Dehydration Causes and Symptoms

Runners, walkers and all athletes should understand dehydration causes and symptoms, along with its treatment. In this article we discuss dehydration, contributors to dehydration, who’s at risk, the symptoms, how to prevent dehydration and its treatment.


What is dehydration?

This discussion of dehydration deals with the loss of water in your body, and this typically accompanies the loss of electrolytes. The basic premise behind dehydration is an inadequate intake of fluids. Inadequate water intake and depleted electrolytes can seriously disrupt your performance and even your life.

Dehydration can occur in as little at 30 minutes of exercise, especially in hot temperatures. The body acts as a heat radiator, and relies on sweating to dissipate the heat generated from working muscles. Sweating also helps to maintain our core body temperature even when we are not exercising. Allowing our core body temperature to be maintained within a safe range is a key element in preventing heat-related medical conditions. The amount of sweating necessary to cool the body down requires adequate fluid intake. Sustained sweating during vigorous exercise will inevitably will lead to dehydration, unless adequate fluids are consumed.

Dehydration has caused death. At a minimum, dehydration reduces an athlete’s performance. Dehydration is one of the most common factors for heat-related sickness such as heat exhaustion and heat stroke. Both heat exhaustion and heat stroke cause numerous deaths each year. The most serious consequence of dehydration is impaired heat loss which can elevate the core body temperature. At some point, heat exhaustion sets in, and a potentially fatal heat stroke.

What can cause dehydration?

Each of these can contribute to dehydration: vomiting, diarrhea, urination, breathing, fever, illness, medications, low-fitness levels, strenuous activity, excessive sweating, sleep deprivation, staying in the sun too long, not drinking enough fluids, and diuretics like alcohol and caffeine.

Who’s at risk?

Adult and young athletes are at risk for dehydration, especially during the summer months, for activity lasting over 30 minutes. Children, due to their smaller size, are at  risk of becoming dehydrated. For all athletes, once dehydration starts, the deterioration can be quick.

Dehydration Symptoms

One or more of the following can indicate dehydration.

  • Headache
  • Dizziness
  • Confusion
  • Clumsiness
  • Excessive sweating
  • Thirst
  • Dark urine
  • Cramps
  • Reddened skin
  • Weak, irregular or rapid heart-rate
  • Low blood pressure
  • General weakness
  • Rapid and shallow breathing
  • Heat exhaustion
  • Heat stroke 

Runners enjoy drinking water

How to prevent dehydration

Hydration as a lifestyle prevents dehydration, and provides the athlete a good platform to supplement with fluid replacements. Live a life of good hydration and avoid chronic dehydration. Let your body perform by taking fluids and electrolytes, strategically. In the examples below, we suggest amounts of fluids. You’ll take in these fluids through diet, juices and H2O. Depending on the length of the workout, you may strategically consume extra fluids before, during and after. Wear proper clothing. Avoid diuretics. Strategy Tip: Strategically, you may want to slow down. This strategy has rewarded many veteran runners who will start out slow and easy and let other excited runners pass them by. If you’ve ever done Race to Robie Creek on a hot April Saturday afternoon, you’ve seen runners already struggling by the half-way point. They didn’t do enough to avoid dehydration and got passed (#roadkill) by those who did. 

One of the best preventative measures is to maintain good hydration as part of your daily and weekly hydration lifestyle. A good indicator of adequate hydration is having to pee several times per day. The color of your urine will be clear or pale-yellow. How’s your urine?

The fluid requirement for most runners is estimated to be around 16 ounces per hour in average climates. Drinking 15-20 ounces of fluids before strenuous exercise (about 2-3 hours) is recommended. Replacing lost fluids during exercise is a strategic decision, especially when the workout lasts more than 60 minutes. Consuming 4-8 ounces of fluid replacement every 15-20 minutes of exercise (depending upon conditions) is a good rule of thumb to follow, especially during longer endurance events. Replacing fluids after exercise allows the body to restore the balance it needs to help muscle recovery. When running, athletes may supplement fluids, electrolytes and sugar intake with sports drinks. Sports drinks usually have a high glycemic index. Choose a sport drink that contains a 6-8% carbohydrate concentration ratio with electrolytes, and be sure to experiment with your preferences in the specific sports drink.

Proper clothing can influence your cooling efficiency. In hotter temperatures, wear light-colored clothes that reflect light, and remain cooler. Choose materials that wicks away your sweat. A special running shirt is made with fabrics that promote wicking, and improved air circulation.TProper clothing helps you stay cool in hotter temperatures. 

Heat acclimatization takes about 10 days. Adapting our body to higher temperatures makes the body more efficient at cooling. 

Medications often have side effects. And some medications are too commonly abused. Overuse of NSAIDs (anti-imflammatory pain relievers) may cause dehydration by interfering with sweating and normal kidney function. Checking with a physician is always best before taking medications while exercising. As a rule of thumb, do not take any medications before checking with your physician. Coach Steve has a good personal story about his first marathon and a NSAID.

Struggling marathon runner

Treatment of dehydration

Important: If you become dehydrated, be quick to cool yourself down. If you are over-heated, stop what you’re doing and drink fluids with electrolytes, and consider getting medical treatment.

Understanding the causes of dehydration is the first step towards treatment. If heat appears to be the cause of dehydration, rapid cooling is recommended. Cooling can be achieved by loosening an individual’s clothing and moving out of the direct sun. Ice can be used if available and can be applied to the athlete’s groin, armpits and neck.

