Heart rate increases when I slow down

[FredMom]

I'm wondering if anyone notices their heart rate increase in response to slowing your pace of exercise- temporarily, before it comes down?  When watching my HR in real time on a treadmill (looking at my Alta HR data on my phone), when I slow my running or walking pace, sometimes my HR responds initially by a short stint of speeding up, like it needs to adjust, before lowering to "match" my activity.  I am someone with a history of atrial tachycardia, which I had fixed several years ago with catheter ablation...so it's possible that it's an artifact of that (though of course I'd rather hear that this happens to others at times!)

[t.parker]

It is nothing unusual. See one of my runs (just zoomed in section when I reduced my cadence and switched run into walk to lower my HR and stay in zone):

 Despite dropping the cadence (in grey) and slowing down to walking pace you can clearly see that HR stays elevated little longer and it increases for a few seconds until it starts dropping. The green line is elevation (this segment is pretty much flat so the terrain has no impact on my HR).

The higher your HR is the longer it will take to decrease it and it may keep increasing for little longer. Mind that HR monitor I use has no lag but most of wrist based sensors introduce lag which may shift the increasing bit slightly to the right (and make impression of taking more time). Also, in the example above this "spike" isn't big because I kept my HR in very narrow range. If you are worried consult your cardiologist 🙂

[FredMom]

Oh, very interesting- thanks so much for your reply. It does seem that the HR not only stays elevated, but increases just after slowing your cadence- which is exactly what I thought was odd.  It seemed like my heart reacted to its need to 'adjust' by bumping up briefly before coming down. Since I've learned a bit about the electrophysiology due to my own 'short circuit', these things are on my radar so to speak 🙂

[Heybales]

It's more the fact that the HR is delayed compared to the level of activity. Going up and coming down.

Hence the reason HR-based calorie burn estimates are so terrible and inflated for anything interval in nature.

That bump is likely due to something even prior, or the fact you stopped breathing as deep but body still needed more oxygen or had to clear out more CO2.

It's interesting to look at the heart lag time on an increase to activity too.

Or the 2 min after a workout when just standing around and obviously the level of exertion is very low but it takes a while for the HR to lower.

[t.parker]

@Heybales after all, the body is a complex machine and it takes time to speed up and slow down processes and it has to work out how to do it efficiently. It's like a big locomotive, takes time to gain speed as well as it takes time to stop. The human body is no different (well... maybe a little bit as we don't look like locomotives :)). It's actually very visible for me during spinning when I try to keep my HR in a particular zone. If I want to get to the border of the zone I can add effort but when I see 151 (and the zone ends at 153) I stop pedalling because my heart will reach 153 anyway. The same happens when my HR drops (I give less power) and I see 141, I start more intense pedalling but my HR will manage to drop to 139 or so before it will start going up. It looks more interesting if you overlay it with power output because once you drop/increase the intensity the change in power output is immediate but heart is more "smooth" in its behaviour 🙂

Edit: I think you may find this interesting. It was one of HIIT workouts of 15 intervals based on power output:

 It shows quite well the relation between power and HR. Power is instant, HR very smooth. Although, in this example HR drops immediately when my power output also drops but the explanation of it could be that technically my HR couldn't increase any more.

Edit(again): @Heybales I did more digging through my records and found better example on the bike:

It's pretty much what I mentioned in the beginning about staying in the zone. I think this smooth speed up/slow down is better visible for lower ranges of HR. When my HR started reaching 153, I dropped power, it still spiked a while but then dropped a bit so I added more power. Interesting thing is that for the same effort it still drops smoothly for quite a while. Humans are very interesting machines 😄