Inaccurate power meter or anaerobic contribution?

Background: I was laid off at the start of the pandemic so I’ve had plenty of time to follow my trainerroad training plan. This has been great and leading to pretty consistent #quarentgainz. FTP is moving up in leaps and I’m approaching my personal power bests from previous years where I’ve been fit, but not exactly trained.

I have been using a Kinetic Trainer as my primary power source for TrainerRoad and a Stages left arm power meter for Zwift as I will often ride my TR workout on Zwift.

My last training block on TR ended with a rest week 5/18-5/24. Last week I did four large outside rides, and am starting a new training plan today.

I’ve received the following power results on the following days and am curious what to make of it.
5/12: Zwift Race: Had an power change to 277 (Zwift also updated my power to 278) - PM: Stages
5/25: Ramp Test: have a new FTP to 279; also set new seasons best 5 minute power: 339 - PM: Stages
5/31: Zwift Race: FTP to 292; 5 minute power: 353 - PM: Stages
6/1: Ramp Test: had an interrupted Ramp Test due to emergency (was at 105% FTP); started new test: FTP estimated at 279; 5 minute power: 342 - PM: Stages

So the race on 5/31 was VERY short (2.6 miles) and I started warming up 70 seconds before the start of the race. Was it a power meter issue or this anaerobic contribution I keep hearing about or something else entirely?

Thanks for reading, appreciate your input if you have any!

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Hmm. You have been massively ramping up your training from a low base so its quite possible your FTP has gone up that much. You should probably decide based on how well you are coping with the TR workouts or do a longer effort (8m+) soon on fresh legs and see what that gets you.

Bummer about getting laid off :frowning:

Thanks @david! A couple more data points from this week:

Monday: Ramp test: FTP of 279W
Tuesday: Zwift Time Trial: 20 min power of 292W…which translates to ~277W FTP
Wednesday: Trainerroad workout with an FTP of 279W was at the upper end of my abilities, about what I expect from a first workout on a new plan.

So I’m convinced 279 is the number!

Thanks for the kind words on employment, it must be noted, I never would have had this awesome block of training, gotten all the projects done, or even been paid as much had I been working the last 2 months.


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Think of your FTP akin to your body weight. You are measuring multiple times over one month on multiple scales and getting a variety of results clustering around 279. Your FTP and your body weight actually varies every day, every week, every month according to multiple internal and external factors. There is really no precise fixed figure just the best current estimate. If you change test conditions (eg ramp vs 8x2 vs 20min vs 60mn vs zwift race estimate) they would all give a slightly different figure even if you could test on the same day and remain fresh. The main purpose of having your FTP is to plan appropriate training loads. I think within 2% is reasonable for finding the correct zones. This is because zones themselves are a human construct of a categorical system imposed on a completely continuous physiological variable. Ultimately, you are progressing, which is great, and you have a very good idea of your best estimate of FTP which is also great!


Fair enough! As I’ve been fond of saying: the absolute number of FTP only matters on social media. Otherwise it is just a reference point.

Additionally, I increased my minimum FTP estimation duration to account for the fact that I obviously have a fair amount of anaerobic contribution. Which meant my estimated FTP was no longer unreasonably high.

All is now right with my world.

thanks all!

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