As far as I understand it, one answer can be probed as follows.
TSS and CTL amount to the representation of training load -- the map as it were, not the territory itself.
The algorithms behind them are constructed such that even if training is held constant (7,5hr vanilla in your example) from a certain point in time on, the metric does not stagnate immediately but keeps growing at a decreasing rate for quite some time. So, doing the same thing over and over would still continue yielding a higher CTL, until it doesn't.
As TSS and CTL are derived from threshold pace (or power, or HR, depending on user settings), the picture becomes more complicated if one updates their threshold as they go along, but the basic logic of the metrics does not change.
The territory I think you already covered yourself: as a person becomes fitter, their paces tend to increase at least slightly, so they cover more distance (and/or metabolise more substrate) over the constant time budget they have. Hence the athlete in this example keeps embarrassing their body a bit more, even if progression becomes very gradual.
There's more to than just that, though. For performance to be linearly related to load (CTL), then (r)TSS would have to be an absolute (not relative) measure, you would have to ignore fatigue, and you would have to assume that there is no upper limit to somebody's performance ability.
None of these are true, of course, which is why sirpoc's claim confuses people who too much (or too little) about it.
As far as I understand it, one answer can be probed as follows.
TSS and CTL amount to the representation of training load -- the map as it were, not the territory itself.
The algorithms behind them are constructed such that even if training is held constant (7,5hr vanilla in your example) from a certain point in time on, the metric does not stagnate immediately but keeps growing at a decreasing rate for quite some time. So, doing the same thing over and over would still continue yielding a higher CTL, until it doesn't.
As TSS and CTL are derived from threshold pace (or power, or HR, depending on user settings), the picture becomes more complicated if one updates their threshold as they go along, but the basic logic of the metrics does not change.
The territory I think you already covered yourself: as a person becomes fitter, their paces tend to increase at least slightly, so they cover more distance (and/or metabolise more substrate) over the constant time budget they have. Hence the athlete in this example keeps embarrassing their body a bit more, even if progression becomes very gradual.
100% agree with everything here and these were some of the observations I was trying to make.
If you stick to the 7.5 hours and you get fitter without updating your threshold pace, your Load seems to go up. If threshold pace were accurately updated daily, Load would be more flat. But over a very long period of time, you should become capable of running the workouts faster and faster relative to threshold pace, which makes Load go slightly up.
And in fact you may HAVE to run them faster to threshold pace to get the same stimulus. For example, let's say for some interval workout when first starting out, you ran them at 90% threshold pace. That was effective as it consistently got you above LT1. Running any faster (closer to threshold) was too much metabolic and/or mechanical stress and would've been counterproductive. Now 3 years later, running the same workout at 90% of your (much faster) threshold pace no longer gets you above LT1 because LT1 has been squished much closer to LT2. Additionally, you can now handle the stress. So you run that same workout at 95% threshold pace. Even accounting for accurately updated threshold paces, Load has gone up.
Also worth reiterating that increasing volume is still better (until it's not). If you want to keep "expanding" your training with the low-hanging fruit, then volume increases are it. That's how you get the most improvement. Having said that, someone who has stagnated may actually need to decrease Load, not increase it, so an honest self-evaluation is important. And furthermore, anyone whose volume is "maxed out" for their lifestyle at a relatively low level should still train and race with optimism that they have a lot of improvements to make. Eventually, they ought to change their training in search of a more potent stimulus after "low volume" subt intervals have been wrung dry.
This post was edited 33 seconds after it was posted.
As far as I understand it, one answer can be probed as follows.
TSS and CTL amount to the representation of training load -- the map as it were, not the territory itself.
The algorithms behind them are constructed such that even if training is held constant (7,5hr vanilla in your example) from a certain point in time on, the metric does not stagnate immediately but keeps growing at a decreasing rate for quite some time. So, doing the same thing over and over would still continue yielding a higher CTL, until it doesn't.
