On Fast Talk episode 54, Dr Seiler said (loosely transcribed, not direct quotes):
- roughly 80% of 60 min for zone 2 bottom / zone 1 top. That gets you in the ballpark, if its too high adjust down. Most of the rides will be 60% or 70% so there is a margin of error. Be conservative and don’t overestimate your ftp.
- most people over estimate their ftp
- get off your a** and really do a 60 min power test
For myself, it is roughly 60-70% ftp (and ~72% of HRmax) and the “talk test” or “first deep breath test” are likely better ways of determining your LT1/VT1 (and then riding under it).