Do You Need a Drink?
John Hudak
Some Notes on Hydration
By the time someone becomes thirsty, the body has already sensed a decrease in the level of fluids or an increase in sodium concentration. So you only really get thirsty "after" you have experienced a significant loss of fluid or changes in your sodium level.
In 2004, the Food and Nutrition Board of the Institute of Medicine released Dietary Reference Intakes for water and electrolytes. They established Adequate Intake levels of 130 ounces (16 cups/3.8 liters) daily for men, and 95 ounces (12 cups/2.9 liters) for women.
Water plays an important part in the smooth functioning of your body, from cooling the body, to lubricating joints and protecting important tissues (like the brain and spinal cord).
Water helps you maintain a constant body temperatures under different environmental conditions as well as exercising. In the summer the cooling part is important to think about, especially when you are exercising outside. Not wearing a shirt may seem like a good idea, but unless you wear sunscreen while exercising, direct sun exposure to the skin is thought to be cancer producing.
Cotton shirts vs. wicking? If your body uses sweating to cool its internal core temperature, then wearing cotton shirts will eventually start to limit evaporation due to the fabric's tendency to "hold" water (cotton will also get heavy). Dri-fit and other technical shirts that aid in wicking the sweat from your body are probably the best thing to wear. Light colored shirts reflect the sun better than darker colored ones. White objects reflect all colors and therefore are cooler. Black objects absorb all colors and are therefore warmer.
The balance of fluids in the body throughout the day is the result of your intake of fluids versus your output of fluids. Intake comes from the water we drink, some of the food we eat, and through internal production by your body.
When you are not exercising, your greatest fluid loss is from urine output. Sweating during exercise can result in significant fluid losses, even when it is cold outside, and during aerobic workouts in the gym. Fluid is also lost through exposure to warm or humid weather, in the air you exhale. There is a good amount of fluid loss experienced when traveling, especially by plane.
The body cools itself by sweating, the sweat being the primary mechanism for getting rid of excess heat. Children have smaller surface areas, and are more prone to become dehydrated if they participate in strenuous outdoor activities during the summer.
People suffering from heat exhaustion may feel weak, have cold and clammy skin, have a weak pulse, and may experience faintness, fatigue or nausea. Heatstroke is characterized by hot dry skin and a very high body temperature; and can come from overexertion in extreme heat. If you feel any of these ways during exercise, stop immediately so that your core temperature can go down…look for something to drink or in extreme conditions, ask someone for help.
Remember…if you feel thirsty while you are exercising, then you already are dehydrated. If you exercise a lot, it is recommended that you drink 8 ounces of water every hour to keep yourself hydrated.
One way to tell if you are dehydrated is to notice the color and quantity of your urine output. If the urine is clear or close to the color of lemonade, then you are well hydrated. If the color is darker, near that of apple juice, then you may be dehydrated. Note that the color is darker in the morning, and will also be darker if you take a lot of supplemental vitamins (the extra vitamins get output this way). Volume of output is also a sign of dehydration…if you don't seem to be outputting at least four full bladders every day, then you should drink more water.
My next post will be about types of water bottles, hydration packs, and the comfort they may hold.