Two to three percent fluid loss in a 150 pound individual represents three to four and a half pounds of body weight or one and a half to two quarts lost water. To prevent dehydration during exercise, athletes should drink fluids before, during and after activity. Even exercise in cold weather results in sweat production and requires adequate fluid replacement. Although electrolytes such as sodium also are lost through perspiration, the immediate need is for water alone. In most circumstances sodium and other electrolytes can be replaced after exercise.
Many athletes think the extra electrolytes and sugar in sport drinks provide an edge in competition.
Unfortunately some of these special drinks are too concentrated with sugars, electrolytes and flavoring agents. They hinder water absorption. As a general rule, dilute beverages that contain sugar and electrolytes with plain water before drinking. A Guide for the Professional Working with Active People. During exercise or athletic events thirst is not always a reliable gauge of fluid needs.