In my recent article, Is It Ever Too Cold to Exercise Outdoors?, I mentioned some of the physiological adaptations that were possible to get by training in hot conditions. That idea seems to have peaked some of your curiosity. I received a number of questions asking exactly what heat adaptation means, what the benefits are, and how to go about getting them.
I’ll get to that in a minute, but first a story:
A few years ago, I ran a marathon in Chicago in hopes of qualifying for the Boston Marathon. I had trained hard and was prepared to give it my all. I was on pace to achieve my goal time but the sun was getting high in the sky, the temperature was rising, and so was my heart rate. I was only nearing the halfway mark, so there was no way I was going to drop my pace. I dug deep and pressed on. But then I started to get worried as runner after runner in front of me dropped their pace and dumped more and more water over their heads at every aid station. Finally, when a very formidable runner that I had been running near for about 20 kilometres suddenly careened wildly across the road and then proceeded to face-plant on the cement, I decided it was time to reconsider how hard I was willing to push for this BQ (Boston Qualifier).
I finished the race, and after a lengthy lounge under a shady tree in the park, I got myself back to the hotel and took a cold shower. I then found out that between the time that I arrived at the starting area and the time that I crossed the halfway point, the temperature had gone from 59°F (15°C) to 80°F (27°C).
Later that night I was sipping a cold beer, exhausted but no worse for wear, I couldn’t help but wonder how that obviously well-trained runner pushed herself to the point of face-planting.
Your Body and Heat
Normally, your skin, blood vessels and sweat levels adjust to the heat. But these cooling systems will eventually fail if you exercise in high temperatures (and high humidity) for too long.
When you exercise in the heat, your body circulates blood away from the core and closer to the skin (aka sweat), where it can be cooled more effectively by maximising the thermogenic effects of evaporation. But by shunting your blood to your skin, that draws oxygen away from your working muscles while also lowering the amount of blood that your heart can pump with each beat. Because you are losing fluid you are also losing blood volume and this places additional demand on your already hard-working heart. This gets even worse if it is humid outside. In a high humidity situation sweat won’t evaporate from your skin and that, in turn, pushes your body temperature even higher.
Normally, your skin, blood vessels, and sweat levels adjust to the heat. But these automatic cooling systems will eventually fail if you exercise in high temperatures (and high humidity) for too long.
As blood (and fluid in general) becomes a precious commodity and your heart is forced to work harder and faster, your heart rate gets higher and higher, your breathing becomes faster, your blood pressure drops, and your core temperature rises.
If you keep going past this point, eventually, your body will send a message to your brain to “stop this madness,” and that is when exercise goes from being fun to uncomfortable or difficult to straight-up impossible. That is clearly what happened to that poor face-planting marathoner.
Dangers of Exercising in the Heat
According to the Mayo Clinic, Heat illnesses include:
- Heat cramps: sometimes called exercise-associated muscle cramps, which are painful muscle contractions that can occur with exercise.
- Heat syncope: a feeling of lightheadedness occurring after standing for a long period, or standing quickly after sitting for a long time.
- Exercise-associated collapse: feeling lightheaded or fainting immediately after exercising, which can occur especially if you immediately stop running and stand after a race or a long run.
- Heat exhaustion: when your body temperature rises as high as 104 F (40 C), you may experience nausea, vomiting, weakness, headache, fainting, sweating and cold, clammy skin.
- Heatstroke: a life-threatening emergency condition that occurs when your body temperature is higher than 104 F (40 C). At this point, your skin may actually be dry from lack of sweat.
Incidentally, later that night in Chicago, my friend and I were endlessly amused by the uncontrollable twitching and pulsing that my calf muscles were doing (a thing called fasciculations). My calves fully cramped (very painfully) a few times and the constant twitching kept me up much of the night and honestly started to freak me out a little. It really looked like a swarm of calf-snakes were trying to burst through my skin. This was likely just due to dehydration and a slight electrolyte deficiency.
Looking back now, had I known that this cold-weather-Canadian was going to be racing in what I would consider hot weather even for “Vacation Brock,” I would have absolutely added some heat adaptation protocols to my training program. In fact, two years later I did just that while training for an Ironman Triathlon I was racing in Thailand in December.
The Science Behind Heat Adaptation
Even the Mayo Clinic says that if you're used to exercising indoors or in cooler weather, it can take at least one to two weeks to adapt to the heat. In a 2010 research study called A heat acclimation protocol for team sports, they saw a noticeable difference in just ten days. After only four 30-45 min sessions of intermittent exercise in 30°C, with 27% relative humidity, the 17 well-trained female athletes showed a lower core temperature and an accompanying rise in thermal comfort which resulted in an increase in their overall exercise capacity.
In a more recent study on the physiological responses to overdressing in 13 well-trained runners, they saw similar advantages from simply wearing an uncomfortable number of layers while training. In this study, they tested the heart rate, core temperature, mean skin temperature, sweat rate, and extracellular heat shock protein in 13 (seven male, six female) well-trained runners. They had the runners run on treadmills for about 60 minutes and compared physiological and cellular responses to exercise in 40°C, with minimal clothing and in 15°C while wearing five bulky layers, including a wool hat, winter mittens, a rain jacket, and plastic pants.
The overdressed runners didn't entirely overheat the way they did in the actual hot conditions, but it still triggered some of the desired adaptations. Ten of the runners reached a core temperature of 38.5°C, which is the magic temperature where heat adaptation begins.
