Should ERG be easier in terms of maintaining objective WATTS? I find keeping target watts in a workout interval easier in ERG than in resistance mode. In resistance mode the low end power and significant decrease in RPMs associated with rest between intervals drops from 90-100 to 50 rpms to genearate 75 watts. When starting each VO2 interval the power surges to 450 or 500 watts then drops to target power when changing gears.
Is VO2 best done in ERG?
Thanks!
Hey there,
It shouldn’t really be “easier” or “harder” since you still have to crank out the power – ERG mode just allows you to focus on pedaling without changing gears/resistance. The trainer takes care of that for you.
Most athletes actually prefer to do shorter efforts like VO2 Max in Resistance mode instead of ERG mode. ERG mode usually has a slight lag when getting on/off the power, which can become annoying when doing repeated short efforts. In Resistance mode, you can spin up much more quickly than ERG/your trainer can, allowing you to change power more quickly.
Those surges/drops in power you’re experiencing can be “trained out” by focusing on them and by practicing shifting more smoothly. If you’re surging way above the target power, try not to hit the start of the intervals so hard. Instead, try to “slide into” them a bit more if that makes sense… Ramp the wattage up powerfully, but smoothly and with control – don’t just hammer it blindly. You’ll get the hang of it pretty quickly. 
You can also adjust the strength of the resistance that Resistance mode will provide if you find that it’s too hard/easy to pedal at times (like during your recovery intervals if you’re going down to 50rpm). Check out this article for more info:
Hope that helps – feel free to let us know if you have any other questions!
I started using resistance mode about a year ago for all workouts and never looked back. Yeah the power isn’t exact like it would be in ERG mode, but power isn’t exact in the real world either. I’ve gotten pretty good at staying within 5-10 watts of the target. Definitely just my opinion and preference though. I’m guessing most people use ERG exclusively, with the exception of some using resistance for VO2.
ERG mode allows you to self-select cadence. For resistance mode, your cadence is dependent on the gear you choose for a given power output. Either approach will drive adaptations, but I find resistance mode to be a much better representation of riding in real life. Particularly if you run gearing with larger jumps between gears. Being comfortable putting out power across a range of cadences is a good skill to have. Not saying you can’t get there with ERG mode, just that resistance mode is going to force more time at difference cadences if you are sticking to the power target.
I think what you’re saying here is that even in your easiest gear you can’t stay below 75 watts unless you slow to 50 rpms. Is that true? If so, this could be an issue with the low wattage and your trainer. Here’s a post from a similar thread that might help you.
May also need to play with the resistance slider to get the range they want. I keep a tight cassette on my trainer bike and couldn’t get into 11 last night so had slider set higher than normal. But then I’d hit a recovery interval and I couldn’t get down to the 80?? I think watts without bumping the slider back down.
What I see is that keeping RPM high keeps the effort to maintain watts at a moderate level versus slowing down cadence that creates much more pedal “flywheel” resistance. I’m not sure but it may be similar to the spiral of death that I heard about during FTP testing.
The surges are not from hitting or hammering blindly at the start of an interval hard, its more of result of the flywheel adjusting from a really low target power e.g. 67 to 200. I need to spin up to reach the correct watts that leads to the spikes and then slow down the cadence to try and maintain a target RPM. I have adjusted the strength of the resistance by backing it down to 35% and then back up to 56%.
I am experimenting with the lag that happens between high and low or vice versus targe power.
I am thinking the ZWIFT HUB Trainer and the fact that I’m on a 2 x 10 setup could be a factor with the results.
Exactly. The RPMS need to be really low to back down to the lower wattage. I’ve adjusted the % resistance to try and compensate. It works somewhat but is needed between each VO2 interval.
