Here is a post I did well over a year ago. I am reposting it due to the hot, humid weather we have encountered over the past couple of days. And now that summer is coming upon us, it is vitally important to stay well hydrated before, during, and after working out.
Water is an important substance that is required for pretty much everything done in the human body. It allows for chemical reactions to occur, lubrication, nutrient & vitamin delivery (in the form of digestion), waste disposal, heat dispersion, and temperature regulation.
The adult human body is composed of 45 - 60% water. The brain is made up of over 80% water. Muscle is composed of 80% water whereas fat is only 20%. As a result, the lower a person's body fat percentage, the higher the percentage of water.
Activity level and environmental influences (temperature and humidity) affect the amount of fluid that is lost from the body. If a person is inactive, the approximate water loss would be 2500mL. The fluid would be lost by the following methods: urination, evaporation/perspiration, respiration, and from the gastrointestinal tract. The body can only produce a small amount of water throughout the day through metabolic processes. The remainder has to be ingested in the form of liquid or food.
Exercise increases the work of muscles which, in turn, causes heat to be generated. To dissipate the heat, sweat is produced in order maintain body temperature. The rate of respiration also increases with exercise in order to supply the muscles with adequate oxygen resulting in greater water loss. Up to 4 liters per hour can be lost through exercise. When the body has lost as little as 2% of fluids, performance is impaired.
What happens when the body is in a state of dehydration?
Blood plasma is comprised of 92% water. When the body goes into a dehydrated state, the blood volume is reduced. This makes the cardiorespiratory system work harder in order to circulate blood and oxygen to the vital organs and muscles. If the dehydration progresses enough, nausea and vomiting ensue which further contributes to the dehydrated state. By this point, the athlete's performance has dropped by 30%.
The body reacts to dehydration in 3 ways: decreased saliva production, decreased blood volume (as mentioned above), and increased blood osmotic pressure. These 3 reactions stimulate the thirst center. However, the thirst center is very slow. By the time the athlete realizes he/she is thirsty, the body is already dehydrated. As well, it has been found that the thirst mechanism is depressed during exercise. This leads to further dehydration.
How can I avoid dehydration?
First thing is first... never rely on thirst to tell you when to drink. It is good to get in the habit of drinking throughout the day even if you don't feel thirsty. Drink smaller amounts more frequently. If it is a day in which you are exercising, it is important to start the hydration process 2 - 3 hours before training by taking in fluids on a regular basis. Then, approximately 15 minutes prior to exercise, consume about 250mL. It is also recommended to drink 250mL every 15 minutes of exercise but if you consume too many fluids, Mr. Pukie will probably make a visit. If the exercise lasts less than an hour, the body usually has enough electrolytes and carbohydrates stored in the body to maintain optimal performance.
How much water do I need?
The exact amount of water that an individual needs each day varies from person to person and a number of other factors. Some of these factors include weight, physical condition, activity level, and the external environment. The recommendation for men is about 16 cups of water per day (3.7L - and for our neighbors to the south - a little less than a gallon). For women, around 12 cups (2.7L - which is 0.7 gallons). But, as mentioned earlier, the more you exercise, the hotter/more humid the environment, or even the more lean you are, the more water you require.
But drinking all that water is hard to do. How do I do it?
The solution to this is quite easy. Carry a water bottle with you at all times. Have a couple of sips or mouthfuls every now and then. If you are sitting at a desk or in front of the television, keep the bottle or glass right in front of you or in your field of vision. That way you can be reminded, eventually instinctively, to take a couple of sips. Your body will stay well hydrated. Your muscles will pack a lot more punch and provide you with astonishing results in your performance.
Stay tuned for Part 2.
Stay tuned for Part 2.
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