Tuesday, 16 July 2013

Is it good to train in the heat?

So, I guess it's hot out.  And as a result, training has been tough.  In addition, my AC isn't working, so I'm a little extra discombobulated.  I've heard that there is a strong correlation between high temperatures and violent crimes; is this true?  If not, it should be!

But one positive thing may come out of all of this agony: the heat may be making me faster.

It's a question that I've thought about many times.  Training in the heat should help one perform better in the heat.  Even from a mental standpoint, getting used to having the sun beating down on you while you push your limits intuitively seems important.

However, does training in the heat help overall performance?  I have (wrongfully) assumed it was better to train in more comfortable temperatures to allow for a higher level of exertion without having to worry about hydration, overheating, or the sheer mental strain.

However, there is some research out there showing that it may actually be a good idea to train in the heat- even if you are planning on competing in the cold.

Study #1

Take, for instance, this 2010 study.  In the study, a group of cyclists underwent a 10-day heat acclimation process.  Basically, they rode pretty easy (50% of their max) in a hot environment (40 degrees C).

Their change in V02max (maximum ability to consume oxygen), time trial results, cardiac output (how much blood the heart can pump per unit of time), and lactate threshold (the effort level when you start producing lactic acid) were measured.

To no surprise, they athletes showed an improvement in all parameters when re-tested in a hot environment.

However, when re-tested in a cool environment, the athletes amazingly showed significant improvements in all categories: V02max (5% improvement), time trial results (6% improvement), cardiac output (9.1% improvement+/- 3.4%), and lactate threshold (5% improvement).

So, simply put, these athletes had more efficient circulatory systems, and went faster because they rode in the heat.  The best part is they didn't even have to push hard in the heat- all they did was follow a protocol that kept them at 50% of their max effort.

Study #2

It's not as though the above research is the only body of evidence showing this type of positive change.  Take for instance, this study.  Long story short, the subjects consisted of 8 high-end rowers.  They were given no fluids and did a series of rowing activities over the course of 5 days in a hot environment (once again, going pretty easy).  This was then followed by a 2K time trial.

By the 5th day, the rowers showed a 4s improvement in their TT.  Interestingly, they ended up losing more weight in that last day's effort (3%) then their first day of testing (2.1%).  However, the fluid content of the blood (plasma) actually increased form day to day.

Once again, by going easy in the heat and allowing for some dehydration, the athletes saw an acute improvement in performance.

Why does it work?

So why is there this spike in performance?  Researchers believe the answer comes down to that increase in plasma volume shown in the second study. This review article does a great job of summarizing the topic.

An increase in plasma in our blood is not related with an increase in red blood cells, so why does the oxygen transporting capacity, and more importantly our performance, improve with a plasma increase?

When we become dehydrated, our bodies quickly learn to adapt to the stress they are being put through.  As a result, we retrain excess fluid in our blood (more than we otherwise would), a state which is logically named hypervolemia.

The authors explain, "Hypervolaemia serves to minimize cardiovascular stress by preventing significant reductions in mean arterial pressure, central venous pressure, and cardiac filling, thereby maintaining or improving stroke volume."

In short, the added fluid volume in our blood vessels helps us to pump more blood through our circulatory system.  It also helps to maintain a healthy blood pressure as we hammer away.

Practical Application 

The bottom line of this research is consistent with what is common sense for most of us- we train hard and beat ourselves down as much as we can (provided we can recover and avoid injury), and our bodies will adapt and perform better as a result.  However, just like mileage and intensity, there are limits to training in the heat (which you can very easily figure out, as I wrote about here).

It's hard to train in the heat,  there's no doubting that.  That being said, this research shows you really should not avoid it.  Just like the exertion of a tough interval session, this added discomfort of suffering through a sweltering workout will pay dividends whether you are racing in the heat or on a cooler day.

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