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!
