Low cadence and abrupt loss of power?

I did Whiteleaf +1 a few days ago. I finished the workout but I had two issues. The first is I had to drop my cadence down to 40 or 50 rpm to be able to finish the interval. I usually started the interval at 95-100rpm and by the end of the hard start I am down to 80rpm. As I continue with rest of the interval at the lower wattage my cadence would drop down to 40-50 rpm and a couple of them I had to stand to finish the interval. With 3 to go I got through the hard start and almost immediately had to stand to keep going on the lower wattage. All of a sudden I could not push the pedal down and came to a stop. The trainer ergometer stopped and pedaling was super easy and as I got back up to 80rpm the ergometer mode kicked in and I was able to pedal by getting way back on my seat and pushing the pedal over the top like I was doing single leg leg presses on a weight machine with each pedal stroke. I kept that up for about 2 minutes and around 25prm. I recovered during the rest interval and finished the last 2 sets without having to stand or do the leg press impression.

Has this ever happened to anyone else? I didn’t cramp up and I had no idea I was not going to be able pedal. Willing to add weight workouts to my training if recommended. Any comments would be appreciated.

Yes. Totally normal. In ERG mode, pedaling slower and slower and the resistance going up and up as a result is known as ā€œthe spiral of deathā€. The key to preventing this is to hold cadence at a maintainable level (50+ rpm) so that the resistance does not continue to increase. If you can’t hold a reasonable cadence, then lower the ERG power so that you can, or switch ERG mode off. The resistance totally going away when you got to very low cadence is normal behavior for many trainers. The assumption is the rider was caught in a ā€˜spiral of death’ and the resistance is cut to allow them to return to a normal cadence at which time resistance is applied to achieve the ERG power. For further explanation google (or AI) ā€œtrainer spiral of death.ā€

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Can you clarify what you meant by ā€œhad to drop your cadenceā€?

You couldn’t spin at the target power? Or the resistance fell away and your power overshot?

In erg mode you should be able to maintain any cadence of your choosing. But being at 50rpm on a threshold set is very low. TR advises 90-100!

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Not sure that this has anything to do with what you are experiencing but I’m tacking it on here in case there’s some connection. I always find that if I let my cadence get below 54rpm the kickr bike will ā€œlet goā€ and suddenly free wheel. I have to keep spinning and wait for erg mode to kick back in and get me back up to the designated watts. Drives me crazy. I’ve tried changing the gearing (suggested elsewhere) but it doesn’t change anything.

I find that as I get tired my cadence drops. Especially in erg mode and hard sweet spot or threshold.

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Same here and it’s that muscular fatigue that causes my cadence to drop that is my limiter. I think it’s really a sign that you’re ā€œfailingā€ the workout at that power and you should drop the power down, erg or otherwise, to what you can do to finish the interval. And respond truthfully in the post workout survey as you probably need a workout that’s a touch easier. Dropping from 85rpm to 70 rpm for the last minute or so is fine.

To clarify, I was fatguing and my cadence was slowing so I stood to pedal. Standing helped for maybe 5-10 revolutions and at the top of a downward stroke it was as I was standing on top of a brick wall! Even pulling down with my arms and locking my knee would not move the pedal. I sat and relaxed my legs and erg mode shut off and I brought the cadence above 80rpm and erg mode resumed. I finished the interval by remaining seated and placing my sitz bones behind the wings of my saddle and pushing as hard as I could when the pedal was at the 10:00 position to the 2:00 position. I did that for at least a minute before the interval ended and started the recovery interval which was 2 minutes long. I finished the last 2 hard intervals seated.

If you have ever started up a hill in too hard a gear and stood to keep pedaling but the gear was too big and the pedals stopped, it was kinda of like that except the pedal stopped much faster on the trainer than I’ve experienced outside.

After reading what others wrote here, my theory is my cadence slowed too much for erg mode to operate properly and before it turned off the motor froze momentarily before erg mode shut off.

I could maintain the wattage at 50-60 rpm, but not at 70 or 80. And as Bryan pointed out that is probably an indication that the interval was too hard! I was doing my best not to give up!

I experience cadence drops when an interval is at the right difficulty, but that’s only from 90 → 80 or so.

Cadence drops with fatigue are normal, but dropping to 50 is really low. Based on that I would agree with Brian that the interval is too hard for your current level of fitness.

If you haven’t already I’d recommend doing either a ramp test or a 20 min FTP test. I suspect that your FTP is set quite high. Don’t be discouraged if it drops 20W (or more). You’ll get better training by completing workouts at a lower intensity than by failing ones which are out of reach!

You may also need to calibrate the turbo. I’ve had issues in the past where i calibrated the turbo on a cold morning and the resistance at a given measured power was ridiculous.

I was in your position when I started training (although that was in Zwift). A friend gave me essentially the advice above - my FTP was about 40W lower than it was set in app. My training was much more productive after a hard reset.

Hope the training goes well - let us know how it goes!

Oh, absolutely. I get this too. If my cadence drops as far as 80 I know I’m struggling.

I wanted to understand if it was equipment or fitness causing such a large scale drop.

Before you start adjusting the target power, I’d recommend at least trying a couple of workouts in Resistance mode.

If you’re getting tired, that ā€˜sucking at the heels’ feeling as your cadence naturally drops but the torque goes up can really exponentially affect your RPE.

I’d rather complete an interval at 5 watts below target average power at a reasonable cadence than either fail it or slog through it. My legs would know the difference the next day!

Nice convo already going, but wanted to add the following article that may be helpful:

Erg Mode Explained

I prefer to not use erg mode especially for intervals…if you are failing I suggest lowering required watts/time and stopping when hard fail as you can’t complete the session you won’t get any benefits from trying to continue and likely you will feel discouraged.

I don’t use erg at all any more. I prefer to vary my cadence from 65 to 130 rpms on intervals and shorter non interval runs…I’m on a Kickr v5/Zwift for my intervals at this time of year in Northern NY…it is 34f right now lol.

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Thanks! I read the article. Definitely explains what happened to me.

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I understand about not wanting to use erg mode. At this point, I plan to continue using erg just to make sure I reach my power numbers. Yesterday, I completed English +2 and actually felt good. I knew I was going to complete the workout and my cadence stayed around 85rpm for all the hard intervals and I never stood. The hardest intervals were 264w for 70sec 40sec at 84w and repeat.

Whiteleaf was 264w for 60 sec then 185w for 120sec. It is my opinion that longer sustained intervals are my weakness.

I live in Ithaca, NY, mvmadore. And you?

Just outside Watertown

123 miles further North!