XSSR, wattage and fitness response

Trying to get my head around XSSR and fitness response, so I have formed two hypothesis.
Given a set fitness signature, is any of these (approximatively) correct?

Doing [x] XSSR gives the same expected marginal general fitness improvement regardless of the wattage required to deliver [X] XSSR
Doing [w] watts impacts the same neuro-muscular (peak, HIE, TP) area of fitness regardless of the resulting XSSR

Hi Jacob,

The first hypothesis is correct. Strain rate normalizes the workload across all athletes, regardless of fitness signature. The second is pretty close, the same absolute wattage affects which parameters are affected by the resulting strain. i.e. near PP sprints will train PP far more than TP, while 20 min efforts will train TP far more than PP. In this regard, both the absolute power and power relative to MPA matter.

Hi Scott.

Thank you for the reply.
You write: “In this regard, both the absolute power and power relative to MPA matter.” A follow-up question on this. Let’s hypothetically assume I have brought my MPA all the way down to my TP and I from there ride at TP. Will this impact my PP even though I am riding at quite a low wattage?

Nope. Only affects TP at that point, because the absolute intensity is not high enough to put strain on the peak system. However, the rate at which strain is placed on the low system will be dramatically higher than when you started.