ERG impossible but Resistance manageable

Hello everyone,

I did Mount Deborah today (7x3min @ 105-09% FTP w/ 4 minute rests btw intervals). I’ve been doing TR for about two years and I can just tell you I could never have finished that workout on ERG. My legs and lungs would’ve blown up. But lately, I’ve been using resistance mode and did so today as well. I found the workout vigorous but entirely manageable. In fact, it was (almost) fun. There was never a question of quitting, TR says I hit all the numbers and my HR never got above 86% MAX. So I’m just wondering if more seasoned riders can explain what’s happening and whether I should care.


I can finish a w’o in ERG but I’ve had to drop my FTP a bit to do so. With an ERG ramp I struggle to 250w (my last test was sub 230w) but in a non ERG 20mins test I can always do 250w+ and if I get my pacing right I can get an FTP of 280w :thinking:

Right. What’s up with that?

I have similar experiences. When I’m doing above threshold intervals, I often find resistance better, but not ‘easier’. My theory is this: when you are above threshold, if you drop below your target for say 5-10 sec, erg says you need to pedal harder so it ups the resistance. Instead of gettin that short ‘micro recovery’ you are forced to push harder, when you would have just brought it back up on your own. You end up getting a bunch of small ‘erg death spirals’ and they eventually catch up to you.

Another advantage of rest for supra-threshold is that if you just don’t have it that day you can push it at whatever you do have, say 97% without erg crushing you.


There’s a few possibilities here:

  • Your spin isn’t fast enough. If your legs and lungs are both burning that’s usually a good sign to me that I’m asking my legs to do more of the work. Grinding away rather than kicking and pulling a faster RPM over the top and around the bottom. If I spin too fast my HR will max out way before my legs give up. Changing to resistance mode might have put you in a gear that’s more comfortable and locked you in rather than erg that lets you pedal any and all speeds at the same wattage.

  • Your spin isn’t consistent enough. In erg, if your constantly speeding up and slowing down you’re fighting the resistance constantly.

  • Your trainer is wonky. Some trainers struggle at certain power outputs. They develop too much heat and then the brakes don’t work as well so they are constantly grabbing and releasing. That pushes you over target and under target over and over. Each of those over targets add up.

Could be something totally different, too but these have been my experience. :slight_smile:

  1. What test and trainer method did you use to establish your FTP?

  2. What bike gearing are you using in ERG vs Resistance?

It is not uncommon for people to have a different experience here when they use ERG in one gear range, while using something different in Resistance. In those cases, flywheel speed is playing at least some part in the mix. There is also a general difference in power around the circle for some riders between modes, and that can depend on cadence and overall smoothness.

Thanks for this, Chad. For my FTP, I used the TR ramp test on a Saris H3 trainer, the same outfit I have used for two years. In ERG, I use the small chainring and a steady cadence btw 95-100. In resistance, I use the large ring and a steady cadence of 90-92 for suprathreshold workouts like Mount Deborah and 85-90 for long interval sweet spot workouts.

FWIW, when I’m in resistance, my TR readings are much closer to the readings on my Garmin (within about 2%), whereas when I’m in ERG, my TR readings are about 10% lower than my Garmin. Also, and again FWIW, this is not the first workout where I have had this experience. Two days before I did Mount Deborah I did Buffalo -2, which would’ve been very tough in ERG but was entirely manageable in resistance. Basically, it’s as if my FTP in resistance is meaningfully higher than it is in ERG, which makes no sense to me. And if you’re wondering, I calibrate the trainer regularly.

Thanks again. Any wisdom would be most welcome.


Perhaps you have already explored this, but gear choice is critical when using ERG. The inertia from your trainer could be impeding your ability to complete the intervals as prescribed. Using the small ring for example could actually have the flywheel moving so slowly that you could literally be reaccelerating it with each pedal stroke. Your power could read in range but the instantaneous torque or pedal phase could be pre-fatiguing your muscles. If you aren’t already, ensure you are using ERG in an appropriate gear. I would recommend a nice straight chain line in the big ring. It tends to keep the flywheel from spinning so fast that catching between intervals is impossible and so slow it is like riding through peanut butter.

Have you tried Erg and large chainring? I’m on a Kickr (wheel off) and that’s the combo I use to better simulate riding outside.

