rubiksoval

How would this be more useful than using average speed as affirmation?

That's what is actually real and what actually matters. And seeing as how Strava is estimating that wattage based solely on that speed, why resort to estimations instead of the actual thing?

WhyFi

It's definitely a coarse tool and probably not that much better than a stopwatch on a given course but, in theory, I guess it would be the flexibility to change routes and even out things like forced stops/slowdowns that can impact average/moving speed.

Sy Reene

Pretty much yup.

Hey, one thing I was peripherally aware of that Strava added at some point early this year but not clear it's factored into calculated power, is wind direction and speeds, and/or how well this helped or is a non-factor.

caloso

I have a power meter and have observed that Strava’s power estimations are worthless. As someone else pointed out, it doesn’t know what the wind is like, whether you’re riding in a group, whether you’re sitting up or in the drops, what you’re wearing, etc.

Barry2 

I was using a HRM and Strava to monitor estimated power numbers on my rides. The estimates showed my power as unacceptably low.
So I spent a bunch of money and installed a power meter on my bike. Now I know for sure that my power is unacceptably low.
The Strava/HRM numbers were plenty accurate for the price I paid for them.

Barry

RChung

There are differences in road surface in Zwift and, of course, there's also drafting. I haven't uploaded Zwift files to Strava but I've analyzed the "physics" model in Zwift with a calibrated power meter to estimate CdA and Crr for different setups. For example, the Jungle loop has really bad road surfaces and Zipp 808's don't really work well there.

[Edited to add] You can buy faster wheels or frames in Zwift. I wish you could buy better tires and tubes.

Grouperdawg

I love having a power meter, I look down at my watts way more than speed. It’s the only metric that is what it is no matter what. Not just for training too, I like looking at it when I’m up front especially with weaker riders I can gauge what they can stay on with.

I’ve had my power meter for almost a year now and understand it a lot better than when I first got it. I can’t see how you could create an algorithm that knows what’s going on during your ride, Drafting, wind, pavement, rolling resistance, etc etc imho it’s a stat I would not look at as an estimate. I also use my watch as a back up during rides if my bike computer battery is low and rarely is the power within 20 watts of my bike computer upload on strava. If you were riding flat with no wind and by yourself and all other variables entered were right, you might get a rough idea. Even in a group ride my average power can be 50 watts or more different then another rider if one of us stayed up front a lot more and also if a significant weight difference.

Het Volk

I would put it this way...and this is from experience with a Quarq power meter on my road bike and now a power meter on my Wahoo Kickr.

Power meters on road bikes themselves i have become less enamored with from a training perspective. Riding outside, unless doing a sustained climb, it almost impossible to really dial in a decent plan and stick to it. Traffic, wind, stop lights, and all sorts of aspects to the unpredictable nature of riding on the road makes training with power difficult. So they are really only useful (from my perspective) analyzing races, long climbs or on a trainer.

Which gets met to the Wahoo Kickr, which my cross bike sit on. Now, I can actually use power to train. I can dial in an intervals, lock in a power setting, (makes 20 minute tests really effective), and nothing gets in the way of my training plan with power.

If you are using Strava as a training tool, it is very rudimentary. And its power feature even more-so.

rubiksoval

It sounds like a power meter showed you how much coasting/soft pedaling you may typically do outside, which I believe is a huge boon and an area most riders can really make substantial and effective changes.

It's pretty easy to simply move beyond that, though, and focus on keeping constant pressure on the pedals the entire ride (which is a huge change for many).

Of course, I can understand traffic and lights, but that's where you have to choose routes. Not every ride is a workout, but those that are have to be appropriately planned. Just like with nutrition and freshness, routes with minimal stops have to be used if they are at all available.

Not sure how wind affects anything, though. Everything else you simply have to keep pedaling hard. Only using indoor training to utilize power is a massive waste, in my opinion. Unless you're looking to become a Zwift champion or something, performance happens outside.

Het Volk

I ride outside every day I can. But if doing a Zone 2 base period, on the trainer I maximize the training because on the road, it is tough to stay dialed in on one zone.

Het Volk

I ride outside every day I can. But if doing a Zone 2 base period, on the trainer I maximize the training because on the road, it is tough to stay dialed in on one zone.

I find the power meter while on the road best for post ride analysis or, occasionally to keep me either toned down or a signal to tone it up.

ericcox

I kind of agree with both of these. I'm very new to using a PM on my outdoor bike. I definitely prefer indoors for very set workouts based on zones, but I find the data on outdoor rides very useful for setting a sustainable pace (making sure I'm not going too hard into the wind early in a ride, for example), and for avoiding long lulls (on downhills with a tailwind, for example). So the use of the power meter is different for training versus a non-structured ride, but still helpful.

