Heat adaptation: Preparing the human weapon system

  • Published
  • By Capt. Michael Bolduc
  • 8th Medical Group
The summer season is in full swing here at Kunsan Air Base. Along with the good times associated with this time of year comes a host of human performance threats to include heat stress.

In the last two years alone, the 8th Medical Group has treated 14 heat-illness cases. There are some variables we have little to no control over, like the wet bulb globe temperature and how long we will remain in MOPP 4 during an exercise.

However, there are a number of steps we can take to become more resilient in this potentially debilitating environment.

The best heat stress mitigation strategy is adaptation through exposure, or heat acclimatization. Simply put, biological adaptations occur that reduce future physiological strain. The most important biological adaptation from heat acclimatization is an earlier and greater sweating response.

Other adaptations include a reduction in electrolyte loss and earlier skin blood flow. Heat acclimation can also improve your physical training test score. According to a study conducted at the University of Oregon, heat acclimation improves aerobic exercise performance and provides the scientific basis for employing it to augment physical training programs.
So how long do these performance enhancement adaptations take to occur?

For the average Airman, heat acclimatization requires about two weeks of heat exposure along with progressive increases in physical work. However, by day two of acclimatization, significant reductions in physiological strain have been observed. About 60 percent of the adaptations occur by the end of the first week and 80 percent occur by the end of the second week.

Now that we understand heat acclimatization, we can quickly improve our work capacity while decreasing the likelihood of succumbing to heat illness in black-flag type environments. How do we do it?

1. Maintain peak physical fitness levels. Even workouts conducted inside of a gym can create a microclimate of heat stress exposure.

2. Take your workout outdoors when possible. Increase training and heat exposure volume as your heat tolerance permits. Initially, you will have to decrease exercise intensity and duration in order to account for the effects of summertime heat and humidity levels. This caution applies to individuals getting back into a consistent exercise routine, as well as those in great physical shape already.

3. Heat acclimatization increases the sweating rate, which increases water requirements. If you don't account for this, dehydration will negate many of the thermoregulatory advantages
conferred by heat acclimatization and high physical fitness. For each pound of body fluid lost, you should drink about one-half quart of fluid.

4. Limit the use of thermogenic (weight loss or pre-workout energy) supplements during vulnerable conditions. These tend to increase energy levels and blood flow, leading to an
increase in body temperature. Although an increase in body temperature is a desired effect during heat acclimation, when taken during MOPP 4 or black flag-type conditions you may find
yourself at the MDG clinic. There is a laundry-list of other potential threats to be aware of as we conduct our day-to-day operations in South Korea this summer. I will cover some of those in subsequent articles. For now, we can focus on reducing the statistic presented earlier regarding local heat stress illness cases. PT regularly, spend time outside, drink lots of water and sports drinks, and abstain from thermogenic supplements during extreme heat.

Implement these heat stress mitigation strategies and you will have one less threat to contend with this summer.