Virtual Power indoors, power meter outdoors?

Does anyone have any experience with mixing virtual power when training indoors on the turbo and a power meter for outdoor rides? Is the potential discrepancy between the two too much to use both effectively or does TR have a feature to set different FTP/zones for each method?

I ask because I am thinking of switching my power meter (spider based, so too much of a faff to swap constantly) over to my CX bike, to use as a winter training bike now that the weather is turning naff and the roads round here slowly turn to rubble. In an ideal world I could then leave my road bike on the turbo and use speed and cadence sensors to still train indoors. Thoughts?

I don’t have experience with virtual power. However, the popular thought is that even using two different power meters introduces enough variation for the two to not be comparable. Virtual power,I think, will likely be a larger variation so I would avoid it if at all possible.

If you really need to proceed like this, I might recommend doing two FTP tests (1. indoors with virtual power and 2. outside with power meter). At least this way you can compare like-for-like.

Then, if you’re doing TR workouts outside AND inside then you can adjust the intensity for each workout according to the discrepancy you found in your 2 FTP tests.


I used the Kinetic Inride on my dumb trainer for a year, powertaps on my road bike. When I put a powertap wheel on my trainer rig, it read…a little higher than the Inride.

Splitting hairs is fun, but see the big picture. It’s all just getting tired, and if you develop a good sense of perceived effort you’ll get in the right place. virtual is in the ballpark. look at it along with HR and PE, you’re probably doing what you need to do.

(a recent Scientific Triathlon podcast had a great point – amateurs tend to focus on the details and miss the big picture; pros nail the big picture and don’t obsess over the details)

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You could just do one FTP test on the trainer recorded on TR with virtual power and on a head unit for the power meter and compare the numbers. Even just create a workout that goes from ~50% to 120% in 5-10% increments and compare the virtual power from TR and the head unit power meter data to get a good idea of the discrepancy along the full power curve.

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It depends, as others have suggested, do a test to see how close the virtual power curve is for your trainer. I’ve seen friends with virtual power to be over 50% off from what they are realistically doing.


Whilst I agree with the general statement - focus on the bigger picture - personally I find this is not applicable here. As bigger picture I see nutrition / sleep & rest / consistency. Obsessing over details would be discussing oversized jockey wheels and weighing every screw on the bike.

Personally outdoors for long slow rides I could live without power (Zone 2 rides). Indoors I wouldn’t be happy with virtual power, HR or PE. Those values are all too inaccurate / can change due to external factors (tire pressure, caffeine, sleep). When doing intervalls this would leave me unsatisfied because I would know that I don’t hit the power target and either underperform (and miss out on possible gains) or overdue it (and might not be able to finish the workout, accumulate too much training stress etc). Guess it depends on the person, but I would be demotivated by default due to that / maybe also lack the experience to hit the right zones by feel.

My personal solution would be putting the CX bike on the trainer. I know, a bit more work. The upside is, that you probably have to clean your CX bike more regularly then and a clean bike is a fast bike :grinning:

You could do that, but its often noticed that FTP varies between indoor and outdoor riding, even with the same power meter. The discrepancy here could be as big or even bigger than the difference between the OPs power meter and virtual power

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That’s a good suggestion, one of the main motivations behind my thinking is to give the CX bike a bit more use as it only really sees use for races (looking less and less likely this season), the occasional skills session and a bit of commutercross.

To me, this all depends on how you’ll use your CX bike outside. If you are doing power based workouts on it then you probably need your power meter. But if you are just riding around doing endurance/tempo outside then you really don’t need to stare at a power number as you should be able to do it by feel.


I have the same setup as you (VP indoors, power meter oudoors) and use a seperate FTP for each. I test the indoor value pretty regularly as that’s where I do most workouts where I’m concerned with staying in a narrow power range. It’s a fair bit higher (~20W) than my outdoor values, but it’s consistent enough for my purposes.

Outdoors my estimation is admittedly a little shakier, mostly because I usually can’t be bothered testing twice :wink: However, because most of my riding outdoors is endurance or longer race-specific work where I’m pretty dialed into PE, I find some combination of adjusting my indoor values down/extrapolating from harder rides plus a bit of fudge factor is usually sufficient.