There really isn't a gray area when it comes to hydration- either you're doing it right or you're doing it wrong.

Hydration is science; it refers to maintenance of water in your blood and correlates to a very definitive molecular formula. As an athlete, think of hydration as your body's cooling system and performance pump. Just a 2% loss in body weight due to dehydration can reduce athletic performance by a staggering 20%. Yes, you read that correctly... all the months of hard work and grueling training sessions can be negated by dehydration. In addition, for every liter of fluid lost: your core temperature increases, heart rate rises, glycogen stored in muscles are used more rapidly, and lactic acid increases.

A very basic primer on how the body functions: there is no 'plain' water in the body. It's a mix of electrolytes (sodium, potassium, magnesium, chloride) and glucose. 95% of your fluid absorption takes place in the small intestine via the 'Sodium Glucose Co-Transport System'. One molecule of sodium is pulled from the small intestine into the blood vessels by one molecule of glucose; subsequently, water gets absorbed as it always follows sodium. Too little glucose and not enough sodium gets absorbed – too much glucose will slow absorption and cause GI distress.

Immediately after prolonged training or events, athletes can be dehydrated, mildly hypoglycemic (lower than normal blood glucose levels) and have low electrolyte levels. Low blood glucose levels can be dangerous as glucose is the primary source of fuel to the brain. Good hydration within 45 minutes of a training session or event is essential to recovery. Fluids along with protein and carbohydrates soon after will help avoid injury and help to repair and rebuild damaged tissue.

While there are almost as many different hydration products as there are reality-star “housewives” on Bravo, there are very few that actually work to keep you from getting dehydrated. Zero calorie hydration options don't work (as explained above you need glucose to transport sodium) and high simple sugar options (most commercial sports drinks) don't work because they require more fluid for effective absorption. Fancy waters (coconut for example) help with hydration but they are not a solution for competitive endurance athletes and best left as a smoothie add in or post party beverage. I use and highly recommend SOS Hydration. It completely changed my training and performance and I've seen it work with countless athletes and professional teams. There are other good options; Osmo and Skratch Labs are also on my list of approved mixes.

Key points to remember:

Hydration is an ongoing process and requires a daily balance from the foods you eat and the fluids you consume. It is especially critical 2-3 days BEFORE race day.
Hydration is essential for optimal performance.
Hydration aids recovery.
Most 'hydration' products don't actually work-choose wisely.
Drinking water is NOT enough in endurance sports.