The relationships between heart rate, work rate and duration

Training
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Firstly, thanks for reading this post.

I’d like to tap into the experience of Intervals users to try to shed some light on a few vague ideas of mine which revolve around the relationships between heart rate, work rate and duration.

First question: do you find that your AeTHR and AnTHR (LT2HR etc) remain stable over time even when outputs at these intensities change? I’m also interested in the relationships between these heart rates so if you could post your heart rates as well that would be really interesting.

Second question: where does your heart rate at sweetspot (let’s say 88% FTP for the purposes of the question) sit in relation to your AeTHR? If you could mention your age and training status that would be cool.

Last question: during long sub-threshold sessions my HR tends to rise linearly before eventually a gentle exponential rise sets in as decoupling takes hold. My thought would be that this serves as a marker of having exceeded current capacity to the extent where meaningful adaptation will be triggered. As an example, a recent 90 minute sweetspot (88% FTP) interval saw my heart rate stabilise at 140BPM between 20 mins and 80 mins before heading to 150 BPM in the final minutes of the interval.

Background: a reading of Fast After 50 last year sent me down a rabbit hole of further reading from which I have yet to emerge. I’m 51, long time cycle tourist but not a racer, just started the build phase in training for my first 24hr race this summer (at the Nürburgring), self coached. FTP currently set at 260 but this might be a shade low. AeTHR 140 ish; AnTHR 160 ish, lab-tested last November. MaxHR around 185.

Any thoughts on any of the above greatly appreciated.

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How are you defining and/ or measuring these? Happy to share but need to compare apples to apples

In the round I would agree with this…but as you will know HR can be affected by many variables and so would want to observe this behaviour a few times to ensure this is the case

3

Hi Olly
The lab test was a standard ramp lactate test with the HRs noted at the turn points on the lactate curve. I use the talk test to keep an eye on the thresholds: power is up at both since the test but the HRs seem to be about the same. I likely shouldn’t conflate lactate turnpoints with ventilatory thresholds but given the uncertainties outside of lab conditions it seems a reasonable use of terms!

1 Like
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Excellent, thanks. I was half expecting to be politely told I was being simplistic. Nice to hear it’s a reasonable assumption.

5

I wouldn’t say it’s a marker of capacity per say (in that you can continue to pedal when you start to decouple - well at least until you - eventually - hit max HR!) but I would say it’s a marker of endurance form a HR perspective depending on how quickly said decoupling escalates