Sudden change in FTP calculation since the latest update

wiko34
2 days ago

  • 0 1 day ago

    It seems you wrote something in the screenshot but it's not readable.

  • +1 1 day ago

    From what I can tell, you added text over a screenshot from Garmin Connect (web).
    It seems to say:

    “Well, I will be 91 next week but does this sudden drop on May 9th, from around 2.30 to 1.40 make sense to you? Using a Garmin 1040 Solar and power pedals and the Garmin HRM Pro. I believe there was a Garmin software update around that time to one unit.”

    Based on the visible data, what you're seeing is a sharp drop in FTP expressed in W/kg not in absolute watts so the most probable causes are:

    • A wrong body weight value; either manually entered, or pulled incorrectly from a connected smart scale or synced app.

    • Incorrect crank length setting on your power pedals;  this can result in large power inaccuracies.

    I suggest checking:

    • The FTP (in watts) chart for that period;

    • Your weight graph around May 9;

    There is no change in Garmin's way of calculating FTP. Here's my own chart — nothing dramatic has happened in years. Slight smile

  • +1 12 hours ago in reply to 5155879

    Thanks for your feedback. You have better eyes than I. Unfortunately, the size restrictions made my comments basically unreadable.  The other comments were: Rode on May 7=41.77 km Ave Speed 20.2 km/h, May 9=30.95 km @20.6 and May 10=72.2 km @ 19.6.  The rest of the comments relate to incorrect HRM readings which I now believe have no bearing on FTP (unless they affect Power).

    That sudden consistent drop also showed up on my Garmin S2 weight scale which I use every morning just in underwear after getting up. The S2 transfers this data to my iPhone and Garmin Connect. It shows: May 6 =74.05 kg, May 7= 73.58, May 8 = 74.28, May 9 = 73.38 and May 10 =73.08. It doesn’t transfer it to my Garmin Edge 1040 Solor which shows my over a year ago  inputted weight as 73 kg. So, my weight info has not really changed to account for this drop witch leave power (N.B. same sudden change in the scale when clicking on “Watts”.

     I enclose the Max 20 Min Ave Power for the last 6 months. Info,  I really only started biking again in April and only tried my newly late Jan/25 purchased indoor wahoo indoor system using my other S-Work Venge bike briefly as I had some set-up problem with Swift I am still working on and having been away.  Yes at my age my power output is not that great, but it seems to have got up in April and again in May from previous months, so that sudden drop is difficult to understand. Most likely the current reading is more correct, and the reading was out before, but why given weight and power info shown. It was last year also always at the 2:30 level and my weight has always been fluctuating between 71 to 75 kg over the last 12 months, based on the S2. You don’t show any sudden drop on May 9 so my drop seems to be a puzzle given weight and power info. The crank length setting was correct when I attached the power pedals to my in August/24 delivered 54 Specialized S-Works Creo SL SW Carbon.  Same length as my 56  S-Works Venge bike. Just checked it and the app shows the correct length per info from Specialized for both bikes of 172.5 cm  So that is not the issue either. Good that I checked as the App told me to install a firmware update for both pedals but that should have no impact on that sudden change. .

  • +1 12 hours ago in reply to wiko34

    I was unable to post the picture. It showed for the last 5 month an average of 63 w and Feb & Mar below that Ave line and Apr and particularly May above that line.  Thus no reason for the May 9th sudden drop.  Based on my manual calculation I may even be below 1.40 so it looks that prior to May 9 the calculation was incorrect, Yet weight, Power, and Crank length no real change. I write this off as an unsolved Puzzle and go with current calculations which I at my age probably cannot get higher. Too bad my HRM v/s iPhone watch gets confused by Premature Ventricular Beats which thus incorrectly reports all other measurements which take HR into calculation making my monitoring my health via Garmin tools weak. 

  • 0 18 minutes ago in reply to wiko34

    Even if you didn’t change anything manually, it’s worth checking the FTP (watts) and weight graphs in Garmin Connect around May 9. Sometimes values get updated by a smart scale or a connected app.

    Another thing to consider: Garmin devices sometimes lose sensor connections mid-ride. If your powermeter disconnects, the device may record zeros instead of “no data,” which drags down the average. If such a ride is used to estimate FTP, the result can be unrealistically low.

    Drastic FTP drops are rarely due to chronic conditions. Tthey’re usually caused by acute incidents like injuries. Not even COVID knocked mine down by more than 10–15%.And you're right: these algorithms are built around “average” users: average age, weight, fitness, and health. But no one is truly average.

    Here’s an example: I still run regularly despite having early-stage knee osteoarthritis. Every time it flares up and affects my runs Garmin detects a VO2max drop.