For over twenty years, F. Batmanghelidj, MD, author of Your Body’s Many Cries for Water, has researched the role of water in human physiology and health. Water is the body’s primary component. It makes up 75% of the body and 85% of the brain.
Water is a basic need for cellular health. Cells both contain and are surrounded by water. In dehydration, cell membranes become less permeable, hampering the flow of hormones and nutrients into the cell and preventing waste products such as oxidants that cause cellular damage from flowing out. As Dr. Batmanghelidj says, dehydrated cells shrivel, resembling prunes instead of plums.
Water does more than act as a solvent for nutrients and oxidants. It generates energy as it flows through the pump in a cell’s membrane. Water is also necessary for the metabolic breakdown of ATP, another source of cellular energy. In addition, water acts as a bonding adhesive in the cell structure. On a larger scale, water is needed in order for the digestive system to break down and digest food: and water increases the efficiency of red blood cells in collecting oxygen in the lungs.
Evaporation is the body’s primary protection against overheating. Through this process, the body transfers heat from its core by evaporating sweat from the skin and respiratory passages. It is important to understand, however, that sweating alone does not cool the body. To produce a cooling effect, the sweat must be evaporated to lower the skin temperature. By blowing cooler air over the skin, sweat vaporizes and heat is released. Humidity impairs evaporation, which increases the rate of sweating, causing a greater loss of body water, which in turn leads to more severe dehydration. In a Yoga class, humidity may be high, depending on the heat source, the room ventilation, and the number of students participating. Humidity will increase if the ventilation is poor and there are lots of students exercising and sweating. A separate concern is the practice of wiping sweat from the body using a towel. If the sweat is removed from the skin, evaporation will not occur, and heat will be retained. Sweating will subsequently increase, leading to a greater loss of body water and increased dehydration.
The ideal situation is the prevention of dehydration during exercise. To achieve this goal, exercise good hydration practices before participating in a “hot” yoga class. The recommendations for hydration before, during, and after exercise are as follows:
1. Daily intake of 8-10 glasses of water (8 oz. per glass) for normal activity, not including exercise.
2. At least 2 hours prior to exercise, drink 16 oz. of water or fluid without caffeine.
3. If possible, determine body weight while hydrated, prior to exercise.
4. During exercise, drink frequently and early, before you are actually thirsty. Your goal is to replenish fluids at the same rate you are sweating. The maximal rate of replacement is between 20-40 oz. per hour, based on absorption of fluid by the stomach.
5. After exercise, evaluate change in body weight. Consume fluids to return to body weight prior to exercise.
Since the environment in a “hot” yoga class increases body fluid loss, the above guidelines become even more important. Of additional concern, caffeinated beverages such as coffee, many teas, and sodas will increase fluid loss by increasing urinary output. Wine, beer, and other alcoholic beverages cause fluid loss as well. If you drink beverages with caffeine or alcohol, consume equal amounts of water (in addition to the daily recommendation of 8-10 glasses) to avoid dehydration.
Thanks to Owner, Director, Robin Duffy, Being Yoga at www.beingyoga.net for this article
