Exercising in the heat: Hydration

This is our first blog post here on Patch.  I hope we can share some fun and useful content on running, endurance sports, nutrition, race events and general fitness topics.  Given the extreme heat this week, I thought it would be a good idea to share some ideas about how to train safely in higher temperatures.  Whether you are an athlete, exercising to get fit or even someone who works outdoors in extreme weather like today, staying hydrated is extremely important.  But there is a lot of science behind this topic and there are a lot of products on the market besides good old fashioned water.  So what’s the best approach and what should you think about when hitting the road in high temps?

In addition to heat exhaustion, runners or anyone training outside in this weather have two opposite problems to worry about.  The first is obvious: dehydration.  That is, not replacing the water we lose through sweat and evaporation through breathing while exercising.  The old wisdom was simply to guzzle as much fluid as possible to offset that sweat loss.  But we now know that consuming too much water after sweating heavily creates the possibility for other problems.  When we sweat, we lose more than just water; we lose essential electrolytes like sodium and potassium.  Drinking too much water when our bodies have lost a great deal of sodium can cause hyponatremia, sometimes referred to as water intoxication.  Sodium plays an important role in maintaining our overall level of hydration as well as keeping our muscle and nervous systems properly functioning.  Those processes require a delicate balance of water and electrolytes.  When that balance is disturbed, we create the risk of hyponatremia which in severe cases can cause heart failure, pulmonary edema and can in fact be fatal.  

How much water and how much electrolyte you need is personal.  Everyone is different, but the best way to understand it, is to understand our sweat rates.  To figure out your sweat rate, strip down and weigh yourself just before you exercise.  After you are finished exercising, weigh yourself again and add back any liquid you drank while you were exercising to your starting weight.  Subtract your end weight from your starting weight and divide that by the number of hours you exercised and that should tell you how much you sweat per hour of exercise.  This number can fluctuate based on the temperature you are working out in, so it’s a good idea to keep track of those conditions.  Do that a few times, and you should start to get a sense of how much fluid you need replace per hour of exercise in both warmer and cooler conditions.  As far as sodium goes, this is also somewhat personal, but some studies have shown that athletes training in warmer conditions tend to lose between 500 and 700 milligrams of sodium for every 32 ounces of sweat. 

As an example, I tend to sweat at a rate of just about 32 to 40 ounces per hour in hotter weather.  That means that for every hour of exercise, I need to replace about 32 ounces of water and about ~600 milligrams of sodium.  

So this leads to the last dilemma.  There are a ton of sports drinks on the market that offer hydration plus electrolytes (sodium).  And for some, these off the shelf type products like Gatorade might be fine.  The problem is that many of those products are also loaded with carbohydrate, most commonly in the form of pure sugar.  Some of us out there might be exercising not just to improve performance, but to lose weight to simply look better.  We might also have specific dietary concerns, or use specific products like energy gels to get carbohydrate while exercising. 

For me, I would need to drink about two 16 ounce bottles of sports drink every hour to get the right level of water and sodium.  That’s about 250 extra calories per hour with some sugary sports drinks.  Fortunately, there are a ton of great products out there like Nuun (pronounced ‘Noon’) that come in a tablet form that you simply add to regular tap water and that add electrolytes (sodium) without adding any additional calories. 

So to sum it up, here is a list of tips we thought might be helpful:

1)      It goes without mention that exercising earlier or later in the day when its cooler is definitely the way to go on hot days like today.  Alternatively, days like today could be a good day to substitute running and walking with gym workouts.

2)      If you are going to exercise in hotter weather, drink plenty of fluids before, during and after your workout.

3)      It is a good idea to try and understand your sweat rate to get a handle on how much fluid and electrolyte (sodium) you need to replace while exercising.

4)      There are lots of good products on the market to help you get both fluids and sodium that go beyond the off-the-shelf sports drinks.  Experiment with different products to see what works for you.

5)      Both dehydration and water intoxication (hyponatremia) are serious, potentially life threatening conditions.  It’s a good idea to understand the causes and symptoms of these conditions, especially if you are going to exercise in high temperatures.   There is plenty of free material on the web but you may also want to talk it over with your doctor especially if you are starting a new course of exercise.

Thanks for reading our first post!  I hope that it was helpful.  Stay cool!