  1. OK, you are using VERY different gearing between ERG and RES.
    • Small ring in ERG will give you less “help” keeping the flywheel spinning. I find it is more taxing on my legs than the same power in the big ring.
    • Big ring in RES is giving you more “help” in keeping the pedal stroke moving. Again, this is my experience and we have seen others report the exact opposite.
  • All that said, and in light of your comments, I think you are “getting help” while in RES mode that you are not in ERG, and that is why RES feels easier/better to you compared to ERG. That lower flywheel help in ERG can result in notable difference in RPE and fatigue over time, and particularly with harder effort intervals.
  1. Additionally, you tested with the Ramp test, but did not state the trainer mode or gearing used. [edit: I see you mentioned small ring for the test below, which aligns with my theory.]

    • My main reason for asking is that I feel it is very important for people to test in the same mode and gearing that they plan to use in most of their training. It’s fine and even good to mix it up in training for a range of reasons.

    • But because of the noted differences in modes and gearing, I think it is very worthwhile to test and train as similar as possible. So, if you test with one mode and gearing, and train with a different one, I think you are skewing results and outcome a bit, maybe enough to cause issues like you redescribe.

  2. You mention power accuracy via Garmin, but what exact power meter are you using for this comparison?

    • Regardless of that info above, it is a known issue that most trainers report higher power data values as the flywheel speed increases. This has been shown on the Hammer series in particular, where the faster gearing and flywheel speed report higher power data when compared to slower flywheel speed. So this also parallels your comments (assuming a reasonably accurate power meter in used for comparison).
    • This matters, because you are essentially getting “more help” with elevated power data when using a faster flywheel speed. Which means that this is the 2nd factor (after flywheel speed itself) that is making the RES mode and faster gearing “easier” on you.
  • Yes, that is essentially the core issue here. You are getting “double help” from the faster flywheel speed and elevated power data when in RES at the higher gearing. It is the core reason I recommend training and testing in the same mode and gearing.
  • Once we confirm your final test details, it is likely that you may have tested in one way, and effectively switched to training using another way. In essence, shifting the experience when compared to the FTP as derived using other modes and gearing.

Edit to add one question: Are you using the trainer for power data or a separate power meter?


Thanks, Sarah. This is a great suggestion. I take it this would apply when I’m taking the ramp test as well (which I also did in the small ring). I’m very grateful for this.



This is written backwards. His power in Garmin is consistent with RES in large chainring.

Might as well say something like triple help ffrom riding 18mph and elevated power data from using 50x15 gearing and elevated outdoor FTP.

I’d say Erg and little chainring is showing a penalty, for the reasons cited by @Sarah

Well, he just said he tested in the small ring:

  • So if he is now swapping to the large ring, regardless of the trainer mode and regardless of the data difference, he is essentially training at a different flywheel speed than he tested at. Again, in my experience, that leads to the faster gearing/flywheel speed feeling easier / more manageable to most riders.
  • Sure, you can call small ring a “penalty” if you start with your foundation built upon a big ring FTP test… but that is the opposite of what the OP did here (tested in the small ring, now training in the big ring).

This is fascinating. For the test (and for my training until recently), I always used the small ring. So until recently, I’ve gotten less “help,” as you describe it below. That means that by going to resistance mode, I actually switched two variables—mode and chainring—which apparently gave me a double, and artificial, boost. Who knew? As others have suggested, a possible compromise might be to switch only one variable—viz., stay in ERG but train in the big ring.

As for your other questions, I use a Garmin Edge 830, which provides a power reading. I also get power readings from TR.


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Yes, exactly: The Garmin readings are about 2% higher than the readings I get with the RES/ large chainring combination.


  • But is this connected to a different power meter (pedals, crank, etc.), or the same H3 trainer as you are using in TR?

If you are connected to the same trainer with both devices, there is “no power difference” other than the sampling and/or smoothing you have applied to TR or the Garmin.

  • Claiming a different power from the same power device (trainer) is like saying you are getting a different distance from a single tape measure because you are looking more through your left eye vs the right eye. It’s only different in how you read/display since the “tape measure” (power meter/trainer) is identical and shared.
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Sure, that is a fine idea. But do keep in mind that you have a difference from your “tested” gearing to your “training” gearing. So, as I said above, you may be best to take a new test in the preferred gearing and stick with that to see what happens.

ERag vs RES, I find the micro adjustment of ERG to be too much, when on the edge. RES feels easier to me in that scenario. Mostly because watts can go up and down and you don’t get continuous adjustments.

I see. Yes, it is connected to a different power meter, the crank. My Garmin is not connected to the H3 trainer.


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Yes, I think I’ll take a new ramp test in the big ring. Thanks to all who weighed in.




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