Ok, I found this other thread that seems to describe when I experienced this week. But it’s really old and I’m wondering if there’s some solution to what I experienced my last workout. (thread)
I had a very challenging VO2Max (for me) yesterday. The intervals were 5m long. After a couple of intervals, somewhere around the 4m mark I was lit. Took a lot of mental effort to keep the cadence up and it would drop if wasn’t on point.
Problem was with ERG, if it dropped below a certain point the force requirement would shoot up and if I let that push the cadence lower…it’d just spiral.
One that caught me enough to push down real low had me standing up in the saddle and literally mashing with all my might to keep them turning. The watt target was still in the ballpark, but the force to get the cranks going was so insane it was almost impossible to ramp back up to a decent cadence.
It’d be a lot more manageable if there was a cutoff where it went ahead and let the power drop off target. Then, at least, you’d be spinning at a decent cadence and could be like “oh, shit, need to pick it up to get the power target back”.
It really wasn’t that low before I felt to spiraling. Like maybe 60 or 50….on the lower end of what I’d expect on a very hard hill climb.
I might try dropping out and in if it’s easy to toggle. I do like ERG managing the force target in almost every other case since it removes one more thing for me to get distracted by.
Getting caught in a spiral of death simply means you can’t put out the required power. If you can’t maintain the required power at a reasonable cadence (80+) then slowing cadence won’t help. Maintain or increase cadence, and if you can’t, then decrease the intensity. That’s the beauty of ERG mode. It’s a merciless taskmaster. If you can’t cut it, it won’t let you cheat.
So power (P) is torque (τ) times watts (ω), P = τ * ω.
Say ERG has you at 300W target. You have to figure the angular velocity on the crank for a cadence /waves hands, but you’ll need like ~ 30 N torque or 173 N force on the pedals. And it increases non-linearly as your cadence drops.
For cadences of 80, 60, 30, 15, 5 it jumps up to ~200, ~275, ~550, ~1100, and ~3300 Newtons respectively.
The system that controls how much force you can dole out is almost entirely muscular strength. And there’s an upper limit to that that’s totally unrelated to your cardio.
The spiral is if you get do get tired or distracted for a moment, you can dip under the threshold of your muscular strength. And then even if you had the cardio fitness to be like “oh shit, I dropped the ball for a second there” and spin back up…you can’t. Because it’s shifted to a strength problem.
So I get the intent of ERG to hold it consistent, but it if you do drop without some kind of limit on the force scaling you can jump 1000’s of Newtons. And what would have been a momentary lapse of a few seconds kills the whole interval. Which seems counter productive.
Seems like a lot of extra stress, rather than just turning off erg mode and trying to stay at or above the target watts for VO2 workouts (which you’ll have to do in ERG mode, anyway).
The accelerations required to get out of the low-cadence spiral can be super draining too. Yesterday I did a workout in Erg mode (KICKR) on a bike with a spider PM, and recorded power from PM as I wanted to check calibration of the KICKR. During harder intervals I noticed that dropping cadence then punching back up to 90+ really spiked power output, and resulting average and NP for those intervals ended up ~5-10% higher than expected target power. If you have erg smoothing enabled you generally won’t see these differences, it all gets lost in the smoothing.
TL;DR-keeping it smooth and steady not only feels easier, it probably IS easier in terms of power.
By looking at the full workout, I can see that the first interval went awesome, the second one you struggled a bit, and the third one you struggled the most to keep the power target.
So I think you’re getting good workarounds from others already:
