Cool, Cool Water

This afternoon I skipped rope and swung a kettle bell outside for about an hour. It was a beautiful, hot summer day - 95 degrees. Though most times it's smarter to do workouts earlier in the day during the summer to avoid the added stress to your body from the heat, sometimes it feels good to exercise and get really hot, sweaty and exhausted.

Today was one of those days. Dripping with sweat and breathing in the hot air, I kept thinking about my favorite country and western song, "Cool Water" by the Sons of the Pioneers. Although it's about cowboys herdin' cattle out in the desert, not exercise, it perfectly captures that special feeling we have towards water, especially on a hot day because the human body is over 70% water. When at rest, the human body is at thermal equilibrium when the outside temperature is at 82 degrees F.

Dehydration is a side effect of exercise because our body heat rises with metabolic rate. Most times dehydration is no big thing, as it wasn't to me today because I could get to water in a matter of seconds - I working out on a deck right outside outside our kitchen and had a water bottle nearby. (But I've gotten in trouble in the heat; see "The Self-Made Road to Hell and Back" in a 2008 blog.)

Our bodies have an incredible system of controls to maintain our core body temperature at a normal 98.6 degrees F. Just 8 - 10 degrees above this, we are delirious or dead.

The body cools itself by routing blood to 3 million sweat glands that use a fine network of vessels near the surface of the skin to give off heat via sweat. If you're interested in learning more about all the processes, pick up a copy of "Surviving the Extremes: What Happens to the body and Mind at the Limits of Human Endurance" by Kenneth Kamler, M.D., who has been a physician on several expeditions into hostile environments. He explains in detail the body's response to heat in an incredible story of survival of an ultra-marathoner who got lost during a race in the Sahara Desert.

As long as we have the fluid in our systen to sweat, everything is fine. However, when you add intense exercise with hot ambient air, you begin to loose body fluid fast and start to be unable to dissipate your internal heat fast enough. Assuming you have been drinking enough water before you exercise, most times dehydration is not a major concern if you are working out, or even racing, for less than an hour. Longer than that, replacing fluids becomes more critical and challenging.

The key indicator of dehydration is loss of body weight. When you lose 1-2% of body weight, which is typical of a hard workout or run on a summer day, you're usually fine. At 2% loss you will start to feel some discomfort and performance is affected because dehydration begins to interfere with the utilization of glycogen (needed to produce physical energy) in skeletal muscles, the ones that lift, run or turn the crank on your bike.

Between 3% and 4% you start having severe cramping, and even dizziness or nausea. At 5% is the danger zone for heat exhaustion or sun stroke. Again, this is more likely to occur when you exert for more than an hour. Most of us don't get to this stage

As long as you're sweating, that's a good sign, but your body is still under stress. As you dehydrate, your blood plasma decreases, causing the blood to thicken which then causes your heart to beat harder. Your brain also dilates (opens) your blood vessels as wide as possible to help dissipate the heat, which also taxes the heart further to deliver blood to the muscles that need oxygen and nutrients. You see how this can lead to a vicious cycle.

Remember that as you exercise, you cannot replace all the fluids that are lost at the same rate. It takes time for anything you drink to get through your gut and into your bloodstream. But adding fluids as you exercise to offset losses works, especially if it's hot.

Thirst lags dehydration. For this reason, the American College of Sports Medicine recommends 1/2 to 1 cup of fluid for every 15 minutes during exercise, whether you are thirsy or not. You can speed the transit time from gut to bloodstream by adding a small amount of sugar. If you are working out or competing for more than an hour, you can also add some electrolyte like a little sodium or potassium, which is basically what's in sports drinks like Gatorade. Below you'll find a recipe for a rehydrating drink that works and tastes great.

Note that drinking fluid will not lower your core body temperature. Research shows that even drinking ice cold water has no impact, though it tastes good. The only way to lower your core temperature is to lower your metabolic rate, which means you either slow down or stop altogether.

A TOJ knows that as time or intensity of exercise goes up, along with the outside and core body temperature, so must fluid intake. Summer, heat, sun, sweat -- and cool, cool water.

Electrolyte Rehydrating Sports Drink

2 cups coconut water

2 tablespoons sweeter of choice (alternatives to cane sugar include agave nectar, honey, stevia, and medjool dates)

Juice from 1/2 lemon

Juice from 1/4 lime

Sea salt to taste

Blend all ingredients in a blender until well mixed.

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