Originally Posted by
climber7
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.
It actually doesn't really matter which is right, as even people with a dedicated power meter who test indoors and outdoors have slightly different numbers, probably due to variations in wind, temps, and even position due to the various inclines/declines on the road versus the dead-set motion on a trainer. Watt differences have been reported by many to be 20-40 watts difference, even with repeated testing, so it's recommended that you test both indoors and outdoors for best results in extrapolating how you'll fare in an outdoor ride/race based on trainer numbers.
If you're repeatedly testing and training on the same trainer though, you can measure real performance gains even if the trainer is a bit off, as long as it's consistent.