Trainer Difficulty - That Question

Hi all,

Yes, that question again. But if you see the image below it shows all my recent races.
Notice how my stats (mainly wattage and w/kg) remain almost the same for every race apart from my most recent one tonight.

The difference to see me jump to 2.6w/kg and 208w power? Changed my trainer difficulty setting from default (50%) to about 25-30%.

I’m led to understand that trainer difficulty doesn’t make any difference to the power you have to put out, but makes hills “smaller” in the sense a 5% incline is relatively lower with the TD lower.

But my stat today - I imagine purely because of my TD alteration and not just a sterling effort - has impacted how fast I can compete.

Is it fundamentally “gaming the system” or is it more a case of the TD at 30% suits my style of riding and allows me pedal fast but easier?

First, understand that for the last race your FIT file has not been processed yet (see the green lightning bolt - it will turn blue when the high precision data has been processed). You can’t compare short duration or normalized power against previous efforts yet. The average power will probably stay about the same but many of the other numbers will change.

A better way to think about it is that lower TD makes it possible to do a steadier effort. In races this is a mixed bag - sometimes you really need to do less steady efforts (more reactive to gradient changes) to stay with the group, because most riders will delay shifting and increase power on short climbs. So lower TD can make it more challenging. But if you are the type of rider who can do higher average power by doing a more steady effort, lower TD can make that easier. It also makes it easier to keep the power on during descents, without shifting. On a route like London Classique, I would expect that lower TD would not make a huge difference since it’s not very lumpy.

Another thing - if you look at the progression of all of your power duration numbers, there is a pretty clear trend that you are getting better. Your heart rate numbers are all over the place so it’s hard to tell if you can use that to gauge how hard you were working, unless you’re confident in your HRM.


I just checked your race on ZwiftPower and your FIT file has been processed. Your normalized power went up compared to what you shared from before processing, and compared to other recent rides it’s elevated. That’s the opposite of what you would expect from lower trainer difficulty (you did a less steady effort). I would attribute this more to how your rode than your settings. I think you just had a good race. Perhaps you were also well recovered from previous efforts and motivated to hit it.

Have a look at your Category Enforcement data on your profile. Go to, My Feed, My Profile, and click on More Info. Look for power PRs from today.

Race-wise, felt similar to normal as far as effort and keeping in the front group.

Just seemed strange that the very first time I alter the trainer difficulty I then have my best performance (as far as those two figures).

I understood trainer difficulty had no impact on this so would have expected 2.4w/kg again, but maybe I just had a better race than normal, or a group that pushed me that little bit harder than sat taking extra breathers.

Will keep an eye on it. I certainly haven’t had a change of circumstance (eg same weight, no injury, same bike setup, same prep).

I did see someone do a video on 0%, 50% and 100% … he got roughly same time up a 100m incline, but said he felt more effort was given on 100% and much more tired.

Its one of those weird settings that, named “TD”, makes you wonder if you are gaming it a little. I guess not.

Will see how I fair over the next few races. May drop it back to 50% and then see if my stats drop along with it.

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You might also try trainer difficulty at 0% on a longer route with rolling hills to understand the effect of more steady pacing. Over a short distance, or on a mostly flat route, I doubt you would notice much difference.

usual argument: “watts is watts”

reality: someone who has to change gear less often and is in full control of where and when they exert their power, rather than the trainer forcing it upon them, is going to be exposed to less spikes in effort and therefore have higher average power output due to having a “smoother” ride.

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Yep, but the reality is that the gear combinations available on their cassette and chainring is going to affect that in the same way.

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Paul, does setting TD to 0% mimic a pan-flat course?

With ERG-mode engaged, I can definitely feel a change in the trainer’s resistance even for slight changes in gradient. If I’m doing a workout involving Z5, or above, I always dread hitting (even a slight) downhill since the trainer’s resistance increases. I don’t know if this effect is related to the trainer I’m using (Neo 2T) and/or the fact that I don’t generate much raw power so I’m quite sensitive to even small changes in gradient in trainer resistance.

Yes it means the game should never tell the trainer anything about incline. I have no way of measuring whether it works perfectly but it feels true to me.

That seems odd to me. I wouldn’t expect incline changes to be sent to the trainer if you’re in ERG mode. I don’t use ERG mode enough to have any experience to share about that phenomenon.

Thanks Paul. Yes, I don’t fully understand ERG mode TBH.

Most of the time, these slight variances in resistance based on course gradient changes don’t cause me a problem. I’ve got a feeling it’s something to do with the Neo 2T and how it responds to downhills. I need to do a bit of research. In the meantime, I’ll try setting TD to 0% next time and see if it helps :+1:

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You are correct @Paul_Southworth when in ERG Zwift don’t send incline data to the trainer.

I have experience the placebo effect in ERG when your mind expect a increase in resistance on a incline and you “feel” the resistance.

I have tested it using a different app to control the trainer but looking at the screen you “feel” the resistance change.


If your trainer is working properly, then the resistance that you feel in erg mode should be entirely independent of the terrain. Any sensation you get that downhill is hard (with my Neo 2T, I’ve had this doing intervals down the big hill at Innsbruck, too!) is purely psychosomatic, because your brain can’t reconcile the speed of the moving images with the amount of resistance that your legs are feeling. Try draping a sheet over your screen when you’re doing a workout in erg mode, and you won’t be able to feel anything other than the power being requested of your trainer.


Thanks Tim.

Funny thing is, I feel these changes in resistance when doing workouts on Tempus Fugit (which I know isn’t dead flat but it’s pretty close most of the time). In fact the last workout I did on Tempus I increased my TD to 50% and I could sense a difference (inclines felt ever so slightly harder and descents slightly easier, as you would expect in free-ride mode).

ERG seems to be working as it should. Did a workout yesterday and dual-recorded it (Neo versus Assiomas) and the difference was less than 1%.

I also came across this old thread (Resistance changes based on slope despite ERG mode).