Same for me… If I have to hold 320W for 20’ on the TT bike outdoors I’ll likely crash out before I finish the interval… Being cross-eyed with lactate coming out of your ears and eyeballs, doesn’t help with noticing pot holes and so on
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Digging up this old thread which is fascinating but sadly inconclusive. I particularly appreciate the lactate testing, as it sometimes feels like we outdoor-dominant riders are being gaslit by the folks who claim we just need more fans or mental fortitude.
Here are two tests that I hope someone who is experiencing less power output indoors will be able to run to shed some more light on this issue:
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Use their trainer outdoors in very low temps, such as <30F. This should immediately prove or dispel the temperature hypothesis. (Happily I do not live somewhere where it gets cold enough to try this.)
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Use a system such as the e-flex motion or rocker plates to add movement to the trainer experience. I have my doubts about this as I’m pretty sure the marketing copy for these products would be full of claims such as “boost FTP by 10%!” if there were even a modicum of reality to this line of thinking. But I don’t know what the difference could be if it’s not either muscle recruitment or temperature. (I will probably eventually break down and run this test myself.)
And lastly, one more reason I don’t think it’s down to temperature is that my outdoor FTP doesn’t seem to care if it’s 40F (as long as I’m wearing throat protection) or 100F (so long as I’m acclimated), and I produce my best numbers on climbs where I’m getting all of 8mph of relative windspeed.
- It’s not gaslighting when it DOES actually help some riders. The fact that it isn’t the solution for you does not invalidate it for others where it clearly does work. The implication related to that loaded term is overblown IMO.
- I have not bothered to do a hard numbers comparison, but I can guarantee you that turning off my fans for a hard workout would lead to really poor performance for me, period… compared to inside or outside.
The issue here (like anything in our training world) is that no one feature or option is right or perfect for everyone.
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Cooling in particular is a legit issue for many, but we clearly see that despite the best efforts of some it is not the cure to their power delta.
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With respect to motion, I have not bothered to do structured testing with / without because I know that the comfort side that motion provides for me is superior to rigid. I have some gut instinct to what it does for me related to power (neutral in regular pedaling, better for over Threshold standing efforts up to sprinting) that mean I will never go to rigid. But I also have seen enough here to know that others have very different results.
I get the idea behind your tests, but without a relatively large sample size, N=1 testing won’t likely shed much better light than what’s already shared above. What works for some won’t work for others. We have some likely contributors, but those are not absolute.
For those that have applied all the suggestions and still fall short, I am not sure what else to mention. I do think that some riders may be having issues with the trainer and related flywheel effect. Even some of the best setups seem to be lacking compared to real riding outside, which I think could be a real factor for at least some riders.
Someone more adept at physics analysis could likely run some numbers to see what we actually get from some of the leading trainers in various gear combos. Then contrast that from some use cases of riders at various speeds and road grades. From the mentions I’ve seen by people who have looked at calculations like that, most trainers fall short in really mimicking what at least some riders get outside.
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I was reading there was a discrepancy with data after users did a firmware update on P1 Pedals. Either the left or right pedal were having trouble keeping a consistent connectivity. giving the rider inconsistent data, this was some time ago and since were discontinued.
I think this is the most important thing why there is a difference in indoor vs outdoor ftp for some riders. (for me at least). For me, everything above FTP is lower in power then outdoors. The flywheel (virtual or fixed) used on those trainers creates for me some extra fatigue in some muscles to get over the full pedal stroke to overcome the inertia. Maybe it is due to pedaling technique, position, I don’t know. But the difference in inertia definitely plays a role in indoor riding.
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Agree 100%
And that also explains why is for somene who is used to trainer is even “easier” inside…
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the thing you’re missing is referring to temp, and although temp is a factor the issue indoors is airflow. temp is a factor, but airflow is what helps to dissipate the heat your body generates. I use 4 fans and my power is virtually the same indoor vs outdoors. no one is gaslighting, airflow is a very real thing and a lot of folks don’t have adequate airflow
Yes, airflow is more important than temp… but i think that inertia is the biggest factor. Same as if you are not adopted to riding uphill or into the headwind… HR and RPE would be different for the same watts
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The additional factor related to the flywheel is trainer mode. From all the discussion here, I expect that ERG vs Resistance vs Standard vs Level vs Simulation plays a part too.
