The Heat Is On!

Twenty-five years ago a shocking event during the Bix 7 forever altered my thinking about “heat waves.” When I first learned of Charles Crowe’s death at the half-way point of a 7 mile race, I had no idea how it would impact my running then and now. A year after his death, I experienced first-hand the effects heat and humidity have upon runners and walkers. Now, 25 years later, his story has even greater urgency. 

Quad City Times, Davenport, Iowa, 27 July 1997, page 2

Yes, he was 62 years old, but he was a seasoned race walker – in physical condition for the race, he lived in the area so he was acclimatized to the weather and water was available on the course. What went wrong? Was his age a factor?

Thermoregulation

Whatever your age, it is important to understand thermoregulation. This is how our bodies both conserve and dissipate heat. Dissipating or releasing heat, is essential during a “heat wave.”

In cold weather, our bodies conserve heat by:

• shivering to create metabolic energy and thus warmth, and
• utilizing vasoconstriction, the shrinking of blood vessels, to shunt blood toward our core, which protects our major organs and keeps blood flowing from our heart and lungs and to our brain.

While in warm weather our bodies dissipate heat by:

• vasodilating, or expanding blood vessels, sending more blood to the surface of our skin so that heat can leave the body and
• utilizing sweating and evaporation as long as the humidity of the environment is low enough. Interestingly heat loss through the evaporation of sweat (or water on the surface of our skin) is one of the most effective ways we can cool our bodies, which is why hot, humid environments are even more challenging to race and exercise in!

So the question is: Is age a factor in thermoregulation?

Before Charles Crowe’s death, a 1993 study concluded that “aerobic fitness, acclimation, and hydration state are far more important in determining successful ability to exercise in hot environments than is age.” 

At that time – 25 years ago - he, and many other runners and walkers, believed their age was not a factor in heat-related illnesses.

Now we know better. Recent studies (2014) have found that the age of walkers and runners IS a factor in heat-related illness. Researchers found that, "Age was the only variable to significantly correlate with whole-body sweat rate. This would suggest that when the stimulus for sweating is equal for all participants ... aging may have a larger influence on whole-body heat loss capacity than the fitness level or specific physical characteristics of the individual."

The researchers concluded that middle-aged and older adults might therefore have an increased risk of heat-related illness when exercising in hot weather. “Decrements in whole-body heat loss capacity were apparent as early as the age of 40 and declined with advancing age. We conclude that not only should older adults be cautious of the risks associated with performing physical activity when ambient air temperature rises, but middle-aged adults should also be aware that they could be more prone to heat-related illness compared to young individuals.”

These studies clearly show a reduced thermoregulatory function with aging.  

You don’t mess around with heat and humidity ... especially if you are over 40 years old.

So what can be done to combat or prevent the effects of high heat and humidity?

Most importantly, be aware of these age-related, thermoregulatory factors:

• Age-related changes to the skin such as poor blood circulation and inefficient sweat glands
• Heart, lung, and kidney diseases, as well as any illness that causes general weakness or fever
• High blood pressure or other conditions that require changes in diet, such as salt-restricted diets
• Reduced sweating, caused by medications such as diuretics, sedatives, tranquilizers, and certain heart and blood pressure drugs
• Taking several drugs for various conditions (It is important, however, to continue to take prescribed medication and discuss possible problems with a physician.)
• Being substantially overweight or underweight

Then follow these general guidelines:

1. Acclimatize your body to higher temps and humidity. When the weather becomes hotter and more humid, it will take 7-10 days for your body to acclimatize. Be patient and be extra cautious especially during a heat wave and even when there is one, random day that is unusually hot and humid.

2. Stay in good physical condition. Better-conditioned people have a higher blood volume, better oxygen consumption, sweat rate and more efficient use/replacement of energy stores. Avoid “going all out” when you haven’t exercised for some time. This is especially important if you “hibernate” during the cold weather and then up your activity during warmer weather. Again, be patient and cautious until your body is reconditioned and acclimatized.

3. Fluid replacement is critical in high heat and humidity. Fluid replacement starts before physical activity, continues during it, and doesn’t stop until long afterwards. Drinking to thirst and keeping urine clear (not dark yellow) are good measures.

4. Wearing light-weight, light-colored clothes of open-weave natural fibers or fluid-wicking fibers help increase evaporation and cool the body.

Twenty-five years after his death, Charles Crowe isn’t remembered just because he died from heat stroke. He is remembered, first and foremost by family and friends, as a “fantastic guy.” Obviously, his was a life well-lived.

References:

Intermountain Healthcare (2017, September 15). What is the effect of heat and humidity on athletic performance. intermountainhealthcare.org. Retrieved August 4, 2022, from https://intermountainhealthcare.org/blogs/topics/sports-medicine/2014/06/what-is-the-effect-of-heat-and-humidity-on-athletic-performance/

Larose, J., Boulay, P., Sigal, R. J., Wright, H. E., & Kenny, G. P. (n.d.). Age-related decrements in heat dissipation during physical activity occur as early as the age of 40. PLOS ONE. Retrieved August 4, 2022, from https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0083148

Malcolm, C. (2021, December 30). Handle the heat: Heat acclimation for endurance running. iRunFar. Retrieved August 4, 2022, from https://www.irunfar.com/handle-the-heat-heat-acclimation-for-endurance-running

Millyard, A., Layden, J. D., Pyne, D. B., Edwards, A. M., & Bloxham, S. R. (2020, June 15). Impairments to thermoregulation in the elderly during heat exposure events. Gerontology & geriatric medicine. Retrieved August 4, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7297481/

U.S. Department of Health and Human Services. (2018, June 27). Heat-related health dangers for older adults soar during the summer. National Institutes of Health. Retrieved August 4, 2022, from https://www.nih.gov/news-events/news-releases/heat-related-health-dangers-older-adults-soar-during-summer