Trouble doing sprints in wrokout mode.

I have Vortex trainer.

Was in workout mode where I had to do quick sprints at 245W for 20 seconds and then drop to 80W for 15 seconds.

The problem I had was when the wattage changed.  It took me about approx 7 seconds to get to 245W.  And then very hard to get down to the 80W.  Needless to say I was ‘Failing’ the interval.

So how am I supposed to accomplish this kind of workout if the power wattage is not making it possible?

Is there a technique required to perform this kind of workout?

Was using ERG mode to do the workout.

ERG is bad for sprinting or short intensive speed bursts.  The problem is erg wants to lag behind.

Turn off erg, and keep level resistance at 3 or above.


ERG is great is for steady power efforts, and over under.  But for it to be really effective on sprint type efforts it needs to predict the rise really fast.

Thanks for reply Matt. 


I have a Vortex trainee.  How would I set trainer difficulty 

To 3


disable erg mode in workout screen.  Adjust resistance using mobile app.

Thanks. I will try it out and update this thread. 

Hi Bruce, 

I agree with Matt about the ERG mode and short intervals but you should also check one more thing. 

  • Launch Zwift, go to settings -> power display -> and check “instant” instead of 3 seconds average.  (It will make it easier for you to tell how much power you’re producing at given moment)

Hope it helps! Thank you and Ride On! 




What i typically do if i want instant power, is i typically pair my garmin head unit and have that display instanteous.


Given the duration of the sprint

10 seconds vs 60 seconds will help determine if you want to use 3 sec averaging. 


What i typically do for sprints is use my gearing to rapid increase wattage at first, then i bring my spin up.

I use a CompuTrainer with Zwift. It only take maybe 2 seconds for the wattage to get out of the ‘fail’ zone and to the target wattage. But during the build up of resistance it feels like riding on the road. Watts build quickly, rpm increases, efforts is very similar. I have my bike on a slightly rocking platform, but still I miss the real road feel as far as bike movement is concerned. Otherwise the effort is comparable.