Water makes up approximately two thirds (between 60 - 70%) of your body weight. That is 7 St 7lb of water in an 11 stone person.
Water is the prime importance for the regulation of body temperature, all of our bodily functions and chemical reactions occur in aqueous solution.
Daily losses are relatively high, even under normal / moderate temperature and activity. The body needs to replace its entire mass of water every 11 - 13 days.
Water is lost largely through urination as well as by evaporation in breath and sweat.
The kidneys normally very carefully regulate the balance of water retained in the body, but excessive losses can result from vomiting, diarrhea, vigorous exercise or high temperatures.
It should be noted that even small losses of water (2-3 % of body weight) can seriously impair performance.
As a rule of thumb 1 oz of water should be consumed per kilogram of body weight. For example a 70kg person should drink 3.5 pints of water or eight 8oz. glasses per day.
A good indication of healthy water intake is the color of your urine, - except first thing in the morning, it should be colorless or a pale yellow.
Many sports people and regular exercisers fail to drink sufficient amounts of water.
An interesting point to note is that for every gram of glycogen used, 3-4 grams of water is lost.
An hour prior to exercise aim to drink at least 2-cups/16 oz. of water.
During exercise take regular sips of water, or 4 - 8 oz every 15 min's.