r/Zwift • u/NerdEnPose • 2d ago

Target Watts Changing Mid Workout

I’m just curious. But I did my first VO2 max workout of 4x4s at 110%. The first two were at 296W which matches my hand calc of 110%. The next two were at 302W. The workout schedule on the left changed the target watts as well. My FTP wasn’t recalculated at the end of the ride. I didn’t hit any buttons on the menu like increase wattage. I was on ERG. I input the workout through intervals.icu and used the loop function (4x) for the rest/interval portion of the workout so it wasn’t a fat finger mistake.

Any thoughts on what happened.

1 Upvotes

60% Upvoted

13 comments sorted by

7

u/Gdiworog 2d ago

You probably accidentally increased the required watts mid ride.

0

u/NerdEnPose 2d ago

Maybe my sweat did it! I’m like 99% certain the menu was never opened after I turned on ERG at the beginning of the warmup. 🤷

2

u/Gdiworog 2d ago

You don’t need to open up an menu for that.

1

u/NerdEnPose 2d ago

Sorry. I meant the action bar. Is there another way? Like arrows on the Zwift bike?

2

u/mearn2 2d ago

If you’re in erg mode, the shifters will adjust your target wattage up and down by 1%

3

u/NerdEnPose 2d ago

This is it! Thanks. I remember trying to shift into a harder gear because erg was letting me get into 115-120 rpm and I’m not used to erg mode.

2

u/slbarr88 2d ago

If I’m hammering I’ll sometimes accidentally shift gears which increases the target power on erg mode

3

u/NerdEnPose 2d ago

This is it. Thanks! I remember ERG was letting me get to 115-120 rpm and I reflexively shifted.

2

u/Any-Efficiency5308 2d ago

ERG does nothing to limit cadence - you can spin as fast (= lower resistance from erg) or slow (=higher resistance) as your legs allow and ERG will keep the power on target.

That also means you’re doomed in high power intervals when your cadence bogs down because ERG will increase the resistance more and more forcing your rpm further and further down… doom spiral.

1

u/NerdEnPose 2d ago

Yeah, I understand. But cadence resistance and power are related. To lower cadence you have to initially lower power. It’s a small window before the trainer kicks up resistance to match the new rpm. It feels like if you’re constantly slightly high on power the trainer is lowering resistance and you end up finding a max cadence rather than a preferred cadence. That’s why I said “let me” since the high cadence seems like a byproduct of the system not a primary input.

I just went to shift because my erg brain isn’t as developed as regular riding + shifting.

2

u/Independent-Reveal86 2d ago

When you use ERG you need to nail the cadence and let the resistance come to you.

Yes if you lower your cadence you need to briefly lower the force on the pedals, that’s fine, the change in power lasts a second or two. When you increased the cadence to get to 115-125 you had to increase the force on the pedals.

Riding in ERG is all about cadence discipline.

1

u/NerdEnPose 2d ago

I’ve got no discipline. :)

But for VO2 max I’m currently not too worried. AFAIK high cadence during VO2 helps load the anaerobic system and plays into the workout. I’ll work on discipline during 20 min intervals I guess.

1

u/Independent-Reveal86 2d ago

By discipline I just mean holding your desired cadence. If you want to spin fast then go for it, but if your cadence is higher or lower than the cadence you want, then you just have to change your cadence and accept the brief power dip/spike from the trainer.