Amateur and elite athletes around the world understand that if they reside in a hot and humid environment, they will acclimatize to the heat. Many books and journals state that it is best to acclimatize to the race specific environment 2 weeks to even 4 months prior to your event. For example, if you wish to partake in Ironman Hawaii, many authors state that it is beneficial to train in that environment to become acclimatized to the heat, especially if you reside in an environment farther from the equator. But what if we live in an environment where we are exposed to heat for 4-6 months out of the year? do we fully acclimatize to the heat throughout the duration of the summer? Does anything interfere with our bodies acclimatization?
Anthony Bain, a Masters student at the University of Ottawa, working alongside Professor Ollie Jay in the Thermal Ergonomics Laboratory, posed the question - do we acclimatize to the heat since we reside in the environment? Bain’s study, which was published in June 2011 by the European Journal of Applied Physiology, tested the present knowledge that individuals who live in hot and humid regions would exhibit increased skin blood flow, decreased core temperature, and the sweat response would occur at a lower core body temperature due to heat acclimatization. The participants completed two trials; one trial in the last 2 weeks of May while the other was within the first two weeks of September. Each trial consisted of biking at 60% of their VO2peak for 90 minutes in duration. The temperature of the room was 22.4 ± 1.0⁰C with a relative humidity of 37 ± 15%. Core temperature, skin blood flow, and heart rate were monitored during the trials. In addition, Bain had the participants record an Activity Log/Lifestyle questionnaire for the duration of the summer. This log consisted of their activities performed (inside or outside) and whether they worked in or lived in air conditioning. What did they find?
Bain concluded that no heat acclimatization had occurred throughout the summer months which were evident between the two trials performed for each participant. There were no significant differences between sweat rates, core temperature and heart rate. In addition, all of the participants worked in an environment with air conditioning and 50% of them lived with air conditioning in their homes. Anthony Bain explains that since people are not exposed to the hot and humid weather for significant amounts of time, they do not acclimatize to the heat. Just because an individual resides in such an environment, if they constantly expose themselves to a cooler climate, they will never fully acclimatize the heat. Since all the participants were working in an air conditioned environment, no changes in physiological responses occurred between the two trials. The main message Bain wanted to portray is that you cannot assume you have been acclimatized to the heat since you live in the environment. Bain states, “Many people have a false sense of security while running in the late summer months thinking that they have properly adapted.”
So how do you fully acclimatize to the heat, especially if you plan on completing an Ironman in a hot and humid region like Hawaii? Simple, do not solely train in the environment, but live in it too. Just because you run or bike in the heat does not mean you will acclimatize to it eventually. You need to continue the exposure to the environment before AND after your training. If you are staying in a hotel for 2 weeks to 4 months prior to the event, turn off the air conditioning in your room and open a few windows. You can also spend as much time as possible outside in the natural environment to reap the benefits of heat acclimatization. The more time you spend in the environment, the better your body will acclimatize to it. Remember, physiological adaptations do not occur overnight, they take countless hours of constant exposure to occur.
To read the full journal article: Does summer in a humid continental climate elicit an acclimatization of human thermoregulatory responses? - European Journal of Applied Physiology by Anthony Bain and Ollie Jay – CLICK HERE.
A key thing to note from this post is that despite society's poor view with regard to sweating, it is actually a sign of fitness. The sooner you start to sweat, the more easily you are able to regulate your core body temperature.
ReplyDeleteThis is also affected by sweating efficiency, which is a whole other topic relating to amount of sweat and sweat glands that are active. Studies on sweat differences between men and women are currently underway and papers are in the writing by a Mr. Daniel Gagnon, Ph.D. candidate in the Human and Environmental Physiology Research Unit at the University of Ottawa, whose direction is under the leadership of Dr. Glen Kenny.