Why don't outdoor workouts take into account a need to increase FTP?

@Nate_Pearson @Jonathan

Earlier today I was on a ride and listening to Mitch Docker’s podcast, Life in the Peloton (link here). He was talking to Tom Southam about the difference between trainer FTP and outside FTP.

This is a question I posted to @Jonathan this week as I certainly see a big difference between indoor trainer FTP and outdoor FTP and I was wondering how you consider this difference, which Mitch says is around 7% when loading Outdoor workouts.

Indoor I do everything on a Tacx Neo 2T and ERG mode all through TR and currently showing 270 FTP based on a ramp test that didn’t go so well 3 weeks ago.

Outdoor I use stages dual-sided Dura-ace power meter and via intervals.icu showing 325 FTP from a ride earlier this week. Having just completed English +4 yesterday and managing to hold well over the VO2Max levels I was wondering:

a. Why you don’t consider all training inputted to TR as a measure for FTP as Intervals.itu does

b. Do you add/subtract -7% on an indoor trainer vs. outside workout?

Not everyone has a higher FTP compared to inside and for some it’s the opposite.

The 7% you’ve stated won’t apply to everyone.

Using different PM’s that don’t align well doesn’t help matters in this area.


Or your FTP indoor is not correct because ramp test is underestimating your FTP like it can overestimate it also…

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You need to do the same test indoors and outdoors. Personally I’d do the standard 20-min or Friel’s 30-min. Do something longer, not shorter.

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Recently did the 8-minute indoors and outdoors, same Stages PM. No big difference between the two so I don’t bother with tweaking the FTP based on being outside or inside. What I do though is stay in the upper range of the prescribed outdoor workout intervals.


There shouldn’t be a 7% difference. I would check your environment. Proper cooling being the number one reason.


Like everyone said there shouldn’t be a difference really. Your FTP is what it is. Whether you can or can’t achieve that indoors versus out is a matter of environment, nutrition, the day, sleep the days before and a bunch of other things.

One thing to consider is an outlier workout outdoors. If you’re crushing hills or segments and easy on everything else you could end with a high 20 min number and showing you higher FTP when its not a true representation. Always use the same PM and protocol for FTP testing so you’re not under or over estimating. My guess would be your FTP lies somewhere between those two numbers.

On cooling: I found raising my fan up about 6 inches off the floor made a massive difference. More than I would have believed before I did it.

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That’s a pretty large difference. I agree with others that either your cooling really bad or the ramp test underestimates your FTP, or both.

My FTP is largely the same indoors and out.

The other possible factor is differences in power measurement. Power measured at the pedals will likely be 1-2% higher than measured at the hub on the trainer due to drivetrain losses. And smart trainer power measurement is generally significantly less accurate than dedicated on-bike PM’s. And that’s even before considering the force curve on dumb trainers.


Using the same powermeter I find my outdoor ftp to be no different. If anything it’s easier to get a power pr indoors because no cars / wind / undulation

Just make sure to get a fan that hits you where you need it


Seems to depend on the trainer too?

On an old CycleOps mag trainer, very consistent 30W indoor vs outdoor difference across all environments, and across several different outdoor PMs, almost like it’s 30W of “drag” even though that’s not technically the case. Adding +30W to outdoor intervals over the recommended number seems always to work perfectly. The Garmin freaks out the whole time.

I always find a difference between indoor and outdoor power as well. I used to put it down to a difference in reading between my Stages left arm crank and my Wahoo Kickr and that my Stages reads higher.

Last time I did my indoor ramp test I had my Stages recording as well and both peak powers came in roughly the same.

When I test out on the road I do 2 x 8min as I don’t have a suitable stretch that will allow me to ride at that intensity for 20 mins. It’s a gentle rise of 2/3% gradient. I can always ride 10-15 watts higher but I would never complete my indoor workouts if I set my FTP to the number generated from the 2 x 8min test.

I’ve now put it down to cooling and the fact I can perform much better on a 2 x 8min test rather than the ramp test.

Will check out that Podcast

I’m the same, although my results on the ramp have gotten closer to the 8 min. Still it’s 6% lower via ramp.

I also test higher outdoors. For me it’s likely cooling, the psychological effect of going no where on the trainer, and the fact that outdoors I typically would test on a hill. I can put out more watts outdoors, and more watts in climbs.

The reason TR doesn’t have two FTPs is because we shouldn’t either. However my take is test indoors if you have a lot of indoor work on the horizon, and outdoors if you plan on training outdoors. Sounds like a few of us here should prioritize indoor cooling strategies as well.

Most people do, there is a reason, Trainingpeaks/WKO, other training software packages, every coach I have ever spoken to etc… set an indoor and outdoor FTP.

Riding position outside tends to be a bit different, people tend to test on inclines. Plus the bike outside moves beneath you even if only a little (even seated, I recently noticed this briefly looking a the top tube while putting out a high end sweet-spot effort) , this all makes a difference IMO.


Further to my last post, it would be interesting to know if people that use ‘rocker plates’ have indoor / outdoor FTPs that are closer together, guess we would not be able to account for all the other significant variables (heat, motivation etc)

I have a rocker plate and as I mentioned earlier, my FTP is pretty much the same inside and outside.

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Hopefully coaches aren’t telling you that, because they shouldn’t be making definitive blanket statements like that. After two years of training mostly indoors with a dialed setup (no rocker plate), I find my indoor and outdoor FTPs are similar if not the same. I’m not 7% stronger outside. I wouldn’t ever tell one of my athletes a definitive “add 7%”. I’d test them and find out if I needed to. If someone trains most of their time indoors, the gap closes substantially.

They say nearly all end up having a different FTP outside, of course they test this. I never mentioned the 7% posted earlier. So in your opinion do a majority have the same FTP indoor/outdoors?

I don’t think a majority train enough indoors to make them similar or the same. For a lot of regular TR users with good indoor training setups, I’d bet they are similar. There is probably a difference because a majority of riders don’t spend as much time working indoors.

But the answer depends on the individual.