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Keeping Hydrated While Exercising: Needs Depend on Level of Exertion

Water, sports drinks and chocolate milk are the best ways to replenish fluids and electrolytes.

Warmer weather is here and with that comes the added risk of heat-related illnesses, such as heat exhaustion or heat stroke. More commonly, dehydration is a major hazard to those who engage in physical activity in the heat. Dehydration can lead to loss of coordination, muscle cramping, fatigue and exhaustion.

We all know that we should be drinking eight glasses of water a day, but many exercisers are unaware of the guidelines past that. Below outlines the basic strategies the experts recommend for fluid replacement before exercise, during exercise and post-exercise (recovery).

Pre-Exercise:

In a resting state, one should always be properly hydrated. To ensure this, be sure to drink at least 8 (8-ounce) glasses of water. This should not be difficult to achieve. For a quick reference, one Poland Spring water bottle is 16 ounces, so you would only need to drink a minimum of four bottles of water to meet those requirements. 

It is important to note that every person is different, so your individual requirements may be higher than this. Whatever your fluid intake may be, be sure to drink so that you rarely become thirsty and so that your urine is pale yellow most of the day.

If you have planned physical activity, be sure to drink an extra 16 to 24 ounces (depending on the intensity) of water at least an hour before the event. The American College of Sports Medicine recommends 17 ounces of fluid about two hours before exercise to be safe.

During Exercise:

The basic rule of thumb is to drink when thirsty to prevent dehydration. Fluids should be taken in consistently throughout exercise to avoid this. Drinking 4-6 ounces of water every 20-30 minutes would most likely be sufficient for hydration.  Many people choose to hydrate with sports drinks (ie, Gatorade, Powerade, etc), but beware of added calories. 

Sports drinks should be used to replace electrolytes lost during long bouts of exercise (90 minutes or more). Any exercise shorter than 90 minutes or so does not warrant the use of electrolyte-enhanced drinks that can have as much as 45 grams of sugar and more than 300 calories per bottle. It would take about 30 minutes to “burn off” the calories ingested in just one Gatorade.

The experts maintain there is no replacement for good old-fashioned water, so save yourself the money and calories. Again, there is not a “one-size-fits-all” prescription. If you are a heavy sweater or extreme temperatures/humidity are present, increase your fluid intake accordingly.

Post Exercise:           

You probably have seen many sports drinks marketed as “recovery” drinks, and there is scientific basis for this. Clearly, it is important to rehydrate with water (until pale yellow/clear urine is present), however replacing muscle fuel (glycogen) in endurance athletes is also an important part of recovery.

This is to ensure that your muscles heal quickly and are able to perform for your next bout of exercise. To do so, sports nutritionists state that recovery drinks or meals with a 3:1 or a 4:1 carbohydrate-to-protein ratio ingested within two hours (but ideally within the first 30 minutes) can optimize muscle recovery. 

Interestingly, current research shows that lowfat chocolate milk contains the perfect mix of carbohydrates and proteins to refuel muscles after a long bout of exercise! Consider this delicious, healthy and inexpensive alternative to fancy sports drinks or powders.

There is a common misconception that caffeine before or during exercise can lead to dehydration, however there is no scientific basis to this myth. There is clear scientific evidence that caffeine is a safe stimulant as well as has many benefits during exercise, including enhanced performance, decreased perception of effort, and increased energy and endurance.

This is of course, as always, in moderation. I would not recommend chugging three Red Bulls prior to an event. The safe upper normal limit is about 550 milligrams of caffeine (or about five cups of coffee). 

I hope this article provides some baseline knowledge on fluid replacement strategies this spring and upcoming summer. Don’t let the heat deter you from your exercise plans! As long as you are properly hydrated, coolly dressed and “sun safe” (sunscreen and hats), you can maintain the same level of physical activity as before.

If at any point you should feel severe breathlessness, light-headedness, dizziness, loss of muscle control or fatigue, nausea, vomiting or chills, discontinue exercise and seek shade and water. If the symptoms do not improve, seek medical attention immediately.

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