Oh boy. That's a loaded question round these parts. Plenty of people on both sides of the isle.

For starters, a search hear on the forum might be useful "TSS CTL ATL TSB" yields lots of useful threads. Andrew Coggan is the developer of the concepts and posts here infrequently. A similar google search including "coggan" in the search terms is also informative.

Its basically a method for managing training load which can be thought of as time x intensity. I'm really oversimplifying....read the threads.

It was developed for cycling. TP has extended the concept to other sports, notably swimming and running. I find it modestly useful for running. I find it almost worthless for swimming.

In order for it to be useful in any way you need to know your functional threshold with some degree of accuracy in any sport you plan to track this way. Then efforts are scaled relative to your threshold.

Regarding your specific question and your "fitness" level increase...no, its probably not legit. Until TP has a mass of data to work from and accurate thresholds in the sports you want to track, it will not be "legit". It takes about 3 months of data for TP to stabilize. So, until then it will be ramping up simply due to the accumulation of data, not because of some real change in your "fitness".

https://www.trainingpeaks.com/...performance-manager/

(Ignore the byline, BTW...I know that writing both "Dr." and "Ph.D." is redundant, but the folks at TP apparently don't.)

ETA: About 10 y after I introduced the PMC idea in the early 2000s, the sports science community finally caught on. Many of those more recent studies are cited in this blog post:

https://www.scienceforsport.com/...onic-workload-ratio/

:-) They could have added MS, too.

They should have gone for the trifecta: BS, MS, PhD.

(You know the joke about what MD stands for, correct?)

Well in that case, "Esq., J.D." here I come!

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@floathammerholdon | @partners_in_tri

Don't be shy - that's Dr. Cloy, Esq., J.D.! ;)

I have been on TP Premium for the last 5 years. I find almost all of those measurements helpful. Over time, I have learned what I can/cannot handle from a ramp rate perspective.

Don't believe I do. I probably should since my dad's a physician, though.

BS = ...
MS = more of the same
PhD = piled higher and deeper
MD = much deeper