Aero vs sitting up (FTP & training) & adaptive / predictive FTP

I know some of these questions have been beaten to death but I’ve read through several threads and this point hasn’t really been directly addressed and I couldn’t find any papers to support or refute my questions below. I am primarily concerned with power output and training adaptation in both aero and sitting up positions; but, I know position, types of bikes, etc. have been talked about at length elsewhere here. FTP testing in particular might not be as prevalent with predictive FTP out now :wink: so I adjusted the scenario I was thinking about just a little

FTP Testing Aero vs. Sitting scenario
I get that if a rider is racing in aero he/she should train in aero, but I don’t think that necessarily means “testing” in aero. If the cyclist’s muscles and body can put out “X” amount of power (let’s just say 300 for a nice easy number) while sitting up, and “Y” in aero (285), then if you always train at 285 then wouldn’t you be short-changing your training? The cyclist’s over-under threshold intervals, which are already in a tight window, might turn into 100%-90% as opposed to 105-95. Therefore, should the cyclist in question test in their most power-producing position and train in aero to that? Or, would adaptation to training stimulus change based on what the rider can do in that position?

By extension: Training on a road bike vs. TT bike (can extend to sitting up vs. aero position)
So that said, if a rider is able to put out more power on a road bike than a TT bike, are there more power gains to be had by mixing training between the two? Staying on the TT bike to keep flexibility and position up and dialed; like for z2 rides and threshold rides. Getting on the road bike to push out threshold rides and anything above threshold… particularly further out from race day, and move more exclusively to TT bike the closer the event is. As an aside, I personally wouldn’t touch VO2 intensity on my TT bike anyways because ideally, would never get there unless on a hill climb and trying to push over the top. So once it gets that hard anyways its time to sit up or stand.

Thirdly: Predictive FTP
Progression levels adapt to energy systems and ability to crank out workouts, so that wouldn’t change so much with position changes. However I believe it’s been a feature request to include multiple bikes to accommodate different positions for the following reason and logic… Would frequently changing positions across a season affect the machine learning / predictive FTP? Would it throw off the output by those 10-15 watts at the end of a season? A rider’s capabilities to put out power probably wouldn’t change much more than 10% or 15% no matter the type of bike (I have no science to back this up), but being able to add which type of bike we are on would be a useful data point added into the millions of data points in TR’s database.

Thoughts on any of the above?

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Resurrecting an older thread, it seemed to be affecting it for me. Over the summer I did a lot of outdoor and particularly upright/drop road biking as oppose to dedicated TTing. AI FTPD rose to circa 13% over what I am currently using (up to 28% different on my end of season TT form). I did smash the AI FTP D number last May (2021) but I have put that down as a hero day.

This is the constant bug bear in the TT community. Last year I managed 254W as my best in a 25m TT on the TT bike (it was a horrid day wind and rain…well for me! some got good weather at the start and managed a 55) I then did the Leo 30m TT on my road bike on a sporting circuit course and managed 270W for 75mins. So much more power for longer. That said I train mostly on the road bike as a/ I find that if I raise my threshold 5W on the road bike it goes up 5W on the TT bike and b/ I don’t notice a sudden rise in power on the TT bike when I start riding it more regularly in the spring. Oh and I look forward to riding my Ridley Helium in the summer sun, whereas I suffer my TT bike to race as I like competing. I suppose that’s why I won’t be challenging the top guys in a TT - that and a lack of talent and being old! :grin:

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Frank Overton, founder Fascat Coaching, said physiologically we only have one FTP.

Go smash it on the primary bike and adapt secondary bikes as much as possible.

I’m getting a TT bike soon after not having one for over a year. FTP is floating between 310 and 335 these past few months, but even 5% reduction due to aero position is 20 watts.

Like you said, and it’s probably marginal, but physiologically, if I can put out more KJs sitting up or in the drops, and do the easier workouts in aero position to adapt that way it might be the best of both worlds