CP and MAP/Vo2Max are calculated and are changing daily calculated with every new activity…strong short efforts (2-5min) are lowering your CP. MAP is calculated from 5 to 8min efforts…as long as you don’t have Vo2Max over the Category limit you can downgrade. I know this is not perfect but i believe that how it works.
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How are we using it wrong? The CP calculation is only as good as the data that is fed into it. If people haven’t provided true all out efforts in the shorter durations and then start doing so then it is certainly possible that their CP is going to be lowered as a result. Note I’m saying possible and not probable - someone that regularly does hard long efforts but never does all out shorter duration efforts isn’t going to have a good CP calculation and it could be over estimated as a result.
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i would go as far as to say it’s both possible and probable. not that it would change much in practise because i doubt too many amateur and hobby cyclists are picking up barbells enough to get unusually good at those kinds of specific efforts. and speaking from experience, you do pay for it. my cp is exactly as trash as zwift thinks it is… raw strength and aerobic fitness is a juggling act
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In @Ian_G_WMZ_Cyclones_7 case his CP is 248W and i believe is the results of efforts of 12min at 257W and 3min at 278W.
Everyone is looking at his 20min Power that was over 3,2w/kg but that i think isn’t the reason he was upgraded.
Now if he would do 3 min effort 330W to 350W his CP would go below 233W that is the limit for his 73kg.
If you look at the other thread explaining how the CE parameters are calculated it states (with regards CP), "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". Furthermore it states, “It also helps to solve the ‘cruiser’ problem because short duration efforts can alter the curve and ultimately your CP”*.
Taken in combination, these two statements would seemingly suggest that any improvement in rider performance within the 2 min to 50 min data window that Zwift is using will increase your CP?
It would be nice to have someone “in the know” clarify this in broad/general terms; no need to give away trade secrets.
It is not really a secret here is some good information:Critical Power and W’ Explained For Cyclists (inc. Critical Power Calculator) — High North Performance
Ignore the calculator and focus on the description
CP in layman’s terms using the old 95% of 20min model as a comparison point, and completely missing a lot of nuance but i don’t care about sports science enough to be pedantic about it:
big short term power = shorter TTE at threshold (i can only hold z4 steady state for maybe 14 minutes) = lower CP relative to their 20min
low short term power relative to long term = probably aerobically dominant (can probably hold their z4 for 40mins+ with relative ease in comparison to me) = higher CP relative to their 20min
unfortunately zwift races, for many reasons unrelated to power entirely, strongly favour the first type of rider so the second type (your typical TTer or steady state climber) gets shafted in zwift races, broadly speaking.
edit: TTE = time to exhaustion
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No, they just provide better data to the calculation to give a better estimate. Short duration efforts alter the curve but they can alter it either way.
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I think you may have explained it as have others such as Arend and Dejan who have also posted how higher short term numbers can actually lower your CP.
Here is my intervals.icu details for the last 84 (green) and 60 (blue) days. The biggest difference between these two periods was a ride at the start March where I did 350w for 9 minutes (I suspect my power meter was over reading on that day as it’s not an achievable number for me being about 10% higher than possible). That ride has now fallen outside the 60 day limit so I went from a B to a C according to category enforcement.
The really interesting thing is my CP (3.07) with that higher figure is actually lower than without it (3.15). But, while my CP has gone up notice how my W’ has plummeted from 33734 to 23197. I seems you can’t just look at CP in isolation and need to use W’ to get a full picture. Nobody can look at the green and blue lines in my chart and come to the conclusion that the blue line is the stronger but if you go by just the CP number then that is what it says.
I have to assume that some other factor (MAP?) was the reason I was a categorised as a B.
One more comparison:
Ian’s 20 minute 3.26 (238w), estimated CP 3.4 (248w) according to James
My 20 minute 3.35 (268w), estimated CP 3.125 (250w) according to James
So it really does look like having above average short term power will reduce your CP but if you have a flat power profile you can find yourself with a higher CP than someone with the same 20 minute power.
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Coming full circle then, does this make sense for cat assignments, and/or should there be some sort of validation check added to the ‘formula’ ?
