Failing workouts at higher intensities

Hi all. I did an FTP test 2 weeks ago and it has me at about 210. I’m guessing that when I join a group workout my power targets through the event are based around my FTP.

I have no issues holding consistent power throughout the workout (say 170W), but around 30 minutes into the workout Zwift is asking me to put in higher efforts (say 275W) for like 1 - 3 min. I can’t really even get close to those numbers, let alone hold them for any amount of time without putting in what feels like some colossal effort. Not sure if anyone else has experienced this. I’m using a CycleOps Fluid 2 (new) and zPower. Weight in Zwift is correct and tire pressure and trainer contact is set up per Zwift/ CO recommend settings.

Is 210W the best 20 minute power during your FTP test, or did you do around 220W for your 20 minutes and Zwift calculated your FTP as 210W?

FTP (zone 4) is the power that you can hold for one hour, so of course 170W for 30 minutes will feel very comfortable. You should be able to hold 120% of FTP (which is VO2max or zone 5) for between 5-8 minutes. Anaerobic efforts (zone 6) are between 121-150% of FTP, and you should be able to hold these for 1-3 minutes. 275W is about 130% of 210W, which makes it a zone 6 effort, and 1-3 minutes sounds about right.

If you are not able to hold these efforts, it could be that you just need to do a few more of these workouts to get your fitness up, or that your initial FTP test may have been a bit off. The power profile that Zwift has for your trainer might also not completely match up with your particular unit, causing the estimated power to be off at higher resistances. I don’t know if there is a way to perform a calibration on your trainer, but I would definitely suggest doing so if there is.

Bryan, thanks for the response. I’m not really sure where my power was during the test; 212 is the value that Zwift assigned, which shows up under my profile. This is down from Zwift’s estimated FTP, which was 223. I’m going to do another test in a week and see where that puts me.

From my experience some of the high intensity workouts on Zwift have virtually unachieveable power targets. Do the best you can. Since you’re not using a smart trainer in ERG mode you could just go at say 30 watts less than the target. 

Ditto about Z power being off. My old trainer is a Fluid 2 trainer and I first started off on Trainerroad using this. It was excellent at anything FTP level or less but anything over FTP was a struggle. I’m now on a power meter and smart trainer and things are much better.