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DCRainmaker preview of Stryd running power meter
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http://www.dcrainmaker.com/...d-first-running.html

Looks pretty good.

I wonder if the TIckr X could provide data for their algorithms? Maybe Wahoo could license Stryd's software.

I've got a Magellan Echo that would be great for showing this data. Garmin GPS watches could show it easily as well although I think I purchased my last Garmin a few years ago.
Last edited by: Tom Fort: Jan 30, 15 12:28
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Re: DCRainmaker preview of Stryd running power meter [Tom Fort] [ In reply to ]
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About as useful as a Stages as a cycling power meter.
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Re: DCRainmaker preview of Stryd running power meter [Tom Fort] [ In reply to ]
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I just read the review and I'm more than a little skeptical that the device is providing an accurate measure of absolute power. Ray made it obvious that the developers of the device were leading him through the testing protocol (which is fine as long as he's upfront about it) and I think they left out some very important tests.

For instance the device wasn't tested with varying wind conditions. Running into the wind obviously requires more power than running out of the wind at the same pace. Presumably the hardware is simply a multiaxis accelerometer. I would be very surprised to find that the developers can account for wind speed in the algorithms they use to determine power output.

Secondly, it wasn't tested on a lighter (or heavier) runner. All other things being equal, a heavier running should require more power to maintain the same pace. Simply throwing a weight vest on Ray would have resulted in significantly more power to run the same pace (although this could be confounded by changes in running dynamics... but I'm just spit balling). Perhaps there's a calibration step that requires a runner's accurate weight in order to accurate determine absolute power measurements. But I don't recall seeing a calibration discussed.

Which brings me to running dynamics: Galen Rupp running at 6:00 min/mi is (probably) going to run much more efficiently than I am at 6:00 min/mi. An interesting test would have been to line up three or four runners of equal weight but varying ability and have them run the same pace around the track.

Anyway, this device is not a direct measurement tool (e.g. a strain gauge) and will be limited as such. But I'd like to see a much more thorough testing before I'd consider purchasing one. That said, a running power meter is a super cool idea... I hope that people continue to develop these devices.

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Re: DCRainmaker preview of Stryd running power meter [Nick B] [ In reply to ]
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Nick B wrote:
About as useful as a Stages as a cycling power meter.

you are being generous. i believe the comparable cycling "power meter" is the ibike
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Re: DCRainmaker preview of Stryd running power meter [echappist] [ In reply to ]
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Wouldn't pace and heart rate be a far more direct measure of effort for training purposes?
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Re: DCRainmaker preview of Stryd running power meter [SwimGreg3] [ In reply to ]
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For instance the device wasn't tested with varying wind conditions. Running into the wind obviously requires more power than running out of the wind at the same pace. Presumably the hardware is simply a multiaxis accelerometer. I would be very surprised to find that the developers can account for wind speed in the algorithms they use to determine power output.

Isnt the Garmin 620/920 equipped with this as well? If so just have garmin data (albiet it inaccurate for points you've already mentioned) into the Stryd software.

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Re: DCRainmaker preview of Stryd running power meter [franktheguard] [ In reply to ]
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I don't think that would work. In the review, Ray states:

The pod itself is effectively not much different than your average modern running footpod, similarly with some accelerometers in it. In many ways, the magic here isnt the hardware. Its the software. Its the algorithms that enable the company to see through all the noise of running and produce something that feels and looks like regular power meter data that youd see while cycling.

The algorithms he's speaking of are probably very specific to the location of the accelerometer on the runner's body. A device placed on the swinging arm of a runner will experience significantly difference forces than one placed on the torso; or back as the case may be.

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Re: DCRainmaker preview of Stryd running power meter [Tom Fort] [ In reply to ]
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I just want to be able to display Strava's Grade Adjusted Pace as a field on my watch. That works as a pretty good proxy for my RPE.

