Confused about ERG mode, candence, and effort

(Greg) #1

I am new to the Zwift community and have started doing the 4 week FTP booster training program, which always uses ERG mode. I’m not sure I’m “using” it right, and am having a few problems. I understand the trainer is supposed to change resistance for me and I’m not supposed to change gears.

No matter what, I can never seem to keep the cadence that Zwift wants. On my screen is a constant “spin faster” or “spin slower”.

In sprint efforts, I don’t see how it’s possible to generate the power Zwift wants while keeping cadence roughly the same. For example, if I have to try and put down 500w at 100rpm for 30 seconds, I’m finding it impossible. I can only generate that much power if I am spinning at 120-150rpm (basically as fast as I can possibly go) and still am coming up short in power. The “spin slower” alert flashes the whole time.

I can change gears and get up to power easily, but then my cadence is too low and I get a “spin faster” alert. If I spin faster and use more effort, then my power is way too high and I get a “reduce power” alert.

Is there a way to do this better? I’m finding I’m getting exhausted just chasing the cadence numbers and it is an annoying distraction. I have an older style triple chainring up front and I typically start my workout with it in the middle and halfway through my gears in the rear just so the chainline is roughly straight. Should I be starting in my big chainring instead?

(Cycleops Magnus trainer, FYI.)

(Bob Rumohr) #2

Gear doesn’t really matter. Use big ring with smaller rear cog combo that provides a straight chain to minimize wear.

Be sure your FTP is set correctly in the UI.


ERG Mode

(Lin) #3

Are you doing a calibration before each ride?

When you pair your trainer to Zwift, are you pairing it as both the power and controllable trainer? While both are important, the latter is necessary if you want ERG mode to work as expected.

When ERG is working properly, your gearing will not matter. Zwift will control the resistance of the trainer. You will not need to shift gears. As for cadence, Zwift will adjust power relative to your cadence to maintain the desired interval power. If you are doing 200W and 90rpm and then suddenly drop to 50rpm, the resistance will go up in order to maintain a power of 200W. Likewise, if your cadence increases, the resistance will decrease accordingly so that power remains at 200W.

(Greg) #4

I am not calibrating before each ride, no. I would…but Zwift has a bug right now where calibration with Cycleops trainers is not possible. I calibrate it maybe once a week or so with the Cycleops Rouvy app, but it’s annoying because Rouvy does not support Mac so I have to connect it to a different device, do my calibration, then disconnect and reconnect back to zwift. I presume that the trainer is calibrated but wouldn’t be surprised if it isn’t.

But yes, my trainer connects as both the power meter and controllable trainer.

Interesting about the cadence decrease and power increase. That would explain why sometimes it gets so hard to keep up with the workout if my cadence keeps dropping.

So, when I get to my sprint sections, if I cannot get to my power wattage, then ERG is not working correctly, yes? What sometimes happens now is i just spin harder and harder but I cannot generate enough power.

(Lin) #6

This is called the “spiral of death”! If you cannot keep the cadence up, the resistance will get progressively stronger. Sometimes, you will want to lower your cadence on purpose to target your muscles differently. BUT, if this is occurring because you are worn out, you are entering the inescapable ERG “spiral of death”!

If you cannot get to target wattage in sprints…

  • maybe your trainer needs calibration?
  • do you pump up the tire to the same pressure each time even if you did not calibrate it?
  • is the rear wheel/tire slipping?

Are you connecting via ANT+ or Bluetooth? If ANT+, if it presents multiple options make sure to pick the FE-C option.

(Aaron Zwanzig) #7

Another question: is your ftp set too high? I know that for me, with an ftp of 235, I would never be required to hit 500 watts in any workout for any period of time. My 15 second efforts are usually around 375 watts or so. If you lower your ftp you might find your targets easier to hit.

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(Svenne) #8

For those short intense efforts, i deselect ERG mode and control resistance with the bike gears. I’ve had that issue you’re talking about before and it annoyed me quite a lot of times. So now for those short bursts or high intensity intervals to 1min, i just select ERG mode off and after the intervals i continue with ERG mode on. This way you keep the interval archs but you’ve far better control of it and byebye frustrations. :wink:

(Greg) #9

Thanks for the replies, everyone.

As for my FTP. I did a FTP test and came up with 295. I’m over 200lbs and very tall so apparently this is not abnormal for someone my size and strength. Tons of leverage in my monster legs. But because I have to carry so much weight I’m much slower than others with FTP values considerably lower.

I did a training sesh last night and things went a lot better. Instead of trying to spin out as hard as I can to meet the 500W sprints, I just kept my same cadence going into the interval and my trainer did drastically change the resistance at the proper cadence and I was able to hit the wattage at the proper cadence. I just have to resist pedaling super hard at first and it settles into its groove.

I suspect that on some of my trainer sessions I think ERG mode stopped working partway, as I read that is an issue for some people. Last night everything worked well, so here’s hoping that things continue that way.

(Lin) #10

When doing shortish intervals at high watts, like sprints or short VO2 max intervals, you should get your cadence set before the interval starts. Otherwise, the trainer may not make it to the necessary power for the interval. The trainer is trying to increase power. If you are increasing cadence, ERG mode wants to decrease the power. Combine the two and while it will go up, it will not go up to target as quickly and it might not make it before a really short interval ends.

If you set cadence before hand, you should be able to get to full power/resistance ~3s into the interval. With a short power sprint, you might find disabling ERG works best for you. However, for something like 30s VO2 intervals, if you set your cadence beforehand all should work well.