Running and Hydration: How Much Water to Drink

To live life at your summit, you need to stay hydrated. Too little or too much fluid intake before, during or after your workout can negatively affect performance and increase your risk of injury. The sports & active medicine team at Summit Orthopedics supports runners of all skill levels in the Minneapolis/St. Paul area to achieve their goals and prevent or respond to injuries. Knowing how much water to drink is crucial in optimizing hydration for performance and health.

Day-to-Day and Pre-Run Hydration

Staying well-hydrated supports blood flow, muscle health and recovery from yesterday’s workout. The amount of water needed each day varies from person to person depending on activity level, body size, sweat rate, and several other factors.

Drinking to thirst is the most effective way to ensure you drink enough water. When you drink to thirst, you listen to your body’s built-in signals to know when you need more water. The needed water can come from drinking fluids or eating water-rich foods, such as fruits and vegetables.

To prepare for a run, drink 16 to 20 ounces—or about two glasses of water—over the two to three hours beforehand and another 8 ounces about 10–30 minutes before you start training. If you still feel thirsty, drink to thirst.

How Much Water to Drink During a Run

When you run, you lose fluids through sweat, which helps regulate body temperature. Drinking water during exercise is essential to compensate for lost fluid and keep your body running in top-performance mode.

Bring a water bottle or hydration pack and sip water throughout your run. Continue to drink to thirst while aiming to take in a minimum of 8 ounces every 15 minutes.

Hydration for Post-Workout Recovery

The amount of fluid lost while exercising is called your sweat rate. Your optimal post-run fluid intake is 16 to 24 ounces for every pound of fluid lost during exercising.

To determine your sweat rate:

1. Empty your bladder and put on your running clothes.
2. Weigh yourself just before you start your run.
3. Follow your usual running routine.
4. Keep track of how many ounces you drink while warming up, running and cooling down.
5. If you need to urinate before re-weighing yourself, measure the ounces of urine passed.
6. Wipe off sweat and weigh yourself while still wearing your running clothes.
7. Calculate your sweat rate with the following steps:
   1. Subtract your final weight from your weight before your run.
   2. Add that number to the ounces you drank during your workout—one pound equals about 16 ounces.
   3. If you urinated before your final weigh-in, subtract the ounces of urine.
   4. Divide the last number by the number of hours or partial hours you ran.

Once you calculate your sweat rate, multiply that number by 16 and 24 ounces to get your optimal fluid intake range. To avoid overhydration, drink water slowly over two to six hours.

Weather will affect your sweat rate. If you run outside in all seasons, re-calculate your sweat rate when the weather changes.

When to Sip Sports Drinks

In addition to water, you lose sodium and other minerals, or electrolytes, when you sweat. For workouts under an hour, replacing lost electrolytes isn’t usually necessary. However, if your workout lasts longer than an hour, consider adding a low- or no-sugar sports drink or a salty snack to replace electrolytes. Avoid caffeinated beverages, which can increase dehydration.

Too Little or Too Much of a Good Thing

Too little or too much fluid intake can lead to serious health issues. Drinking to thirst, knowing your sweat rate and spreading your water intake throughout the day will help you stay consistently hydrated. Still, it’s vital to know about dehydration and overhydration.

Dehydration happens when you don’t have enough fluid, preventing the body from working properly. Signs of dehydration include:

• Dark-colored urine or urinating less than usual
• Dizziness
• Dry mouth or skin
• Fatigue
• Lack of sweat during exercise or less sweat than usual

Overhydration, or too much fluid intake, can cause electrolyte imbalance and heart concerns. One type of electrolyte imbalance caused by overhydration is called hyponatremia, which is a low concentration of sodium in the blood. Symptoms may include:

• Confusion or irritability
• Fatigue
• Headaches
• Loss of appetite
• Muscle cramps or weakness
• Nausea or vomiting

Exercise-associated hyponatremia is rare but can be life-threatening. Staying hydrated before, during and after your run can help you avoid dehydration and overhydration so you can reach peak performance.

Want support to reach your athletic goals? Schedule an appointment with a Summit Orthopedics Sports & Active Medicine specialist.