Do you use th same power meter inside and outside?

Oh ya. My Sufferfest FTP is stupidly high compared to what I can do for outside tests of 20-60 minutes. I checked my Kickr power versus a crank based power meter and the discrepancy is not more than you would expect for drivetrain losses. About all I can figure is that I am really good at 20 minute efforts because I do them all the time.

Depending on your cooling indoors and your variability of terrain outdoors, it may be harder or easier to match test numbers in and outdoors, even using the same powermeter.

For me, I can hit higher numbers on my test circuit outdoors. Better cooling and I have more motivation than indoors. Same thing running on a track for a mile test or 5000m test versus treadmill. I can never match outdoor times on treadmill.

Yes, WKO5 supports this and automatically assigns tss based on the workout type.
So I have that set up for all my athletes

My indoor FTP seems lower than outdoor FTP - if I am in the zone outdoors and chasing a KOM on my Garmin, I'm putting out a lot more outdoors than indoors.

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https://www.strava.com/...tes/zachary_mckinney

same

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https://www.strava.com/...tes/zachary_mckinney

Just about everyone except me and a few others. It seems normal.

I seem to be in the minority. I test better indoors than out. Probably due to variability in the ride outdoors, more coasting. But I also generally don't train ftp outdoors, I'd rather do longer cardio rides.

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See your bike fit. https://bikefitr.appspot.com/

Cooling is the issue. I used to think indoors was always lower. I used a basic window box fan for cooling. I now use two ‘commercial’ fans and I can put out the same power inside or outdoors.

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Blog: http://262toboylstonstreet.blogspot.com/
https://twitter.com/NateThomasTri
Coaching: https://bybtricoaching.com/ - accepting athletes for 2023

My indoor tests are frequently on a grade... I tend to test best between 75-78 rpm.

I'll bet I could test outdoors, higher then indoors on a long climb (this has happened before)... But in a normal situation, cadence goes up, hr follows and frankly, on my tt bike, I get moving a little faster then I want to be on the roads we have around nyc.

I've always been able to put out more power indoors than outdoors and for a lower heart rate... I put it down to not having to concentrate on steering/balance, gearing and terrain changes etc, and you can go til you nearly fall off the bike indoors but you cant exactly do that outside (safely). Generally around 25w lower, I imagine going uphill outside i could get it a fair bit closer though.

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@the.lazy.triathlete

https://www.strava.com/athletes/18691068

Yes I use Assioma pedals. I think the resistance on the trainer results in a lower FTP indoors. Plus, motivation....
FTP is about 20 points higher outdoors.

For me short (ie 1-5 mins) FP peaks are higher indoors than outdoors, and my NP for a ride indoors is higher than I've managed outdoors. I put this down to being able to just close eyes, look down, roll around without crashing, and then collapse over the bars at the end, again without fear of a close encounter with the road, or other riders.

However beyond that then cooling does have a strong bearing. I've done 3x 325w for 25min outside and woudln't say I would have liked to carry on, but made it to the end OK. But I've never managed that set on the trainer. Same bike, same Quarq source for the data. Last time I failed on this my wife was riding beside me also zwifting, and she commented that she could feel the heat I was radiating from 18 inches away. I didn't feel too bad, but did have a triple fan blasting me. First rep was just horrible. Absolutely dead at end, just clinging on. Second time was toast after 10 mins, so dropped power to 300 and got to finish. Third rep on trainer started at 300 and was fooked by 5 mins...

So my thoughts are cooling is a big factor (indeed I've done outdoor rides in hot weather and needed to pull back the power to account for the heat), but also there are psychological factors (boredom - so perhaps for some zwift brings out the best, for others outdoors is more engaging), and then finally the 'control'/risk for anything where you're pushing to the very limit self preservation is going to be factor outdoors.

That may influence things for me. I didn't know it could do that.

I've debated updating my DIY excel sheet that is kind of like those models by being able to select which FTP to use for each uploaded activity. But, time is worth things too, so may pay up at some point to let a service mine the data for me.