Using PD Curve to Improve TSS Model?

An often repeated phrase that holds quite a bit of importance

“Not all TSS is created equal”

I’m sure almost everyone noticed a big difference in response to training load going from outdoor riding to TR, and even during different phases of training. Seeing that many people use TSS and some get obsessed with it, it would be nice to have a metric that more closely represents the actual work that we do. I don’t have the physiological background to come up with a formula that could perform such a task, but I can see a couple of ways to develop such a metric.

  1. Divide TSS by energy system
    -Each energy system recovers at a different rate thus would have different ATL/CTL time constants.
    -Better tracking of specific types of fitness (ie. sprint, VO2, Threshold)

  2. Use the PD curve to create a dynamic scale to replace IF
    -Although this helps to make the TSS number less ambiguous it is not as specific as the first point.

In any case, I would love to hear feedback on these ideas.
I believe a solution such as the one I am suggesting could genuinely benefit multi-discipline, multi-sport, and indoor-outdoor athletes alike.

There is already a detailed discussion on the subject here: