ERG Stuck in Workout Mode

I was doing a workout in the Build me Up Plan called Serrated at the end of week ten and my heart rate monitor battery died about 2/3rds of the way through at which point ERG mode would no longer change resistance and was stuck on the power level my battery died at. Not sure if this is a bug, but I rode until the second half of the last interval and then repaired my equipment and put on another heart rate monitor to test. I started the same workout over again with the new HR monitor and ERG mode changed properly.

Any idea as to what happened?

Hi Fez,

It may be a bug but if so, it’s one I’ve not heard of before. Assuming you’re using a separate power meter, smart trainer, or speed sensor, your wattage wouldn’t in any way be connected to your heart rate monitor readings. It seems like it only happened one time and only after your heart rate monitor died, so if it is a bug, it’s one brought on by a very specific set of circumstances, and ones not likely to happen often.

If you’d like us to investigate this matter, we may be able to do so but we’ll need more information about your setup, which is something our team can gather if you write in for support. I’d recommend that you please submit a support request if you haven’t already done so, and a Zwift team member will be happy to help.

Thanks! I sent in a ticket.

I have experienced similar situation multiple times. When connection to one of sensors dies (HRM, cadence), power level during ERG mode no longer changes even when I start next step during workout with different power target.

I tried to switch off/on Kickr - no changes.
I tried to repair sensors from Companion App to AppleTV limited bluetooth - no changes.

My Setup: AppleTV+Zwift, Wahoo Kickr, Wahoo Cadence, Wahoo TickerX, Zwift Companion App.

My FTP Strength workout analysis on Strava:

You may notice that Power output stays within 140-150w after warmup and cadence sensor dies.

I sent in a ticket and they told me that once the battery went dead that some kind of interference prevented the change and it was not a bug. I don’t understand it but that’s all I got.

It doesn’t matter whether it was battery or I just removed my HRM in the middle of workout - power limit should not freeze. I still use my cadence meter with the same battery, it was some kind of connection/visibility error which disconnected device.
So these external factors may change and fails will happen, but it should affect workout in minimal way possible.

I agree with you. I was just passing on what the guy told me and that it wasn’t exactly satisfactory since I have no idea what the mystery interference was.


Did you ever find out what the problem was here? It sounds similar to my own issues…

I’ve been having trouble with my HR monitor (I use a Garmin FR945 in broadcast mode) - I noticed that for some reason (possibly since a software update or a Zwift update) my HR data had started going all over the place during a structured workout in ERG mode (I use Emily’s Short Mix a lot - the HR trace should be a fairly predictable and repeatable metric over the course of my workout).

In desperation I stopped the HR broadcast and restarted it which didn’t help with the accuracy of the data but I also noticed that for the time it wasn’t connected the ERG changes were not delivered to my KICKR trainer. Something is clearly not right here - the ERG instructions being sent to the trainer shouldn’t depend on the receipt of HR data.

I posted links to the activities illustrating the issues in the Garmin forum but having read this I think it’s a Zwift issue:

Any suggestions gratefully received…!