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It may also impact riders differently between steady state efforts and power jumps but I bet it is another piece to the puzzle.
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For those aiming to get closer to their outside power, I’d suggest a basic test using Zwift, Rouvy or other apps in their Simulation mode and aiming to follow a workout as if they were outside. I don’t have any info on whether the Simulation modes differ between apps, but that could be another level of delta here.
True I think. As I said I am in the lower ballpark, because of ‘bad’ muscle usage to overcome trainer inertia? Also, in ERG, I really suck. ERG at FTP is almost impossible for me…
An important element when testing & comparing ERG feel to other modes is gearing used. A lot of the comparisons I have seen did not aim to match gearing in ERG to whatever other mode they used. Without matching that, the flywheel speed becomes a second variable on top of the mode and obscures the real differences between what a rider feels.
For me inclines (to a point), tailwinds, and higher drag tires seem to seem to make it easier to push bigger watts at lower RPE. Likewise, headwinds, flat roads, super low drag tires (think GP 5000’s) and trainers have the opposite effect. To be fair, I haven’t really tested ERG vs simulation vs ?? in depth, but I have yet to make the same power at the same RPE on a trainer.
That said, I think the more you ride a trainer, the less it seems to reduce power.
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Ok, sorry, on the internet it’s hard to read intent, but I didn’t mean that to carry a particularly serious connotation. It’s just the knee-jerk response I see posted everywhere whenever this question comes up. And yes, obviously if you have no fans whatsoever or you’re in a hot room your numbers are going to suffer. But there’s clearly a limit to how much cooling or airflow will help, and for many/most, sufficient fans will not close the gap to 0.
I wouldn’t ask you or anyone else to sacrifice their taint for science, but surely someone has run this experiment out of intellectual curiosity or a commercial interest. That this data hasn’t been announced and/or widely distributed suggests a publication bias (i.e. a negative result is not very interesting).
(And FWIW, there are plenty of kinds of motion that spare the taint but fail to replicate outdoor cycling which, I suppose, recruits different/additional muscles.)
The temperature and airflow are both relevant, obviously, unless you think a hair dryer would be a good tool for body temperature management during indoor workouts. But since you insist, we can modify this hypothetical experiment to be held on a day that is both cold and windy (i.e. most days in the winter in the midwest).
It’s one factor. The other bits are are you are almost completely dedicated to pedaling inside, whereas outside a significant portion of your output is going into stabilizing muscles, especially in gusty winds and rough surfaces.
My heart rate is easily 10 BPM lower for a given power inside vs out
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All of this might have been said before, forgive me for not reading the entire thread.
It’s definitely been done. Lots of general science studies (not necessarily in the context of sport) were done back in the late 1900’s (lol… 80s & 90’s) which showed effects of cooling on HR, lactate, work output, etc., so that might be why it seems like not much has been done recently. Maybe the effect is so well known that it hasn’t been worth studying recently? I don’t even have a ‘definitive study’ on effects of cooling in my head. When we reference lab testing methods, we don’t use any citations for fan cooling… it’s just presumed as a required part of setup.
Seems like from the few more recent studies I have at hand that individual responses are almost universally positive with added cooling, but variable in magnitude. Some respond with large effects, some negligible, but few get worse, suggesting at least that cooling has a very reliable effect.
To your point, cooling can explain some, but not all of the difference between indoor & outdoor settings, and some athletes it will have larger, and in some smaller effects. No gaslighting or mal-intent necessary. A reliable group mean effect doesn’t mean that every individual will observe the same effect.
Here are some pretty pictures of individual responses.
