Category Enforcement - How is my category calculated? [February 2022]

FutureWorks
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Hi everyone.
EDIT: view this before you read anything else CE101.pdf - Google Drive

I have been in dialogue with @xflintx. We have both acknowledged there have been some communication issues, but by opening a conversation hopefully we have been able to bridge the gap a bit, and for that I am thankful that he indulged me as I dug for more specifics. I will try to put this across in terms that are understandable, with the goal being that the parameters are clear, and we can more accurately feedback, and thus improve.

What are the parameters used to determine my category?

Parameter 1 : Critical Power (CP)

ZwiftPower calculates FTP from a fixed metric - 95% of your best 20 minute power expressed in W/KG, plus a raw power number to account for lighter riders. Zwift are replacing FTP with Critical Power. Critical Power is a better calculation that takes in to account all of your best efforts from 2 minutes all the way up to 50 minutes. To find out your Critical Power, you could use a tool such as intervals.icu (free) to upload your ride data. Hopefully in the future, your calculated CP will be shown on Zwift so that you can see it and improve it. Note that often this is a lower value than FTP.

This is better than FTP because the ZP FTP calculation relies on a 20 minute full gas effort within a Zwift race, which is generally rare. It also helps to solve the ‘cruiser’ problem because short duration efforts can alter the curve and ultimately your CP.

The Critical Power number will determine your category in exactly the same way as FTP does today. The boundaries are identical, for both W/KG and pure watts. Note that this is a change from what was communicated yesterday based on feedback, where it did not account for both w/kg and pure watts. This caused issues for heavier or lighter riders. If this affected you, please leave the race and rejoin. This change is now live.

Parameter 2 – MAP/VO2

The second parameter that is used aims to account for specific strengths over and above your Critical Power due to how much this matters in your typical Zwift race. It is calculated by looking at your modelled power between 5 minute and 8 minute durations. It takes the Mean Maximal Power (the average max power between these durations) to calculate your MAP (Maximal Aerobic Power). From this an estimate is made of your VO2 max. Note that the thresholds for MAP are currently set at VO2 Max round numbers, but they are designed to be tweaked / altered / experimented with.

CP Category Boundaries

A: 4w/kg and 250w CP
B: 3.2w/kg and 200w CP
C: 2.5w/kg and 150w CP

MAP/VO2 Category Boundaries

A: 5.4w/kg MAP (60 VO2 Max)
B: 4.1w/kg MAP (50 VO2 Max)
C: 3.9 w/kg MAP (45 VO2 Max)

Your category is the higher of either the CP cat or the MAP/VO2 cat

Please ask any questions related directly to this model here, but leave all wider feedback and discussion in the original thread.

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actually quite reasonable on paper

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looks sound.

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This is an excellent, quick response to the immediate feedback. And speaking from a personal perspective, it’s adjusted the pens I can enter. Kudos!

I hope it sorts out the strange categorisations for other outliers that we’ve seen.

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Thank you @gloscherrybomb and @xflintx this is definitely more like what we were after and sounds great in principle. Good job on the changes!

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thanks for the update @gloscherrybomb seems reasonable and hopefully that can sort the odd categorisations we are seeing.

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These changes are live now, and you should be able to see if your category has changed by removing yourself from the sign ups, refreshing the event, and then signing back up. Some of you may see a change, some of you may not. Notably, heavier and lighter riders benefit more from the changes we’ve made.

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I assume the MAP was also changed from raw power to w/kg

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Phew. Looks fine now and I’m back down to B where I certainly belong. In fact it looks to be a clear improvement on the current ZP categories, albeit I still hope that results-based categorisation is on the roadmap.

Not sure exactly how the MAP threshold relates to the CP threshold - how likely is it (and when) that one is exceeded and not the other, and which is more of a limiting factor in reality?

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I think so? But Flint would have to confirm that.

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Are you still in A cat @Gerrie_Delport_ODZ, or back down to B?

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That still put me in B. I’m a C mixed and I’m really light so i guess that my punishment like every mixe raced that i do :laughing: i struggle to keep up with them on the flat and have to push more than them. I don’t think we can do something for that ?

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Did you quit the race and join again, or tried to enter a different race?

Do you have a rough idea of your power versus the category boundaries explained above? From what I can tell the MAP/VO2 element does not have a pure watts minimum like the CP does, so it could be that.

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Well done @xflintx and @gloscherrybomb - the issue was plain to see but you had more patience than I to hammer it out. Besides, I had people to coach and no time for a 5000-word dissection!

As for CP vs FTP, I hope this is the last time I see or hear someone say that FTP is 95% of one’s best 20-minute power. It is not, it never has been, and it never will. At least a CP model is what it is, whether one is looking 60, 20, 5, or 1-minute power

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Yeah i try a different race. I’m 44kg, and my FTP is 170, i know that my W/KG are high but no way i can follow the B on the flat i can barely keep up with the C ! I have to push 0,5w/kg more than everyone in the race !

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Thanks, this is an interesting use case @xflintx where MAP/VO2 may also need a raw watts floor.

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I already use intervals.icu but can’t see where to find a number for Critical Power. Is it the same as eFTP? If not, how do I find it out of curiosity?

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eFTP does actually use basically the same model, but to be more specific for CP, you can go to Power in the menu and then Options, and select either the 2P or 3P CP model. That’s not to say one of these is the exact model that Zwift are using, but I am sure it will be close.

For me CP is a fair chunk lower than eFTP. But that’s OK, they’re different things.

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Perfect, thanks. My CP is 20w lower than my eFTP but as you say it doesn’t particularly matter so long as it’s consistent.

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