MPA is a powerful concept and the accuracy of it is something I’ve come to appreciate over the years as I’ve done various rides and FTP tests; all correlate very well with what xert has determined. I’ve been very happily surprised at how well xert is able to calculate at what point I will reach exhaustion for all sorts of efforts above my Threshold power.
Where xert is lacking is for efforts below Threshold between LT1 and LT2. The way xert treats MPA I can theoretically ride 1 watt below my Threshold power indefinitely - it is not until I reach Threshold that I actually start to dip into my MPA, like an on-off switch.
There seems to be a need for more of a continuum below Threshold where MPA or some other measure of available power is accounted for. Looking at my “power curve” xert seems to acknowledge that power isn’t infinite below Threshold but it isn’t something that is accounted for in the MPA calculation.
I’m guessing it is more complicated to determine a time to exhaustion below LT2 because there are more energy systems in play but it would be nice to see xert account for efforts below Threshold when determining MPA.