Hot Weather and Heart Rate

Adventure9

I've started using a motorized, no power assist, walk behind mower to mow my yard and get some exercise in the process. I've been wearing a heart rate monitor to see the differences in different kinds of activities. I'm 53, 5'10, 195 lbs. This weekend I cut the front yard and it was hot and humid out. My front yard also has a small hill on it. My heart rate averaged. 133 bpm for 45 minutes.
Today, I cut my back yard. It's pretty flat. Also it was late in the afternoon and a good bit noticeably cooler and less humid. Today my HR average was 115. Some of the change can be attributed to the small hill in the front yard. And I assume some can be attributed to the heat and humidity difference.

Have you experienced significant differences in measured heart rates due to heat and humidity?

troy0

Yes, your heart rate does increase when its hotter or more humid, It could be 20 to 40bpm more so that would equate to what you've seen here.
So many other factors could account for your findings as well though, maybe you were pushing harder, or the grass was thicker, the hill as you mentioned, were you using a catcher and so on.

Simply put, when it is hot, the body must move more blood to the skin to cool it while also maintaining blood flow to the muscles. The only way to do both of these things is to increase overall blood flow, which means that the heart must beat faster. Depending on how fit you are and how hot it is, this might mean a heart rate that is 20 to 40 bpm higher than normal. Fluid intake is very important under these conditions.

Ref: http://www.humankinetics.com/excerpts/excerpts/knowing-what-affects-your-heart-rate-provides-valuable-information

phjorg1

your heart will beat faster if the body is overheated. It's part of the mechanism the body uses to try and cool itself. It's also another reason why HRM's are inaccurate in a lot of conditions. Heat being one of them as the faster heart beat does not correlate to a higher calorie burn. so you get an inflated calorie burn number.

Adventure9

Interesting. It would seem that if the body is working harder in heat, as reflected by the HR going up, then one would also burn more calories?

syed110

Yeah I have experienced the same thing...I find I burn more calories in warmer weather

3dogsrunning

Interesting. It would seem that if the body is working harder in heat, as reflected by the HR going up, then one would also burn more calories?

No. Elevated Heart rate does not necessarily mean calories are being burned. There are a number of reasons hr can be elevated that doesn't relate to calories being burned. While your heart may be working harder that doesn't mean that your muscles are working harder/burning more calories.
You don't burn more calories when your heart rate goes up watching a scary movie. Nor do people who have naturally higher high rates burn more calories.

3dogsrunning

Yeah I have experienced the same thing...I find I burn more calories in warmer weather

Your HRM tells you you are burning more calories because it is reading a higher heart rate but you are not actually burning more calories. Heat/humidity is one of the factors that affect accuracy of HRMs.