I build my own workouts with the Zwift workout editor. When I need to do short high intensity intervals, I make them as a "free ride" block. That way I'm the one controlling the trainer... No spiral of death.

Can the built-in workout files be edited?

If you are using existing workouts, you can use the companion app to toggle Erg mode off for the sprints, and then back on for the long efforts... I started doing that, because I kept "failing" on short 10sec efforts, because of the response lag of the resistance. As was mentioned, if you are designing or willing to recreate the same workouts, just set the sprints as free ride sections (The Zwift Academy workouts do some key intervals at free ride to test your capacity in a similar manner, similarly the Power Up Training Camp workouts did this for the sprint session).


Hopefully that helps.

FWIW, I wouldn't do a workout like that ever in erg mode. I'd use real life riding OR I'd go into Zwift and just free ride.

No need to overcomplicate that with erg mode or something super structured. Then toss in your sprint when you're supposed to. Doesn't even have to be exactly every 5min or 15min or whatever. Just say "on the quarters" of the hour you sprint.

The only time erg is really necessary is maybe for leveling the load really well for 2x20 SS or threshold, 1x60 SS, and tough under/overs.

Last, a more realistic sprint I'd lead into it with maybe a minute of harder work ending with the sprint. Just me. It's one thing to be able to bury it once in a while after cruising forever. It's another entirely to be able to do so when already working kinda hard.

I'd dial it up to power interval power for 30 seconds or a minute then put the cherry on top for each rep.

Yeah, I don't think you're going to have much success with intervals under ~20sec, if regulated by a smart trainer. I mean, it takes two or three seconds to achieve steady state resistance anyway. If you're dead set on doing these as they're designed here, toward the last 15 or 30sec of the 15' interval, try decreasing the bias until it's low enough that you can resist that death spiral. I don't know if that's the solution you're looking for though.

Edit: I agree with the others. Designing your own workouts is my favorite way to go, even if it's just adding a free-ride in where a rest interval is.

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Thanks for the replies. “Spiral of death” is a great term for it.

Shame Zwift doesn’t seem to have very mature prefabricated workouts. Will look at creating a training program from scratch, which was what I was trying to avoid! Lately I've been finding I'm running Zwift in the background and watching video.

Starting to feel like I'm in Zwift only because it's the "big name", whereas TrainerRoad would probably be better for my needs.

I don't think this is Zwifts fault. You're simply using the wrong tool for the job. ERG mode has no place in sprints.

I don't like ERG mode for any purpose. But I understand why many people like it. However, where it has a purpose is in maintaining steady state intensity levels without you having to watch and regulate your power constantly. If you need to watch the workout and anticipate changes anyway, what's the benefit? If you're doing sprints why would you engage ERG mode. All this does is expose the weaknesses of ERG mode and your trainer without any benefit to you, psychologically or physiologically.

Why ERG?

Zwift is not the problem here. At worst it's compensating for your poor decision less effectively than TR.
I'm convinced most people use ERG mode because they are fixated on hitting exact numbers and drawing a power plot that looks just like the workout target. The purpose of power based training is not to blindly follow a fixed prescribed number and draw as consistent and pretty picture as possible. It's to get faster. They are not necessarily the same thing. Aim for the prescribed power levels (if they are appropriate) but don't ruin a workout because you can't separate a simplified model from reality. Don't be a slave to pretty graphs. Cycle.

Erg is useful for the 15’ intervals. The workout is 2:30 at a set power with an 8 second sprint every 15 minutes.

As others have said, a free-mode built into the workout would be the solution.

But sure, I could disable the default Erg and spend 2 hours 28 mins 56 seconds watching the power for the 64 seconds of sprints, but I think the other answers above are superior.

Apologies. I read it as 15 seconds not minutes - thought that was an unreasonable interval!
So, yes, ERG is the wrong tool for the sprints but since they're infrequent, I'd mod the workout file or otherwise disable the ERG if you want it for the rest.

I struggled with this for a while, too. What I have found that kind of helps is to start spinning up/ramping up as you cross into the interval set. You want to be increasing your cadence while the erg mode is kicking in, and I've found those two things kind of cancel each other out.

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@adamwfurlong

Before those massive power sprints I turn off erg mode. Then turn it back on after they’re done. Like the other day it had 15 second sprints at 850w. Ain’t no way in hell I can do that. So I turned off erg and hit my max watts for the 15 seconds.

73% isn't really a power zone I'd be too concerned with the accuracy of long term ERG control.

The reason ERG is popular for SS up to threshold is that the closer you get to threshold, the actual amount/variation/duration gets really important. If you overcook it or undercook it you defeat the purpose.

This "zone" you're referencing for 15 minutes is what? Z2 essentially? That's just free riding.

Yet again, just free ride Zwift and do a sprint at every major mark on the clock. Clock hits 15, do a sprint. Hits 30, do one. Hits 45, do one.

The solution is to not over complicate workouts.

Rider for our company's pro team got some intermediate sprint points in the UAE race on stage 2 and got some camera time. I follow him on Strava. He has been riding outdoors in France most of winter. He's done some sprint rides like you speak of..........outdoors, as a pro. He just seemed to pick the flatter river road routes and toss in his sprints every so often.

If a pro rider doesn't stress Zwift on ERG mode for a sprint and Z2 ride, you shouldn't.

I'm going to disagree with just about everyone on this one. ERG should work fine for the workout you are describing. If you are failing at 300% FTP then your FTP is set incorrectly.

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"...the street finds its own uses for things"