Is the training effect on the turbo trainer lower?

It’s pretty common for a rider’s FTP to be lower on a turbo vs outdoors, for the same relative exertion.

Does this mean that the training effect / potential fitness gains are also lower?

I’ve tried to find some info on this online but can’t find anything. Does anyone know? Thanks!

I have not seen any studies on this. My FTP is the same, inside or out, but have friends who lower their FTP by a constant, something like 15W when they ride indoors. But if they train on the trainer, and gain 10W, they carry that gain to outside riding. The 15W difference is a (close) constant.

Also, many would argue that training effect is better. No interruptions on your intervals, no coasting, just pure efficient work on a trainer.

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If you are doing a lower effort on the trainer then your training impulse will be lower, it is that simple.

That said it becomes muddy as @afader noted, you can get a lot of quality in on the trainer. So you aren’t necessarily comparing apples with apples.

But if you can go to a hill and do say, 5 x 5 at 350w but only do 5 x 5 at 330w on the trainer, you get better bang for buck outside.

So like many things in life… it becomes a bit of a trade off, can you find a stretch of road or a hill that allows you to complete your work? If you can, go there. If you can’t use the trainer.

This study basically summarises what I’ve noted.

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I have not seen a meaningful difference between indoor and outdoor FTP, even with using my trainer as the power meter indoors and Assiomas outside. I don’t do FTP tests outdoors, but do long and hard enough efforts to have a good idea.
I think where a lot of the difference comes in is cooling/thermal issues. I think that many people underestimate the amount of airflow they need indoors, and this can be a real limiting factor. If you have poor cooling indoors and this limits your efforts, then I think you will see a lowered training effect, similar to if you only rode outside on really hot days and the heat limited your power output. If the ‘core’ body temp sensor goes mainstream (and is as accurate as claimed) we may be able to get more data on how much of an effect thermal issues are indoors.

For some efforts, I think that indoors will likely produce a better training effect, as it is much easier to have constant work for long periods of time. 2x45min at sweetspot? How many people can do those efforts outside without some breaks? Indoors there is nothing in the way. Obviously the amount of breaks matter, but I would be hard pressed to do those locally - I either have stop signs/lights, or non-trivial downhill sections. I doubt there is good data on how a few 30 second breaks in a 45 minute interval effect a training session, so things like that may not make a meaningful difference even if indoors seems ‘better’. I also have a hard time keeping a consistent ‘easy but not too easy’ pace outside, and I think the trainer offers a good option from a training stimulus there as well, but it is not as enjoyable as riding outside.

Agree, I was thinking when I wrote my post that long efforts are difficult outdoors.

Where I live I have access to climbs that are up to 25 mins at full gas (I’m bottom of cat 1 from a climbing perspective) and become longer as you ratchet the pace down, so I’m relatively privileged in that sense.

And yeah, if you are capable of getting the same effort out of yourself inside (I certainly can’t!) then you’ll get the same training response.

My own experiences as a lower watt rider tells me that cycling outside is generally harder, especially where steep climbs (>4%) are factored in. The concentration required in maintaining balance at low speeds, managing terrain, and heat all combine to make these efforts harder overall than an indoor threshold workout which is purely taxing to the muscles and cardiovascular system. The only thing I can think of that feels easier outside is the torque required to turn the cranks at low cadence. My Kickr feels incredibly heavy at RPMs lower than 65. But at the same time I’ve never worried of falling over due to low speed toe overlap when indoors.

Thanks, that’s really useful to seem some actual research on it. Guess I need to get myself a power meter!