My power zones: have I calculated my FTP correctly?

A light bike doesn't replace good fitness.

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Posts: 599
Joined: Thu Apr 01, 2010 10:24 am

by CarpetFibre

Hi all,

Had this powertap for a while, only just started using it properly due to injury. The other day I did a 20 minute balls-out effort to calculate my FTP on the turbo. I like the turbo because I can keep my effort very steady indeed, before I was injured I was well tuned to doing 20 minute intervals on the turbo that really hurt. I did them very regularly so I knew I could measure my effort perfectly, despite not having any data whatsoever in those days. Here's the graph - as you can see I wasn't taking it easy - HR through the roof:


228W average. Not bad at my weight but definitely a huge loss from about 3 months ago, before my injury, when by estimation on hill climb times, I could push close to 300W for 20 minutes.
So I calculated my power zones from that as well as my heart rate zones. Now I'm doing a lot of zone 2 training out there just to get some base fitness over the winter - I've got no further goals for the rest of the season and I'm itching to be out on my bike as much as possible having been off for 3 months. Zone 2 for me seems to be 116-164W but when I'm out riding at that pace, it's soul-destroyingly slow. No endorphins, no rhythm - I can barely keep a smooth pedaling style it's so slow, and I'm riding at 160W average right at the top end of my apparent zone 2.

Today I went for a more spirited ride with a mate - just an hour out on the road, a couple of hills as that's what we like to do. This was NOT a hard ride, and it's telling me I did 233W average weighted power for an hour? That's like 20W higher than my FTP. I danced on the pedals up a hill at 300W for 3 minutes and I wasn't remotely knackered at the top - it felt like the effort I started on the turbo for my 20 minute test.

What's going on here? The power meter died right at the end of my 20 minute test on the turbo because it was out of batteries. These subsequent rides have been with new batteries - could this be the issue? As for zone 2... endurance - surely you don't lose this fitness as fast as your top end after 3 months off the bike. Have I still got a lot of residual fitness from earlier that's making my calculated zone 2 too easy?
After coming back from my injury I have to admit I've totally lost my top end power - I just get dropped by my mates on 5 minute hills whereas they were the dropees beforehand. But my all day dieseling around the lanes doesn't really feel like it's taken a hit. 6 hour rides I feel are quite doable in the weekly training.

Sorry if I've rambled a bit. Should I do another 20 minute power test on the road? Or is zone 2 training really that easy?

by Weenie

Posts: 1405
Joined: Tue Sep 14, 2010 3:28 pm

by bricky21

After an extended period of time off the bike I need to adjust my power zones over the course of a few days until it stabilizes. I suspect if you do another test you're going to get a higher number.

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