From the AFAA Manual
"Water
Adequate hydration is important for everyone, but it is especially critical
for regular exercisers to replace body fluids as dehydration is more likely
during and after prolonged exercise and can have serious consequences. At
the least, dehydration may cause decreased performance, headaches, and
constant fatigue. More serious consequences can include muscle
cramping, syncope (fainting), heat exhaustion, and heat stroke.
Although hyponatremia (a serious condition of over-hydration that
can disrupt the body’s sodium levels) is a potential concern for competitive
endurance athletes, the ACSM states that dehydration is a far more
common problem for most athletes and the general public, especially
those unaccustomed to strenuous activity in hot environments.
Recommendations from The ACSM’s Position Stand on Exercise and
Fluid Replacement (1996) include the following.
• Drink approximately 500 ml (~17 oz.) of fluid about 2 hours before
exercise to promote adequate hydration and allow time for excretion
of excess ingested water.
• During exercise, start drinking early and at regular intervals in an
attempt to consume fluids at rate to equal water lost through
sweating.
• Fluids should be between 59–72° F and flavored to enhance palatability
and promote fluid replacement.
• Sports drinks with proper amounts of carbohydrates and electrolytes
are recommended for events longer than 1 hour (American
College of Sports Medicine, 1996).
Additionally, check the color and quantity of your urine (it should be
clear and copious). Weigh yourself before and after exercise. For every
pound of weight lost, drink 2 cups of fluid.
AFAA recommends drinking
1–2 cups of water 5–15 minutes before your workout, and a minimum of 3
ounces every 20 minutes of exercise. During hot and humid conditions
and during prolonged and/or intense exercise, even more water is
required—drink up to 8–10 ounces every 20 minutes. After exercise,
continue to drink when thirsty, plus more. For exercise bouts lasting longer
than 90 minutes, diluted juice and/or a sports drink will add beneficial
electrolytes and help maintain blood sugar balance. After prolonged exercise,
juice is preferable because of its higher levels of carbohydrates and
electrolytes."