Dehydration Part 2: Prevention
Water and the Human Body
Why is water so important to the human body?
1. It gives cells their shape and form
2. It helps produce energy in the body (i.e. to help us move)
3. It helps with the digestion process
4. It allows for the smooth transport of necessary elements throughout our bodies (i.e. in the blood)
5. It is important for our senses such as hearing, vision, and smell to work properly
6. It helps to protect our nervous system (i.e. it's in the cerebrospinal fluid around the spinal cord and brain)
7. It lubricates surfaces to help with things like breathing and joint movement
8. It helps to maintain body temperature
9.... and a whole lot more.
Water needs: What To Think About
Several factors need to be considered before determining your individual water needs for a match, among them:
■ field position and intensity of play (i.e. active, attacking midfielders may need more water than untested goalkeepers);
■ duration of play (i.e. overtime games increase water needs);
■ medication use (i.e. certain medications affect things like kidney function and therefore water retention or loss);
■ individual health differences (i.e. some players suffer from diabetes and gastrointestinal distress);
■ individual body differences, things like:
• body weight
• the amount of skin surface area
• electrolyte loss patterns
• how much you sweat
• body temperature reactions to exercise
■ weather complications (from temperature and wind to altitude and humidity).
It's All About the Weather
■Temperature: In general, we know that players need to hydrate more on hot, sunny days than on cold days. However, hydration in colder temperatures should not be ignored. That's because sweating is not as apparent in the cold, where cold winds and lower humidity levels may cause sweat to evaporate faster, preventing players from properly judging water loss amounts.
■ Wind speed: Along the same lines, fast wind speeds increase cooling by way of convection and evaporation - see Dehydration Part 1: How It Happens: Click Here>>
■ Altitude: When playing at higher altitudes, players sweat more and lose more water through breathing. Breathing rates increase as a result of the lower partial pressure of oxygen in the atmosphere*. Higher altitudes are also often low in humidity too, which increases the speed of evaporation (of sweat).
* With a decrease in air pressure at higher altitudes, there is a lower concentration of overall molecules making up the air. As a result, there are fewer oxygen molecules available per breath (less oxygen to breathe). Players playing in higher altitudes, therefore, need to breathe faster or take deeper breaths to try and meet the body's demands for oxygen. In addition, while the percentage of oxygen compared to other molecules in the air actually stays the same, the partial pressure of oxygen decreases (the partial pressure is the pressure of a gas as if it were alone in the atmosphere). The lower partial pressure works against, or slows, gas exchange into the body, from the lungs to the bloodstream and from the bloodstream to the body's tissues.
►Humidity: In humid conditions, the higher levels of moisture already in the air decrease the capacity for sweat to evaporate; decreased evaporation makes the body feel warmer (remember, evaporation helps to cool the body down). So, for example, at a temperature of 24° C and 100% humidity, the body feels and responds as if the temperature was 27° C). That's why humidifier machines in the home can make the house feel warmer.
Water Alone May Not Be Enough
Electrolytes are those essential salts and chemicals needed by the body for it to run smoothly and safely. While we talk about electrolytes like sodium, potassium, calcium, and magnesium as elements to consider for the football player, the body may require other elements to function properly. Please check with your doctor to discuss any special needs that your body may have to participate in a given sport safely (for example, it is not uncommon for players, especially female players, to be found with iron deficiencies).
Signs of Dehydration
The early signs that you are becoming dehydrated may include:
● a dry sticky mouth
● tiredness
● thirst
● decreased urine output
● decreased tearing (especially in children)
● muscle weakness
● headache
● dizziness/lightheadedness.
Signs that you may have a more severe level of dehydration include:
● extreme thirst
● irritability
● confusion,
● lethargy
● low to no urine output or dark urine (the color of apple juice)
● sunken eyes and the absence of tears
● less skin elasticity (skin that doesn't bounce back after being pinched)
● poor skin color
● low blood pressure
● rapid heartbeat and weak pulse
● fever
● and in the most serious situations - delirium, seizures, or unconsciousness
The Important Numbers
Dehydration levels (measured as a percentage of body weight loss) can affect how the body performs and reacts. Moderate dehydration occurs when you lose 3-5% of your body weight with play. Severe dehydration occurs when the loss is 5% or more. "As a rule of thumb, a 5% decrease in body water content will increase body core temperature by 1 to 1.3°C, mainly be impairing skin blood flow." (F-MARC Football Medicine Manual 2nd edition, pg. 131)
"How Do I Know If I Am Dehydrated?"
Two simple ways to determine if you are dehydrated are:
1. Check your weight on a scale before and after play . . . weight should remain about the same if you are properly hydrated.
2. Assess the color of your urine . . . darker urine color indicates too little water in your system (urine should be light in color). While there is not one agreed upon chart, in general, the darker the color, the more dehydrated you are [Figure 1].
Other general tests for dehydration include:
1. Urine volume (output): An output of more than two liters per day, but no more than four liters per day, is normal. (It requires urine collection.)
2. Blood testing (hematocrit): Hematocrit is the percentage of red blood cell concentration in the blood relative to the total blood volume. Normal percentage values vary with age and gender. With dehydration, the blood shows a decrease in the volume of water and, with that, a relative increase in the concentration of red blood cells in otherwise healthy individuals. (It requires blood to be drawn and laboratory assistance.)
