I think I understand CTL to basically be your average TSS per day for the last 42 days. If I understand that correctly then to reach CTL (or Strava fitness) of 100 you would need to average a weekly TSS of 700, or a daily TSS of 100, in other words average 60 min at threshold per day (or 120min at 50% threshold) for 42 days.
Is this the right understanding?
Thanks and Merry Christmas/Happy holidays!
For TR, yes, they use rolling 42 day average of your TSS as their version of CTL.
Other platforms exponentially time-weight CTL, placing more emphasis on TSS of recent workouts, so itâs not always an apples-to-apples comparison. CTL itself is a TrainingPeaks term.
TSS calculation is not correct, however. Youâd have to ride for 2hrs at 71% to get 100TSS.
TSS = [(time in s * IF * NP)/(3600 * FTP)] * 100
So TSS for that 50% two-hour ride =
[7200 * .5 *.5 / 3600] * 100 = 50TSS
Youâd have to ride four hours at 50% to get 100TSS because in a perfect steady state scenario, IF * NP/FTP just squares IF.
I found this example helpful. So, for example, if you want a CTL of 100, youâd need to be doing approximately 15 hours per week. Itâs a guesstimate, but in looking around, itâs pretty accurate.
Thanks for this, looks like I was tracking how CTL was calculated correctly but I had a misunderstanding of TSS. I think 60 min at ftp would do it.
Yeah, he has talked about using an average IF of .7 in thinking about things like this, and thatâs pretty good when I look at historical averages for my athletes. On lower volume it might be a bit higher, like .74 or .75, but typically when you get up around 15hrs, a .7 or maybe slightly less average is decent, and that would get you a CTL in that 100 neighborhood.
FWIW, when I plug in long group or unstructured rides for people I typically use .7 as an IF to estimate their TSS going into the week to balance things and itâs usually pretty good (unless that person really thrashes themselves).
Yeah I believe the TSS calculation was designed for 1 hour at FTP being 100TSS as the baseline. Dr. Coggan would have to confirm that, but pretty sure thatâs right.
From the TP article on TSS, so almost as good as the Cog confirming.
âBy definition, one hour spent at Functional Threshold Power (FTP) is equal to 100 points.â
Also pg 128 of Training and Racing with a Power Meter, so thatâs either Dr. Coggan or at least Hunter Allen with Coggan signed onto it. 
As rules of thumb go, thatâs not a bad one.
In a recent week where I didnât have the opportunity to do a nice easy longer (~4h) outdoor ride and did all my riding on the trainer, I did 730 TSS in 12h45m.
I am not sure I could have done that two weeks in a row and I am certain I could not have done it three weeks in a row.
Weeks where I do get to do a nice easy longer outdoor ride give me ~720-750 TSS in ~15h and that feels very sustainable for me just now. TR seems to agree. I havenât had a yellow day since 1 Dec and the last red day I had was on 5 May
Yep, though notice that doesnât mean FTP is max 1 hr power. Some riders may never be able to generate 100 TSS in one hour.
Yes I was just trying to use that as an easy example for TSS, but Iâm glad I used both examples because it highlighted that I thought TSS was a little different than it is. I really appreciate everyoneâs input
Whilst we are on the subject of CTL, Iâll repeat this extract from https://www.trainingpeaks.com/learn/articles/the-science-of-the-performance-manager/
"For example, experience to date indicates that, across a wide variety of athletes and disciplines (e.g., elite amateur track cyclists, masters-age marathon MTB racers, professional road racers), the âoptimalâ training load seems to lie at a CTL somewhere between 100 and 150 TSS/d.
That is, individuals whose CTL is less than 100 TSS/d usually feel that they are undertraining, i.e., they recognize that they could tolerate a heavier training load if only they had more time available to train and/or if other stresses in life (e.g., job, family) were minimized. (Note that this does not necessarily mean that their performance would improve as a result, which is why the word âoptimalâ in the sentence above is in quotes).
On the other hand, few, if any, athletes seem to be able to sustain a long-term average of >150 TSS/d. Indeed, analysis of powermeter data from riders in the 2006 Tour de France and other hors category international stage races indicates that the hardest stages of such races typically generate a TSS of 200-300, which illustrates how heavy a long-term training load of >150 TSS/d would be (since the average daily TSS of, e.g., the Tour de France is reduced by the inclusion of rest days and shorter stages (e.g., individual time trials), and it is generally considered quite difficult to maintain such an effort for 3 wk, much less for the 3+ mo it would take for CTL to fully âcatch upâ)."
This also made me remember that my Strava FTP was set higher than it actually is. I wish it would sync to TR
Maybe not in a steady effort, but I feel most can get there in a Zwift Race or Crit for instance, with some âNP bustersâ.
No need to ask him, just plug in the numbers and youâll get 100 TSS.
Well, you never know whether he actually agrees with Allen on that 
You can simplify it to TSS = (time in hours) * IF^2 * 100. I wonder why IF^2 was chosen over another power of IF.
Yeah I know the numbers work out that way, my point was he specifically designed TSS to be defined that way (such that 1hr at FTP = 100TSS) as the reference point, and as you know thatâs what they said in TRWAPM.
The year record attempts were sustaining around 1,000 TSS per day for 365 days. Which puts those records in perspective.
I think the industry has moved on from season PLANNING with TSS/CTL because itâs a foolâs errand. The industry hasnât moved on from FTP*** except for people for whom its in their interest to do so because theyâre selling something else. **
TSS has its uses. Primarily I use it as a check sum, and itâs also a really good tool for long term REVIEW.
*** I would include FTP and critical power concepts in this same discussion.
** These are just my opinions.