Another study compared heat acclimation to pre-cooling by applying icy towels to nine amateur 5k runners’ head and neck, dunking their hands and forearms in nine degree Celsius water, and strapping ice packs to their chests, backs, and upper legs for 20 minutes. This precooling protocol gave the runners a 3.7 percent improvement in performance. But only five days of 90-minute training sessions that kept their core temperature above 38.5°C, led to a 6.6 percent improvement in performance. And interestingly, doing both the heat adaptation and the pre-cooling led to a seven percent improvement.
In another study that focused on the effects of heat on gut more than on the muscles, they found that gradual exposure to repetitive exercise and non-exercise heat stress can improve heat transfer from core to the skin. It can also create more efficient cardiovascular function, decrease heart rate during hot exercise, decrease skin and body temperature during hot exercise, increase blood volume, and decrease electrolyte loss via kidney filtration.
Ok, one last study before we jump into the tips!
Researchers from the University of Otago in New Zealand enlisted elite rowers to row for five days for 90 minutes per day in a study from the European Journal of Applied Physiology on the effectiveness of short-term heat acclimation for highly-trained athletes. The catch was that they were rowing in a room that was 104°F and 60% humidity. They didn’t have to row hard, just hard enough to overheat them slightly.
In the end, there was a 1.5% increase in 2,000m rowing performance. Now keep in mind that these were pro rowers, not your man-on-the-street, so 1.5% is impressive. The researchers figured there were many reasons for this increase, most notably the 4.5% higher blood volume (which again is more impressive in a pro athlete than in an average person) plus an enhanced ability to mentally handle slight dehydration.
How To Heat Adapt
There are two ways to do this: passively and actively.
Passive Heat Adaptation
This involves hanging out in dry heat saunas or steam rooms, and although it induces the same cardiovascular and sweat changes as active heat training (which I will get into in a minute), it doesn’t require as much recovery or the embarrassment of dragging a stationary bike or kettlebell into the sauna.
Both a sauna and a steam room have been shown to achieve solid results, so choose your favorite or go with whichever one you have the easiest access to. Begin with 10-15 minutes of passive heat training, and gradually build up to 45-minute sessions every two or three days.
Adaptations can occur within as few as ten days but if you’re using passive heat training for preparation for a race (like I did for Thailand), then start at least four weeks—or as many as eight weeks—before your big day.
Active Heat Adaptation
If you are going to be competing in the heat, then active heat training is the way to go.
You probably guessed that this one involves actually exercising in the heat. This can be done easily at home in a small room with a heater or humidifier under the bike or next to a treadmill. If you have access and won’t get your gym membership revoked, doing a workout in an actual sauna or steam room is even better.
You can do either a steady exercise (like jogging on a treadmill) or interval training (like a Tabata set on a bike). But remember, this is hard on you! Especially at first, so if you begin to get too hot and it becomes a struggle to continue to exercise comfortably, you will still get benefits and adaptations if you stop exercising (or turn off the heat). Allow your heart rate to slow and your body to cool, and then (if you are up for it) slowly get back into your workout. There is a cool name for this hot method of starting and stopping: controlled hyperthermia.
If you are going to be competing in the heat, then active heat training is the way to go. You truly need to experience the physiological and psychological responses to hot weather racing to be more than just good at sweating on the day. You will need to have hot weather grit.
Active training is certainly more uncomfortable but it will yield faster results than the passive heat adaptation. You will only need to do 45 to 60 minutes of moderate-intensity exercise in the heat for 7-10 consecutive days or four to five times a week for two to three weeks to see good results.
Here are some quick and dirty ways to acclimate:
- You can entertain yourself or learn while you’re sweating by bringing a book (that you don’t mind getting wet or sweaty) or an mp3 player into the sauna while you are doing passive heat acclimation.
- Do some low to mid-intensity workouts in the sauna or steam room. For example, you can bring a resistance band into the sauna and do side raises, bicep curls, front raises, leg raises, and planks and any other exercises that you can do without accidentally punching the walls—or other sauna goers.
- Or as I mentioned before, if you are exercising on a treadmill or bike trainer, keep the temperature turned up in the room and the doors and windows closed. If that isn’t good enough, bring a heater or humidifier in the room.
- Or, like that study from the beginning of this article, put on some extra layers!
One word of caution, you will start to lose the positive adaptations of heat training in about seven days, so plan accordingly. If you are doing this training for a specific event or race, I would suggest continuing up to four days before the event.
No matter how acclimated you are, you will never be completely immune to the dangers of exercising in the heat.
Before we wrap up, I want to make sure you know that no matter how acclimated you are, you will never be completely immune to the dangers of exercising in the heat. So, if you are planning to compete seriously in a hot climate you still need to do the following:
- Drink plenty of fluids.
- Dress appropriately.
- Avoid midday sun.
- Wear sunscreen.
- Wear clothing that breathes.
- Dump water on your head and face.
- And above all else, keep your wits about you!
The very last thing you want is to have a big race PR attempt cut short because of a face-plant that leaves your skin (and pride) on the hot Chicago asphalt on an unseasonably hot October morning.
For more info, tips, and to join the conversation, head over to Facebook.com/GetFitGuy or twitter.com/getfitguy. Also don't forget to subscribe to the Get-Fit Guy podcast on Apple Podcasts, Stitcher, SoundCloud, Spotify, Google Play or via RSS.
Tidak ada komentar:
Posting Komentar