Beating the Heat!

It’s hot. If you live in the Louisville area this is not news to you. It’s been over 90F for the last week and looks like temperatures will continue to top 90F for at least the next week. So what affects does this heat and humidity have on your body as you run or bike?

Recently, in a group of elite cyclists completing just a 30-minute time trial in moderate heat of 90F, their overall power output was lower by 6.5% than when performing a time trial in a thermo-neutral environment of 73F. So yes, even in elite cyclists and moderate heat exposure, your performance decreases.

So how do you combat this? Get your body acclimated to the heat. When you exercise in the heat, many physiological compensations occur. In the heat when you begin exercising, your body starts to produce extreme amounts of heat. As a matter of fact, when you begin exercising approximately 70-80% of your total metabolic contribution is produced as heat – signifying how easily your body can heat up and the importance of dissipating the heat that is produced.

I won’t bore you with the details, but your body cools itself by sweating and turning your skin into an evaporative cooler. However, there is a point when you can no longer sweat, causing increased heating….this is when you become dehydrated. When this happens, water starts to be taken from your muscles and skin at an expense to maintain your blood volume. Getting acclimated to the heat increases your blood volume and your total fluid available for sweating.

It takes between 7 and 14 consecutive days of moderate exercise in the heat to get acclimated. But these gains can be lost just as quickly. So get acclimated leading up to your race and be sure to drink plenty of water while in the heat. If you become dehydrated, you will undo any acclimation your are building.

2h15m on the bike.
Good workout between zone 2 and zone 4.
45 minute spin class included in the workout.
Avg HR = 124 bpm

2h25m on the bike.
Tried to keep my HR in the high zone 2, low zone 3 area for this one.
Lots of speed and power (hill) intervals. Legs were burning!
Avg HR = 127 bpm

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