Average watts

[si_c]

For the Strava estimated power, wind assistance/hinderance isn't accounted for well iirc, but give it the best weight data you can (you; kit you're wearing on ride; bits in jersey pockets; bike; any extras fitted to bike; the bidons etc).

I did that before I got a power meter when I was commuting daily, the estimated power output on a flat out and back was around 20% out. Consistently and regardless of things that make a substantial difference such as temperature and wind direction/speed.

 

[si_c]

I confess that my tests were done only on the Cragg Vale climb, which takes me over 25 minutes. That is long enough to get a good idea of what I could do on a longer, more varied ride. The calculator suggested that I had done 221 W. My power meter measured 215 W. Those figures are pretty close!

This is absolutely the best case for estimated power - constantly climbing so the biggest factor will be weight related drag with overall speed low enough that aerodynamic drag is a very small factor.

If no long hills are available then a flattish route taking 20+ minutes without stops for junctions etc. would give some useful data.
If there is a strong, gusty wind (like here today!) then any estimate is going to be more of a guesstimate!

Any wind will make it a guestimate, especially if you have a strong tailwind or a light headwind or if you are sitting particularly upright.

 

[Dogtrousers]

Just out of in

I confess that my tests were done only on the Cragg Vale climb, which takes me over 25 minutes. That is long enough to get a good idea of what I could do on a longer, more varied ride. The calculator suggested that I had done 221 W. My power meter measured 215 W. Those figures are pretty close!

If no long hills are available then a flattish route taking 20+ minutes without stops for junctions etc. would give some useful data.

If there is a strong, gusty wind (like here today!) then any estimate is going to be more of a guesstimate!

Just out of interest I just put in the figures for a 1.8km, 6.7% generally quite consistent (except for a short 10% bit) climb I did last weekend (no noticeable wind) and the answer was within 1.5% of the measured value!

There's some flukery in there because I don't really know how much my bike + gear weighs, how much water I was carrying and stuff. So I'd be surprised if my weight figures were within 5%.

 

[esoxlucius]

I confess that my tests were done only on the Cragg Vale climb

Well if wind is a hindrance on the accuracy of Strava then I'd have thought Cragg Vale could possibly be one of the worse tests you could do.

Climbing Cragg Vale can be brutal once you get onto that barren last couple of kilometres towards the reservoir at the top.

 

[ColinJ]

Well if wind is a hindrance on the accuracy of Strava then I'd have thought Cragg Vale could possibly be one of the worse tests you could do.

Climbing Cragg Vale can be brutal once you get onto that barren last couple of kilometres towards the reservoir at the top.

True for Strava guesstimates, but I was measuring power so I wasn't too bothered. (Strictly, I WAS bothered because I was trying for a PB, but we are discussing power here.)

I once took nearly an hour to do that climb because of a headwind from hell. On another occasion I had to stand in my lowest climbing gear to get down the hill against a freak northerly headwind from hell!!

I thought that it would be interesting to check the numbers for my last 10 power metered rides. My FTP (based on me doing the Cragg Vale climb as fast as I could) was around 200 W. These 10 rides were done at a more sustainable level of effort...

1 hour 36 minutes, 178 W (Normalised power 178 W)
1 hour 27 minutes, 164 W (Normalised power 163 W)
3 hour 16 minutes, 155 W (Normalised power 154 W)
1 hour 15 minutes, 184 W (Normalised power 182 W)
1 hour 06 minutes, 181 W (Normalised power 183 W)
1 hour 03 minutes, 179 W (Normalised power 186 W)
1 hour 00 minutes, 175 W (Normalised power 168 W)
1 hour 48 minutes, 174 W (Normalised power 174 W)
1 hour 24 minutes, 153 W (Normalised power 154 W)
1 hour 05 minutes, 173 W (Normalised power 185 W)

So, my power up the long climb gave me my FTP value. Bike Calculator comes up with a similar number. That number suggests what I might do on longer, steadier rides over variable terrain, and the data for those 10 rides support that.

 

[esoxlucius]

I once took nearly an hour to do that climb because of a headwind from hell.

Lol, I can relate to that. One of my most embarrassing moments on a bike came on Cragg Vale. On one particular very windy day a few years ago I was going up there and could see three guys up ahead staggered. We were all strangers, we just found ourselves lumped together on this climb from hell.

Towards the top we came together in a sufferfest. I was at the back and it was hard enough even sheltering. But my bravado got the better of me and I pulled out to overtake the other three, putting a fair effort in to do so. Huge huge mistake on my part, lol.

I got to about 20-30 bike lengths in front and I was spent, my goose wasn't cooked, more like burnt to a crisp! I was totally dead. And then it happened, the other three passed me, all looking at me tutting and shaking their heads. Lol. Ugghhh, I shudder just thinking about that day, lol.

 

[roubaixtuesday]

Strava will be reasonably accurate on a hilly ride, where most the the power goes to defeating gravity, which is easy to calculate and invariant.

Strava will be miles off on a flat ride, where most of the power goes to aero drag, where wind conditions, bike design and rider position are unknown.

 

[esoxlucius]

Well, I did it. I downloaded the Strava app on my phone and went out for a short ride yesterday afternoon as a tester.

And low and behold it did actually give me the information I was curious about, average watts. It said for the duration of the ride I averaged 155w!

Thing is, after what you guys have said on this thread, that figure means absolutely diddly squat to me now.

One, I don't know if it's truly accurate, and two, I don't believe there's anything I can take from that figure to tell me if i'm any good or not!

