Water is one of the most important components of the human body. Making up almost 2/3 of the body, water assists nearly every part of the body in functioning efficiently. Just to give you an idea of how important water is to our health, consider this: our blood is made up of 92% water, and our brains and muscles are each made up of 75% water. Water plays a critical role in regulating body temperature, cushioning and protecting joints and vital organs, delivering nutrients and oxygen to all the cells in the body, and removing waste from the body.
For athletes and individuals who exercise regularly, staying sufficiently hydrated is also critical to exercise performance. The body can lose more than a quart of water in one hour of exercise, and if there is not enough water for the body to cool down through perspiration, dehydration occurs. Exercising while in a dehydrated state can result in exhaustion, muscle fatigue, loss of coordination, heat exhaustion, and in more extreme cases, heat stroke.
The Food and Nutrition Board recommends that women consume 91 ounces of water daily, and that men consume 125 ounces daily, with approximately 80% of your daily intake coming from beverages, and 20% through food.1 People who exercise regularly need even more, especially if they are working out in warm to hot weather. Women typically do not require as much hydration as men due to smaller body size, slower perspiration rates and electrolyte loss, and lower metabolic rates during exercise.
However, the rate at which individuals sweat and dehydrate varies depending on length and intensity of exercise, altitude, and temperature. There are two simple methods that will help you determine your individual hydration needs. First, monitor your urine. You should have a large amount, and urine should be pale (unless you are taking vitamins or other supplements, which can darken the color of urine for several hours). Dark, concentrated urine generally means you are dehydrated. Second, weigh yourself before and after exercise. Drink 16 to 24 ounces of water for every pound lost after a workout.
To ensure that you are properly hydrated for your workout, be sure to consume an adequate amount of fluids 24 hours before you exercise. You should also prehydrate with 17 to 20 ounces of water at least two hours before exercising, and drink 7 to 10 ounces of fluids every 10 to 20 minutes during your workout. And as stated, after completing a workout, consume 16 to 24 ounces of water for every pound of weight lost to help your body recover and rehydrate for your next workout.2
Though water is generally the best fluid replenisher for most individuals, if you are engaging in high-intensity exercise for longer than 45-60 minutes, sports drinks containing sodium can help to replace electrolytes lost during your workout faster than water. Individuals who sweat profusely during a workout or who have a high amount of sodium in their sweat (evidenced by salt stains or rings on your workout clothes) may also want to opt for sports drinks, and monitor their diet to make sure they consume enough sodium.
1. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2004) National Academy of Sciences. Institute of Medicine. Food and Nutrition Board. http://www.nal.usda.gov/fnic/DRI//DRI_Water/73-185.pdf
2. Casa DJ, et al. National Athletic Trainers’ Association Position Statement: Fluid Replacement for Athletes. J Athl Train 2000;35(2):212-24.