and help retain needed fluids. During exercise, start drinking early and at regular intervals to prevent dehydration. Fluids should be flavored to enhance palatability and promote fluid replacement.

During exercise longer than one hour, carbohydrates should be ingested at a rate of 30-60g per hour to maintain oxidation of carbohydrates and delay fatigue. An example is drinking 600-1200 ml/h of solutions containing 4-8% carbohydrates. These carbohydrates can be sugars (glucose, sucrose) or starch (maltodextrins).

It’s recommended to include sodium (500-700 mg/L of water) in the rehydration solution ingested during exercise longer than an hour because it may enhance palatability and promote fluid retention.

After exercise in situations in which we need rapid and complete recovery from excessive dehydration, 1.5L of fluid should be consumed for each kg of body weight lost. Consuming drinks with sodium will help the attainment of rapid and complete recovery of hydration status by stimulating thirst and fluid retention.

A practical example of the above guidelines would look like this:

A male who weighs 70 kilograms (154 pounds) should drink 420-560 ml (15-19 oz.) two hours before training. A typical bottle contains 500 ml.

Figure out your sweat loss in training (such as 1.5L per kg lost in training/race). Let’s say our 70kg male had a pre-training weight of 70.38kg and a post-training weight of 68.75. He drank a 350ml bottle during training (1g/ml), so adjusting for this, he lost 1.98 kg in 90 minutes (1.63kg + .35kg). To calculate his sweat rate, divide the weight loss by the number of hours he trained: 1.98 / 1.5 = sweat rate of 1.32L/hour.

For recovery, our man needs to hydrate with 1.5L of liquid for every kilogram lost. Since he lost 1.98 kg, he should drink 2.97L in first hour or so after exercise. This would be approximately five bike water bottles, which often contain 500 ml (1000mlequals 1L).

Being dehydrated can significantly stress your aerobic system more than it needs to be stressed due to lowering overall blood plasma volume. This means your heart has to pump harder to produce the same effort because there is less oxygen available to your muscles. Just staying focused and having a hydration plan can optimize your fitness and ensure you stay mentally focused and able to hit those VO2 Max numbers in a race when you need to.

You put time in training and preparing for a great season. You dial in your nutrition. You have some serious goals. Hydration is vital to peak performance. It is not a side note or something to be taken lightly if you are serious about success. The only solution is to devise a strategy and stick to it.

Try setting your watch to beep every fifteen minutes to remind you to take big gulps from your bottle. Don’t wait until you are dehydrated to start drinking. Gastric emptying is slower once you’re dehydrated, which can lead to cramps and discomfort. The goal is to drink early and often. Big gulps increase the rate of gastric emptying, so practice this in training and be prepared to use these strategies on race day.

Make hydration a goal. It could be that last missing link to your success!