So I’ve mentioned this many times, but I’m kind of focused on this subject at the moment. That many people use a PMC chart to determine three or four things.
- Am I doing too much or too little (TSB, ATL)
- How much should I increase my volume or intensity
- How fit am I (CTL)
- Should I increase my intensity to make up because I don’t have enough time?
The problem becomes when people focus too much on it. Again, like @Ivegotabike mentioned Goodhart’s Law comes into play. Most measurements, like CTL and FTP should not become a strict target.
If you just use TSB to try to make sure you’re not doing too much, or to align it with other modalities for recovery, it’s pretty reasonable. Or it can be.
In general there’s so many flaws to TSS and really all of it. Meaning doing 20 minutes at threshold after a warmup is completely different stress than doing 20 minutes at threshold after four or five hours (Dr Seiler mentions this). Another example is a 4x5 with good rests versus 20 minutes all out are also completely different even though they can be the same TSS.
There’s a lot of science that proves how flawed this modelling and TSS is. But again, since there is no alternative use it but tread lightly.
This article has verified many of these flaws.
https://journals.humankinetics.com/view/journals/ijspp/17/5/article-p810.xml
So, TrainerRoad uses this modeling, so do most of the other popular platforms. On paper XERTs MPA modeling has improved on this.
My big point: the math is fun and all. And if it inspires you, that’s great. I just would suggest to not relying completely on math to make your training decisions. Learn to feel it, let your body help guide you.