Winter Hydration: Don't be fooled by the cold!

By Kimberly Brown, M.S., R.D.

When a chill's in the air, many athletes aren't as worried about losing fluids as they are in warmer months. But dehydration remains the number one performance inhibitor among athletes even when temperatures plummet in winter. Here's how to stay on top of your fluids this winter

1. Don't Wait Until You're Thirsty
At the onset of thirst, an athlete is already 3 percent dehydrated, reducing performance by 15 percent. To prevent dehydration, sip fluids throughout the day until your urine flows clear to pale yellow. Daily fluid needs vary depending on body composition and weight. Use the following equation to estimate daily fluid needs:

Body weight (in pounds) / 2 = daily fluid needs in ounces

Be creative with your fluid intake, as this equation factors in not only water but non-caffeinated and non-alcoholic fluids as well. Try adding a hydrating fruit like melon at breakfast or a hot bowl of soup at lunchtime for added hydration.

2. Top Off Your Tank Before Training
Before you go conquer the cold or head off to the gym, top off your tank by sipping 16 to 24 ounces of fluid one to two hours prior to exercising, especially if you work out first thing in the morning. After an overnight drought, many people wake up with 1 to 2 percent less body water, which can severely affect the efficiency of a workout. Choose water before a workout, but if you're prone to cramping, consider a sports drink or salty snack like pretzels with your water.

3. Drink While You Sweat
To maintain fluid balance during exercise, it's important to replace fluids lost through sweat and urine. Fine-tune your fluid intake regimen by determining your sweat rate. Weigh yourself before and after different workouts. Every pound of body weight lost during exercise equals about 16 ounces of fluid. For example, if you consistently lose one pound during a 30-minute run when you're not drinking anything, your fluid needs are 32 ounces per hour. Be sure to note your workout environment (an indoor Spinning class or outdoor run in snowy conditions), as sweat rates will vary in different conditions.

If your workout lasts less than an hour, water is a fine choice. Beyond an hour, however, a sports drink with a 6- to 8- percent concentration of carbohydrates will help enhance performance. During the winter months, consider drinking warm broth during longer runs or hikes to help replace sodium and fluid losses and to keep your core body temperature from dropping too low.

4. Don't Forget Sports Drinks
In addition to fluids, replacing electrolytes is critical in training sessions longer than one hour. The primary electrolytes include sodium (generally bound to chloride), potassium, magnesium (best absorbed when bound to gluconate) and calcium. These electrolytes are involved in metabolic activities and are essential to the normal function of all cells, including muscle. An electrolyte imbalance includes symptoms similar to dehydration: nausea, vomiting, muscle weakness, muscle cramping, muscle twitching, overall fatigue, labored breathing, the sensation of "pins and needles" and confusion. The table below shows the function of the principle electrolytes, dosage goals during exercise and performance daily intake (PDI) recommendations for athletes.

Failing to replace electrolytes during exercise longer than an hour can be life threatening. Several athletes have suffered "water intoxication" (hyponeutremia), when blood sodium levels drop dangerously low, causing an electrolyte imbalance and triggering seizures, coma and even death.

5. Rehydrate
For every pound of body weight lost during exercise, drink 16 to 24 ounces of fluid to rehydrate and enhance recovery. Sports drinks are best for post-workout rehydration because they contain sodium (increases fluid absorption) and carbohydrates (replenishes lost glycogen).

Kimberly Brown, M.S., R.D. is a sports nutritionist and competitive endurance athlete based in San Diego, Calif., who provides nutrition coaching and meal planning to athletes worldwide. You can contact her at kjmuell@hotmail.com.