A few things:
Threshold can be defined as your pace/power you can hold at quasi-steady state. IMO the gold standard would be an Max lactate steady state test (the highest power you can hold for 30+min at a steady lactate level) 60min TT is a good enough guesstimate for that, and was one of the first definitions of FTP. It’s possible that someone’s 60min power is slightly higher or lower than their true threshold, usually a bit higher.
Tempo has 100 different meanings. All three of these can be more precisely defined as percentages of each other.
…snip…
I’m not trying to crap too hard on FTP, but it’s such a mixture of aerobic and anaerobic power (especially in the ramp/20min) that it’s not very useful for pure aerobic or anaerobic efforts.
First, most of that has very little to do with the OP. Which is simply that when a runner describes a tempo effort (very close to threshold), they mean a significantly harder effort than a cyclist does…a cyclist’s tempo is roughly 10-15% lower relative (to threshold) effort than a runner’s tempo.
Second, you are conflating the various short-duration-approximations of FTP with FTP—which has always been defined as the power one can hold for approximately an hour. However, very few people like to do 60’ tests—so, shorter duration approximations have been proposed (30’/20’ SS, 20’ with 5’ blowout, ramp tests, etc). These sub-60 min test are NOT alternate** definitions** of FTP—they are simply poor estimates of it, for all the reasons that have been enumerated 1000 times on here.
This is what rmt and I were agreeing NOT to get into, because its not relevant to the OP’s question.
MLSS/LT1 is a better baseline for Z2 than FTP%.
No its not—not, in a practical sense. Very few people have access to a lab for determining MLSS—even if they do, such testing is expensive unless you’re a lab-rat. And, home Lactate measurements are of questionable value. Further, it presumes that there is some major penalty for training at some point just above/below MLSS—there’s not. It further presumes that your MLSS on training-day, is the same as it was on lab-test-day—its not. But again, none of that is relevant to the question asked by the OP.