You Don’t Drink Enough Water Throughout
Just like cramming for a test, binge (water) drinking the morning of a long run
won’t hydrate you properly. Aim to drink about 2-3 mL perpound of body weight
at least 4 hours before your run. If you chug an entire liter of prerun water,
the kidneys will flush it out, causing frequent midrun bathroom breaks. You may
even dilute the body’s sodium balance and increase your risk of developing
hyponatremia (or water overload) during your run. Instead, keep a water bottle
handy all week and drink throughout the day. Your urine color should be light
yellow (like lemonade). Once it gets too dark (like apple juice), you’re
Another good way to determine hydration
status is a sweat test, says Chrissy Carroll, R.D., USAT Level I Triathlon
Coach. “Weigh yourself, without clothing, before and after a long run. If
you've only lost 1 to 2 percent of your body weight, you’re in the hydration
sweet spot. If you've lost more than 2 to 3 percent of your body weight, try
hydrating a little more during your long runs.”
There is no standard fluid
recommendation for runners because every runner has a different sweat rate,
speed, body size, and training efforts. A good starting point is to drink 0.4
to 0.8 liters of water in the first hour. For a run lasting longer than an
hour, consume 0.5 to 1 liters of sports drink to replace lost fluid, salt, and
carbs. If you lose more than 2 to 3 percent of body weight during your run,
drink 1.5 liters of fluid for each kilogram of body weight lost.
You Avoid Salt
at All Costs
We know a diet high in sodium can lead to serious health conditions like
chronic high blood pressure. But that doesn’t mean salt is always the enemy.
Salt losses vary greatly based on sweat rate, but many runners lose an average
of one gram of sodium per liter of sweat, making salt a key player in keeping
you hydrated. Hot and sweaty conditions mean replenishing your fluids and
sodium levels is even more important. Add an extra sprinkle of salt to your
dinner, or snack on a handful of salted peanuts.
Your Fuel Consists of Gels and Chews But
No Sports Drinks
“Many athletes prefer the convenience of
gels for fuel,” says Carroll. Gels and chews have plenty of sugar to
avoid midrun bonk, but they don’t always have enough sodium to maintain fluid
balance. “Add an electrolyte mix to your water or incorporate a salt tablet
during long runs or races.” But be sure to try this in training to make sure it
works for you on race day.
You Don’t Get Enough Magnesium or
Most runners know about sodium, but
sweat also contains magnesium and potassium, which play a pivotal role in
maintaining fluid balance and muscle function. Most Americans don’t consume the
recommended 400 mg of magnesium and 4,700 mg of potassium each day. A
deficiency in either mineral can exacerbate the symptoms of dehydration and
cause extreme muscle cramps.
A well-balanced diet, rich in fruits,
vegetables, grains, and legumes will ensure you get enough of these nutrients.
These sources are particularly good choices.
Magnesium: Leafy greens, almonds, pumpkin
seeds, tofu, flaxseeds, broccoli, lentils
Potassium: Bananas, sweet potatoes, beets, tomatoes,
oranges, pomegranate juice
You Don’t Listen to Your Body
You’ve seen the scary photos of runners being carried across the finish line or
collapsing just after crossing it. But there were likely warning signs. Even if
runners tried to hydrate, they may have ignored the symptoms of dehydration.
“I understand those Type A tendencies to
‘stick to the plan,’ but when conditions are different, like on a warm day or a
more intense pace in a race, you may need to adjust your plan on the fly,” says
The earliest sign of dehydration may
present as dark colored urine or a slight headache. As dehydration worsens, you
may feel extreme thirst, debilitating muscle cramps, fatigue, and sometimes
even a decrease in heart rate. It’s necessary to recognize and listen to these
signs because dehydration can do more than hurt your race performance—it can be
As soon as you start to notice these
symptoms, table the long run, grab a sports drink, and take small and frequent
sips. You don’t want to overload your stomach with fluid, so stick to your
original hydration plan of 0.5-1.0 liters per hour. If you lose more than
2 to 3 percent of body weight during your run, drink 750 mL of fluid for each
pound of body weight lost.