I spend a lot of my time walking around in some quite extreme heat. I’ve always been fairly fit and this is physically quite tiring work. I’ve noticed that my heart rate has dropped quite a lot in the couple of month’s I’ve been doing this job. Last night I measured it lying down and it’s now down to 40BPM. Is this normal, is it going to grind to a halt, am I going to die?

it’s most likely a positive adaptation to the heat/exercise

you are going to die though

I’m reasonably fit ans mine resting is 43bpm and i’m not worried.

If it continues to drop at the current rate you will die – there’s a strong possibility that you have heat-induced cardiac expansion syndrome where the size of your heart expands as it swells in the heat and consequently your HR actually falls – in simple terms, your heart is getting larger, pumps more per stroke so actual heart rate falls.

Normally that wouldn’t be a major issue, but as your heart continues to expand, eventually it will simply run out of room within your thoric cavity, compress other organs to the point where they stop functioning – do you get breathless after anaerobic exertion? This is a warning sig.

The good news is that at 40bpm you’re in the early stages of the process and it’s still reversible. If you have access to a deep freeze or even a large chest freezer where you can sleep, your heart will return to normal size within a couple of weeks.

I should point out that I’m not a doctor and I have just made this up, so please don’t be too alarmed.

it’s most likely a positive adaptation to the heat/exercise

Adaption to heat? Not heard that before…?

Adaption to heat? Not heard that before…?

Your body acclimatises to exertion in heat, from memory it take around ten days of regular activity in very hot conditions to reach about 90% of acclimatisation, you dissipate excess heat more effectively, sweat more etc.

I suspect a falling RHR would tie in with that. It’s why there’s a huge media hullaballoo every time the World Cup or Olympics takes place somewhere very hot and why athletes go to advance training camps in similarly hot areas before the actual event kicks off.

It’s also why southern Spain in July is hideous. You could, if you can be bothered, use a turbo or treadmill in a sauna for something like 30 minutes a day for a couple of weeks for a similar effect before heading off, someone I know who was doing the Marathon des Sables trained along those lines in the weeks leading up to it.

That’s all off the top of my head mind, and very probably wrong in parts, so please don’t believe it all, but I think there’s something to it.

Your body acclimatises to exertion in heat

Interested to what the adaptions are.. I may google this 🙂

I love the heat, and tend to do better in races when it’s really hot. Often wondered why this might be.

Interested to what the adaptions are.. I may google this

There’s a surprise… I think basically, your body simply becomes better at dissipating excess heat, primarily through more efficient sweating, but I’m sure you’ll get to the bottom of it soon 🙂

Well I’m hardly going to subscribe to a load of scientific journals just to get to the bottom of something pondered in an idle moment at work, am I? 🙂

My resting heart rate varies between 36 and 40 bpm. Not dead yet, so you would appear to have some longevity on that basis.