Last week’s column addressed the heat that’s been around for most of the last few weeks. This past week also had increased humidity, unusually high nearly every day. I check the temperature and humidity as soon as I get up each morning and together they set the tone for my exercise.

When we exercise, the body warms up and body temperature increases. The body is amazing at self-regulating temperature, and when body temperature rises, a cooling mechanism kicks in. The body re-directs blood from the deeper, more central parts of the body, like the internal organs and muscles, and into the blood vessels that are closest to the surface of the skin.

And then you start sweating. Sweat is the body’s main mechanism to cool itself. Sweat is made up primarily of water, with some salts, which play a role in the movement of fluids between and among cells in the body. Sweat is produced inside the body, and then exits the body via the pores in the skin. The water in the sweat evaporates into the air, which cools the underlying blood.

Even without heat and humidity, extended bouts of strenuous exercise will lead to dehydration as the body sweats to dissipate heat. Dehydration is dangerous by impairing performance because fluids are not circulating the way they should within the bloodstream. Muscle cramps can occur while other issues on the less dangerous end include headache and light-headedness.

If the air surrounding the body is humid, sweating becomes a less efficient way to cool the body. The higher the humidity, the less efficient sweating is. Most early mornings recently, I have returned from my run with water droplets on my skin. That’s sweat, sitting on skin, unable to evaporate.  When sweat can’t evaporate, it doesn’t cool off the body. The body keeps pumping out sweat, but the body temperature does not drop.

Humidity causes any exercise to seem more difficult because the body is actively redirecting blood away from the muscles. The muscles are working less efficiently because the supply of oxygen has been drastically reduced and it seems like extra effort is required. The heart has to work harder to drive the circulatory system because the blood is thicker and sludgier since part of the water that usually keeps blood at the regular consistency has been made into sweat.

At this point, it should make sense that humidity magnifies the effect of heat. If it is hot and not humid, sometimes called “dry heat,” sweat evaporates normally and the body will be cooled. These conditions have their own dangers because fluid loss might not be as apparent until thirst takes over. What we call “heat-related illnesses” are often caused by a combination of heat and relative humidity, together called the heat index. Heat cramps, heat exhaustion and heat stroke are possible in high heat index.                 

Sports and energy drinks are popular among some adults and teens and are touted as a way to replace lost electrolytes in heat and humidity. But what you’re getting is more sugar and more empty calories, for many people it’s more than what they are burning.

It has long been my opinion that sports drinks, specifically Powerade and Gatorade are a marketing ploy that does little to quench thirst and hydrate the body. One 20-ounce bottle of Powerade contains 130 calories and 34 grams of sugar, about 8 teaspoons. Gatorade is a little higher at 140 calories and about 8.3 teaspoons of sugar. For my money, both of these drinks don’t do the job because the excessive sugar slows ingestion of good fluids. Either stick with the water or mix 20 ounces of water with a 20-ounce sports drink.

With high humidity, leave the hardest workouts for another day. Work hard to stay hydrated and do your best to maintain fitness, cross train where possible and keep a positive attitude.

The Run for the Greenway is this Saturday, July 16, at Knox Middle School. Look for this and other events at www.salisburyrowanrunners.org.