Oh, and strava data really doesn't match my pm.

RChung

Different riders respond differently to different amounts of structured training. Coggan used to say his book is "Training and Racing *with* a power meter" not "Training and Racing *by* a power meter."

People trained pretty effectively with just a HRM, and before that with just a speedometer, and before that with just a regular training route and a wristwatch. Training is one of the least demanding things you can do with a power meter. That's especially true if you're only using it for indoor riding -- that's why many training apps can use just a known trainer and a speed sensor.

[Edited to add] So, training is a relatively simple use for power, and training in a controlled environment is even simpler. Much of the semi-arcane stuff underlying the WKO-ecosystem is based on normalized power, not average power, because of the recognition that riding outdoors on real roads in real wind with other real riders is highly variable. NP was devised as a way to normalize or standardize a highly variable ride into something that could be compared to other rides. If all you're doing is riding for a targeted time in a targeted zone on an indoor trainer, I can see why you don't see much value in on-bike power. Nothing wrong with that. Some people prefer it, some have other needs.

Het Volk

Never said I did not see value. But what I did find was that structured training is more difficult when trying to target specific zones over specific times outside, while training. I still use it for ride/race analysis, and helping me identify if I am coasting too much on a ride or going to hard (via the Garmin Edge which I can set alerts).

rubiksoval

But that's what I'm saying. You can "learn" to hold steadier power. It's just something you have to practice. I started out with a powermeter and my watts were all over the place. Now I routinely do rides with my average and normalized power within 5-10 watts of each other with less than 10% of the ride in Z1. It's just something you develop over time as you pay attention to it. No alerts or anything else needed. You just have to keep checking until you dial in your efforts.

I don't get what post ride analysis you need for a regular training ride on the road. Do you take notes and stick them to your handlebar for the next training session? If you have the power meter, look at it and adjust your effort accordingly.

RChung

Right, sorry, I was being imprecise. You said you didn't see *as much* value in it from a training perspective. It's inarguably easier to stay within a targeted zone for a targeted time in an indoor environment, which is superb if one's goal is to be the best at sticking to a plan. But, as Mike Tyson said, "Everyone has a plan until they get punched in the mouth."

asgelle

I would add that it's worth noting the normalized power algorithm uses a 30 second rolling average because many metabolic processes have a half life of about that duration. That is, fluctuations shorter than that (especially those on the order of a few seconds) have minimal impact on training adaptations so it isn't necessary to try to slavishly ride in a narrow range around a target.

RChung

And the "zones" themselves have mostly gray boundaries. Coaches like well-defined boundaries because it simplifies their prescriptions and makes it easy to see if clients meet their assigned targets, but there's no RCT that shows that strict adherence to a workout plan produces the best outcomes. There are a lot of workout plans that address the same thing: if there were only one best surefire way to achieve an outcome, all workouts would look alike. That we can get to roughly the same place via different routes suggests that the destination isn't terribly path dependent.

Het Volk

Your making an argument against power meters and just “ride, ride lots, and ‘fartlek’ intervals”

cybirr 

This a data point of one rider. May of this year I started using a power meter. Here is two attempts from the same Strava segment just days apart, with and without the meter. Similar weather/winds.



4.85 mile circuit

Very close numbers. Other examples of similar segments show similar results. Probably a range of up to 10% for longer, consistent segments. Variation goes higher for shorter segments. However, if it's a sprint or a variation of sit/stand the discrepancy goes wild. I think it's an interesting approximation but not usable for much outside of long, consistent efforts with little variation of speed, cadence or elevation.

RChung

This is pretty funny.

Grouperdawg

i wonder if strava uses other riders power meter data for segments

rubiksoval

I pulled this from a KOM I have. Same segment, power meter, and bike, just the wind and clothing is different (I'm noticing my clothing, winter vs. summer, can impact my speed by 1 mph+). I've done it a number of times, but nearly all of my segments are pretty much like this with significant variations in power needed for particular speeds on particular days.

rubiksoval

Nope. Different weights, different set ups, different conditions. It'd be completely pointless.

Grouperdawg

It all seems pointless to me but the estimates would be closer if they did this. Segments with climbs where wind isn’t as big a factor and they used rider weights from their profiles probably work somewhat.

For example; when I look at KOMs for a segment; I look at the top ten or so that used a power meter and I can get a rough idea of what power is needed to be competitive on that segment.