Originally Posted by MoAlpha

Don't know if it matters, but FTP is based on a the highest effort level where lactate production and clearance are in equilibrium (LT2). At the dawn of the power era, Andrew Coggan coined the term FTP for a SWAG at a power level corresponding to that state, to use as a peg for training zones. The 60 min comes from the fact that this level was more or less what an elite rider needed to sustain in order to ride a competitive 40 km TT. In reality, the sustainable duration for LT2 (FTP) ranges from the 30s to 70 or better.