Re-hydration or replacing lost fluids is essential in correcting dehydration. Fluids containing some salt (electrolytes) are helpful. Salt and water work together to allow our bodies to achieve a healthy balance. The salt acts to draw water through permeable membranes, which aids in the distribution of fluids throughout the entire body. Too much salt however, can have a adverse affect, by pulling too much water. The more dehydrated a person is, the less salt one should administer. Assess the level of dehydration, start by administering water and then add a sports drink, most of which contain safe amounts of sodium.

When dehydration is extreme, the body stops sweating. As a result, our core body temperature will increase to high levels, causing heat stroke. Heat stroke is a serious medical emergency and requires medical attention. Individuals require intravenous saline solution to correct this degree of dehydration and it may take 48-72 hours under supervised medical care to correct heat stroke. Heat stroke is life-threatening.

What is the best method for calculating the amount of fluid a person needs during exercise?

  1. Non-exercising adults, calculate by taking your weight, and dividing it by two. Example – 140 lbs / 2 = 70 oz per day.
  2. Exercising adults: drink the amount calculated in #1, plus enough to replace the fluids used during exercising. Determine the replacement amount by weighing yourself before and after exercise. If you loose 2 lbs, drink 2 pints (32 oz). Do this calculation a few times over the course of the training season. Then, come race day, you’ll have a very good idea of the amount of fluids to drink during exercise. 
  3. Hot or humid days may require additional fluids.From a basis of hydration as a lifestyle, athletes will start the race fully hydrated, and strategically drink during the race. 10-20 oz additional may be needed on hot and humid days. Athletes will place themselves on a scheduled drink pattern during the race. For example, 4-8 oz every 20 minutes when the exercise lasts over 60 minutes. What’s optimal? Experiment and discover while training.

6 Hydration Suggestions

Here are 6 suggestions for staying hydrated. Don’t take hydration for granted but instead consider hydration as a strategy. 

6 suggestions for staying hydrated.

  1. Drink 4-8 oz every 15-20 minutes, or about one 20 oz water bottle per hour. For workouts lasting more than 60 mins.
  2. Drink half your body weight in ounces each day.
  3. Experiment by weighing yourself before and after endurance exercise to determine water loss. 1 lb = 16 ounces of lost water lost.
  4. Start your day with 8-16 oz of H20 or juice
  5. Carry water with you during the day; sip all day long.
  6. Eat high water-content foods such as fruits, vegetables, soups, yogurt, etc.

Use Aid Stations

Even the largest and best-managed race courses have been known to run out of water and/or cups at an aid station, especially for the slower majority of runners and walkers. This is one of the reasons coaches recommend that you carry your fluids during a long-distance event, refill your water-bottle at the aid-stations, and drink on a fixed, practiced schedule. At each water/aid station, refill and drink.

Why people DON’T DRINK enough water?

These are the common reasons runners and walkers don’t consume sufficient fluids while training and running a event.

  • fear of going to the porta-potty too frequently
  • porta potties cause lost time, especially waiting in line
  • Drinking makes the stomach upset
  • I don’t feel thirsty

These common reasons are usually found in inexperienced runners who have not practiced hydration. Over the course of a 3-6 month training season, runners can learn when and how much to drink while minimizing time spent peeing. Have you ever seen a fast runner in line to pee?  

Examples: determine your H2O requirements

Example #1

A lady who weighs 125 pounds and is exercising for 15-minutes each day, is not pregnant, is not breastfeeding, does not live at high altitude, lives in a dry climate, drinks no alcohol, lives where the weather is not very hot or very cold, and is not sick with fever or diarrhea should have 72 ounces of water today, or 2.2 quarts. In a healthy diet, about 20 percent of her needed water may come from the foods she eats, thus if she eats a healthy diet, she can get by drinking only 57 ounces (1.8 quarts) of water per day.

Example #2

A lady who weighs 235 pounds and is exercising for 15-minutes each day, is not pregnant, is not breastfeeding, does not live at high altitude, lives in a dry climate, drinks no alcohol, lives where the weather is not very hot or very cold, and is not sick with fever or diarrhea should have 127 ounces of water today, or 4 quarts. In a healthy diet, about 20 percent of her needed water may come from the foods she eats, thus if she eats a healthy diet, she can get by drinking only 101.6 ounces (3 quarts) of water per day. As you can see, a larger person needs to drink more to stay hydrated.

Sources of water

Sources of water include the foods we eat. Vegetables, fruit and other foods contain useful water for good hydration. But water must be used too. Foods such as butter, oils, dried meats, chocolate, cookies and cakes are low in water. Your body also produces metabolic water: When food molecules are broken down for energy, carbon dioxide and water are formed. This metabolic water accounts for 10-15% of the daily water requirement of a sedentary person.

Your body is a heat radiator

We sweat, it evaporates, and we are cooled. This is the natural way our body gives off heat, like a radiator. However, in high humidity this process works less efficiently.  When humidity is high, sweat does not evaporate as well. It only rolls off the body in heavy beads. When sweat cannot evaporate, body temperature continues to rise and our body sweats even more. 

Fluid Loss and Body Size

Your body size is important in determining the quantity of water you need. Thin people might tolerate heat better than heavier persons. Weight means more work, and more work means more heat production. More heat production requires more blood being diverted to the skin to dissipate the heat, and this results in less blood available carry oxygen to muscles. The result? Slower performance. A physically fit person has a efficient radiator, giving off heat better. The hotter the temperature and the longer the activity, a larger body size requires better hydration management.