As TSS and CTL are derived from threshold pace (or power, or HR, depending on user settings), the picture becomes more complicated if one updates their threshold as they go along, but the basic logic of the metrics does not change.
The territory I think you already covered yourself: as a person becomes fitter, their paces tend to increase at least slightly, so they cover more distance (and/or metabolise more substrate) over the constant time budget they have. Hence the athlete in this example keeps embarrassing their body a bit more, even if progression becomes very gradual.
Good post. Sirpoc and and a few others posted in the thread somewhere, that even if you do the same thing for half a year from ctl of 0, your load would still increase until it doesn't at around day 190 I think it was. Someone might correct me on that. In theory, every single run you have ever done is included in any calculation, it's just weighted more heavily for the last 42 days.
It's also worth everyone remembering that load is framed as a fairly good guide, but never the entire picture. Most other sports would probably accept volume/load is the primary driver. The irony being, a lot of old school runners already know this. Mileage is often the key and coaches would have them just run more mileage. All that in reality is doing is piling on more load.
With load, there is obviously a point where you reach diminishing returns, in that you can't just keep increase volume/load and keep seeing incremental gains. Why tracking load seems to work pretty well for this method is twofold.
1. The pattern of training is nicely consistent. So some flaws in how load is calculated however you choose to do so, doesn't matter as much as it all evens out in the end.
2. As hobby joggers, we are are highly unlikely to reach the point where running more/increasing load, doesn't result in some sort of improvement, so we can use load as a nice basic tool to frame that and the pmc is a really nice way of glancing at our training and just keeping an eye on it.
There's obviously a lot more happening in training, but volume is just load really and volume is really the key to any running program, no matter your philosophy.
Is a shame btw Jan is being allowed to spam as there's been some good chat lately.
What happened to the guy who was interested in re-evaluating Coggan's original equation last week? Would love an update on that.
Sirpoc and and a few others posted in the thread somewhere, that even if you do the same thing for half a year from ctl of 0, your load would still increase until it doesn't at around day 190 I think it was. Someone might correct me on that.
You would be 90% of the way to plateau in about half that time.
I have read the book and found it really helpful. I am bought into the method. I however don't understand how to know what's sustainable to start out. I understand the concept of progressing slowly but I have no idea how to know where to start. I'm thinking right now that I should start really low, even if it's unnecessarily low, but I'm concerned by doing that I could be wasting months of training. I think I've averaged 35 for the past year, then 50 and 55 for the years before. Do I try to build to 50 in a few months or try to sustain around 35 or less?
The book gives a good guide. If you are already doing 5 hour weeks, the 5 hour guide is the place to start is the suggestion. If you are only running 4 our weeks, there is a beginner program which is essentially NSM life to start from. If you already do 6 hours, you can jump in on that but if you are extra cautious maybe the 5.5.
I mean this is just common sense. You aren't going to go from 4 hours training to 7 in the book. Likewise, if you are already doing 8, you aren't going to start at 4.
I was running 5 regularly, so I just jumped on in that and it feels way easier already than my old schedule. Again, I will just follow the guide in the book. Consolidate that level of running of volume for a while before maybe in 4-6 weeks, starting to sprinkle a few minutes on here.
Anybody who is a “beginner” or maybe they took a hiatus from running for an extended period of time and are getting back into the swing of things probably shouldn’t jump right into this method. I know the book as a guide for 4.5 hours per week but if somebody is newer to running, or returning to running, going from 0 to three workouts a week, no matter how easy they workouts are, will be tough. I think it probably makes sense to build easy volume first, up to around 5 hours a week. How long that takes depends on a variety of factors. After five hours feels good, and this may take several weeks, add a sub-t day. Do that for a couple weeks. Maybe months. Then you can either increase the number of hours or add a second workout. Not both. From there you can play around with increasing easy volume and increasing threshold volume either by adding a third day or adding minutes to the two days. It all comes back to slowly increasing load over time.
