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 causes and symptoms 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, along with restoring electrolytes, can seriously disrupt your performance and even your life.
Dehydration can occur in as little at 30 minutes of exercise, especially in hot and/or weather. The body 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 which may initially be caused by dehydration. The amount of sweating necessary to sustain adequate heat dissipation during vigorous exercise inevitably will lead to dehydration unless adequate fluids are ingested.
Dehydration will diminish an athlete’s performance and can lead to death if not corrected. 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 dissipation which can elevate the core body temperature to dangerously high levels resulting in heat exhaustion and potentially fatal heat stroke.
What can lead to dehydration?
Strenuous activity such as running requires adequate fluid and electrolyte replacement, else dehydration causes and symtoms will occur. Excessive sweating due to hot or humid conditions can rapidly dehydrate individuals unless corrective action is taken. Each of these can contribute to dehydration: vomiting, diarrhea, urination, breathing, fever, illness, some medications such as an anti-inflammatories, low-fitness levels, strenuous activity, excessive sweating, sleep deprivation, lack of heat acclimatization, staying in the sun too long, not drinking enough fluids, and diuretics like alcohol and caffeine Each of these can lead to dehydration.
Who’s at risk for dehydration?
Adult and young athletes are at risk for dehydration, especially during the summer months, for any activity lasting longer than 30 minutes. Without proper hydration, the body can quickly lose water and other essential elements running the risk of kidney problems or even death. Children, due to their smaller stature are at an increased risk of developing dehydration. For all athletes, once dehydration starts, the deterioration can be quick.
- Excessive sweating
- Thirst (dehydration begins before you get thirsty)
- Dark urine
- Reddened skin
- Weak, irregular or rapid heart-rate
- Low blood pressure
- General weakness
- Rapid and shallow breathing
- Heat exhaustion (increase in core body temperature and heart-rate)
- Heat stroke (very high core body temperature, reddened skin, initially normal to profuse sweating, death)
How to prevent dehydration?
Drink fluids before, during, and after exercise, wear proper clothing, be acclimated to heat, avoid excess alcohol and certain medications.
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 the output of relatively frequent urine that has a clear or pale-yellow color. On a regular basis, frequent dark colored urine indicates a real possibility of chronic dehydration.
The fluid requirement for most runners is estimated to be 500 ml/hr in average climatic conditions. Drinking 15-20 ounces of fluids before exercise (about 2-3 hours), is highly recommended. Replacing lost fluids during exercise, especially when the duration is longer than 60 minutes, is critical. 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 as well as aiding in muscle recovery, especially when the fluids contain high-glycemic carbohydrates such as sports drinks. Choose a sport drink that contains at most a 6-8% carbohydrate concentration ratio with electrolytes.
Proper clothing can influence your cooling efficiency. It is best to go with light-colored clothes as they reflect light and in turn, remain cooler than darker clothing. Choose materials that wick away the moisture, which allows for better air circulation, thus facilitating more rapid cooling. Cotton is not a good choice because it does not wick moisture away from the body.
Heat acclimatization takes about 10 days. Adapting to the heat helps our bodies make the necessary adjustments to promote more efficient cooling.
Certain medications such as 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.
Treatment of dehydration
If you become dehydrated, be quick to cool yourself down if you have also over-heated, and re-hydrate with fluids and 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 should 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, and pull too much water through the membranes, leading to further dehydration. 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?
- Baseline fluid requirements (recommended daily) for non-exercising individuals can be calculated by weighing the person in lbs and dividing that number by 2: for example – 140 lbs / 2 = 70 ounces fluid replacement necessary for daily hydration maintenance.
- Exercising individuals need to add to the minimum daily fluid requirement. The most accurate method for determining fluid replacement for an exercising adult is by weighing themselves before they exercise and again afterwards. The change in weight represents the amount of fluid necessary to restore proper fluid balance. For example: a140 lb runner loses 1 pound of fluids during a run. Since 1 pint (16 ounces) of water equals a pound, a pint is needed to replace the fluid loss. This is in addition to the minimum daily requirement above in #1.
