If you’re running a 5k on up to a half marathon, hydration matters, but it’s not terribly tricky. The focus should be on making sure you consume enough fluids to prevent dehydration, but if you’re out there for several hours – or a lot more – you need to be even more concerned about avoiding over hydration, also known as hyponatremia. Hence the Goldilocks Principle. You must make sure you drink enough, but if you drink too much, you’ll be in big trouble.

“The Real and Simple Truth About Dehydration and Performance.” by Jeff Gaudette. Competitor.com

“Drink to thirst, an Excerpt from Tim Noakes’ Book Waterlogged.” Runner’s World

USATF Announces Major Change in Hydration Guidelines

“The Running Doc’s Complete Guide to Hydrating During Training and During Races” by Lewis Maharam. The New York Daily News

Tim Noakes on the Serious Problem of Overhydration in Endurance Sports in Outside Magazine

“Study Cautions Runners to Limit Their Water Intake.” by Gina Kolata  The New York Times

“How Much to Drink During a Marathon.” by Gretchen Reynolds. The New York Times online