Road Power

[BSRU]

First time today I rode on the road with a power meter(Stages), the past year and a half I have only had a power meter(Powertap) on the bike attached to a turbo.
Very interesting to see that 33% of a 2.5 hour ride was in power zone 1(active recovery), probably due to the undulating nature of the ride(11m per km). This also caused the normalised power to be 40w higher than the average power.
Also the first time I have managed to acheive 1000w(for a very short time), no where near it on the turbo.
Obvious drawback to a turbo is not being able to simulate getting out the saddle on a steep climb, certainly felt it.
It revealed that the guestimated power value produced by "RideWithGPS" is in the right ball park and that hrTSS considerably underestimates TSS.
Don't really need a power meter but just into measuring stuff.

 

[huwsparky]

Agree with regards to turbo. Can't seem to make the numbers on the turbo either. Don't really use it for any max efforts as it's pointless. Usually just do over and under sessions only on the turbo. Don't think I'd use it at all if I didn't have a power meter though.

 

[lukasran]

yeah when i ride outdoors i find a lot of the time spent at 0 power. all that coasting adds up to a fair chunk of time. nowhere to hide on the turbo though, its nearly all effort. i also cant produce same power indoors than out but i think you will find that is the norm amongst most people. stick your powertap on you stages bike and see if they reading the same to be on correct side

 

[HLaB]

There was an article on some web site the other day about FTP being down at leas 30w on a turbo (peak will be down even more). Out side you benefit from momentum but turbo's usually fix the wheel so there's no freewheeling or building up of momentum. Outside you benefit of air cooling too and when thats the right balance you operate most effectively. They listed other factor too but those two were the most significant.

 

[Bollo]

There was an article on some web site the other day about FTP being down at leas 30w on a turbo (peak will be down even more). Out side you benefit from momentum but turbo's usually fix the wheel so there's no freewheeling or building up of momentum. Outside you benefit of air cooling too and when thats the right balance you operate most effectively. They listed other factor too but those two were the most significant.

Your FTP is only a very specific indicator of your ability to produce power with respect to the way in which it's measured, both in terms of the equipment used and the testing protocol.

For example, based on the TrainerRoad 8 minute FTP test performed on a freshly calibrated Kickr, I can bang out an FTP of about 315W (approx 4W/kg). If I try to ride at 315W on the same equipment for an hour, it gets messy - I know because I've tried. My 'true' FTP based on the definition of an hour's steady effort is probably at or under 300W. I've always been better at shorter term, punchier efforts, so this isn't a surprise. Another rider with a nominally lower FTP based on an 8 minute test but with better stamina would probably have me over 60 minutes.

Because of this I don't tend to sweat (no pun) my absolute FTP, because it's not a number that can be compared meaningfully across different types of effort. It is useful if I want to scale workouts on the kickr and keep an eye on my level of fitness by looking at longer term changes.

 

[HLaB]

Your FTP is only a very specific indicator of your ability to produce power with respect to the way in which it's measured, both in terms of the equipment used and the testing protocol.

For example, based on the TrainerRoad 8 minute FTP test performed on a freshly calibrated Kickr, I can bang out an FTP of about 315W (approx 4W/kg). If I try to ride at 315W on the same equipment for an hour, it gets messy - I know because I've tried. My 'true' FTP based on the definition of an hour's steady effort is probably at or under 300W. I've always been better at shorter term, punchier efforts, so this isn't a surprise. Another rider with a nominally lower FTP based on an 8 minute test but with better stamina would probably have me over 60 minutes.

Because of this I don't tend to sweat (no pun) my absolute FTP, because it's not a number that can be compared meaningfully across different types of effort. It is useful if I want to scale workouts on the kickr and keep an eye on my level of fitness by looking at longer term changes.

I'm only quoting FTP because that what the article looks at but the basic conclusion regardless of what measure you look at (FTP, max power or sustained ave power) power is down on a turbo compared to the road (no momentum, no air cooling).

As an aside thats not your FTP its a prediction based on an algorithm; your true FTP would be a power level you could maintain over an hour and remain Functional. Its relatively easy to inadvertently bias an algorthm based on a snippet by pushing too hard in it.

 

[BSRU]

Used the power meter yesterday on a 100kn ride to surpress my usual over enthusiasm at the start of a ride and at the beginning of any climbs.
Completed it in about the same time as last year but wasn't dying on the last climb after 92km which usually really hurts.
Also had loads of energy left for the last 10km so I could give it some gas allowing me to ride home at a very good pace(for me).

 

[Joshua Plumtree]

Your FTP is only a very specific indicator of your ability to produce power with respect to the way in which it's measured, both in terms of the equipment used and the testing protocol.

For example, based on the TrainerRoad 8 minute FTP test performed on a freshly calibrated Kickr, I can bang out an FTP of about 315W (approx 4W/kg). If I try to ride at 315W on the same equipment for an hour, it gets messy - I know because I've tried. My 'true' FTP based on the definition of an hour's steady effort is probably at or under 300W. I've always been better at shorter term, punchier efforts, so this isn't a surprise. Another rider with a nominally lower FTP based on an 8 minute test but with better stamina would probably have me over 60 minutes.

Because of this I don't tend to sweat (no pun) my absolute FTP, because it's not a number that can be compared meaningfully across different types of effort. It is useful if I want to scale workouts on the kickr and keep an eye on my level of fitness by looking at longer term changes.

Why not do both an hour FTP test and an 8 or 20 min test. Not one after t'other obviously! See what the percentage difference is between the two, then use this figure to work out your FTP when doing the shorter test in the future.

 

[Bollo]

Why not do both an hour FTP test and an 8 or 20 min test. Not one after t'other obviously! See what the percentage difference is between the two, then use this figure to work out your FTP when doing the shorter test in the future.

I'm afraid you've missed my point. All I'm saying is that.....

An FTP value is just a convienient single-number summary of my ability to produce power for an arbitrary-ish time period in a controlled, repeatable environment. It can't capture the full complexity of the dynamic physiological processes and external factors that determine my ability to generate power across a wide range of real-world scenarios.

Your 'FTP' depends on how you choose to estimate it, or more precisely any test that doesn't follow the definition (ride like a bugger for an hour and keep it level) will be approximate.

But the points above don't really matter (or at least not to me!). More precisely, 315W using an 8 min test or 300W for 20 mins. Meh! But if I started to see my power drop consistently for a sequence of 8 min tests on the same kit, then I'd be bothered. Also, if I pick a TrainerRoad workout, I want to scale the effort so that it makes good use of the time I'm putting in on the Kickr. Enter my FTP again. Beyond that, I repeat meh.

It's also worth remembering that metrics like normalised power and hence TSS, TSB and the like are based on empirical models that will only be approximate for any single rider. The numbers can be instructive, but they're by no means 'the truth'.

Baaaaack to the OP and Hlab's point, I think Hlab and me are agreeing that power output across different riding scenarios are very difficult to compare directly. The only bit I don't understand is why real world scenarios would give consistently higher power than turbo efforts? Max power is the only one I could believe from direct experience, as the damped resistance provided by turbos would make it difficult to get the high cadence AND high torque that usually supplies the peak power measurement on a ride. But max power is the least useful measure.....