It’s getting hot out there and the record-setting temperatures are only going to increase as we move deeper into the summer. Constant exposure to our carefully climate-controlled world has left a lot of people susceptible to overheating, heat illness and heat stroke. You can try your best to avoid the heat, or you can incorporate heat acclimation training to not only improve your heat tolerance, but also your muscle tone, aerobic endurance, and longevity.
As I’ve said many times before, your body responds to stressors by activating genes to protect itself against future strain. Lifting heavy weights tears muscle fibers, so your body builds stronger muscles to better handle the load next time. The sulforaphane in broccoli is actually a natural insecticide, but when you eat it, it triggers a host of antioxidant and detoxifying enzymes in your body that protects you from other environmental toxins. Aerobic exercise causes oxidative damage to your mitochondria, so your body creates more of these little power plants to lessen damage in the future. Not only does your body adapt to defend itself against the primary stressor, but these improvements offer a host of secondary benefits. The same is true of heat. Heat stroke can be extremely dangerous, but safely conditioning yourself against the heat will protect you from overheating and grant additional fitness and health improvements.
Please start slow
Let me be extremely clear on this important point first; you can really hurt yourself if you push too hard, too fast. I always find the people that are the least conditioned tend to be the ones that overdo it most. They figure since they’re late to the party they need to work extra hard to catch up. While this can lead to some incredibly unpleasant soreness or even injuries with your typical workout routine, it can actually cause brain damage or death when pushing too hard in the heat. If you’re already in good shape, you can acclimate to heat more rapidly, but if you’re out-of-shape, take it extra slow.
Your brain will slow you down anyway
In previous articles, I’ve mentioned all kinds of subconscious tricks your body performs to “protect” you from what it perceives as starving to death when you try to lose weight. Your body has a similar defense mechanism to prevent you from overheating when it’s hot outside (which actually is quite useful). We’ve all felt it. Step outside on a hot day and you’ll immediately feel slow and sluggish. That’s because muscle generates heat, so your brain preemptively recruits less muscle and reduces your power output as soon as you start moving to limit heat production. It’s a great trick to keep you safe, but it can be a bit of a bummer for anyone hoping to compete in an outdoor event. For anyone doing an outdoor race this summer, heat acclimation needs to be part of your training regimen our your times will suffer greatly.
Two weeks to gain, three weeks to lose
Heat acclimation can come pretty quickly, but unfortunately, you can lose it nearly as fast. Most research concludes that while the majority of adaptations come in the first few days of heat acclimation training, it takes about two weeks to maximize all benefits. Already conditioned athletes can acclimate in half the time.
Once your body adapts to the heat, it will maintain the conditioning even if you miss a few days of heat training, but after a full week, adaptations will begin to diminish with a 75 percent loss after three weeks. You don’t need to stay hot all the time and researchers have found that sleeping in an air conditioned room or using cooling techniques like cold immersion after a heat training session do not interfere with adaptations.
Stay in the heat and build up the work
Heat acclimation is best triggered with aerobic activity. Just remember, whatever method you chose, make sure you start slow. The basic concept is that you need to be out in the heat for about two hours a day and slowly increase the heat and activity level each day. You don’t need to exercise two hours each day, just be outside. Moderate intensity interval training is a great way to slowly build up your tolerance. If you are training for a race, then you really do need to work up to the length of time of your event. If you’re just working for your own benefit, shorter, more intense workouts will work just as effectively as a longer, slower one.
Exercise in the heat is the key to triggering adaptations. Exposure to heat isn’t enough unless you crank the heat up in a sauna. There is research demonstrating the same benefits to performance and longevity without needing to exercise in the heat, but that requires sauna temperatures over 174 degrees F (79 degrees C) or higher.
The primary benefit of heat training is it makes your body far more efficient at maintaining a consistent core temperature. Activity generates heat and your body will either dissipate that heat or shut down. Once your core hits 104 degrees F (40 degrees C), exhaustion sets in almost instantly, no matter how aerobically conditioned you are. You’ll also feel pretty lousy, and possibly start to suffer symptoms of hyperthermia like muscle cramps, fatigue, dizziness, headache, nausea, vomiting, and weakness. This is also the point when you should consider it a medical emergency. At 105 degrees F (40.5 degrees C), you cross a threshold where the heat actually damages your brain and organ tissue.
When you become heat acclimated, you develop several adaptations that enable you to keep your core temperature in a normal range:
Sweat glands become more resistant to fatigue and begin sweating at lower temperatures. This means you start the cooling process earlier and can maintain it longer.
Decreased mineral levels in sweat. Unacclimated people excrete more sodium, calcium, copper, and magnesium in their sweat which can quickly lead to an electrolyte imbalance. Decreased mineral loss once again allows sweating to last longer without ill effect, and it conserves important minerals like magnesium that help power performance.
Increased blood flow to the muscles, heart, and skin. Heat trained individuals have greater blood volume, a lower heart rate, and improved circulation which reduces the strain on the heart and improves aerobic capacity.
Additional benefits of heat acclimation
As you can see above, the adaptations that improve your heat tolerance also improve your aerobic fitness. Aside from the increased blood volume, the increased circulation means more glucose and fatty acids can be delivered to your muscles so they won’t need to rely on local glycogen stores for fuel. This effectively increases the total amount of fuel available before exhaustion. Reduced effort to circulate the blood also decreases the strain on the heart and it reduces the amount of energy your body needs to expend strictly for cooling.
Conservation of minerals like magnesium enables your mitochondria to work more efficiently and repair any damage caused by oxidative stress. Heat training also activates other protective pathways that confer additional benefits.
Working out in hot temperatures activates the aptly named heat shock proteins. These enzymes help protect other proteins from incurring heat-related or oxidative damage. For proteins to function properly, they need to maintain their specific 3D shape. Heat and oxidative stress can denature proteins which means they lose their proper shape and function. Worse yet, these misfolded proteins, also known as aggregated proteins, then build up and cause dysfunction. Atherosclerosis and neurodegenerative diseases like Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease are caused by aggregated proteins. Some heat shock proteins function has chaperone proteins to prevent this kind of misfolding. Other heat shock proteins help create a net muscle gain by preventing muscle breakdown from oxidative stress during exercise.
Heat training also activates the FOXO3A pathway which is the master regulator of many stress-resistor genes. It protects against oxidative damage to DNA, it improves immune function, it helps clear out any aggregated proteins that do form through autophagy, and it’s strongly associated with human longevity, particularly a reduction in the risk of death from cardiovascular disease.
Optional for all, mandatory for some
Most of the studies on heat acclimation were done by the military or departments concerned with outdoor worker safety. I think these groups and any people hoping to compete in summertime events should definitely incorporate heat training into their plans to properly acclimate beforehand. The other group that really needs to work on adapting their bodies to the heat are student athletes. Heat related deaths among high school and college athletes are still on the rise despite all the recent attention. While more coaches are aware of the dangers, that doesn’t mean they know the best methods to prevent it from happening. Student athletes are also much less conditioned to the heat than ever before because of the prevalence of air conditioning, and quite frankly most athletes at that age don’t worry about their safety or really prepare before preseason begins. Have your student do some kind of heat acclimation work at least one week before his or her first practice. It doesn’t take a lot to prepare and it will drastically decrease the chances of any kind of heat related tragedy.