Is TSS of Sub-threshold Zones/Levels Created Equal?


@Landis You could say everything you just said and substitute the word TSS with Time in Zone. Could you not?


Sort of but, not necessarily. Perhaps you’ve read this…if not check it out:

edit: @tshortt that ^^^ wasn’t the right article. It’s an ok read so I’ll leave it. Trying to find the right one for you. I’m not even sure it was TP. It may have been from Alex Simmons or Frank Overton (?) they talk about training as a continuum and talk about training the three systems and indirectly TSS…


FasCat just did a podcast on CTL in general and CTL for masters specifically. Really good listen.

Frank O shut down a 50yo guy trying to explain that he thought he needed a CTL of 130 for Haute Route and broke down why 15-80hrs a week isn’t something you should do even if you can as a masters cyclist.


Yeah I hope I didn’t imply that! Push it up as high as possible given (age, work, family, history, health etc…). 90 is about as high as I’ve ever seen it and I was lying cheating and stealing every minute to get it. Not sustainable. That was late 40’s…


Regarding both TSS and CTL, and this has been said elsewhere on the forum, it’s also a reflection of your events/racing. The example was a track rider training for Flying 200m will most likely not be able to drive either metric up as high as a rider training for a 200km road race.

Your macro (aka holistic) level has to function first and foremost and trying to substitute that with micro/independent factors and metrics just isn’t going to work.

I dunno, some times it’s all just gobbledygook to me. :man_shrugging:

(also…I think @Tanner1280 and myself are doing eerily similar stuff…hi friend! :grin: )


Finished my SS and doing my Z2 now @Captain_Doughnutman:)


@Landis I didn’t read that you were implying that either, so it’s all good.

@Tanner1280 I think the reason Frank Overton can use CTL/etc like he does is that a big part of his plans are comprised of subthreshold workouts (at least until his Race Intervals plans). He is Senor Sweet Spot, after all. :stuck_out_tongue:

Anecdotally, in the past, I’ve felt that the PMC metrics track really well with how I was feeling aerobically when I was in phases like FacCats “sweet spot up the wazoo” or TR SSB Vol 1. When I’ve progressed to SSB Vol II or a homegrown training block that introduced high end work, the PMC metrics just stopped being even close to reality. So before throwing the baby out with the bath water and dismissing TSS based metrics, I’ve wanted to get to the bottom of it


I have a 3hr/220 TSS SS ride today and a 3hr/210 tomorrow. :+1:

My sustained power has really increased, I’d say doubled in duration, but the waning high-end makes me sad. I’m good at it and I enjoy it but it’s not overly specific to my A race so just lots of SS and THR, but once that’s done with I’ll be back at it!

Sorry – off topic!


This is near exactly what I’m doing. Although I wouldn’t view your age as a CTL limiter as much as type of work. I’m 10 years older than you (and probably 10 years less mature!) and I got my CTL up to 99 in Dec doing SusPowerBuild/Threshold work. It’s fallen and will probably end up in the low 90’s at the end of my personalized SSBHV plan.

This my similar-ish weekend workout: Attempted Murder.
And my Tuesday workout: Sweet Spot Over-Under +2.

Yup! Totally me last season – all roof, no foundation.



So I ended up with 3hr 20min at .88IF today… at a normalized power that was my FTP on the ramp test a couple months ago. And I’m not feeling buried or unduly tired. Tomorrow is a 3hr Z2/Z3 ride and I’ll end up around 850TSS for the week. Next week is rest and I’ll build one more time. Probably time to bump FTP up too.

I found it hard to take the jump from the TR plan progression when I was seeing gains, but I’m now glad my A race got pushed two months. I may use a modified TR plan for race prep. Still deciding.

Keep fighting the good fight old man!


Agreed. TSS by itself without knowing anything about the breakdown isn’t sufficient as a summary metric. Needs to be augmented by time in zone.

I’d add to your energy systems: oxidative fat system vs oxidative glycogen/glucose system also helpful to distinguish.


This is why TSS isn’t as relevant to someone using a fully packaged training plan app outside of giving a very broad measure of comparative stress. The plan calculates ramp rate and attempts to give optimal loading and recovery should they follow it properly.

It’s very useful to an athlete that is self coaching or working with a plan using the PMC. They have to be aware of what system(s) they are currently training and have a clear understanding of what their overall fitness goals are.


I have thought about this as well, the normalised power algorithm works off a lactate ramp to the power of 4, in that it raises all the powers to 4.

As you say though, for a rider with a high V02 max relative to threshold this will be less than 4 and for a rider with a low V02 max, it will be more than 4. Probably in the range of 3.5-4.5.

A cool feature on trainingpeaks would be allowing the user to change this value based on a lactate test. I think this serves very little functional purpose and wouldn’t be worth the effort for the company as the normal TSS and normalised power equations work well I think, but it is a cool thing to get into and think about.


Xert will almost always generate higher XSS than TSS values when it comes to structured workouts both low and high intensity. For example, you can score higher than 100XSS in one hour when hard efforts are done under fatigue. Also short, sharp efforts can also cause XSS to be much higher than TSS. Where TSS makes up the difference is on longer rides where there are many stops. TSS can be higher then XSS in these cases.


Any thoughts about CIL (Chronic Intensity Load)?
It may not be a solution for single workouts but when charted with CTL It paints a nice picture.


@bhrylski I was ignorant of this metric. I just read the TrainingPeaks article about it. Thank you so much. If anyone else has thoughts I’d love to hear them. Specifically, what is the consensus within the community about it? Is it widely used?

Good stuff! :+1:


@tshortt I got wind of it through the WKO4 facebook forum, I wouldn’t say its the most popular or that it is without flaws but its a really nice way to compare outdoor-in season training to indoor HIT/TR training


According to someone from a WKO4 forum who has looked into replacing IF with a model based on the PD curve, the difference it makes in most cases are minuscule.

An idea I had to solve the problem in a different way would be to break TSS into zones (aerobic/anaerobic, Z1&Z2/Z3&Z4/Z5&Z6) and have essentially a report that tells you where you spent your TSS. This could also translate into Aerobic Acute/Chronic Training Load vs. Anaerobic Acute/Chronic Training Load ect…


My question would be why does it only take 1 hour and 30 minutes of riding at a steady 70% of FTP to accumulate the same stress as an hour at 100% FTP? That is contrary to the common conception that it should be a much lower stress score, whether TSS or XSS.



1.5 hrs at 70% FTP is 73.5 TSS

1 hr at 100% FTP is 100 TSS

IF is squared in the TSS formula.

So the former is less stress using TSS. I assume using XSS also?