The New Rule Of Hydration

Remember when the only guideline for staying hydrated during exercise was to drink--and drink often? And plain water took the podium as the perfect sports drink? Thanks to new insights on how our bodies process fluids and other nutrients while we're working up a sweat, the conventional wisdom on when and what to drink is evolving. And although the rules may have changed, the objective remains the same: improved performance and optimal health. Here's a look at the old and new views on hydration.

Old: Drink ahead of your thirst.

New: Drink according to your thirst.

For years, sports nutrition experts advised athletes to drink "ahead of thirst," that is, to drink before getting thirsty and more frequently than what thirst dictated during exercise. Experts warned that by the time you feel thirsty, you've already become dehydrated. However, recent studies show that being in this state of slight dehydration has no negative impact on performance or health.

"The idea that thirst comes too late is a marketing ploy of the sports-drink industry," says Tim Noakes, M.D., a professor of sport and exercise science at the University of Cape Town, South Africa. While thirst is not a perfect indicator of hydration status, it does appear to be a good indicator of the optimal drinking rate during exercise, according to Noakes. "The answer is just drink as your thirst dictates."

Old: Aim to completely prevent dehydration.

New: Aim to slow dehydration.

You've probably been told to drink enough fluid during exercise to completely make up for what you lose through sweat. In other words, the goal is to weigh the same before and after your workout. But the latest research has revealed problems with this advice.

The recommendation to drink enough fluid to prevent weight-loss is based on the false assumption that all the weight lost is from body fluid evaporating as sweat. However, recent studies show that a significant amount (as much as 60 percent) is actually due to the loss of water stored with fat and carbohydrate molecules, which is released from the muscles when these stores are converted to energy. So, instead of drinking to completely replace the fluid you sweat out during exercise, aim for keeping thirst at bay. Respond to your thirst right away with small amounts of sports drink, but don't allow your thirst to build to the point that you're forced to guzzle down a full bottle at one time. Taking a few sips about every 10 to 12 minutes will help you stay hydrated and avoid stomach upset.

Old: Use either a sports drink or water for hydration.

New: Use a sports drink instead of water.

Prior to 2003, USA Track & Field's hydration guidelines suggested that water and sports drinks were equally good choices for hydration during intense physical activity. But, based on new research concerning the risks of blood sodium dilution, the USATF revised its hydration guidelines stating, "A sports drink with sodium and other electrolytes is preferred." Athletes in other sports are now following these guidelines as well.

In short, sports drinks simply hydrate better than water does. Your body absorbs fluids through the gut and into the bloodstream faster when their osmolality, the concentration of dissolved particles in a fluid, more closely matches the osmolality of body fluids such as blood. Because a sports drink contains dissolved minerals (key electrolytes such as sodium, calcium, magnesium, potassium, and phosphate) and carbohydrates, it's absorbed into the bloodstream more quickly than water, which has fewer or no dissolved particles.

Water is fine for short (less than an hour) workouts of easy to moderate intensity in which you don't sweat a lot. But in any workout where sweat losses are substantial, and especially in warm weather, use a sports drink.

Old: Caffeine exacerbates dehydration.

New: Caffeine does not affect dehydration.

Caffeine is a known diuretic, which means it increases urine production and has a dehydrating effect. But research has also shown that during exercise, the body is able to circumvent the diuretic influence of caffeine, which can boost athletic performance by stimulating the nervous system and reducing perceived effort.

A new study conducted at the University of Birmingham in England found that caffeine increases the rate at which supplemental carbohydrates (those consumed during the workout as opposed to those already stored in the body) are burned during exercise. In the study, cyclists received either a 6 percent glucose solution or a six percent glucose solution plus caffeine during a two-hour indoor cycling test. The rate at which the supplemental carbs were burned was 26 percent higher in the cyclists receiving carbs with caffeine, concluding that the caffeine may have increased the rate of glucose absorption in the intestine. By providing fuel to working muscles at an accelerated rate, caffeine helps athletes work harder for longer periods of time.

But don't overuse it. Reserve caffeine consumption for races and occasional high-intensity workouts. "The best use of caffeine as an ergogenic aid [energy booster] is prior to competition," says Jose Antonio, Ph.D, author of Supplements for Endurance Athletes. "The beneficial effects of caffeine on athletic performance are reduced with habituation, so the more often you rely on it, the less it will do for you."

Although no major sports drink brand contains caffeine, some flavors of sports gels do, such as Gu Chocolate Outrage, Strawberry Clif Shot, and Chocolate Accel Gel.

The Cardinal Rule

One principle of proper hydration hasn't changed: Practice makes perfect. Experiment with various hydration strategies to learn what works best for you. Try different sports drinks in varying amounts, and hydrate at different times during your workout to discover the optimal mix.

So, thoughts on this new hydration research anyone? What do you drink during your workouts and why?