Hey Guys!
I have been using trainer road for 2 months now, and I love it. I’m starting pedalling after a 1.5 year stop and I can see already some interesting results.
Over the last weeks I managed to squeeze in my schedule several outside rides, and looking at the data of my powermeters (I use assioma outside and the indoor trainer inside) I notice how I can push considerably higher watts outside.
Is this something happening to some of you too??
(I have checked my assioma during a few indoor sessions and the watts reading are correct.)
Very common out doors you benefit from things like air cooling, inertia and power may be more deliverable up an actual slope and there tons of other variables I can’t think of at the moment, The only thing I can do more powerful indoors is a long threshold session where I cab close my eyes and get everything out but a lot of folk can still do that better outside.
This is very common. There are a few factors in play - being able to move outside vs. on the trainer, sometimes your fit is better when you’re rolling and can adjust; cooling is the big one. Air flow over you outside at 20mph is substantially more than even the best fan will give you.
I’ve seen huge discrepancies and smaller discrepancies. You can train it down. During the hottest times of year, I would often see a 20-25W difference between what I could do at threshold in my garage on the trainer vs out on the road (like 280 vs 305W for 3x20) was not uncommon for me. I see it in most of my athletes as well, to varying degrees.
Alot of the differance will be different measurement methods, your trainer will measure after draivetrain losses but outisde your pedals will meaure before this. Depending on the state of your drivetrain this could be 10-20w.
Like others are saying, air flow plays a huge factor and so does mental strength. I’ll go a bit further with air flow. If your outdoor power is 10-15% higher, you’re not doing it right, you just need the proper fans or you need to adjust mentally for indoor riding. Micro breaks and other stuff like that can make it feel easier outside, while the trainer is relentless.
For me it’s also about moving. Seeing things whizzing past at 36-40kph (or faster if I do the interval on a slight downgrade. ), or watching things at sea level getting further away if I’m doing it on a climb. It gives me a rush. I enjoy it more, I feel better, I can ride harder. Compare this to zero movement on a trainer, stuck in a room.
There is no reason to believe one is similar to another.
Use your assioma indoors and a power match or link capability so that your trainer reports the same values and your pedals and then you are getting comparable data.
You can establish the difference through testing, but it may vary by different amounts at different power levels, talk to your trainer provider support if you want to go there.
As other athletes already said, this issue is very common!
Ensuring you’re well-cooled while training indoors is key. My power indoors and outdoors for a given rate of perceived exertion is nearly identical when I have good cooling – when I don’t, that gap can open up wide.
Something like an air mover/blower (industrial strength) fan helps me a lot. Some athletes even like to use multiple fans if they are heavy sweaters/overheat easily.
It’s also worth noting that you mentioned using a power meter on your bike, and then the separate power meter on your trainer. It’s possible that the meters read differently from one another, which could also be contributing to the power discrepancy you’re seeing here. If you use the same bike that has a power meter on your indoor trainer, I think it would be worth ensuring that PowerMatch is enabled so you’re at least using the same power meter both indoors and out.
Ambient temps help a lot also. If you can (e.g. portable AC or extra window unit), cooling the room to < 65F is ideal. I do my long Z2 rides around 250-270 and I don’t think I could even train inside at that heat generation without really going crazy on temp/air flow/humid control, ymmv.
Also, there are industrial blowers sold to consumers and there are industrial blowers. You want the latter.
I know it seems like a whole big thing but…if you are capped by 10% or more due to heat are you even training. Do you even lift, bro? ect
I have the same issue every year when i switch from outdoor to indoor…
A lot has to do with temperature and airflow. With these condition (24-25C indoor), I heat up pretty quickly and my power drops 5-10%.
Also getting used to the trainer takes 3-4 weeks (for me).
Usually after 5-6 weeks (later in the fall when temperatures drop to 14-18C), My indoor FTP will match the outdoor FTP that I had during summer.
A friend of me trains the whole year out and indoor (als with heat), he has no difference in power…
I think (for me) it’s a combo of temperature and just getting used to the trainer…
), or watching things at sea level getting further away if I’m doing it on a climb. It gives me a rush. I enjoy it more, I feel better, I can ride harder. Compare this to zero movement on a trainer, stuck in a room. 
