I don’t do erg mode on ADZ and nor does my group.
I do erg mode only on fan flats or Tempus Fugit.
But I think this would be a great test to prove or disprove the theory since:
- You have a lot of experience on the alpe
- You’re passionate about this “ERG mode is easier” subject
- You have a pretty good sense of your best average power up the alpe (I mean: what you could do now)
So if you can set your ERG power to get a much better time than your actual best effort you’ll know how much easier it is, or if it’s just as hard - and we can see if the theory is sound. You can delete it off strava after sharing the data here etc.
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This got me pondering the pros and cons. If we ignore power dips from gear changes and pedalling in the wrong gear for a moment:
- it’s faster to push above average power uphill than it is to maintain a steady average power throughout. On the Alpe this translates to pushing above average on the steeper inclines and below average on the less steep bits
- different physiology means some lucky people can do this more than others without overcooking it and getting to the point that average power starts to drop
- some people are better at delivering steady power without ERG mode and avoiding short dips which cause speed to drop
In other words, I think it will be a personal thing:
- If you’ve got an extreme diesel engine where going over your FTP spells disaster, or you tend to get the pacing wrong, then ERG mode with a constant power target should be faster (if the boredom doesn’t get you)
- If you can cope with varying power and pace yourself well then sim mode (or ERG mode with adjustments as Tom suggests) should be faster.
- Gear changing will reduce the sim mode advantage though, and might make it slower depending on you/your trainer/TD setting.
TLDR version: It depends.
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I had one person in ERG mode at 3.9w/kg doing his “climb” up the ADZ and did notice on the flat hairpins he could catch me up a bit because his power wasn’t varying, while I had to quickly go up a few gears to keep my steady power.
Ultimately my overall lap power was was higher (I kept 4.2w/kg overall) so I eventually got away.
Where I’m not as efficient is on those gradual gradient changes - while the folks in workout mode riding at fixed power keep the one steady power output where mine dips while I’m getting the right gear.
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That all makes sense; it’s a trade-off, and it will be different for everyone.
I’m on a SB20 so the gear changes don’t affect me that much, and I think I’m fairly good at pacing myself, so doubt ERG mode would give a better/easier time.
But if you’re doing physical gear changes with trainer difficulty set high then it doesn’t surprise me that you could lose more than you can gain by modulating power based on gradient.
That’s correct, I have the trainer difficulty all the way up and do actual gear changes (using Kickr Bike). I’m still pretty good at pacing on there.
Send me a link to that Strava file, your height and weight for that ride and what bike you used. I can do a ERG workout up the Alpe. (Offline). Doing ±255w should be a 45 minute Z3 workout.
I’d be very curious to see the results to this.
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Me to. I would say free ride will be faster because of skill and using power where it makes the most difference.
One thing I’m wondering is how big of an advantage you would think ERG mode gives. So for instance, if right now your best time is 45:57 in sim mode what time do you think you could do with ERG mode?
My guess, since you’re seeing people ‘fly by’ you, is you’re thinking the advantage is substantial, like not just the ±2% you’d see with different trainers, but something really big.
So, what do you think the magnitude of the difference is?
I ask this because this week I did two Alpe rides (happy to post the data), I did the first in sim mode it averaged 203W up the alpe, unfortunately ERG mode does not allow me to set a 203W target, so I chose a 205W target for my ERG ride, and the ERG time was a bit faster. But I would expect it to be since it was on average 2W higher with myself using the same weight, height, and bike.
I could for instance do 205W for the first 10 switchbacks, then swap it to 200W for the second half of the ride for it to average closer to 203W, but the times were pretty close for the 203W-205W runs, so I just expect them to be even closer.
So I guess the question is… It sounds like you’re saying the advantage is huge, how much do you think we should see ERG beat out sim mode? If it’s just 2-4% then that’s really just the difference between 2 trainers that have a ±2% variability, and definitely not something to worry about.
interesting how much faster was it?
So, today’s ride (ERG mode) had my strava segment for the Alpe at 1:11:38 with an average power of 205W.
When I did a sim-mode ride it was 1:12:09 with an average power of 203W. I wasn’t trying to optimize this ride, just trying to average somewhere between 200-210W.
Perceived exertion was about the same.
I can try doing another ERG run to see if swapping it down to 200W after the 10th switchback would get me closer to 1:12:09 for ERG mode, my guess is it’s going to be close.
yeah, that is probably what you’d expect around 1% faster with around 1% higher average power.
maybe the answer to the question is it makes no difference? haha
One thing I could try is optimizing a sim-mode run (really pushing a lot harder on the steeper parts, and really relaxing on the corners). Then doing an ERG run with whatever that average power came out to… There might be a bigger difference if I did that maybe?
I think it might be more to do with what you do on the less steep bits, this is where sim mode can gain a lot of ground, maintaining speed around corners instead of dropping power and losing speed then having to try and build it up again going up the steeper parts
So let’s say I’m trying to average 203W for the whole alpe. If I were to try to best use those watts in sim mode would you drop watts around the corners yet keep an eye on the speed to make sure the speed stays consistent on them? Then go back and push a bit more after the corner? You would then do slightly less power on the corner, slightly more everywhere else, but not such a big drop on the corners that you drop your speed?
Do you think at that point normalized power might be something to look at as well?
Yeah, if I did it that way it would be good for sure. Not sure how to get that info though because intervals.icu gives me normalized for the whole ride, but not for a sub-section of the ride.
Edit: I don’t have strava premium, so i use intervals.
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Sure it does. Just create an interval for the sub-section and then make sure NP is one of the fields it shows for intervals. 
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The point of the post is to compare times up the alpe in ERG vs Sim.
I think those flying by is probably alot lighter and probably on “spesial” trainers like spinbikes with speedsensors.