Plot it against LTHR instead of Max HR.
Interesting. I can just about imagine an inflection point in my curve - it’s hard to see, but it falls right about where my power lands if I “just ride” indoors. About 78% FTP, 75% max HR. I don’t have any lactate data to confirm, but it makes sense to me you would automatically gravitate towards that zone.
I haven’t got an explanation for it, or why it is sometimes easier to see. I think the second inflection point at FTP is because you max out sustainable oxygen supply and thus anything above it is less dependent on HR. But I could be completely wrong!
I think this is always true - you’re just changing the denominator from one value to another, so this may change the slope of the curve slightly, but won’t change the shape (e.g. introduce a curve / inflection that wasn’t there before).
Context: 41y/o, Ftp ~3.5w/k. Noob (2020 is my first year of riding, a bit of structure, 260 hours).
you can see the two thresholds in my curve, but I’ve been training with those parameters, so the curve is not “spontaneous”…just checked my brother’s curve and it looks more like @cwiggum 's
Yes, I’d agree you’d have to be a bit careful with interpretation - you can definitively affect the curve with your training, for example, if you do a block of low cadence work at a certain power, HR will likely be lower in that region. My curve looks more like @bpm’s, but I’ve done very little above-ftp work recently, which might explain the sharp top. But I do think it is a very interesting observation, and intuitively it makes sense to me that changes in energy metabolism would be somehow reflected in HR.
I wonder if the overall shape of the curve has something to do with type of fitness. For example, if a “diesel” type rider has a different curve to a sprinter?
That’s what I was wondering as well after reading @bpm interesting analysis. In my graph, I do feel that I have plenty of data at all the power levels. I don’t do alot of vo2 power work, but there should be enough data there. From ftp down (350’ish w) I have tons of data representing every part of that graph.
@old_but_not_dead_yet I get what the article is saying, but…but… if you have a power curve with lots of rides at different intensities/durations over a meaningful period. Don’t you automatically start seeing the patterns predicted by the physiology?
I fall into the category of ‘not well trained’ but it’s interesting how different those HR / FTP calculations are. 75% Max HR=202W on power vs MaxHR curve… 75% FTP=247W, or a +/-22% difference. I think it’s closer to the ftp value than the HR value based on the RPE & other indicators. Guess my heart sucks?
Hard to tell how much I’m “overfitting” due to my eye naturally gravitating to 75% and 95% of LTHR, but those do seem to be the kinks for me here. Interesting that this would suggest I should be doing my Z1 rides at more like 200W, I typically try to get them more in the 230W - 240W range (damn ego…) based on something closer to 70% of FTP. Seems like pushing this curve to the right is a good goal for me.
@old_but_not_dead_yet thanks for pointing out that inferences based on HR deflections are not new. I don’t have access to the article you cite, but as far as I can understand, the Conconi test to measure the HRDP has been linked/studied in the context of the anerobic threshold and LT2. For example, I do have access to the following review which contains the figure below. This makes clear that the inflection around LT1 is not necessarily of their interest:
Nevertheless, is your point that there is a literature on HR inflections at/around LT1? This seems to be measurable using HR deflections, at least in principle.
Maybe this inference is more precise than has been shown for LT2, when there are multiple deflections, as I and some others have observed.
@splash - very interesting. I’m more diesel than sprinter - WKO types me as TT. This highlights the question - Is the second deflection a real effect that can inform as a measure of LT1, or is it created by some training program, or is it only present for some rider-types, or is it due to some other idiosyncracy?
How might my training differences explain a change in curve shape? Each period involved SSB and SPB/GPB with long 4+ hr rides. However, early on, I would do Z2 outdoors just zooming around. The past 3 months I have been doing Z2 on the trainer, trying to follow coach chad’s advice ie maintain pressure, spin and relax.
Maybe the lack of clean long intervals at particular power levels around Z1-Z2 in my earlier sessions served to mask the structure that is now visible? This would suggest that 15min+ steady intervals spanning a power range from Recovery to Tempo/SS, can reveal an LT1-related HRDP at lower powers.
Since others also see two inflection points, could the lower-inflection be a useful training focus, along with feel etc, in something like an ISM training model? Thanks for your collective inputs!
Conconi’s test isn’t reliable even under controlled laboratory conditions. There’s no reason to think that it would work any better in the field, especially there’s really no physiological reason why any non-linearity in HR should correspond to metabolic responses.
No, I was simply pointing out that the idea of trying to identify some threshold or another has been around for decades, and that it has never gained acceptance.
I don’t know. It could also be that it’s a self-enhancing inflection point - because you ride there more, your data near it becomes different, making it more obvious, which means you identify it as some sort of threshold…
Fair enough - assuming the non-linearity that I am highlighting has been studied and rejected. To be clear, LT2 threshold may not be well defined based on HRDP but I don’t yet understand how that means LT1 is also not well-defined based on HRDP, in cases when LT1-proximal deflections are present in the curve (my main point of interest). I need to read more and learn.
This is interesting. Non-linearities let us usefully define thresholds as a short-hand. And, in general, threshold mechanisms lead to non-linearities. Since I am to understand there is no metabolic threshold in play, the issue seems to be how strongly one believes that thresholds can serve as a useful short-hand.
I certainly don’t mean to debate this point, others have and will. I am mainly interested to know if others see this HR effect, and if it can serve as a useful observation for monitoring training ie proxy for LT1.
@splash I don’t think this is a necessarily an error bar-related issue as varying the amount of my data ie the date-range duration - doesn’t change it much, but that is also a good point for consideration. Thanks for your comments.
Yeah all this ‘analytical what is LT1’ seems a bit much. Ride around in high-ish z2. Pay attention to your breathing. Let it start to change then back it off a nudge… if in doubt try to do it for 4-5 hours.
I’m with y’all, just ride high z2 ish and focus on sensations. Soon enough you can feel changes in breathing and HR.