This seems key to me. You are pointing to poor preparation for a demanding interval.
I would expect muscles without proper fuel and/or rest to “get tired” and be unable to meet workout demands, especially in longer intervals. It all sounds like A+B=C to me.
The basic nature of ERG and the fact that it will continue to hold a prescribed power target, even if you fatigue and slow your cadence, is a very different response compared to training in Resistance mode.
Resistance ends up with a “relief” for the rider when they slow their cadence, because the power is directly related to their pedaling cadence. Faster = harder, slower = easier.
ERG flips that on it’s head, and if we slow our cadence, we get more resistance slapped in our face vs the relief from RES above. This extra resistance, at a slowing cadence, tends to exacerbate the muscular demand and leads to a vicious circle called the “Death Spiral” in many cases.
You drop cadence from fatigue, trainer adds resistance (to hold power target), and you get beat up repeatedly until you hit the “clinch” where you can pedal no more because the trainer has clamped down far more than you can handle.
All else equal, and even in light of your fueling and rest issue, you are experiencing the demand of ERG mode use vs RES mode use. That extra “demand” from ERG is one reason some people like it (me) while many others hate it. ERG can be an unrelenting master and make workouts a bit more challenging, especially if you are not up to the particular workout on tap for the day.
That is the reason many like RES, is that then can quickly adapt by slowing cadence or shifting to an easier gear, to get some relief and maybe continue the workout at reduced effort.
The same is possible with ERG mode, if you use the TR Workout Intensity adjustment, to lower the workout power targets a few percent. So you can adapt with either mode, on the fly, the way you do it just differs a bit.
ERG mode contrasts to outdoor riding since you can shift and reduce intensity for say 15 seconds and still nail the power target of a 20 min interval, for workouts when tired seems better.
I however do love how ERG mode keeps you honest and obliges you to meet the power demand at all times, for me this extra demand is also appealing.
But if feeling a bit tired I would not recommend FTP intervals, either go out or reduce them to 90 to 95 % FTP.
Yeah, I think ERG has it’s uses, and can be leveraged even more once you know a few of the tricks (like using Workout Intensity to fine tune to meet your fitness on any given day… and you can increase as needed on those hero days, just like you can on the down days too.).
And as you mention, ERG is NOT like riding outside. I am fine with that and see this a more of a “workout” goal than aiming to replicate outside, at least when knocking out intervals.
I use ERG for most intervals in TR. I sometimes roll simulation mode in Zwift (which is more like Resistance mode) for my Endurance rides. Getting more “road like” feel in those cases and adding in the need to control my power are the reasons behind that.
Like many tools, I think using a blend is good, and picking based on your needs and preferences is beneficial.
There is also a psychological aspect to it. I find for the longer intervals (5+minutes) if I listen to 180 bpm music I can get lost in just listening to the music and my cadence tries to match the beat. Since I use erg mode the power hits the right target
Very true. That can sure play a part for any interval, the pain and discomfort mentally can kick us as hard or harder than physical at times. I focused on the muscular side from the related info, but head related issues are worth a look too.
I find that I too easily fall into the ERG spiral of death and strain muscles. I hadn’t used it in months until Tuesday’s ramp test. The new powermatch seemed to be more tolerant of a gradual step up rather than immediately ramping up the ERG resistance. I think I could get away with holding a 85rpm cadence to stay out of the ERG spiral of death; I was spinning 95-105rpm to avoid it.
This is a very interesting thread. My sense from using ERG mode is it helps (more than std mode) in pushing my own ability to hold a % of threshold out for a longer duration when on the real bike in the real world.
This is clearly a subjective experience so hard to back up other than to say this is how it feels for me.
I think there is a really interesting PhD thesis / experiment opportunity here …
Interesting theory. I have a friend who really struggles to keep his output up when doing outdoor training rides and I wouldn’t be surprised if this has a part to play in it.
My take is that Erg mode has helped me up my cadence and keep a smooth pedal stroke and this has helped me on outside rides, although that wasn’t the goal. Before doing a workout in Erg mode I do a 20/30 minute free workout starting at quite a low power output and let my cadence come up naturally without forcing it. When I’m pedalling easily at >90 I then start the workout proper in Erg and I’ve found my legs feel a lot better than going straight into the workout.