During 40-min submaximal target 70% HR cycling session, energy expenditure & total external work are increased with fan cooling. https://doi.org/10.1080/02701367.2021.1946467
In a small study of 7 cyclists completing 20-km TT, power output was increased and TT time decreased for most participants, but by variable amounts.
In a workplace/occupational study of 135 min arm cycling at fixed HR 110 bpm, still air cooling (air conditioning) or hot air fan conditions improved workoutput similarly compared to hot still air, with a trend for greater improvements in the AC condition.
As others have said, the biomechanical differences indoor stationary trainer vs outdoor dynamic, are probably under-appreciated and IMO way more interesting to consider! Cadence, stabilisation, muscle recruitment, attention & focus, inertia, resistance variability, etc.
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Thanks for the references. I agree that studying motion would be interesting. That is the “science” (scare quotes because case studies are probably the best we can hope for) I was referring to. Hence the potential for commercial interest – from those selling movement devices.
FWIW I have engineered myself enough movement to spare my undercarriage, but it’s not the kind of movement that simulates outdoor riding, at least aesthetically. The fact that these two movement related goals both exist seems to interfere with the ability to discuss one of the goals in isolation (eliminating physiological discrepancies between training modalities).
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Thanks. What do you mean by ‘movement devices’? Like rollers? More than only case studies for that. Strong personal recommend for rollers with resistance if reproducing more ‘road-like’ movement/recruitment patterns, and preserving perineal integrity indoors is of interest 
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If this is regarding a Kinetic Rock n Roll trainer vs a rigid trainer, I did a little bit as my Rock n Roll was out of action for a month or 2. I don’t recall seeing any significant reduction in power when using a Kinetic Road Machine.
*I am one that produces more power indoors for any given heart rate.
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What you call knee-jerk I consider a practical starting point. In troubleshooting (which most of these “Why is my power inside so much lower than outside?” questions really are in essence…) you have to start somewhere. Most of the time we get a simple statement with little or no supplemental info from the poster about their setup.
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Just like when someone calls tech support about their PC not working, a starting question of “Is it plugged in?” is necessary unless the caller already gave us that info. The fan question is that starting point in my process for helping unless someone clearly covers it from the start. It’s about covering the many variables in total, but I start with that since it is common that people have insufficient cooling and it is reasonably considered one of the largest factors of those to consider.
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So starting there makes sense and anyone with depth of knowledge will move beyond that once it is ruled out or addressed.
- I have published a video of my use with a saddle pressure mapper showing rigid and multiple levels of stiffness in a rocker. That is the only public info I have seen about motion and saddle pressure. I have heard from more than one maker about their internal testing the correlates with my testing results.
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Sure, you can take that absence as a negative but per above, I have heard that others see the benefits in data. I have no idea why they have not published it, but I don’t take the absence as something hinting that these don’t work.
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And regardless of any testing I or others have done, the proof is in the pudding… when we see countless comments from many that implemented motion and found comfort there vs rigid. Not everyone gets that, but I’d wager the adopters are over 50% of those that give it a shot.
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Sure, there are two possible goals here and they are not necessarily linked. Comfort can happen even with “backwards timing” as seen in many rocker plate videos. But when you get proper timing and use like I and others have, I believe that is a “better” solution than rigid. There is NOTHING natural or realistic about locking a bike in a vertical plane.
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I’d love it if some university or other group would take on the topic of motion vs rigid indoor cycling from comfort and power production standpoints. It’s of keen interest to me but I sure don’t have the time or tools to make that happen.
Off the top of my head, here is a quick list of some of the variables that I cover in these questions:
- Cooling
- Bike Fit Setup (same or different)
- Power Data Measurements Devices (same or different)
- Trainer Flywheel vs Typical Outside Riding Speed / Inertia
- Motivation via App and/or Distraction
- Rigid vs Motion
- Fueling & Hydration
Yes I suppose rollers are the og movement devices, but I was thinking of rocker plates and other devices that work with a smart trainer. I am not able to find studies that compare rollers to stationary trainers either though.