Is it a common argument?
I just ride my bike outdoors, and work a lot off RPE in terms of sustainable efforts. I see ftp as just something you can test and then use to easily scale workout power intensities on the turbo. Sacrilege I know.
There’s also the reality that what you can manage in 20 mins indoor when fresh will bear no resemblance to what you can manage 5 hours into a race outdoors when fatigued (unless you are a pro)
Same here, I don’t really see a difference between inside and outside power. I will see lower HR on inside endurance rides, but not on intervals. Most of my inside rides are on my road bike and Kickr direct-drive.
FTP= work rate in Kj/second (watts) at MLSS which is reflecting the breakdown of glucose to pyruvate and the rate mitochondria use that pyruvate. Perhaps I’m misunderstanding your post but, that is physiology 101.
Please, let’s not turn this into another “What is FTP?” thread. There are plenty of those to comment in already.
During TR workouts, I don’t freeride or race indoors. Also, all of my Base and initial Build is spent indoors. I do 100% training indoors form November until late March/April.
Yeah but, understanding the physiologically of what is going on behind the scenes so-to-speak at threshold is the point. Just because we don’t take blood every test doesn’t mean the physiology isn’t happening. I guess that’s my position I’m trying to make. If we are going to split hairs and stick to ftp is a proxy and not physiological…whatever.
Honestly, that is all over my head. I was just trying to avoid a repeat of the deep dive into the weed’s that exists in so many other threads.
I think it’s fine to talk about FTP at a higher level here with respect to the OP at the top (Inside vs Outside).
So I echo Frank Overton and other coaches when they say there is one physiological ftp inside and outside. Again, we all get it’s a proxy. Physiology is happening just the same.
I don’t specifically try for PRs indoors or out, they just occur. Also, in the Midwest a 2 min hill is considered long and hard to come by, so not a lot of opportunity for it to happen organically. I race XCO, XCM and MTB 100s, so power is punchy and not sustained.
Step 4 - air condition the room! My man cave has a wall mounted AC. I blast it at 60F and run two fans in the humid summer.
Well, it’s a given that you have to use the same power meter indoors and out if you want consistent numbers.
Wind speed was higher in the outdoor trial than in the laboratory trial (2.5 ± 0.6 vs. 0.0 ± 0.0 m·s−1, p = 0.02)
Love this cheeky line from this abstract.
This isn’t as crazy as you might think. All my 3, 4, and 5min PR’s are from the trainer. If you’re doing VO2 the @empiricalcycling way (which I now completely believe in) they are essentially all-out efforts.
For me, similar to @MI-XC as a mountain biker, putting out consistent power over those durations isn’t easier. Certainly all my true max efforts below say 60sec would be higher outdoors.
Just another anecdote.
While I mostly agree, I am much more motivated outdoors. Trucking along at 24 mph, enjoying The outdoors, focusing on handling my bike, have a strong impact on RPE.
I responded but for some reason that response was flagged.
Anyways, I can link to statements that say FTP is not a precise physiological marker like you state, but kinda one if I understand the argument. That calls into question the idea there is “one” FTP. That also suggests psychological factors influence FTP (I.e., 40-70 min power), which I’m guessing most people would agree with. That would be a potential factor to consider in the present discussion.
I can also link to statements by a well known physiologist that argues FTP is not a physiological boundary who has stated that despite that, what matters most is identifying a threshold intensity zone - so don’t over think it.
My take away from this and personal observation? All in all, there shouldn’t be a major difference in producible power numbers outside vs inside. But there is room for some variation due to a host of factors.
Definitely those workout sections where the text advises ‘ok, now get aero’…those suck indoors. But outdoors it seems like I’d rather ride in that aero position. Maybe perception of speed has an outsized impact on RPE. Not sure. Something is going on there, though, you are correct.
The whole point of FTP is that it doesn’t require being in a lab, it doesn’t require any physiological testing. That’s what the F is for, functional, a test you can repeat without a lab or needing to take blood samples. It’s not a physiological marker.
Good catch and totally agree. That explains the massive difference between the groups and from my own experience cooling is crucially important. Especially reminded of that when doing the occasional ride in a hotel gym with insufficient airflow.
For my own setup - with really good cooling - I do think it is reasonable to believe that there are still differences between indoor and outdoor though. My trainer does not allow any (lateral) movement and starting to suspect that smaller physiological asymmetries (that apparently many cyclists have) are playing a bigger role in rigid setups. But believe the biggest effect is coming from the design of smart trainers and their flywheels, leading to slightly different power profiles and pedaling biomechanics. For some this might be irrelevant, for others more important. And certainly not claiming it disqualifies indoor training. But do think development of better smart trainers will help to really close the gap.
Yup. I covered all those mostly equipment related aspects above. TR has their list that is very comprehensive for most of it. And the lack of motion aspect was also covered by another commenter and me since I am a strong proponent of adding motion to indoor setups. The are all parts of closing the gaps once the cooling aspect is well in hand. 
I have a wheel on trainer and this past weekend I rode outside for the first time in awhile and feels so much easier to put out power. I assume inertia has a huge impact on this. Also, inside even though I use two or thee fans I just don’t think they are as effective as cutting through the wind going 20+mph.
Depends on the specific trainer, but many of the wheel-on trainers have less flywheel effect when compared to many of the wheel-off ones.
I wish I knew enough about physics to run the calculations needed here. I’ve heard of someone sharing some calc’s long ago, but never saw the data myself. Would be great to see the real effects compared between inside and outside.