You're all probably right, a power meter is arguably the best way. But like I said, I'm only curious at this point, my power output isn't the be all and end all. I'm only a recreational cyclist, it doesn't really matter at the end of the day.

 

[esoxlucius]

Oh, and regarding the "free" Strava usage. I've already had alerts about the 30 day free trial and then you pay, which I haven't clicked on.

It is my understanding that the very basic Strava is free, where it gives you a nice little map where you've been and some ride info too. But as soon as you want to add extras, then you start paying. Is that about right?

 

[N0bodyOfTheGoat]

Well, I did it. I downloaded the Strava app on my phone and went out for a short ride yesterday afternoon as a tester.

And low and behold it did actually give me the information I was curious about, average watts. It said for the duration of the ride I averaged 155w!

Thing is, after what you guys have said on this thread, that figure means absolutely diddly squat to me now.

One, I don't know if it's truly accurate, and two, I don't believe there's anything I can take from that figure to tell me if i'm any good or not!

You're all probably right, a power meter is arguably the best way. But like I said, I'm only curious at this point, my power output isn't the be all and end all. I'm only a recreational cyclist, it doesn't really matter at the end of the day.

You could plug ride section details into http://bikecalculator.com/ and see how it compares to Strava's power estimate.

What you take from this power estimate depends on how you rode yesterday on your first Strava recorded ride. You may get a bit more insight if you used a heart rate monitor (ideally a chest strap for better accuracy, the sensor in my newish Xiaomi 5 Lite smartwatch is pathetic, from an "athlete" exercise perspective... It thinks my max heart rate yesterday was 105bpm, my Coospo chest strap recorded 169bpm on my ride on a 0.5 mile 4% climb at an effort I wouldn't have been able to sustain much longer than the 2mins it took on my ebike in maximum assistance mode).

 

[Dogtrousers]

If you were to start using a HRM, and figured out your MHR you could familiarise yourself with your HR zones and after the ride you could see how much time you'd spent in zones with names like "easy" "aerobic" and "threshold".

If you were to start using a PM and figured out your FTP you'd get broadly similar info. The power zones would have similar names. And they would have wattages associated with them.

Both of them would enable you to classify what kind of effort you were putting in and to plan your future rides according to the type of effort.

But you probably already know (from perceived exerton) if that was a "tough, pushing it" ride or a "taking it easy" one. The digital toys just confirm and quantify this.

So it's really a question of whether you find the use of digital toys an enhancing experience or not. Personally, I do. I love my gadgets. But I don't kid myself that they are necessary.

 

[esoxlucius]

I love my gadgets. But I don't kid myself that they are necessary.

It would be nice to have all the clippets of info from a ride, just out of curiosity more than anything. But that's where I struggle because to get this info it does involve gadgetry and technology. That's where I fall flat on my face, I'm a bit of a techno phobe.

I suppose at the end of the day my lungs, heart and legs are the only "gadgetry" I need to tell me whether I'm giving myself a good workout or not, and every ride I go on they seem to shout very loud at me, lol.

And you're right, unless you cycle to pay your mortgage and feed your kids, where performance is everything, then it is totally unnecessary really.

 

[ColinJ]

I enjoyed the power meter donated by a cousin so much that I bought another one for my best bike.

I soon discovered something that I had never really realised... Even the slightest uphill drag requires a huge increase in power to maintain speed. I thought that I rode along trying to maintain a steady effort (power) but in reality I try to maintain my cadence (speed). Obviously, steep climbs are different, but on 1-2% drags my speed tends to stay the same as on the flat; I just push much harder without even realising it. About 150 W to do 27 km/h on the flat, but 225 W to do that speed on a 1% drag!

 

[midlandsgrimpeur]

One, I don't know if it's truly accurate, and two, I don't believe there's anything I can take from that figure to tell me if i'm any good or not!

As discussed in the thread, Strava is not particularly accurate IME (I have used a PM for around 10 years). I think one of the main issues is its reliance on speed as part of its calculation. If you are going slowly (without a PM) it records an incredibly low power output, it can't factor in head winds or other conditions which mean you could go 3-4mph slower than normal but actually be cycling at a higher power output. As above, it doesn't factor in rider weight, aerodynamic profile and son on, all of which have a noticeable impact on power output.

As for are you any good or not, this is a long and complicated question that relies on a lot of physiological parameters! From personal experience and as someone who has done a fair bit of testing under lab conditions, you really need to know a fair few things such as; MAP (Maximal Aerobic Power), Vo2 Max, Gross efficiency, aerobic threshold/lactate threshold and so on. Most cyclists who get quite serious will go off power numbers and use max power for 60, 20, 5 and 1 minute(s) (usually expressed as watts per kilogram of weight) to give a good indicator of where they are at.

As a very (very) basic rule of thumb, if your 60 minute power (i.e. the maximum wattage you can sustain for 1hr) once divided by your body weight is anything above 3.0 watts per kg then that is a pretty decent level (way beyond most fit recreational cyclists). 4.0 watts/kg plus you are at the very upper end of amateur cyclists and 4.5 w/kg+ you are in a very small minority.

 

[esoxlucius]

Well, it would seem that given all the info I've received in this thread, my opening sentence in my initial post, "this could be a very daft question but I'm going to ask it anyway", is indeed a very daft question! Lol.

I should have known that nothing's as straight forward as you'd like it to be. I think I'm pretty good anyway even though I can't measure it, lol.

Thanks for all the input guys, it's been an eye opener that's for sure.