John P post workout on one of the first really hot and humid days of the year
Heat acclimatization is an important consideration when in preparation for a race or sporting event. It's quite common for people (especially us Canadians) to be holiday racers. ie. going to Florida during the winter to do a marathon. Although the thought of moderate to hot temperatures and flat races in Florida sounds nice, you won't be fully performing to your maximum potential, with out a little extra preparation.
Heat acclimatization can take upto 2 wks. The rate at which certain bodily functions adapt are all different.
Cardiovascular function - the initial 1-5 days
Thermoregulatory adaptations (i.e., increased sweat rate, earlier onset of sweat production), coupled with cardiovascular adjustments, result in a decreased core temperature. This response is maximized after 5 to 8 days of heat acclimatization.
Plasma cortisol concentration increases during the initial days of heat acclimatization (high concentration generally indicates the strain experienced by the body) this is amplified with intensity of the exercise. Levels return to normal after 8 days of acclimatization.
Heat illness:
The most common heat illnesses among athletes are heat cramps, heat syncope, and heat exhaustion.
Heat cramps are usually without warning and happen in the arms, legs and abdomen. This happens most often after several hours of strenuous exercise in individuals who have lost a large volume of sweat, have drunk a large volume of water, and who have excreted a small volume of urine.
Heat syncope (fainting) occurs most commonly during the first 3-5 days of heat exposure. Fainting typically occurs when the ambient temperature or humidity rises suddenly, or when a non-acclimatized athlete performs exercise in a hot environment. Heat acclimatization reduces the risk of fainting to nearly zero, after 3-5 days of exercise/heat exposure.
Heat exhaustion is the most commonly diagnosed form of heat illness among athletes, despite the fact that its symptoms are often vague and differ greatly from one situation to another. Clinical descriptions include various combination's of headache, dizziness, fatigue, hyper-irritability, tachycardia, hyperventilation, diarrhea, piloerection, hypotension, nausea, vomiting, syncope, heat cramps, as well as "heat sensations" in the head and upper torso. This explains why heat exhaustion is defined as the inability to continue exercise in a hot environment. Heat acclimatization significantly reduces the signs and symptoms of heat exhaustion, after 8 days of strenuous, intermittent activity.
"Most experts agree that intense physical training in a cool environment improves physiologic responses and speeds the process of heat acclimatization. During training in cool conditions, optimal physiologic adaptations may be achieved if strenuous interval training or continuous exercise, at an intensity above 50% of VO2max, is performed for 8-12 weeks. Maintenance of an elevated core body temperature appears to be the most important physiologic stimulus.
The physiologic adaptations to exercise training in a cool environment are lost after several weeks or months of inactivity. In contrast, heat acclimatization adaptations may vanish after only a few days or weeks of inactivity . The first adaptations to decay are those that develop first: heart rate and other cardiovascular variables. The rate of decay of adaptations is affected by the number of heat exposures per week, the number and format of training sessions, and the degree to which core body temperature is elevated. Athletes with high VO2max usually will lose heat acclimatization adaptations slower than individuals with low VO2max." - Encyclopedia of Sports Medicine and Science
What does all this mean for me?
CrossFit or High intensity intervals/training can help you prepare for a competition in a hotter environment than you live in.
If you have had a little bit of a lay off from working out, try to find a cooler time to train and work your way up to full heat and humidity.
People that are acclimatized will recover faster and out perform those that aren't.
Spring/Fall/Winter Training tip:
when preparing for a hot race, you can spend your recovery (the following 30 mins) in a sauna or small washroom or closet with a heater pumped up and the stress response/adaptation will be similar to training in a hot environment. This is an economical/easy way to be as ready as you can be without training in the heat.
