2. You exercise while parched.
When it comes to working out, the importance of drinking water is clear. “Nearly every cell in the body is composed of water—without it, they don’t function efficiently during exercise,” says Dan Judelson, PhD, an associate professor of kinesiology at California State University in Fullerton. Translation: You’ll fatigue faster, and your workout will feel tougher than it should. In recent studies, Judelson discovered exercisers who were dehydrated completed three to five fewer reps per set while strength training. Part of the problem is that dehydration decreases the body’s levels of hormones that are necessary for strong muscles.
On workout days, drink an ounce of water for every 10 pounds of body weight (i.e., 15 ounces if you weigh 150) 1 to 2 hours prior to exercise. Then keep sipping during and after your session to replenish what you lose through sweat.