I’m an Audax / Randonneur style rider. For 600K, 1000K, and 1200K events, there is a huge drop off in the power curve on Day 2, 3, or 4 of events. Ten to twenty percent drop off depending on how badly the first day crushes you.
For purposes of more accurately calculating TSS and all the other stress / fitness / fatigue type numbers, would it make sense to lower FTP for Day 2, 3, and 4? For the same RPE, my power is much lower.
For example, on Saturday I did a ride with a TSS of ~600. On Sunday, I did a similar effort (based on RPE), but the TSS is ~400 and all that “active recovery” time sure didn’t feel like active recovery.
To be honest, FTP is a bit of a dynamic figure even within a single day. But that’s a whole “next level” conversation of personalized physiological tracking…