If you wait to drink until you're thirsty, it's too late: You're already dehydrated. For every 2 percent of dehydration, you lose 10 percent performance. The solution isn't to over-drink, as that can just wash out necessary electrolyte solutes. Instead think consistent hydration, and aim to drink six to eight ounces every 15 to 30 minutes throughout the day. Source: Daniel Matheny, senior endurance coach at Carmichael Training Systems in Colorado
