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Beat the Heat: Hydrating in Hot Weather
Beat the Heat: Hydrating in Hot Weather
By Rebecca Scritchfield, MA, RD, LD
May/June 2009
For the Washington Running Report
It is no secret that water is essential. Of all the nutrients, it is the one most likely to cause death in a deficit. (Pretty serious.) Exercising in the sweltering heat and humidity in DC can make it difficult to stay hydrated. But how much water do you need? Is it possible to get too much? What about sports drinks? I'll answer these questions and more in this article so you will be the "hydration hero" among your training buddies.
Here is the bottom line; the point of drinking is to prevent dehydration during exercise. Drink too little and you can become so dehydrated it makes you prone to a heat illness. Drink too much and you can end up with hyponatremia, a condition of low blood sodium that can cause brain swelling. Both dehydration and hyperhydration can be life threatening and require quick medical attention.
Adequate fluid intake before, during, and after exercise is important for health and optimal performance. The recommendations that follow are taken from the American College of Sports Medicine's position stand on hydration, which is based on research evidence.
Before a Workout or Race
Your hydration plan begins well before you take your first stride. Your pre-race meal or snack should have adequate fluids-about 16 to 24 ounces. Include juice, water, or sports drinks in your last meal or snack before training or competition. Continue to drink 16 to 32 ounces of water per hour before race time. Be sure to consume the last 8 to 10 ounces of fluids about 15 minutes before exercising. Sports drinks may provide a performance benefit over water if consumed an hour or less before the race simply because the sugars in the drink provide quick energy.
Hydrating Short Distances
If your run is less than an hour long, you are trained, and it is not excessively hot outside, your risk of getting dehydrated is small. Drink small amounts of water as needed every 20 minutes. You don't need a sports drink, but if you prefer the taste, the sugar and electrolytes certainly won't hurt you.
Endurance Hydration
Training sessions and races that last longer than 60 minutes require particular attention to hydration. Even with the best intentions, many athletes fall short of replacing 100 percent of fluid losses by replacing only about 50 to 80 percent. Your goal is to keep up with sweat losses as much as you can.
The general guideline for hydrating during endurance events is 4 to 8 ounces every 15 to 20 minutes. Drink at regular intervals or whenever there is an opportunity to drink. The cups at water stations tend to have only about 4 ounces and there is about 2 miles between stations. Even if you hydrate at every station, it might not be enough to make up for losses. This is why you should run with a fuel belt, especially in long-distance races like marathons, 20-milers, and half marathons. Personally, I walk through every water station at the half marathon distance and greater to give myself time to drink. I also begin hydrating from the first station.
Sports beverages containing water, 6 to 8 percent carbohydrate, and electrolytes are beneficial in endurance events. The carbohydrates help maintain blood sugar levels and fuel muscles, the water helps replace sweat losses, and the sodium helps create thirst and water retention. Performance benefits occur if you take in about 30 grams of carbohydrate an hour. Don't worry if you can't tolerate sports drinks. You can always consume plain water and the multitude of gels, beans, and blocks for the sugars and electrolytes.
After the Finish
Because most athletes do not replace all fluid losses, they finish races dehydrated. So you should immediately begin drinking after completing a race or workout. Drinking 16 to 24 ounces of fluid for every pound lost during exercise will provide rapid recovery from dehydration. Make it a habit to drink as much fluid as you can and follow that up with a salty, high carbohydrate meal to help replace glycogen and electrolytes. Keep drinking fluids the rest of the day.
Hydration Problems
Losing more than 2 percent of your body weight can lead to dehydration. Add heat to the equation and your problem could intensify to heat exhaustion or heat stroke. Some early signs of dehydration include lightheadedness, headaches, decreased appetite, fatigue, dark urine, irritability, nausea, and GI upset. If you experience any of these issues during an event, you should walk, begin rehydrating, and ask for medical help. It is not something to "push through."
Signs of Good Hydration
You can check your urine on a regular basis to see if you are properly hydrated:
- Urinate every few hours throughout the day.
- Urine should be clear to lemonade yellow and be of significant volume.
- Morning urine should not be dark and small volume.
Personalized Hydration
If you want to get real personal hydration advice, you should make an effort to know your sweat rate and plan to hydrate accordingly. Weigh yourself nude before and after an hour-long run. If you lost one pound (16 ounces), you need to hydrate with one pint (also 16 ounces) of fluid each hour of training or racing. The goal is to lose no more than 2 percent of your body weight per exercise session to avoid dehydration. Be sure to measure your sweat rate several times a year. It may change with the seasons and your fitness level.
Practice Makes Perfect
When my clients have problems with hydration, usually it is because they do not practice it enough. Just as you train your body with running, you need to train it with fueling too. Do not do anything on race day that you did not try first in training. Practice your ideal hydration schedule on training runs so you can learn the skills involved in drinking during exercise-and more importantly how your body responds.
A well-hydrated athlete is a happy and healthy one!
Rebecca Scritchfield is a registered dietitian specializing in performance nutrition and weight management. She regularly runs marathons and half marathons in the DC area. Visit her Web site and blog at www.elitenutritiondc.com. Send correspondence regarding this article to: rscritchfield@gmail.com.