burnthesheep

In the real world, your speed is your speed. In Zwift if your trainer misses picking up a few rev's in your cadence in a sprint that could mean you wind up going slower. In real life you still go whatever you're going to go, the reading on your meter might just be different.

All things Zwift is a grain of salt and usually not what is optimal in real life.

If you care about such things, I think the best thing to do would be to join one of the numerous Z1 "stay together" group rides where they lap a flattish short course like London or Richmond with the sprint banners. Then they turn off the banding for the sprint. Try stuff out. Try different postures or ways of racking the bike on the trainer for Zwift. See what you can get.

In Zwift I can't figure it out. I'm always a solid 300w or so less on my peak and probably 400w less on my "hold" when sprinting. So, any Zwift racing ending in a sprint I'd just not make out too well.

Zwift is also a grain of salt as DCRainmaker said he gets funny figures on some smart trainers for sprints. Then he has given the feedback to the vendors who claim to do firmware updates.

deacon mark

Lots of NFL lineman have legs way stronger than Usan Bolt. But could dust them running at any distance easily. Tells me power is about efficiency and task specific.

merlinextraligh

In my experience you can “game” max power on a power meter for a second or two with a lot of torque in a big gear. However, I think it’s mostly a measurement error.

Real world, start out in a gear you can turn 100rpm. Shift up one. when you start feeling that spun out, bang one up shift, get on top of that, and before you spin it out the race is over.

Redbullet

Stupid question: How do you accurately measure your cadence on Zwift or on any other indoor cycling application?

My trainer reports some sort of generic cadence with delays of 3-5 seconds in updating and it is also very dependent (some +/- 20%) on my position on the bike (standing vs on the saddle). A cadence sensor mounted on the crank does not do a much better work: just that its reading does not depend on my position, but the delays are long and its jumps between figures have nothing to do with real life, where it sends a smooth and very consistent reading to a Gamin device.

Trakhak

I know next to nothing about how the software works, but BigRing VR has a "Preferences" section where, among other things, you can change the frequency of cadence updating. I just leave it at the 3-second setting.

MinnMan

My pedal based pm, Favero Assioma, also functions as a cadence meter. I have no reason to doubt its accuracy, but what do I know?

MinnMan

My sprint power won't impress anybody, and personally I don't pay much attention on the road, as I don't race, but I do care on Zwift. For a while, I couldn't break 600 watts for a 5 second sprint, but then one day I was in an easier gear and I did 650 W. Normally, my sprint was at 95 RPM, but the better power was at 105 RPM. Lesson learned.

I'm somewhat encouraged by the people saying they get higher power on the road than on a trainer. Maybe my 5 second power numbers aren't as pathetic as I've assumed. (I'm 72 kg)

RChung

There are ways to check, if you wanted to know. Most people don't.

MinnMan

Well, if I could count really fast and use a stopwatch....

Seattle Forrest

Power = torque vector * angular velocity aka cadence.

Your pedals can't be wrong (about cadence) by much and still hit the +/- 2% accuracy spec. Or whatever it is for yours specifically.

@RChung knows more about this than anyone and pointed out the that one second every few rides where I'm doing 140 rpm but not really isn't the only time it ever makes a mistake. He uses PMs differently than most people and needs more precision, for practical purposes you can just treat your pedals' cadence as right and bob's your uncle.

RChung

That's probably a fair assessment. Times when cadence (and therefore power) can be off are when you're accelerating really hard, or when you suddenly go from pedaling hard to coasting. In many power meters that use accelerometers for measuring cadence, you can see anomalous power readings. Another situation is when you're mountain biking at very low cadence because you're trying to "muscle up" over an obstacle. Accelerometer-based cadence seems to be confused when you're pedaling really slow at very high crank torque. But most riders really don't care much about those situations.

Not just accelerometer-based cadence can be off. I used to have a reed-switch sensor for speed and it used to go crazy occasionally, where I'd see speeds of a couple hundred km/h for 2 seconds. So I examined my data files and realized they all occurred on a certain route, a particular distance from where I'd habitually hit the lap button. So the next time I went out that way, I counted that distance from the place where I hit the button and right there in the middle of the road was an understreet power vault. That power vault was leaking EM and it was interfering with my sensor. I bet the FCC didn't like that. Maybe not the public health dept, either. You can find out some interesting things if you pay attention to when things go wacky.

topflightpro

Years ago, before I had a PM, I noticed at that my HR always jumped to 250 at the same spot on every ride, regardless of effort. I figured it was a powerline or something.

woodcraft

Max Power on Zwift - cousin to this guy?