I'll let Coggan chime in on your bullets. As for your hypothetical, the light came on for me when I realized FTP is an absolute number while TSS is relative. So whether your FTP is 200 or 500, as you stated, a 100 TSS would equate roughly to an hour at FTP.

To increase CTL you need more TSS. Which means either (a) more time in the saddle or (b) higher intensity (IF) workouts.

Thanks that helps. I think I'm confusing fitness and strength...

So CTL can really be described as fitness relative to their own threshold. And two athletes can have the same CTL, even if one has a higher FTP.

All things being equal- FTP goes up, CTL goes down.
It is just math.
That said, you may or may not need to adjust training.
Good training is good training.
Chasing CTL numbers is not the best way to train.

I'd qualify this as, if your FTP increases and you update that in the software, CTL goes down for the same volume/intensity. But if your FTP increases during the course of training, and you don't update the software, your CTL would likely increase because higher intensity workouts would be relatively easier. But yes, it does demonstrate why chasing CTL is not the best way to train.

I waver on how I use Trainingpeaks....I've had some off days when the numbers suggest I should be solid, and great days when the numbers aren't so optimistic. On the other hand, my CTL overall does paint a generally accurate picture of how I'm feeling.

Maybe. TSS is a function of duration and intensity. Intensity = NP / FTP. So if your FTP goes up AND you ride the same NP then intensity drops (as does TSS and CTL).

The rides that suck are the first ones at a new and improved FTP setting with an IF > .9 (ala Sufferfest).

I never like to hear it describe as fitness, like Strava does with their version of "CTL."

It is what it says it is: training load.

Just bringing that up because if you increase training load beyond what your body can handle, your fitness declines. If I view my past 10 years of CTL the 4-5 peaks correlate really well with the 4-5 times I trained way too hard and dug myself into a deep hole and performed like I had zero fitness.

CTL is pretty far from fitness in my book.
The people who tend to have the highest CTL's (other than pro bike racers) tend to be riders with a low FTP who train a lot of hours.

i'd say fitness/FTP is a consequence of CTL, assuming you do it right (ie not bury yourself in a box in a deep hole). the assumption is that a high CTL will produce a high fitness (at least relative to the starting point). fitness is a somewhat vague concept incorporating cardio/aerobic capacity, muscle state etc but also in name referring to being fit for purpose which of course a fatigued athlete is not.

of course the point of training peaks performance charts and stravistix fitness trend is to illustrate the interaction between CTL driven fitness and fatigue and how too much of a good thing can lead to poor performance just as much as not enough can

to the original point:
- you train, raising your CTL and hopefully your FTP (at least in the long term)
- in the short term your FTP doesn't change enough to warrant an update to settings so repeating the same workouts gives the same TSS and hence CTL, although it is technically slightly less effort for you
- in the long term you do increase your FTP settings so all of a sudden you get less TSS/CTL from the same workout.
however in practice you should be basing your workouts on % of real FTP rather than any static number so your workouts adjust progressively, getting harder as you get fitter but resulting in the same TSS (as long as you are adjusting your FTP setting within reason to match your changing actual FTP)
i'd also say that for a well-trained athlete, FTP changes are generally pretty small over time so much of this is irrelevant, unless you substantially change your training

Hmm...I wouldn't state it quite that way. At least not anymore. I see fitness as a consequence of well-applied training stress. But I view CTL as descriptive rather than prescriptive, e.g. it's something I use to help characterize what my training has been, and to help constrain future training. But I don't seek higher CTL values to try to get fitter. (I think Coggan himself has used the descriptive/prescriptive taxonomy before, but it may have been in a completely different context).

I am not quite sure that I understand because I do not see this as being a blanket statement. It seems like one would need to look at the other aspects of data to come to that conclusion. Being on other forums and watching discussions with road cyclists from Cat 3 and up who have decent FTP (not taking racing skills in to account) seem to have a decent amount of CTL (training for race season or in race season) if that value is shared in the discussion. In many of those discussions, CTL was a sidebar metric given as if it were to speak of training consistency. (edit: most of the time progressive overload over the span of weeks/months was the major part of these discussions.)

In a general conversation from someone who is using a power meter and they told me that they currently have a CTL of 105+ I might assume they have had to train consistently in order to get up to 105+. If they are training consistently they may be in fairly decent shape or fitness or they may not. If they said they had a CTL of 60 I might assume they have had some interference to training consistently, such as, family matters, illness/injury or something else that is not allowing them to train on a consistent basis or they could be training consistently but without enough intensity to yield much training load.

So I am bit confused by the highlighted portion. I must not understand you personal definition or perception of fitness.
Don't you need more information about the individual's data over a span of time to make a proper assessment?

edit: For my own personal use I will take a quick glance at CTL in the PMC at times just to see which way it is trending. At the moment and coming out of a respiratory illness in January where it hit 50 CTL it has been trending upward and is in the low 70's as I increase the duration and intensity trying to get back up to my former sFTP. So in my case CTL is rising as a result of increasing the training load and I am seeing an improvement in fitness out on the road with sustainable power output over the span of miles. I can't wait until I get into the 90+ CTL and yet I look at the ramp rate with hope that I manage that training load as best possible. I want to train harder now, but I am having to wait on my body to adapt at its pace.

100% agree with with. This is aside from what the OP was asking, but his question stems from replacing a precise term, Chronic Training Load, with a very abstract term, fitness, that is loosely correlated.

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just your average age grouper . no one special . no scientific knowledge . just having fun.

Thanks all. That's certainly cleared things up. I think the cause of my confusion was the persistent reference of CTL being equal to fitness, but I'll now think of it purely as training load.

Training load. That is the best way of thinking of it.
With a CTL of say 50 you need to be averaging 50 a day to maintain it.
As you get it to say 60 your FTP may well have increased and if you do your workouts as a percentage of FTP they will stay at an average of 50. Therefore you need to work harder or do more to maintain an average of 60.

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My foray into time trialling at the age of 60
https://sixtyplustimetrialling.wordpress.com/