[Closed] FTP estimation for strava

Do a 20 minute climb as hard as you can. Yr FTP will be around 95% of that power

(Is all this "just" strava's power estimates? they seem wildly variable when I've done road rides without a PM but better than nothing. You could just look at heart rate using the same 20min ride, then a max HR after a 2-3 min full on effort - that'd be easier to use during a ride if you have no live power info)

Strava power estimates really aren't very accurate but, if you're a regular cyclist (riding once or twice a week and ok with the occasional climb) a power to weight ratio of 2.5 is perfectly reasonable.

My average power on rides went up instantly by 10% when I fitted Assioma power meter pedals relative to the Strava estimates, then continued to go up over a few months.

I’ve added 30% to the Strava estimate.

Now how much of that is being able to see a reading on the Garmin and not slacking, how much is more riding over lockdown, and how much is Strava underestimating I don’t know, but some is the latter.

And to be fair, if Strava is making a sensible estimate then some riders (the aerodynamic ones maybe) will get their power overestimated, and some the upright, wide ones will be underestimated.

I would get the same estimated power for riding the same loop at the same speed on the road bike or MTB. Not likely, but Strava doesn’t know.

As mentioned Strava estimated power is just a guesstimate so not to be used for setting zones. There is no correlation to wind so you could be pushing 300watts into a headwind for 20mph or you could be riding with a tailwind putting out 120watts for the same speed.

Heart rate zones would be better if you don’t have access to a power meter.

Strava's estimate is a simple - you weigh X kilos, your bike weighs Y kilos so to move that mass along that segment takes Z amount of energy (joules), Power is force * distance/time, i.e joules/sec. There's an assumption that you are on a decent surface and on a road bike so if either of those aren't true then you'll be putting out more Watts to maintain a given speed. There's probably some adjustment for CdA based on weight and speed.

Heart rate is a distant third when it comes to estimating effort better to use RPE if you don't have a power meter, it doesn't take much figuring out and is surprisingly accurate.

Terrain makes a huge difference to the power you can apply at the pedals - even a slight decline means I struggle to apply anywhere near FTP but conversely an incline means I might be in bottom gear to keep below FTP. So if your route took you over one of the passes you might be at 150% FTP for 20 mins then zero for a couple of mins on the other side so your "average" would be artificially high.

I’ve pushed it up to 250w that gives me 43mins in z7 still. Is that realistic?

No!

Z7 in a seven zone power model is flat out sprinting, the sort of all out effort you can hold for 5-15 seconds. You might hit that level for a second or two now and again doing something like standing to put the power down on a short steep ramp, in a typical three hour hilly ride I might, stress might, accumulate a minute in Z7. I think this link is public - https://intervals.icu/activities/5044248187/power but you can see how little time is spent in the higher zones. That was on a rolling course aiming to keep at about 75% FTP so there's a bit of compensation on the climbs to counter the coasting on the descents.

Personally I'd ignore estimated time in zones, without a reasonably accurate FTP they are meaningless. Just go on RPE, for threshold work it should feel about 8 out of ten, for endurance its 5-6 out of ten. If you can hold a conversation but not sing you are going at the right pace for a three to four hour ride.

What frustrates me about the Strava estimation is they could make it so much better for people who regularly use a real power meter. I ride about 50/50 with and without a power meter (let's say only on the road) and it seems they could update my personal model based on the real data. Clearly there would be bike weight/aero differences, but it would make it much closer, esp as I mostly use a HRM on both road bikes.

Strava can’t even get average power correct reading from a power meter

Wait; do you have a power meter or not?

If you have a power meter, why are you using strava's estimated power figure?

If you don't have a power meter, how are you planning to gauge training based upon zones?

Why don't you just do a ramp / 20min / 2x8 min test?

I don't understand the question.

I have exactly the same thoughts as continuity.

There's no point having power zones if you aren't training with them. If you can't measure power, you can't train with zones.

Wait; do you have a power meter or not?

If you have a power meter, why are you using strava’s estimated power figure?

If you don’t have a power meter, how are you planning to gauge training based upon zones?

Why don’t you just do a ramp / 20min / 2×8 min test?

I don’t understand the question.

I don’t have a power meter. I do use strava. My FTP was estimated at 200w (2w per kilo)
Now strava does some nice estimated graphs which I wondered if they would / could be of use. (After all someone has created this stuff)
However the graphs use my estimated FTP which is self evidently wrong.
Hence wondering what it should / could be.
I know recognise that the estimated graphs are only for people who have actual figures from a power meter and do not relate to my efforts.

As has been said already, strava estimated power is so inaccurate it is utterly pointless.

Power is a useful gauge of fitness and progression even if you aren't using zones to train, however the numbers need to be accurate and consistent to be of use. Strava numbers are neither.

Strava estimates are just random numbers I'm afraid.

I use a power meter on my road/gravel bike so my RPE is fairly well calibrated, the numbers Strava spits out on MTB rides is nowhere near realistic.

Heart rate would be a better indicator of how hard you've been pushing

@lesgrandepotato

If you don't have a power meter to use to train to and have no intention of using power to train; why do you need to know your functional threshold power? Why do you want to know?

I know recognise that the estimated graphs are only for people who have actual figures from a power meter and do not relate to my efforts.

English?

If you don’t have a power meter to use to train to and have no intention of using power to train; why do you need to know your functional threshold power? Why do you want to know?

@continuity I thought I might learn something. The old adage if you measure it you can manage it type thing.
My interest was peaked when the graph showed me initial to be only in z1 and z7. That seemed odd. By playing the figures I can ascertain that strava thinks I have an FTP of 300w or so and we know that’s it’s all conjecture and bobbins.

We live and learn.

@lesgrandepotato

Sorry to continue and be blunt, but without a PM you can neither measure it nor manage it. What, therefore, could you lear?

If you deeply cared about placing yourself into some imagined hierarchy of fitness, doing it on the basis of strava estimation is probably not to be advised =].

@continuity that is what I’ve learned. I didn’t know it before, I do now.

I found a graph and became curious. I’m neither fit nor fast. I’m regular person who may be occasionally curious.

One thing I'll say, if you are keen to get fitter, a power meter is a great tool. You can pick one up new for less than 250 quid and even if you don't use it for specific zone training, it's a great guage of fitness and allows you to pace your efforts and track your progress.

I have a power meter but I also have a 20 minute loop that I ride quite often. Unless the wind is strong, my time round that tells me if I'm improving. If the wind's strong I have to fiddle by around 5%