It is also recommended that on hot and/or humid days and additional 10-20 ounces of fluids be consumed prior to exercise (30-60 minutes before). An easy way to remember how much to drink is to drink on a schedule, aiming for at least 4-8 ounces of a sports drink every 15-20 minutes during exercise lasting longer than an hour. Optimal fluid replacement for most runners is approximately 500ml/hr in average climatic conditions.
Key Hydration Topics
Don’t take water for granted. Water is essential for regulating body temperature and many other important bodily functions. When you lose water, it should be replenished for general well-being and performance. Thirst is not a good indicator of hydration since you generally do not feel thirsty until you are already about 1% dehydrated (1% of your body weight). So, if thirsty, you are already mildly dehydrated. Fatigue, heat-intolerance, light-headed (dizziness), and seeing spots are signs of dehydration.
Rules of thumb to stay hydrated:
- Drink 4-8 ounces every 15-20 minutes depending upon climatic conditions while exercising (equivalent to about a 20-ounce water bottle per hour).
- Drink half of your body weight in ounces each day (if you weigh 140 pounds, drink 70 ounces daily) in addition to what you will consume during exercise as noted in #1 above.
- Experiment by weighing yourself before and after endurance exercise to determine water loss. For every pound lost during exercise, that is 16 ounces of water lost = 1 pint.
- Start your day with 8-16 oz. of water or juices
- Carry water with you during the day; keep sipping all day long.
- Eat high water-content foods such as fruits, vegetables, soups, yogurt, etc.
Event Aid Stations… Runners and Walkers beware
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 target event.
- It will make me go to the bathroom too frequently
- Peeing causes lost time, especially waiting in line
- Drinking makes my stomach upset
- I don’t feel thirsty
Examples of determining water requirements.
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.
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 (all other things being equal). Adjust accordingly as you may need for your body weight.
The hypothalamus in your brain regulates your perceived level of thirst. By the time you “feel” thirsty, you are probably around 1% dehydrated. At this level, during your workout or target event, it’s difficult to replenish the fluid deficit already incurred. We need to practice drinking during training runs, and experiment with the type of sports drink and amounts we can tolerate. Water comprises 50-65% of our total body weight, and is critical for important bodily functions, like respiration, sweating and transport of nutrients, and removal of lactic acid from the muscles. Water has tremendous “heat stabilizing” qualities. It can absorb a considerable amount of heat with only a small change in temperature. Water also plays an important role in lubricating our joints. Also, water gives structure and form to the body through the turgor (pressure) it provides against body tissues.
Sources of water
During exercise, especially endurance and extended workouts, drink water and a sports drink. During exercise and thermal stress, your body demands more water. There is water-content in most foods, especially fruits and vegetables. Lettuce, pickles, green beans, broccoli are good examples. Foods such as butter, oils, dried meats, chocolate, cookies and cakes are very “low” in water-content. Your body also produces something called 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.
Hydration and Exercise
When we exercise (especially in the heat), the body is faced with two competing demands: (1) The muscles require oxygen to sustain energy metabolism and, equally important, (2) metabolic heat must be transported by the blood from the deep tissues to the periphery. Consequently, the blood used to accomplish #2 is not available to deliver its oxygen to the working muscles (#1).
Your body as a radiator
We sweat, it evaporates, and we are cooled (the refrigeration effect). However, this process does not always work fully if the relative humidity is too high. When the humidity is high, sweat does not evaporate 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 to offset this temperature elevation. Excessive fluid loss through the extra sweating can occur and blood volume quickly can begin to diminish. Anytime we dehydrate more than 2% (of our total body weight), our core temperature rises, our pulse-rate rises, and our central nervous system begins to show ill-effects.
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 resulting is slower performance. A physically fit person has a more efficient thermal-regulation system that can dissipate body heat faster. Acclimatization to warmer temperatures helps, but takes approximately 10 days for your body to adapt. Regardless, the hotter the temperature and the longer the activity, a larger body size requires better manage hydration management.