TSS and IF

Not sure if this should be a new thread or a continuation here… it would be great to have SYSTM track a rider’s ATL/CTL (acute & chronic training load). Both are related to TSS and IF.

I’m trying to monitor my training load and don’t see an easy way to monitor that in SYSTM. It’s helpful to understand the stress on the rider to gauge recovery, etc

@Joey_Roa It would be nice, but there might be trademark and copyright issues involved. Either way, the immediate and easy solution is to get a free Training Peaks account and link it to SYSTM (and your bike computer if you also ride outdoors). Please ask if you need help doing that.

Thanks @AkaPete… unless I"m mistaken, the free account only gives the workouts ctl/atl… doesn’t show the cumulative (premium feature). :frowning:

That is my understanding too–not sure why I mentally blanked on that when I wrote my previous post.

Here is an article by our very own @Coach.Mac.C that discusses the limitations of TSS and IF. There are two main issues with TSS and IF. The first is that these metrics are based off of FTP with no consideration of an individual’s unique ability to produce or sustain power above threshold. It assumes everybody is identical compared to their FTP. That’s a huge assumption that taints everything else including NP, IF and TSS. The second problem is related, in that TSS favors workouts that exceed an hour in length.

And then we could talk about FTP. Many testing protocols produce an FTP that is higher than the individual can actually sustain for an hour. So it is also flawed.

Downstream of these we get ATL, CTL and TSB that rely on these flaws, and compound the errors such that knowing ones actual fitness is basically an educated guess.


Following up on my previous post, talking about FTP and Time To Exhaustion or TTE. In the modeling for TSS, the assumption is that an individual’s FTP is an accurate measure of what they can hold for an hour. By definition TTE @ FTP is 1 hour. And TSS for riding at FTP for 1 hour is 100. It also represents an IF of 1.00

Now, that sounds great in theory. Except that FTP as calculated by various testing protocols can result in a power level that can only be sustained for a significantly shorter duration, even as short as 30 minutes.

In this case, the cyclist has ridden to exhaustion and only gets a TSS of 50. Should it be 100? Or do we blame it on an inaccurate FTP value? In either case, it becomes difficult to rely on the resulting score when the theoretical assumptions don’t hold true in practice.

Lastly FTP as a component of 4DP is measured with significant fatigue and results in a value that matches my observed 60 minute power within a few watts +/- since the FF test has been scientifically analyzed and tailored to provide an accurate assessment of our abilities as a rider. That includes a more reliable FTP segment. But it can be tricky to pace FF, so it’s still not perfect.

With the foundation right TSS and IF are a little better tools in Sufferlandria (or Systm) yet NP is another calculation that is flawed, and needs to either be augmented or replaced.

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Thanks folks. From the responses, its clear I did a poor job of framing the question. I really want a way of tracking training load to know when I should back off and when I’m good to hammer. I’m old school and my only frame of reference is ATL/CTL and TSB (I’m still using WKO3 to give you a sense).

I’m down with 4DP and the limitations of FTP (I’m nowhere near the as smart in the specifics as many here) but I don’t know when I should recover other than feeling exhausted.

For instance, I try to do simple and sinster each day and I’ve done;
Told off by Angels (Friday).
Nine hammers (Saturday)
Attacker (Sunday)
Revolver (Monday)

I’m fatigued (knackered actually) and was curious about how to measure being too knackered.

Does that help?

I measured knackerdness by tracking my HR variability every morning. It’s been pretty spot on actually.

One thing I’ve learned in my reading is that chasing CTL is not an ideal way to train. Hard efforts force our bodies to adapt as they repair the damage we have done to our muscles.

So we need both hard efforts and solid recovery to adapt. But the PMC only models recovery as a loss of fitness, while in actuality this is where the fitness is gained, but up to a point. Too much recovery and the decay begins.

As far as I know, there is not a physiological model that gets this correct. So that puts us back to using the tools as educated guesses. An educated guess is better than an uneducated one. And the ability to view your training over time has tremendous value.

Also note that for endurance training the PMC is more accurate because the assumptions made for TSS and IF become a bit more reliable for high volume tempo efforts.

My takeaway on all this is that I use the tools as a rough guide but also listen to my body, not being afraid to take a rest (or recovery zone 2) day when needed.

HRV sounds like a great approach @DameLisa. Could you elaborate a bit? Is there an app that you use for that?

Hey Sir Brian,

I agree re chasing CTL or the Strava equivalent proprietary. In fact Strava shows me losing fitness during each day and also across the week as it clearly doesn’t understand intervals work and I only get real gains on my long weekend rides. Whereas my fitness is definitely overall on the up.

I don’t use HRV it to train so much as I use it to account for life stress which can also mean I need a rest. I used to train hard and rest but ignored life stress. I know many coaches use it to fine tune training efforts though.

Training Peaks explains it well:

There are some good paid apps out there, some use the camera on your phone. My Garmin measures mine.

Being female I also have another variability (hormone cycles) which I also track using an app called Wild. This is great because I track subjectivity how I feel, but it also uses a whole bunch of measures from my watch (stress rHR, HRV etc) and what training stress I have and also gives me a fairly good indication as to whether I can smash things up or need to calm the farm on the training front. If I actually add in what I’ll be training, it’ll tighten up the nutritional advice so it is much more aligned with whatever I’m training that day.Just need it to talk to SYSTM’s calendar and it’ll be perfect :grin:


Those are all great sessions. Four days of beating your legs into a pulp will knacker anybody.

That said the training plans put recovery rides (or days off) between the hard workouts.

If you’ve not done so yet, take a look at the training plans as an example of structuring your build weeks.

hi all

i don’t know if this will interest anyone but I reached out to Training Peaks about purchasing WKO5 (their desktop version). It has quite a few bells and whistles that suffering minions and Grunter might appreciate.

I also requested a discount for Black Friday (north american thing)… Anyways… b/c I want to share the numerical analysis of our suffering… here’s the code to get 30% off (until November 30); WKO5Cyber.

And the link to the page for convenience: WKO5 Training and Analysis Software for Athletes and Coaches