Difference between zFTP and FTP?

On ZP, it says that A+ requirement is 300FTP. But on my profile page, I only see zFTP. Are these two numbers the same?

And how is the FTP required for upgrade calculated? Is it 20-min power or 40+min power?

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Hope this post from 28th March help explain the situation.

it was pointed out this would cause confusion

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It does clear some things up, but I’m still unsure whether 20-min efforts are enough to boost FTP, or if it will have to be longer than that. But the answer will probably vary with the individual power curve of the riders

A+ isn’t a category from the CE perspective and doesn’t appear in the table of values that they published about the CE boundaries, so I’m unsure if the old info about A+ on the ZwiftPower site is still accurate but I assume it’s based on the zFTP curve now. Exactly how the calculation works is a secret, but it’s easy to end up with an inflated zFTP by doing only long efforts, not doing MAP efforts. A rider who does that will sometimes end up with a zFTP well above their actual FTP. There is no single amount of time needed to calculate zFTP. A rider who never stays on the bike for 20 minutes would still have a zFTP value calculated (but probably not a very accurate one).

Cheers for the input. I found out today that I should be pretty close, so I’ve decided to give it a go, but I dont want it to interfere with my races, so I’ll just have to do it the hard way (as opposed to doing it by also limiting MAP efforts)

I’d start by beating the 30 minute PR and see how that affects the zFTP value you see on your profile on my.zwift.com. Maybe a TT or pacing a 30 minute effort up the Alpe. That would probably* flatten the curve the most.

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I’ll go for that. Should be this one, right?

Yes. Looks like a good time to go for it since your 90 day fitness is as good as the game has ever seen it. Pretty much all tops.

Well, I punched it up the Alpe for 30 mins and improved my 30-min power. Recovered for a while and punched it a bit towards the top when I saw that a new PR was within reach. So the whole thing also improved my 40-min power. And my zFTP is now above 300. Still red, though.

ZwiftPower only updates when you do an event so maybe if you hop back on for a quick race now…

Well, it did update my FTP, so I am more inclined to think that the requirements are just tougher than I initially thought. My FTP probably needs to be above 4.6wkg as well (which isn’t quite the case even with today’s improvement).

Hey @Thomas_Sorensen_eCKD I swear I’m not stalking you all over virtual-zwiftworld though zwiftpower does say you are on my list of nemesis :wink:

Curious in the end what you learned here with regards to duration-of-effort, whether it was 95%-of or 100% of the effort, when zwiftpower updated after setting a new power, etc? I recognize (and can verify from looking at A+ riders on DIRT with <300W “zwiftpower 20min time” that it’s based entirely on zFTP calcs (where those <300W riders do have >300W zFTP) so it’s a little bit of a black box…

I find myself in the same position you were late last year where fitness-wise getting the spiffy A+ tag might be in reach as a kind-of-silly goal and I’m thinking about it. Would be especially cool if I could do it while at altitude but will be borderline for me so need to engage brain and legs.

Thanks in advance :slight_smile:

I never found out which specific interval was the best for boosting zFTP, but I can say that in each case where I’ve been upgraded to A+ it’s been on the back of a hard run up the AdZ. So 40-min power definitely has an impact on zFTP.

The limit seems to be around 4.6wkg (which I am fast approaching after I’ve started regaining the weight I lost for the nationals without adding power - so maybe our victim/nemesis roles will be inverted before too long :wink:

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I’m not sure the original question was answered. Here’s my attempt.

FTP is an estimate of the power you can produce at your lactate threshold (more precisely at LT2, aka maximal lactate steady state). Go below your FTP and you can sustain that for some time. Go above it and you cannot sustain that effort. This is the one we estimate from a ramp test, a 20 min test protocol (which has a 5 min maximal effort, then 5 mins rest, then the infamous 20 min effort, and if you do this as per protocol it truly sucks). Or as a shortcut, Zwift will estimate it from your 20 min power. That might be a fresh 20 min effort, that might have been from a 19 mins 30s effort after which you soft pedaled, it might have been from a 21 min effort, it might have been from a race where you were staying with the pack but the pack was very much not going at a constant effort. It’s a bit more of a dirty estimate.

zFTP and zMAP are different. Critical power (CP) models are mathematical models that try to predict your maximum power from about 2 to about 30-40 minute durations. As input, they need two fresh maximal efforts, one about 3-8 mins and the other about 12-20 minutes. Consider the graph here. The CP model assumes a hyperbolic relationship between the two input efforts. The asymptote is known as the critical power - it’s the dashed line in the graph, although that overlaps with the solid line of my then-estimated FTP.

zFTP is the critical power estimated by the model, and it’s interpreted similarly to traditional FTP: it’s an estimate of the max power you can sustain for a long duration. It’s usually close to traditional FTP, but they aren’t mathematically equivalent, I believe. I think that zMAP may be the model’s estimate of your 5 min fresh max power.

If you have not done a real maximum short-term effort, then it will assume your max potential power is a hyperbola with a flat slope. This might actually underestimate your zFTP. Obviously a new maximum 20, 30, or 40 min effort would raise the model’s estimate of your CP.

I do understand. Problem for me is that the goal statement is “get that fancy A+ handle for…reasons” and the problem is “been racing FRR and Chasing series so I have loads of short power maximum efforts” combined with “40-minute raw power is really borderline for that A+ 300W minimum”

So was curious if there was anything specific. But sounds like it’s just the honest hard yards that need to be ridden - a 40-minute all-out effort that’s more than 300W should do it (if I can). I’m light enough I’m not worried about the wkg 4.6 threshold (300W is basically 5wkg for me), it’s just that I’m small enough it’s hard for me to actually make wattage :slight_smile:

Thanks for all the insight though, I’ll see what I can do

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lol @Mike_Hardy2272 for me that would be 3.22w/kg, So tiny. i joke. 300w/93kg

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It appears that my zFTP = 1h PB over the last 90 days. My zMAP = 5’30’’ PB (last 90 days). It must be quite similar for most of us I guess :thinking:

My zFTP is between my 25min and 30min best power. zMAP is equal to my 6min best. Not going to even pretend to know why it would be so different for different people. Very different power curves I guess.

usually dead on 6 minutes for me. just off the top of my head i think the info does suggest 4-6 mins for zmap, so i think most should have values in that range. people with flatter power curves can probably expect it to be on the shorter side

dunno about zftp. i’ve seen it around 35 minutes, i’ve seen it lower than my hour power. i don’t do much of that, so it’s all over the place