really? interesting to me. anyone else have thoughts on this? my watts were significantly higher with the KK equation vs. a couple of tests i did on a WattBike and a CycleOps stationary bike, and i was never sure which to trust. it'd be cool if KK was right, though...haha.

OP - don't mean to hijack the thread. as jmX said, 20 min is probably most common. 1 hour is most accurate for determining threshold, though, since functional threshold power - FTP - is actually supposed to be max sustained power for 1 hour.