ERG vs Resistance Mode for Ramp Test - What just happened here?!?

I’m beginning week 5 of my build phase, and it starts with a Ramp Test. As usual, my Wahoo Snap is in ERG mode, I’ve warmed it up for a few minutes, and I’ve done a spin down (I follow this routine before every test). As with previous tests, I get to the end of the test, and I can no longer keep my cadence up, but I’m still holding/gaining watts, so all is well. Eventually, my cadence has dropped, power falls off, and I’m done. That’s just how every test before has gone, so everything seems normal. Then I see the test result…exact same result as my last test (230, which is a few watts less than when I began, sadly). It seems fishy to me, as I’m feeling significant gains on the trail.

So I decided to re-test (one day later), but this time, in resistance mode. I warmed up the trainer, performed the spin down, and tweaked the resistance level a bit (ended up at 30%). As I near the end of the test, I’m able to change gears and keep cadence in the 80-90 range, and as I reach the point where I failed yesterday, I’m still going strong…seems odd to me. So I finish, and my new recommended FTP is 28 watts higher! Now…don’t get me wrong…I like 258 a LOT better than 230, but now I don’t know how to proceed.

This would indicate that ERG mode is messing me up, so does that mean my previous tests were likely invalid? Or did testing in resistance mode give me an artificially high result? Has anyone else seen this, and if so, how did you handle it?

Thanks in advance - Scott

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Was your final gearing in erg mode similar to your start or finish of your resistance mode test? IE were you on the small ring or the big ring and what ring and gear were you in on resistance? One possibility is that the trainer power profile fits low flywheel speed better than it does higher flywheel speed which is very common

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Final gearing in resistance mode was completely different. I ended in a much higher gear. “Speed” on the first test was below 12mph at my failure point…second test was over 29mph. So I suppose what you’re saying makes sense, but it surprises me that there would be such a large variance. I’m thinking the best way to proceed is to train in resistance mode at the higher FTP, and see how it goes.

This experience demonstrates that the differences in flywheel speeds may have a very real and measurable impact on feel and test results.

Generally speaking, I feel it’s best to test using the same mode and gearing that you plan to use most of the time in training. It’s ok and even good to mix it up a bit. But you want to consider the real demand on your body if you test at one extreme and train at the other.