/kj

http://kjmcawesome.tumblr.com/
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Re: DCRainmaker preview of Stryd running power meter [franktheguard] [ In reply to ]
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franktheguard wrote:

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For instance the device wasn't tested with varying wind conditions. Running into the wind obviously requires more power than running out of the wind at the same pace. Presumably the hardware is simply a multiaxis accelerometer. I would be very surprised to find that the developers can account for wind speed in the algorithms they use to determine power output.

Isnt the Garmin 620/920 equipped with this as well? If so just have garmin data (albiet it inaccurate for points you've already mentioned) into the Stryd software.

Wouldn't wind just affect how far you travel (or how fast you go) and not how much power you are putting out, just like a bike power meter? In that sense, who cares. If this thing is measuring (or estimating) push off force to estimate power, then wind should not matter.

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Re: DCRainmaker preview of Stryd running power meter [SwimGreg3] [ In reply to ]
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Yeah, good point. I guess I thought maybe there was something better than a battery in the HRM.

Not sure how on the torso/back you will ever get wind dynamics either.
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Re: DCRainmaker preview of Stryd running power meter [echappist] [ In reply to ]
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echappist wrote:
Nick B wrote:
About as useful as a Stages as a cycling power meter.


you are being generous. i believe the comparable cycling "power meter" is the ibike


It's still early, but if it in fact, responds in the range of what DCrainmaker is showing, it'll be a ton better than the ibike.

This graph from his review is pretty impressive if it's in fact the real deal. Note how HR lags big time (the green flat line), whereas the run power correlates really well with the hill elevation.


Last edited by: lightheir: Jan 30, 15 14:12
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Re: DCRainmaker preview of Stryd running power meter [lightheir] [ In reply to ]
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Too many flat lines in the Pace line, not sure how they are measuring, but poor sampling rate. Also I would say inaccurate, how does HR go up in a 3 minute test on the uphill, but still goes up on the down.with out an increase in pace?

Also a 3 min test with a few 5m hills? The test appears to "look good"I see zero relevant Data in that chart.

.test is too short. not enough sustained output at any grade or speed to show any value.what so ever.

Maurice
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Re: DCRainmaker preview of Stryd running power meter [lightheir] [ In reply to ]
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I wouldn't be too fast to discount it yet, the initial results over the hilly terrain seem to point to it actually giving out legitimate data which is quite surprising. Will be interested to see a further test with his lady and a fat dude with wind, terrain etc.

That being said.. I don't see the point or any usefulness in it! Seems like a proper triathlete toy.. gadgets over training

I learned a long time ago that the only pertinent information you offer is found within the last sentence.
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Re: DCRainmaker preview of Stryd running power meter [kjmcawesome] [ In reply to ]
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kjmcawesome wrote:
I just want to be able to display Strava's Grade Adjusted Pace as a field on my watch. That works as a pretty good proxy for my RPE.

x 2
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Re: DCRainmaker preview of Stryd running power meter [Mike Prevost] [ In reply to ]
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Wouldn't wind just affect how far you travel (or how fast you go) and not how much power you are putting out, just like a bike power meter?

No. The key here is at the end of the sentence: "at the same pace." Running a 6:00 min/mi pace into a dead on 20 mph head wind is harder (requires more power to maintain) then running a 6:00 min/mi pace directly out of a 20 mph. If the Stryd only uses accelerometers on your torso to estimate power output then it is unlikely that it can account for certain environmental changes like wind. Mind you this is my presumption based on my knowledge of accelerometers and signal processing; I don't know what the Stryd algorithms are actually doing.

Bike power meters work the same way: ride into a head wind at 20 mph, then turn around and coast along with the wind at 20 mph and the power outputs will be very different.

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Re: DCRainmaker preview of Stryd running power meter [Tom Fort] [ In reply to ]
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The absolute accuracy need not be that great if it is consistent for each individual. Ray wrote about using it in racing but I would be more interested in using it to judge training effort levels. Maybe I'm not well trained but my heart rate on different days at a given effort or pace varies a lot. If I had a more consistent measure, that also took into account more effectively the effect of hills it would be nice.

