Water helps regulate body temperature, blood pressure and heart rate, as well as transport essential nutrients throughout the body. The fluids in your body also contain minerals called electrolytes, primarily chloride, potassium, sodium, magnesium, phosphate and bicarbonates. When dissolved in fluids, electrolytes take on an electric charge that helps maintain a balance of water within the body, moves nutrients and wastes into and out of cells, and supports nerve and muscle function.
Dehydration occurs when you lose more water and minerals than you take in. Because you lose water and electrolytes when you exercise, it is important to drink enough water before, during and after a workout to replenish body fluids. The longer and more intensely you work out, the more important it is to stay hydrated to perform your best.
Understanding Dehydration: Causes and Consequences
Because hydration levels have a direct influence on muscle, nerve and organ function, good hydration promotes peak athletic performance, while dehydration can negatively affect athletic performance in multiple ways.
When you become dehydrated, the total volume of blood in your body decreases. Low blood volume leads to low blood pressure. This fluctuation in blood pressure can cause dizziness, sensation of palpitations or racing heart beat, and fatigue. This affects many parts of the body by not providing enough flow, which can cause a number of symptoms depending on the severity. On the mild end of the spectrum, this can affect the brain, leading to slower reaction times and difficulty focusing. If severe enough, it can cause syncope, or passing out. For the kidneys, it will stimulate more aggressive water retention. In more severe situations, the kidney can be injured because of this lack of flow.
In addition to water, your body loses electrolytes when it sweats. Sometimes, as a result, this can affect muscle firing, which can cause symptoms of fatigue and cramping.
Signs You May Be Dehydrated
Symptoms of dehydration differ depending on the degree of fluid loss. The risk of dehydration varies depending on factors such as age, activity level and environmental conditions. Regardless of those factors, dehydration can be recognized by a few key signs. Early warning signs of dehydration include:
- Dark yellow or amber urine
- Decreased urine output
- Dizziness, lightheadedness
- Dry mouth and eyes
- Fatigue
- Headache
- Increased thirst
If not addressed in time, dehydration will continue to worsen. Signs of severe dehydration include:
- Confusion
- Extreme thirst
- Fast heart rate
- No or very little urine
- Rapid breathing
Signs of Heat Exhaustion
Dehydration can also put athletes at risk for heat exhaustion, which occurs when the body can no longer cool itself off and begins overheating. In addition to dizziness, fatigue and headache, heat exhaustion symptoms include:
- Cold, pale or clammy skin
- Fainting, passing out
- Heavy sweating
- Muscle cramps
- Nausea
- Rapid, weak pulse
If left untreated, heat exhaustion can quickly progress to heatstroke. This life-threatening condition can cause organ and brain damage or even be fatal. Signs of heatstroke include:
- Confusion
- Fever (body temperature of 103 degrees or higher)
- Hot, dry, red skin
- Lack of sweating
- Loss of consciousness
- Nausea or vomiting
- Rapid pulse
- Seizures
Preventing Dehydration in Sports
Preventing dehydration starts by making sure you are adequately hydrated before participating in a sports activity and taking the local environment into account. In addition to drinking enough water while you exercise, it is also important to continue to drink afterward to replenish lost fluids and electrolytes.
How much should you drink? Hydration needs differ from person to person and activity to activity. If you tend to sweat a lot, exercise in hot weather, or work out intensely for a long time, the more fluid you need to drink to stay well-hydrated. The American Council on Exercise recommends the following guidelines for fluid intake:
When preparing your workout:
- Drink 20 ounces of water or sports drink up to two hours prior to exercising
- Drink 10 ounces of fluids 15 minutes before exercise
While working out:
- Drink 10 ounces of fluid every 15 minutes while exercising
Following your workout:
- Drink 20 ounces of water or sports drink for every pound lost during exercise. Pay attention to urine color in the hours following exercise, as darker urine indicates dehydration.
Treatment and Recovery from Dehydration
If you become dehydrated while participating in sports, the steps to rehydrate and time it takes to recover depend on your symptoms and degree of dehydration.
Mild dehydration can be treated at home by increasing fluid intake. Water is the best choice, but herbal teas can also help. Avoid caffeinated beverages and alcohol, which increase fluid loss.
Moderate dehydration can also be treated at home, but if you develop symptoms of heat exhaustion, go to the emergency room. Drinking water replaces fluids, while coconut water, over-the-counter rehydration drinks like Pedialyte, and sugar-free versions of sports drinks also replace lost electrolytes.
Severe dehydration is a medical emergency. It is treated in a hospital with intravenous fluids and oral rehydration solution therapy. Severe dehydration can lead to heat exhaustion or heat stroke, which is deadly. If you think someone is having heat exhaustion or heat stroke, call 911 right away.
More to Read
- Is There Such a Thing as a Healthy Sports Drink?
- Is Caffeine Bad for Your Heart? It Depends.
- COPD and Dehydration
- Avoiding Dehydration When You Have Heart Failure
Medically reviewed by Claudia Dal Molin, DO, RMSK.
The University of Maryland Medical System is the Official Medical Team of the Terps.
