You are fatigued toward the end of the workout, your cadence falls below 80 and it feels like you are pulling an anchor through wet georgia clay?
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It canāt kill you if you turn it off.
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See point (2) in list:
Not sure why but for me it is natural tendency to increase cadence when getting fatigued. Of course, this is also unsustainable for too long (slowly creeping into VO2max territory) but at least it is not as abrupt as with ERG lockdown.
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Some trainers have firmware updates that let you more gracefully exit the ERG death spiral. You can also stab the brakes to spike your torque and trick the trainer into letting up a little briefly (I should add that only applies if you have a full trainer, not just a rear wheel trainer).
But in the end, the trainers are doing whatās being asked of it, youāre just not holding up your end of the bargain by not producing enough torque for the given RPMs. 
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This sounds like quite a common experience which people love to use stabbing the daggers into ERG mode.
I use a Tacx Neo 2T and there is no death spiral, I find it very fluid, smooth and very natural. You can either hold Watts or you canāt. ERG just doesnt let you wuss out
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I have an H3 and Saris hasnt had an update in sometime. I know I can turn it off and often do. I just wish the entire death spiral thing could get figured out because honestly 200 watts at 70rpm feels alot harder than 200 watts at 90rpm and it shouldnt.
Only if youāre tired. I naturally settle at about 85rpm if Iām doing 200watts (high tempo for me).
If Iām feeling good and drop to 70rpm it feels easier than 85rpm. At the very least for the next 5 or 10 minutes.
Could be a trainer specific thing too.
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Also have an H3 its supposedly one of the trainers with āthe best ERG modeā not sure what thats based on accuracy or what. I do struggle with getting into low RPM death spirals though so have pretty much fully transitioned to using Standard mode and shifting or increasing the resistance. It seems I can run ~20 rpm higher avg cadence in Standard mode compared to ERG mode and often exceed the power target. I miss ERG mode for being able to not have to focus so much on if Iām hitting the power target or not but was often getting <60 cadence when tired/fatigued, whereas with Standard Mode I might have to fish around a bit with the gears but can usually keep the cadence in high 70s or 80s even when tired/fatigued.
I started out only doing ERG mode when I started riding in 2022 but as my FTP went up or maybe got more accurate I went from being able to āfanā the pedals in intervals at 100-120 rpm to grinding in 60-80 rpm transitioning being sitting and standing. Using standard mode however, my power is all spiky but I can beat the power targets for >4.0 PL Z2, SS and VO2 workouts at present with an avg cadence in the 80s, so it doesnāt seem like a āFTP is set too high thingā. Something about my riding seems to make me vulnerable to slipping into a death spiral and getting stuck in there in ERG mode now though.
Partially sounds to me like Erg is doing exactly what itās supposed to. Power is force * velocity. You drop the cadence, you have to increase the pedal force to keep power the same. If you donāt like it, turn it off and just let your cadence and power drop when you get tired.
Another TacX Neo 2T User here. Yes pedal force goes up when cadence drops, but Iāve never found it unnatural or inappropriateā¦ But, there is also the element of what gear youāre in, and trainer flywheel speed. Lower (easier) gear translates to lower flywheel speed, and the trainer will correct on you faster - i.e. less momentum. You can try a higher / faster gear and see if that helps.
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On ERG mode consider power as equal to torque x cadence. At lower cadence torque increases; at higher cadence torque decreases; your power remains the same whichever way you go. More torque means more muscular stress so you will find it easier on your legs to increase cadence and reduce the amount of resistance you have to pedal against.
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Accuracy is fine, but not the reason for it being touted as a good ERG option. The trainer flywheel and resistance adjustment system are matched to each other and perform well in holding a power target as while also giving good āroad feelā from the flywheel (heaviest of any trainer I know).
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That said, this and any other ERG mode use relies on the rider to maintain a relatively steady cadence. Unsteady cadence causes the trainer to adjust resistance aiming to hold the power target. The case above where fatigue sets in and a rider slows their cadence (which drops power) forces the trainer to increases resistance and the death spiral startsā¦
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Are you using essentially the same gear between modes?
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If you use a notably different gearing, the flywheel speed (and associated impact on the rider) will differ. Larger differences mean the load on the rider is a variable in the mix in addition to the mode difference.
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Many people miss the gearing aspect and attribute issues to trainer mode when I really think the core issue is differences from the flywheel speed and associated load on the muscles to get the pedals around. ERG mode doesnāt act fast enough to change resistance in ways that most people can feel once you match gearing for a given power and cadence.
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- That is true regardless of the trainer mode. That is power calculation plain and simple.
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Again, this is the same basic load on the body no matter which mode is used.
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The key difference and why ERG can lead to issues for people is that is āpunishesā people as fatigue sets in by tacking on resistance to hold power when they drop cadence. This is part of why ERG gets called āharderā than other modes at times.
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Other modes effectively ārewardā a rider as their cadence drops by giving less resistance. It gives relief in short or long term (depends on what the rider does around that time) and is āeasierā in a way because of that aspect.
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Itās all relative. 200 watts demand is exactly that. The difference in RPE and actual physiological demand of doing that at 70rpm vs 90rpm is the same not matter which mode is in use.
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The differences come from how and when each of those cadences comes into the workout.
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It also matters related to a personās training history relative to that power level and those cadences. Someone who is more of a spinner, but slips into those lower cadence ranges (especially if itās a result of fatigue) sure could struggle since itās not familiar to them.
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We tend to get good at what we train, so including low cadence work at similar power levels to our higher, preferred cadence are potentially worthwhile. Much depends on the actual needs a person has outside of training, but I find that a lot of people could benefit from stretching their functional cadence range up and down.
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In erg my Kickr v3 starts feeling āmuddyā at lower cadences.
Now here is an interesting way to look at itā¦
200W steady effort:
- 90rpm is 21.2 Nm average torque on pedals
- 70rpm is 27.3 Nm average torque
torque is ~28% higher at 70rpm
From a torque point of view (force on pedals), what 90rpm power is equivalent to 200W at 70rpm?
258W (= 200 * 90 / 70)
So if you are sensitive to feeling the force on pedals, 200W at 70rpm should feel roughly like pushing 258W at 90rpm.
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Iām honestly more curious about whether or not the data supports one setting over another. Do people who train on ERG, as an average, see a better return on their workouts?
My assumption is yes, because it forces more adherence to the workout. That said, I use ERG because I am lazy and donāt want to shift. 
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Iāve yet to see or hear of a study comparing trainer modes and related effectiveness.
Plenty of N=1 anecdotes in the short term but nothing that I consider worthwhile for broad conclusions.
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I also have an H3. About a month ago I switched to standard mode for all my workouts. It just feels more natural to me. And looking back at all the standard mode workouts Iāve done (z2, vo2, thresh, anaerobic) I am either right on or just over the power target for every single interval.
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No! You must never turn it off. It is a battle to the death. Surrender is too horrible to contemplate.
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You can take it or leave it, but I have consistently seen better results when training outside or mixing indoor and outdoor. My first thought is that most people (myself included) overthink the value of precisely hitting targets in erg. However where I live on a 2 hour ride there is only a handful of minutes where Iām stopped at a traffic light, or coasting.
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