Another thought. If you can use this to hold a fixed target power while running a hilly loop with known profile maybe you can use a similar protocol to the platypus thread thing to calculate running efficiency (analogously to calculating CdA)?
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Re: DCRainmaker preview of Stryd running power meter [Tom Fort] [ In reply to ]
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Just fill me with millions of nanobots that monitor all my bodily functions in real time.
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Re: DCRainmaker preview of Stryd running power meter [davros] [ In reply to ]
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goodboyr wrote:
Wouldn't pace and heart rate be a far more direct measure of effort for training purposes?
you bet. this has been stated by those with much more experience than i: the powermeter for running is called a stop watch (at least on the track), and with grade adjusted pace, you get a really good estimate of the effort you are putting in. The only thing you don't get in return is the work done in joules, but everything else can be taken into account (training load, training intensity, etc) when grade adjusted pace is used.



davros wrote:
The absolute accuracy need not be that great if it is consistent for each individual. Ray wrote about using it in racing but I would be more interested in using it to judge training effort levels. Maybe I'm not well trained but my heart rate on different days at a given effort or pace varies a lot. If I had a more consistent measure, that also took into account more effectively the effect of hills it would be nice.
quite a low bar to clear, as effort can already be gauged quite well using time and gradient.

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Another thought. If you can use this to hold a fixed target power while running a hilly loop with known profile maybe you can use a similar protocol to the platypus thread thing to calculate running efficiency (analogously to calculating CdA)?

calculating CdA requires absolute accuracy, and not just the "consistency" that people like to throw out.
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Re: DCRainmaker preview of Stryd running power meter [Nick B] [ In reply to ]
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Nick B wrote:
About as useful as a Stages as a cycling power meter.

If Stages were the only cycling power meter available, it'd be pretty valuable.
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Re: DCRainmaker preview of Stryd running power meter [SwimGreg3] [ In reply to ]
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SwimGreg3 wrote:
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Wouldn't wind just affect how far you travel (or how fast you go) and not how much power you are putting out, just like a bike power meter?


No. The key here is at the end of the sentence: "at the same pace." Running a 6:00 min/mi pace into a dead on 20 mph head wind is harder (requires more power to maintain) then running a 6:00 min/mi pace directly out of a 20 mph. If the Stryd only uses accelerometers on your torso to estimate power output then it is unlikely that it can account for certain environmental changes like wind. Mind you this is my presumption based on my knowledge of accelerometers and signal processing; I don't know what the Stryd algorithms are actually doing.

Bike power meters work the same way: ride into a head wind at 20 mph, then turn around and coast along with the wind at 20 mph and the power outputs will be very different.

Exactly my point. On a bike, power to go a specific speed varies with wind direction. Same with this system. This is exactly what you want. It IGNORES wind, just like a bike power meter and measures only the power you are producing. It does not have to account for wind and should not. On a bike, you have speed and power. On this device you have pace and power. That is all you need. In other words, this system is estimating power by measuring acceleration. The estimate of power is dependent of wind, as it should be.

Using your example, run a 6:00 pace into a head wind VS tail wind and you will have to produce a higher acceleration into the wind, which presumably this device will measure, therefore more watts. Just like a bike pwoermeter. Wind does not matter for measurement purposes.

Simplify, Train, Live
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Re: DCRainmaker preview of Stryd running power meter [goodboyr] [ In reply to ]
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goodboyr wrote:
Wouldn't pace and heart rate be a far more direct measure of effort for training purposes?

Or how about the Powercal? It seems like it would be a better attempt at generating a Watt number than this device.
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Re: DCRainmaker preview of Stryd running power meter [Mike Prevost] [ In reply to ]
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Mike Prevost wrote:

Using your example, run a 6:00 pace into a head wind VS tail wind and you will have to produce a higher acceleration into the wind, which presumably this device will measure, therefore more watts. Just like a bike powermeter. Wind does not matter for measurement purposes.

