Heat Acclimation

Sunday, May 29, 2016

I've noticed a two-fold phenomenon since I've moved to the desert. First, most of my runs have been slower. Second, when I've been able to run in cooler temperatures (like in San Diego) my pace for the same effort level is significantly faster.


This is me running near the ocean in San Diego. I was rather easily doing a 7:15 mile/pace for 10k due to the cooler temperatures and benefits of heat training.

This makes sense in a lot of ways. Running in hot weather impacts performance. The hotter it is, the slower you go. If you tuned in for the US Olympic Marathon trials in February you probably saw the athletes comment about how the heat made it a slow race. The temperatures for that day in LA reached into the mid 70's. If you live in the Arizona desert, like me, mid 70's sounds anything but hot. But these athletes are not just being divas, the science shows that temperature above 60° start to impact running performance. This is why, for example, the Berlin marathon has hosted the last 6 men's marathon records. Berlin is a flat course, but it is also a cool course. The average temperature for the Berlin marathon is between 53-64°, right in the 60° sweet spot.

So why can I run faster in San Diego than Yuma? It's the heat. The heat slows me down, and the cool weather lets me run my best. But there is one more thing going on. I've been running outside in the heat for almost three months. I've logged about 380 miles since moving to the desert. I've run outside even when it's been in the 90's in the full sun. My body has become used to the heat and has gained an advantage from it.



Heat acclimation is a real thing, science proves it! A study in 2010 exposed 10 cyclists to heat when they trained for 10 days. The scientists then measured how the cyclists performed in cool conditions. They had a control group as well. The group that went through heat acclimation performed 7% better in cool conditions after just 10 heat acclimation exposures. That's a HUGE gain! Think about it; if you run an 8:00 min mile and then get a benefit of 7% in your performance you can run a 7:26 mile for the same effort! That's shaving 34 seconds off your mile time just by doing 10 sessions in the heat!

Why does training in the heat work? Heat acclimation improves the body’s ability to control body temperature, improves sweating and increases blood flow through the skin, and expands blood volume allowing the heart to pump more blood to muscles, organs and the skin as needed. In other words you become a super running machine. And unlike training at high altitude you get the benefit of heat training in as little as 10 sessions.

This is what you will look like after doing heat training; a super running machine.

Another study also concluded that the heat may produce changes in the exercising muscle, including enzymatic changes that could improve the amount of work done by the muscle.

But there are dangers. Overheating and heat stroke are very real and dangerous concerns. Dehydration can also sideline you and ruin your day. Some signs of overheating to watch out for include:
  • If you are no longer sweating
  • Feeling very thirsty
  • Feeling sick to your stomach
  • Headache
  • Feeling dizzy
  • Feeling a chill with goosebumps on your skin 
If you feel any of these symptoms, it's time to stop and cool off.  It's not worth damaging your body to train in the heat.
I, unfortunately, have no choice but to 'heat train'. It's just the norm living in the hot desert. If you decide to give it a go here are three tips that will help.

First, hydrate a ton before you go and as you go. Drinking water cools you off and keeps you going.

Second, slow your pace down. The slowing of your pace allows more blood to flow near your skin where it is cooled off by sweat. The point is not to go fast. You will get the benefit of heat training even if you are running at a very slow pace. Let go of any pace expectations.

Third, stay alert for signs of overheating. It's not worth damaging yourself to train in the heat.

I've personally seen the benefit from running in the heat, but it comes at a cost; lots of sweat and suffering!



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