Many thanks Dejan and everyone else who has responded.
Greatly appreciate your suggestion Dejan but don’t understand how registering higher figures will lower my race grade.
Also, 330w for 3 minutes is outside my capability.
As an example, last weeks figures from Today’s Plan, which captures all my Zwift efforts:
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your accumulated T-score 199.0
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your peak 3 sec power 454 W
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your peak 1 min power 292 W
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your peak 3 min power 261 W
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your peak 5 min power 245 W
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your peak 20 min power 227 W
I have a very flat power curve and at my age no amount of training is going to change that.
I am resigned to the fact that masters cyclists such as me and my peers will be victims of the current Zwift race grade protocol so I will stop doing Grade Enforced events for a few months, probably race on another platform and maybe come back to Zwift if my grading allows me to compete in a fair an equitable manner.
Many thanks to everyone for their interest and support, I will leave at that now. Thank you.
Ian Grainger
0419 480 610
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List of events with “Masters” in event name.
I recommend ZHR Masters.
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Not really - the high north calculator spreadsheet will get extremely close with 3 ‘true’ best values, and even closer with 4. We’re talking above 99% reliability. Zwift uses more than 3/4 (we think), but that is just belt and braces.
The key with the spreadsheet is that real max effort values are put in - if you just play with the numbers arbitrarily, you will get some strange results.
@Arend_teRaa and @S_A_Cestria_CC are correct. It is possible to lower CP with very high comparable short term efforts. The MAP category thresholds in part deal with this by ensuring riders with freakishly high short term power are moved up (e.g. anyone deliberately avoiding longer term threshold efforts). The High North spreadsheet is the best thing to use to get a real feel for the Zwift calculation. intervals.icu confuses matters somewhat with their approach.
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I wrote this. Max efforts will affect the curve. In most situations that would increase your CP, but it is possible it could lower your CP as others have explained above. Just 3 data points lead to a very reliable curve, and Zwift is using many data points, so the reality is for most riders with some decent efforts of different durations, the CP calculation will be very reliable.
Like @DejanPresen said, if Ian could do 3m at 350w his CP would probably go down below the category threshold, but the reality is he’s not capable of that - he has a higher/flatter CP. Otherwise he wouldn’t have any problem holding cat B starts!
My personal opinion is that the balance of CP versus MAP (I hate the use of the term MAP here, because that’s not what it is - but that’s a different matter) for the category thresholds is too much on the side of CP - the MAP threshold should be lower. Simply because Zwift races are more dependent on these types of efforts. When race organisers can amend the boundaries this would be a good one to adjust for the majority of race formats.
There is - the MAP element of the thresholds.
BINGO!
This is the true value of CP over FTP. FTP gives you a 2D model of a rider’s capability. CP gives you a 3D model.
This page is THE best description of the whole thing there is. Critical Power and W’ Explained For Cyclists (inc. Critical Power Calculator) — High North Performance
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I found it more consistent when I expanded the formula to look at all the data rather than a fixed 3/4 points. But that could be that there was a better 4:50 power number than a 5 min or something like that. I have all the data in Golden cheetah so I might as well use it. 
Yeah if that’s the case, it is better to use the 4:50 value in the spreadsheet, as the efforts you enter should be true best efforts. If the spreadsheet is giving you 99% reliability though, a watt or 2 doesn’t matter, even if it changes your category. The point of the system afterall is to ball park group riders of similar physiological capacity together.
Once the category boundaries become more fluid this sort of discussion should hopefully go away. Again, the problem is not the CP model, it’s the nature of fixed category boundaries.
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And it is different from Zwift Power. (All that hard work to get just in the right category) 
If anything they’re harder than categorized B as everybody starts together and there frequently are plenty of A’s and even some A+'s in the field, at least for the longer ZHR weekenders race anyway (they don’t seem to suffer from a flat power curve).
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The series has AGE categories - for me it is fair racing.
I wasn’t suggesting it isn’t fair, just that if anyone is expecting easier starts just because its an age based race they will in, in general, be disappointed (there are occasions when the starts are easier, normally when there’s a significant climb early on).