ZwiftPower Categories

Hi

I have a general/technical question regarding the ZwiftPower categories.

My understanding is that it is generally worked out by taking your average FTP from the last 3 races you did in the last 90 days. Based on this data it allocates your category based on the below. (Please correct me if I am wrong.)

  • A+: 4.6w/kg and 300w FTP
  • A: 4w/kg and 250w FTP
  • B: 3.2w/kg and 200w FTP
  • C: 2.5w/kg and 150w FTP

My question relates to weight and whether this skews the categories somewhat.

For example if you weigh between 50-60kg you could average between 4.3-5.0w/kg (depending on weight) and not have to upgrade to from A to B.
Similarly a rider in the same weight range could average 3.5-4.0w/kg (depending on weight) and not have to upgrade from C to B.

In both cases that is quite a few w/kg over the category limits but due to lower FTPs would not trigger a category upgrade.

Does that put all the heavier riders that have to keep their w/kg within category limits at a disadvantage? Or does the benefit of being able to put out more power correct that?

To me it seems a bit unfair to have some riders going significantly above category limits but not get upgraded.

Thanks

So yes a 50kg rider doing 4.5w/kg will be doing 225w so therefore won’t be upgraded from B to A because he did not exceed the 250w minimum.

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Yes, it would be better just to have a single 20-minutes W/kg limit, effectively combining both in a single measure.

But wherever the limit is set and however it is measured, somebody will be just over the threshold and claim to be hard done by. And others will game it somehow.

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The Zwift categories are drawn at arbitrary lines that stand for nothing in reality. Whichever way you skin them, there will be examples where certain weight and power combinations will do well, and others will not, and open up an easy method for sandbagging - managing your output to stay in a category lower than you should so that you can get good results.

It is very easy to stay in a lower category than you should if you avoid big 20 minute efforts. Prime example - ZRL race 3. Most of the ‘top’ B riders contested the sprints rather than the KOM - because an all out effort on the KOM would have got them upgraded.

The only way to fix it is grouping by results (rankings).

https://forums.zwift.com/t/rankings-based-matchmaking-get-rid-of-cats/519476

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Thanks for the replies!

This confirms my thoughts, just wanted to check I wasn’t missing something

@gloscherrybomb the rank based system sounds interesting and may be a better solution to categories, although no doubt there will be those that find issues with it

Not started racing properly yet, taken part in the TDZ 2021 group rides which have me as a B on ZwiftPower

Just going to start racing and give it my best shot and see how I go.

Around 75kg seems to be the optimum weight to be at the top of B,C or D cat. Heavy enough that you have high power but not so heavy that you can’t sprint or have poor 5 minute power.

Or be around 50kg where you can take advantage of the FTP power limits (ie 249W and 50kg would still be a B cat rider but doing 5w/kg)

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W/kg only really applies to the Alpe/ventoux or Epic KOM. Look at an Alpe race results and you will see a nice correlation of w/kg from first to last place (high to low). “Most” races on Zwift have a much higher ratio of flat terrain to any climbing terrain especially where w/kg can accurately group riders.

Take crit city for example, the dedicated route on Zwift for crit races, nice and flat and yet uses the beta sandbagging measure based on w/kg. If Zwift physics in anything like real cycling physics surely it would use total watts as the category system?

But as mentioned above any cat system is flawed unless you have some form of performance system like James mentions above.

If you look at the variability index of races you can see who really is sandbagging and making use of their capacity forcing the rest to race a boring time trial hanging on for dear life. Racing would be so much more entertaining if people were grouped at similar ability allowing for draft to actually play a tactical role.

If you raced 10 of you, how would you approach the race?

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In other words, I have a choice between losing 6kg or losing 31kg. The former sounds more attractive somehow. I doubt I could get to 50kg without removing useful body parts.

Although this is Zwift, I can be any weight I want.

If you google Peter Kay lose 14 stone in a day, it is possible you know :wink:

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Made my day.

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Personally speaking as a low cat C who will never reach B, I think the gaps between categories are too large, 2.5-3.2w/kg. Perhaps we should have intermediate levels, any thoughts or should I just accept I will probably be last? Could age be incorporated somehow, speaking as a 68year old female :grinning:

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I agree, some more cats may encourage people to go ahead and cat up instead of cruising.
This suggestion always generates a fair amount of comments so get ready.

Hi Mary,
I am a low C, too. Yes, the gap could be less (means more categories), but a results based categories would be much better.

Age can not be incorporated in the W/kg ( = power based) categories - power is power, it doesn’t matter how old you are.

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u wot?!

best performing riders in B/C/D are usually either heavyweights or lightweights.
heavyweights who can hold cat limit 20min w/kg can’t be overtaken by lighter riders without them being DQ’d.
lightweights can exceed 20min w/kg by having low raw wattage FTP giving them a huge advantage over the field.

Only in Cat A and above does heavy weight start to become problematic, where the raw wattage/kg required becomes too high for them to sustain.

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some event organisers do categorise events based on age. it is not completely unheard of. the older you get, the lower your w/kg is likely to be due to VO2 max reductions. so it’s not entirely fair for those >60 to be racing 20 year olds :smiley: that’s why we have masters categories etc. in real life.

Of course Age can be incorporated into the rankings… That’s precisely why ZwiftPower has an Age ranking AND a Group ranking. However, their race results do NOT allow for presentation of the results in this manner - which would be a simple fix. The races don’t need to be restricted by age, merely the results. Strava permits age comparisons as well. Age DOES matter, as a matter of pure science, relating to declining VO2max and Heart Rate functions. Zwift should take results of races into account for the rankings, just as is done IRL.

Yes, age does matter, of course. I am 61, not a young boy. But once more - raw Watts or W/kg are physics. There is no difference between a 20 years old and a 60 years old riders with the same weight riding the same Watts (another question would be how long they can hold the power, heart rate, etc.). I bet there are many old(er) people who can easily beat many younger ones.

What I would like to have are categories based on 1) results and 2) age - and I would recommend to use similar categories like IRL.

No Wes. In race you can’t be trying to work out if the rider you’re chasing or is chasing you is in your age group, and so someone you’re racing against. It’s not age category racing if other riders are present and affecting the race dynamics.

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@Mark_Gallagher : You misunderstand. I certainly did NOT say anything about working out such rankings “IN RACE”. To clarify, I merely said that the ZwiftPower race results should be presented in such a way as to be able to examine Age-based rankings. At present, I must do this manually, one rider at a time if I wish to compare my results on the basis of age demographics. Laughably, there is not even an age category (ie “Veteran”, “Master” etc.) for those in my age bracket.

EDIT: I dug deeper into the “race results” page on Zwift Power and must make an update, and fall on my sword. There is a “columns” feature on the race results that facilitates precisely this feature. The UI is a bit cumbersome (like so much else on Zwift), but it gets the job done. So I’ve already got what I need! Cheers,

The races don’t need to be restricted by age, merely the results.

That’s what you said and that’s not an age based race is what I’m saying.

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