• This topic has 7 replies, 5 voices, and was last updated 1 week ago by drew.
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  • Zwift – automatic FTP updates
  • Premier Icon haloric
    Free Member

    Can anyone explain Zwift to me ?

    Normally I just ride and race whatever comes to hand, I’m a bottom half C rider, and Zwift occasionally updates at the end with a ‘FTP update !!!’ message. This seems to go on to your profile, but you can’t view that at zwift.com (afaics) and you can only get to see in the zwift app if you edit your profile. I’ve never done a FTP test ‘cos I’m not normally that bothered.

    My value in the profile was 271 I think. Does zwift auto-update *this* value, or some other value that it doesn’t let you see ?. I don’t remember setting it to 271, so perhaps zwift is doing it. If I drop it down (because you can set it to whatever you want) will I get ‘FTP Update !!’ updates if I ride harder than that value ?. I will have to check.

    I ask because my zwift profile page has the following best ever figures:

    5 sec-> 409, 1 min-> 299, 5 min -> 261, 20 min -> 229

    i.e my best ever 5 minute and 20 minute are less than that profile figure.

    I would expect my actual FTP to be 95% of 229 ? This 20 minute figure at least seems odd.

    This does of course all affect the data I’ve given Robbo for the STW races, but I would to understand it before I fiddle with it.

    My zwiftpower has 282w for 20 minutes, so maybe 271 is correct-ish but zwifts ‘your best’ numbers are wrong ?.

    Ta for any insights.

    Premier Icon robbo1234biking
    Full Member

    I cant help you with how the various programmes auto-update but why not just do a ramp test – they take about 25 mins but only 3-4 mins of real pain (so less than a lap of the volcano). That will give you a figure you can work with then.

    Premier Icon Garry_Lager
    Full Member

    Thought it was just an auto up date whenever you set a pb 20 min power. So 282 for you wold give close to 271ftp – don’t know why your personal bests are not in line with that on the zwift profile.

    It should be obvious to you which is the ‘right’ figure though, as there is a big difference between 229 and 282W for 20 min power. Trying to hold 271W ftp for a sustained time would feel impossibly hard if you were actually at the lower value.

    Premier Icon dangeourbrain
    Full Member

    don’t know why your personal bests are not in line with that on the zwift profile.

    I may well be wrong but seem to recall they’re something utterly bobbins like “your best ride” rather than actual best 20min etc. so if your best 20min was actually on your worst ride it won’t show on your profile.

    Premier Icon haloric
    Free Member

    Turns out it was all a dream.

    I was running the zwift app on my laptop to get at the FTP value (which you can’t get through the website, thanks zwift) when all my actual riding is done on apple tv.

    I foolishly thought that the ‘your best’ figures were for my account, but they are ‘your best on this device’ – my laptop figures are from a ride I did about 2 years ago before I got the atv, the atv has a 20min of 285, which is inline with ZP FTP and the auto-updated profile figure.

    Now all I have to do is work out how to get that 11 minute handicap down..

    I’m pretty sure that any ftp test would be less than what I actually get in a race.

    Premier Icon twisty
    Full Member

    My notional guess based on the figures Zwift comes up with is that it uses a calculation of 95% best 20min normalized power for FTP.
    Whereas other places like zwiftpower use 95% of best 20min average power.

    I think the latter is better for an actual FTP test as it includes the important mental part riding to threshold. Whereas the former is better for capturing your general state of fitness based on efforts from races etc where you’re not trying to do 20min of constant threshold effort.

    Premier Icon dangeourbrain
    Full Member

    the atv has a 20min of 285

    I’m not sure using a quad bike is in the spirit of things. YMMV of course

    Premier Icon drew
    Full Member

    However it is that Zwift calculates your FTP I’ve found it to be pretty accurate. I’ve done one ramp test in Zwift and two half montys in Sufferfest and each time the outcome is very close to the Zwift estimate. Within a watt or two. The hardest I’ve pushed myself on Zwift was in one of the etape stages where I was flat out for 59 minutes and my average power was within two watts of my Zwift FTP which suggests that ,for me anyway, the Zwift algorithm works pretty well.

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