Improving Aerobic fitness, not just power

I’ve searched the forums and have not been able to find some specifics. My question is hard to explain but please bear with me. Is TR purely (ok 90%) focused on just Power? Namely, does TR adjust workouts to not just increase “FTP” but also better heart rate response, threshold, and recovery? This is something that a human coach can do by comparing heart rate / power relations over time. Is TR smart enough to do the same? What about finding finding anomalies? I hope that makes sense.

you improve aerobic fitness by doing more volume, essentially. Everything from endurance to vo2 improves aerobic fitness, it’s just a matter of doing things in the right volume and intensity balance.

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Thanks Hub… but can TR focus on improving one over the other? Namely, does “it know” which I need more improvement on suggesting different phases for specific times.

I think this is a misunderstanding: an increase power of power is an expression of aerobic fitness. Heart rate depends on more factors, but also here, if you FTP increases, then your heart rate at a fixed power will tend to be lower as it is a lower percentage of your FTP than before.

Heart rate is a different kind of metric, because it always needs context. E. g. if I do an endurance workout right after e. g. a threshold workout, my heart rate at a given power will be significantly higher than if I were fresh. Or if I have overextended myself, my heart rate may actually be lower than usual. An experienced coach would be able to explain what is what. TR leaves most of that to you, with the important exception of fatigue monitoring: they have recently released the Red Light/Green Light feature in beta that warns you if you should take it easy (Yellow) or take a day off (Red). I’m fairly certain heart rate is part of the equation, although everything is proprietary.

PS To me the main advantage of a coach is two-fold: (1) Make good decisions for the athlete, e. g. so that they don’t overdo it. And (2) they can help athletes set suitable goals, explain basic concepts of training and keep an eye on the human element. If I had the disposable income, I’d love to have a good coach. But they cost significantly more than TR.


I’d argue TR is more interested in ‘aerobic fitness’ than ftp gains. At least in my experience.


Power over time is arguably the best metric for measuring aerobic fitness, almost certainly if you are trying to measure aerobic fitness outside a lab. HR and other factors can be helpful, but also misleading. I’ll stick a HR strap on during certain controlled situations, but most of the time I don’t even bother since the data is all over the place. Aerobic decoupling (relationship between HR and power over the course of a ride) is something I’ll look at from time to time and I’ll loosely follow my HRV as well, but I find both of these metrics to be minimally valuable. I don’t know if/how TR uses HR (or other things besides power/time) in their training model, but I’d expect these things would be weighted much lower than the power metrics. I think any point of data should be considered as an input to the training model, but it’s hard for me to envision a world where power/time isn’t the key metric.


Here’s the amount of steady power I could hold at a heart rate of 140bpm by year:

2021: 157w
2022: 182w
2023: 217w
2024: 224w

This is from almost purely focusing on power, some outside and some in TR. In general I’d agree with the person above who said TR is more interested in ‘aerobic fitness’. That fitness is what makes higher and higher power feel easy.


How have you measured this? Just curious. Is this something you have tested in each year or have you managed to find a workout to check this - or have you used something like to find the data for you?

yes, its really easy to see that in using the compare chart, like this one:

This one is interesting because I took a longer break October/November 2023. By December my power at ~137bpm had fallen from low 200s watts to ~165W. Then January it was up around 180, and the past month its back up to around 195W. So basically after 3.5 months

My self-estimated (change in breathing) lower aerobic threshold HR is around 137bpm and my top of zone2 riding is 137-142bpm which I established seven years ago and still consistently seeing that on steady training rides and long endurance rides.

@grega your FTP is considered a very good measure of your aerobic fitness, its your upper aerobic marker. Your lower aerobic marker is LT1 or VT1 or that chart above. For most of us not training like elite athletes (15-25 hours/week), what you will most likely find is that your upper and lower aerobic move together. So if you FTP goes up, your LT1 goes up.


HR is highly influenced by other external factors. I would not use it as a basis for aerobic fitness. I can drill my training for 8 weeks straight and do 300w at 140bpm but its because I’m extremely fatigued.


so everyone, everywhere, that has improved fitness year over year, without ‘drilling training for 8 weeks straight’ is really only seeing more power at same HR because they are extremely fatigued? :wink:

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I think @Theyellowcarguy’s point is that heart rate is problematic without context, a lower heart rate at a given power can be the result of increased fitness or fatigue. (Both have happened to me in the past.)

PS I approve of @Theyellowcarguy’s color preferences :grin:

But if you compare EF year-by-year as WindWarrior did, with comparable fatigue patterns (a la 3:1 load/recovery), then it still gives you real picture. Of course, EF for any single workout might be still noisy.


I’m not arguing for dismissing heart rate as a secondary metric, I have been using it for years. I’m just saying that interpreting heart rate needs a lot of context. I initially misdiagnosed my unusually low heart rate at threshold and VO2 work as fitness, but @kurt.braeckel helpfully suggested it was fatigue instead.

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Right, agree with that, seen it in myself as well.

Point I was trying to make is different: you can still compare year-over-year values because assuming full year training, you go through some number of loading/recovery weeks i.e. number of fresh/fatigued days should be roughly equal but if HR is different for same power over whole year, then it is signal, not noise.

Of course, it becomes muddy again if you switch training intensity distribution (pyramidal vs polarized vs threshold, etc) from one year to another.


Ah, indeed, totally agreed. I did not understand you were focussing on averages. Also good to point out that significant changes in training (e. g. volume or distribution) play a role :+1:


Over the long term, HR factors are definitely useful. Things like tracking your longest rides by EF and Pw:HR over the course of several months you’re going to see noise and trends. I just try to get athletes to not obsess about HR during rides. Some coaches prescribe long endurance rides by HR (and of course we used to do this as cyclists and runners all the time), but I don’t find that as effective, personally.

That said, it can be a useful “ceiling” to put on people who might tend to overdo. Most of my canned endurance rides have some statement like “try not to exceed 75% of max HR” as an example. Really just there to remind people not to go crazy on a climb or chasing that person who had the nerve to pass them.


Yeah, I am one of those overachievers :slight_smile:

I feel good cruising long hours at 70% of FTP but I know from experience that I will loose motivation in month or so. But if I limit myself to 80% of LTHR, then can do 3 months of 20h+/week Z2-centric plan with 2 hard workouts per week.

Other than that, I actually don’t look too much into HR either unless it is wildly unexpected (luckily hasn’t happened yet)

EDIT: but I do monitor resting HR. If it has been higher than usual for more than day or two, it means either I am getting ill or have pushed too far with intensity.

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There are some other metrics like TTE which TR doesn’t focus on. So depending on your targets I would try to either stretch your PDC up or to the right. I’ve had a coach for years and yes, incredible value at high price tag though. Then you come to the point you understand the business and your body well enough to do training in your own. Basically, at this point you don’t need any app at all, TP may still be required but that’s it.