If external power as represented by force plates is the gold standard, then running on force plates into a headwind at speed of x will give a different force and therefore acceleration profile particularly for horizontal forces.

Though as you point out since some of the external force changes between the wind vs no wind condition are accounted for by differences in acceleration at toe off, it may very well be good enough. As Ray points out in the review, we won't really know if it's good enough for a little while yet.
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Re: DCRainmaker preview of Stryd running power meter [Kevin in MD] [ In reply to ]
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Kevin in MD wrote:
Mike Prevost wrote:


Using your example, run a 6:00 pace into a head wind VS tail wind and you will have to produce a higher acceleration into the wind, which presumably this device will measure, therefore more watts. Just like a bike powermeter. Wind does not matter for measurement purposes.


If external power as represented by force plates is the gold standard, then running on force plates into a headwind at speed of x will give a different force and therefore acceleration profile particularly for horizontal forces.

Though as you point out since some of the external force changes between the wind vs no wind condition are accounted for by differences in acceleration at toe off, it may very well be good enough. As Ray points out in the review, we won't really know if it's good enough for a little while yet.

Hi Kevin

Yes, thanks. You put it more clearly that I could. I don't really have a good sense of how much that force or acceleration direction changes into a headwind for example. We do tend to lean a bit into head winds, so that may offset the required change in acceleration trajectory a bit and as a result little or no adjustment may be necessary, resulting in the device being "good enough" in the wind.

Frankly, I am not sure how the device can be verified at this point. Comparing the acceleration data to ground reaction forces using a treadmill with force plates is a good start, but I am not sure this tells the whole story.

Simplify, Train, Live
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Re: DCRainmaker preview of Stryd running power meter [Kevin in MD] [ In reply to ]
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Kevin in MD wrote:
If external power as represented by force plates is the gold standard, then running on force plates into a headwind at speed of x will give a different force and therefore acceleration profile particularly for horizontal forces.

However, the underlined part of the statement is not strictly true. Force plates fixed to the ground will measure the force applied to the ground by the runner's foot (F_ground) which would be equal to the sum of forces required to move the runner's center of mass (COM) forward. When running at a constant speed in a fluid like air the sum of forces would be:

0 = F_runner + F_drag + F_ground ---> -F_ground = m*a + 1/2 * rho * v^2 * C_d * A

Where F's are forces, m is the runner's mass, a runner's acceleration, rho is the air density, v is the runner's velocity relative to the fluid, C_d is the runner's coefficient of drag, and A is the runner's frontal surface area. Obviously drag is a pretty complicated topic and has components of form drag, skin drag, parasitic drag, etc. but I think this simplification will work to a reasonable approximation.

So, my point is that a force plate will measure the sum of forces from which power can be calculated. Conversely the Stryd (I believe) only measures the acceleration of the COM of the runner (a in the equation above). Thus variations in the other variables of the equation like a runner's mass or the velocity of the wind relative to the runner will go unaccounted.

However, what I failed to consider earlier is that during the time period in which the running is not contacting the ground and is effectively floating, The F_ground drops out of the equation and any acceleration (or more accurately deceleration) would be due to the fluid. Therefore measuring larger magnitude decelerations during this phase of the gait, and subsequent accelerations during the toe-off or other speed producing phases of the gait, may be an effective way to account for wind speeds.

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Re: DCRainmaker preview of Stryd running power meter [Mike Prevost] [ In reply to ]
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Mike, I think your statement that power meters "ignore wind" threw me off. I think I now understand what you mean: that wind speed need not be known to calculate power.

I had initially assumed that a runner's acceleration vector in time would be unchanged by wind, and therefore unmeasurable by an accelerometer. However, I neglected to consider the period of a runner's gait in which they are not in contact with the ground. In stronger winds, the magnitude of accelerations and declerations required maintain a constant speed would be greater than in weaker wind. Therefore, perhaps it is possible to obtain accurate power measures using only a COM accelerometer.

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