3. Urine Osmolality: Urine osmolality is a measure of the concentration or amount of particles like minerals and wastes dissolved in the urine (the solute), relative to the urine's mass of water, the substance into which the particles dissolve (the solvent). A high concentration of particles tends to be consistent with a darker urine color. (It requires a sterilized beaker for urine collection and specialized, hand-held testing strips. More exact results require professional equipment and/or laboratory assistance.)
Color Confusion
Please keep in mind—urine color can be altered by factors other than dehydration:
■ Very dark urine or urine with a brown, pink, or red color may indicate that other medical problems exist, like an irritation of the urinary tract.
■ Changes in urine color may simply be a result of:
• foods you've eaten (i.e. carrots can turn it orange)
• medications/supplements you've taken (i.e. B Vitamins can turn it green)
• female menstruation (making it redder or darker) -- though any irregular or inconsistent changes over time should be checked by your doctor.
In fact, if you do not know the reason for any change in urine color, please contact your doctor. Also tell your doctor if you have any other coexisting symptoms, such as pain, fever, nausea, etc., that may help the doctor make a proper diagnosis.
The Female Player: The Menstrual Cycle
The female menstrual cycle can be divided into three phases:
1. Menstruation or Hemorrhagic Phase (the time period where bleeding occurs due to the shedding of the uterine lining from the previous cycle; it normally occurs if a fertilized egg has not attached itself to the lining and therefore pregnancy has not taken place)*
*Amenorrhea or the absence of menstruation can be caused by conditions other than pregnancy. Some other causes may include: hormone imbalances, structural issues regarding the reproductive organs or glands, the use of certain medications, high stress levels, low body weight/poor nutrition (especially when combined with high energy exercises, such as football), breast-feeding, and menopause (when menstruation naturally stops in older women).
2. Follicular Phase (the time period when the body releases hormones that lead to the maturing of one follicle within the ovary, while also preparing the follicle's egg for release from the ovary; as the egg grows, estrogen will be released to start preparing the uterine lining for a fertilized egg)
3. Luteal Phase (the time period that begins with ovulation - the process of releasing the egg - and ends when the uterine lining sheds; there is a rise in progesterone hormone levels during this phase that further encourages the uterine lining to thicken)
Scientists have found that during the female menstrual cycle's luteal phase, a significantly higher core temperature (0.25°C to 0.5°C) is required to initiate sweating. Although this change in heat regulation does not appear to affect the ability to exercise, it may or may not affect hydration needs (the luteal phase lasts an average of 10-16 days, which depends in part on the duration of the person's menstrual cycle). It is worth, therefore, considering such factors when evaluating heat stress or the body's response to heat, during exercise. Some recommendations for female football players:
■ Be aware: Pay attention to the effects of heat stress on the body (i.e. on energy levels, on concentration levels, on performance levels).
■ Weigh yourself: Check your weight at different points in your cycle to see if there are indeed any differences in water losses, especially after play.
■ Chart your body temperature: Take your temperature the same time every day, at rest, for a month or two, in order to determine your baseline levels (see chart)* You can also do it before and after exercise to assess your tolerance levels.
* Basal Body Temperature Chart: CLICK HERE >>
■ Use core body temperature pills (under medical supervision only): For more detailed testing of your body temperature, the medical team may recommend that you swallow one of these pill-shaped sensors, which can wirelessly transmit your body temperature from your digestive tract to a hand-held data recorder. This method can provide more exact monitoring of body temperature before, during, and after play.Muscle Weighs More Than Fat?
Fat has a much lower water composition than muscle. Muscle cells are 70- 75% composed of water (adding weight) while fat cells are normally only 10-20% (or less) composed of water. Also, muscle has a greater mass density than fat, so a specific weight of a muscle takes up less space (volume) than the same weight of fat. Does "muscle weigh more than fat?" Yes, if given the same volume of each tissue, muscle does weigh more than fat.
Give Me Chocolate Milk!
Many experts feel that chocolate milk (low-fat milk) has just the right combination of carbohydrates (for energy rebuilding) and protein (for muscle development and growth) to help with recovery after exercise. Milk even contains electrolytes like sodium and potassium (some of the electrolytes lost as you sweat) which may help the body to retain water and to restore its fluid balance. In addition, the slower digestion speeds of proteins and fat from milk* may slow the speed of stomach emptying, keeping fluids in the body longer.ª Milk also contains other body helpful vitamins and minerals like calcium, Vitamin D, and Vitamin A.
* Doctors often recommend drinking low fat or non-fat milk after 2 years of age (that's partly because toddlers start to get more fat from the foods that they eat). If they do not get enough fat in their diets, more fat from milk may be necessary. Excessive fat intake for players, however, in the first couple of hours after a match or between same-day matches in a tournament (i.e. youth tournaments) may slow digestion during a time when the body craves carbohydrates for conversion into immediate and future energy sources.
ª It may help explain why sports drinks after a match (when used without food) tend to show a lower fluid retention level than milk - requiring a longer time for rehydration or the recovery of a normal fluid balance.
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