As far as I understand it, one answer can be probed as follows.
TSS and CTL amount to the representation of training load -- the map as it were, not the territory itself.
The algorithms behind them are constructed such that even if training is held constant (7,5hr vanilla in your example) from a certain point in time on, the metric does not stagnate immediately but keeps growing at a decreasing rate for quite some time. So, doing the same thing over and over would still continue yielding a higher CTL, until it doesn't.
As TSS and CTL are derived from threshold pace (or power, or HR, depending on user settings), the picture becomes more complicated if one updates their threshold as they go along, but the basic logic of the metrics does not change.
The territory I think you already covered yourself: as a person becomes fitter, their paces tend to increase at least slightly, so they cover more distance (and/or metabolise more substrate) over the constant time budget they have. Hence the athlete in this example keeps embarrassing their body a bit more, even if progression becomes very gradual.
The irony being, a lot of old school runners already know this. Mileage is often the key and coaches would have them just run more mileage. All that in reality is doing is piling on more load.
Yep, reminds me of Ed Whitlock's training which was as simple as running 2-3 hours every day at a very slow pace.
Anybody who is a “beginner” or maybe they took a hiatus from running for an extended period of time and are getting back into the swing of things probably shouldn’t jump right into this method. I know the book as a guide for 4.5 hours per week but if somebody is newer to running, or returning to running, going from 0 to three workouts a week, no matter how easy they workouts are, will be tough. I think it probably makes sense to build easy volume first, up to around 5 hours a week. How long that takes depends on a variety of factors. After five hours feels good, and this may take several weeks, add a sub-t day. Do that for a couple weeks. Maybe months. Then you can either increase the number of hours or add a second workout. Not both. From there you can play around with increasing easy volume and increasing threshold volume either by adding a third day or adding minutes to the two days. It all comes back to slowly increasing load over time.
This is where I am at now, experimenting from starting running again after more than 6 months of a break. My training is primarily done based on RPE, but I use Stryd and a lot more metabolic testing than most people.
Started at CTL = 0 at the end of October, with CTL now at about 30, and ATL = 45 (-15 TSB). My ramp rate was high at the beginning (because of the PMC math), but I kept it under about 5 points/day. I went from 0 hours running, to averaging about 4.5 hours/week for the past 8 weeks.
Now I have the same weeks planned until May 2026. I am building to 1 hour a day of running, which is taking time since I'm older. I was cycling 6-8 hours a week till October 2025, and regularly hike or spend time outdoors, so I'm not exactly off the couch.
By May, I will be around CTL = 50 and averaging 6.5 - 7.5 hours of running a week. ATL will be approximately equal to CTL, having carried a ramp rate less than 1 for the previous 6 weeks. At that point, fatigue should be gone, fitness improvements should be noticeable, and then I can decide whether to hold CTL = 50 for a few more weeks (or months), or start building again. I can probably maintain up to CTL ~60-65 on a singles approach with up to 75 minutes of running in a single session per day.
My 9-day schedule. Each session is approx. 45-60 minutes running, 5 minute walk warmup and 5 minute walk cool-down.
Day 1, 4, and 7 - Workout: approximately 65 points including 15-20 minute subthreshold blocks, completely unstructured and based on feel.
Day 2, 3, 5, 6, 8, and 9 - Easy run at LT1, outside or threadmill. Approximately 45 points.
That's it. Besides a regular 3-minute time trial to gauge fitness every few weeks.
It is my impression that most people that don't read forums and such just go out 3 times a week and run something like a 5-7k at a brisk tempo that leaves them short for breath at the end and then go on with their day.
Yes and this has been said over and over and over again but the differences have also been said over and over and over again. Lots of hobby joggers are not disciplined to do this properly and the intervals are a way to prevent them over cooking. The intervals also allow more variety in paces. Why can’t you just accept that this method has been proven to be successful? Is it simply jealousy?