Training Report: Embrace The Heat

Ash tree in the setting June sun from our backyard

Ah yes ... finally summer again!
After one of the longest Missouri winters/cold springs I can remember, my old training buddy, Mr. Sweltering Heat made his welcome return this week.  Yesterday morning's run was 75 degrees, with 92% relative humidity.  And in about a month, this will be considered a "cool day" to run.  It was one of those mornings when all of the windows on the house were dripping with condensation, just like my skin and clothes after the workout.  And while summer runs like this are sometimes tough to get through, leave my legs feeling like Jell-O, my lungs like two giant water balloons, and seemingly steal all of my energy for the remainder of the day ... the are a welcome friend!

For years now, like many of us, I've noticed that I perform much better in fall races as opposed to those held in winter or spring.  I'm much stronger and faster, and at times in the autumn months, I feel like I could run for days.  And while there are some obvious reasons for the increase in energy and stamina, such as losing additional winter weight during increased summer activity, and simply more opportunities to train in better weather conditions, the actual reason is a bit more scientific than that.

Sweating
When summer temp's rise or physical activity increases, our body temperature begins to elevate as well. Acting as an internal thermostat, the hypothalamus gland in the brain sends a signal to the sweat glands in our skin to begin sweating to cool us down.  As sweat beads gather on our skin in liquid form, they ultimately turn to a gaseous state through evaporation.  This transformation from liquid to gas actually ushers away some of the heat generated in our bodies.  (reference 1)  And thus, our bodies begin to cool themselves.

Summer Heart Rate

Problem ... when the relative humidity is very high, this natural evaporation process has trouble doing its job.  With a high level of moisture in the air, evaporation is slowed because there is nowhere for the sweat on your skin to go.  And as your body temperature begins to rise, your heart rate increases as blood vessels begin to dilate in an attempt to increase blood flow from your core to the surface of your skin.  The result is a higher heart rate on hot, humid days.  Some studies show that at a given pace at 75 degrees, this same pace at 90 degrees will increase your heart rate by about 10 bpm. (reference 2)

Make It Work For You!
But this can be a great thing!  If you constantly train with an elevated heart rate at a given pace in summer months, in theory this same pace should be achieved more efficiently with a lower heart rate when the temperature and humidity of the season begin to drop.  Thus ... stronger, faster races in the fall months.

Speaking from experience, heavy training for about 3 months last year in 75-80 degree heat with 85-90% relative humidity was the single most important factor that "pushed me over the top" to my first BQ in a race at an altitude of 5,500ft above sea level in Logan, Utah.  After endless morning runs in the suffocating heat, the higher altitude had no little to no effect on me.  High heat index training and altitude training have similar results on the body.  Both elevate the heart rate, though for different reasons.

Of course there are health risks involved in high heat index training.  As your heart rate increases, care should be taken to listen to your body, rest, and get plenty of replenishing fluids.  Also, it's always a good idea to consult a doctor before beginning any training plan, especially one that increase heart rate from normal training levels.

So ... sure it's hot!  Sure it's tough to breath on those mornings when all you can see is the hazy atmosphere hovering around the dim street lights.  But embrace it!  If you use it your advantage, it can make you a stronger, faster runner ... with your next PR right around the corner!
... be great today!