We always hear, "Make sure you stay hydrated," especially during exercise, but what does that actually mean? How much water should you be drinking to actually stay hydrated?
The "8x8" is a common rule: drinking eight 8-ounce glasses of water, totaling 64 ounces, per day. However, even this recommendation underestimates proper hydration. The National Academy of Medicine recommends that women should get about 91 ounces and men get about 125 ounces of water per day. 20 percent of that should come from foods, so actual water consumption should be about 73 ounces for women and 100 ounces for men. However, when you factor in exercise, fluid intake should increase as well.
During exercise, fluid is lost through sweating and respiration. The average person loses about 17 to 50 ounces of fluids per hour when exercising. As a result, the fluids lost need to be replenished. Director of performance nutrition for Athletes' Performance, Amanda Carlson stated, "Just losing 2 percent of your body weight in fluid can decrease performance by up to 25 percent." Research has shown that athletes often underestimate their fluid needs. In one study, seasoned runners who participated in a 10-mile race underestimated their sweat losses by an average of 46 percent and their fluid intake by an average of 15 percent, resulting in them only replacing 30 percent of fluids lost.
Calculating Recommended Water Intake
Recommended water intake depends on many factors including gender, your environment, your health, level of activity, etc. In terms of activity level, it is recommended you drink 50 to 100 percent of your body weight in ounces. For example, rest days would be on the low end while moderate or high intensity training would be on the high end.
Low end: Body weight (in pounds) x 0.5 = fluid ounces per day
High end: Body weight (in pounds) x 1.0 = fluid ounces per day
For example, if you weigh 150 pounds, your daily water intake would be between 75 to 150 fluid ounces.
When to Hydrate
Every day, your should start your morning drinking 8 to 12 ounces of water. On training days, you should hydrate before, during and after exercises. A guideline from the American Council on Exercise recommends:
Two hours before exercise: drink 16-24 ounces of water
20-30 minutes before exercise: drink 8 ounces
Just before exercise: weigh yourself to get a baseline weight
During exercise: drink 8 ounces of water every 15 minutes
After exercise: immediately weigh yourself and drink 16-24 ounces of water for every pound of weight you have lost
You do not need to replace all of your fluids at once at the end of your workout. Start with 8 ounces and continue to hydrate gradually.
Hydration is key to exercise efficiently. It lubricates the body, improves blood circulation, and keeps you energized to perform better, longer.