Login required to started new threads

Login required to post replies

Prev Next
Re: DCRainmaker preview of Stryd running power meter [dgran] [ In reply to ]
Quote | Reply
dgran wrote:
dcrainmaker wrote:
Andrew Coggan wrote:
A few thoughts...

Combining the above with the fact that runners don't generally have to be able to rapidly change pace the way cyclists do, that they aren't as influenced by environmental conditions (e.g., wind), that they tend to utilize flat surfaces (tracks) for structured training, etc., and I can't see a running power meter having a significant impact on how people actually train and perform.


Honestly, I'm surprised to see you write. Mostly because it really makes no sense.


I'm not surprised and I agree with Coggan. Cyclists regularly remark at how they witness tremendous variability in average speed for the same power output because of the strong effect from wind. The Stryd looks to be an interesting data point but I suspect for many runners it will correlate so strongly with their time piece that it won't add much value. The one case where it may be useful is to aid pacing over longer runs on unfamiliar terrain, but I think most endurance runners already know when they are running a sustainable vs unsustainable pace. This device could help them abide by the plan better.


I can see a running power meter changing the way people train - but would it be a change for the better.

I can see a massive market for online power based training plans and software, it will go the way cycling has. In no time runners will be assuming you can't train effectively without a running power meter and will be going out training tying to stay in zones and worrying about if they have their FTP set correctly and how many TSS they score.
Last edited by: Trev: Feb 5, 15 2:00
Quote Reply
Re: DCRainmaker preview of Stryd running power meter [Trev] [ In reply to ]
Quote | Reply
This gadget is priced at $120. That is incredibly cheap.

If we set aside accuracy there is another consideration here.

If you have power, you don't need heart rate. So it is a minimalist and affordable option.
Last edited by: Trev: Feb 5, 15 2:17
Quote Reply
Re: DCRainmaker preview of Stryd running power meter [Andrew Coggan] [ In reply to ]
Quote | Reply
Andrew Coggan wrote:
A few thoughts...

Knowledge of a person's actual power output while cycling is immensely valuable, because:

1) mechanical power is what moves the bike down the road, and

2) cycling economy/efficiency does not vary dramatically between individuals, such that power provides a reasonable proxy for actual metabolic demand.

With that in mind, consider a running power estimator, i.e., one that relies on GPS, acceleromters, etc., to calculate power:

1) since power is being determined indirectly, the reported values provide no further insight into someone's actual performance than does knowledge of their pace and changes in elevation (although if accurate, estimated power does have the benefit of pinning a single number on things), and

2) running economy varies much more between individuals than does cycling economy/efficiency, such that the calculated power may not provide a valid/reliable indication of actual metabolic demand.

Combining the above with the fact that runners don't generally have to be able to rapidly change pace the way cyclists do, that they aren't as influenced by environmental conditions (e.g., wind), that they tend to utilize flat surfaces (tracks) for structured training, etc., and I can't see a running power meter having a significant impact on how people actually train and perform.

A running power meter would have to be accurate.

To give an example of how inaccurate or unreliable power readings can be I did a little experiment on a treadmill at the gym which shows speed gradient and watts.

I don't know how they calculate power but it was misleading and thus useless.

I was getting approx 240 watts for running 6 mph on the flat and 180 watts for walking 3 mph at 15% gradient. But heart rate and perceived effort and breathing was harder at 180 watts. The machine although it alegedly takes into account weight seems to vastly overestimate flat running. Incidentally if you do a quick wattage calculation from speed gradient and weight the 3 mph 180 watts is near enough.

A cycling power meter when calibrated etc correctly is +/- 1% to 2% accurate. Even a slight gradient in cycling results in a massive wattage increase to hold the same speed. 20 mph on a 2% gradient would need 80 more watts than a 1% gradient for an 180lb rider. But the same increase in gradient for a 180lb runner at 8 mph would require only approx 30 watts more. So for a running power meter to detect changes in power on small gradients it would need to be very accurate. Note most triathletes wont weigh 180lbs.

To detect any changes in wattage due to slight wind or slight gradients a running power meter would have to be even more accurate than a cycling power meter.
Quote Reply
Re: DCRainmaker preview of Stryd running power meter [Trev] [ In reply to ]
Quote | Reply
There are many power points needed for data collection... the shoulders and arms, quad, calf (for high kick back), top of foot. As that one mount point will report only 240watts just like a bike... but here there are more moving parts the influence power that really the person is probably at 340w

http://www.coupleofathletes.com
Quote Reply
Re: DCRainmaker preview of Stryd running power meter [synthetic] [ In reply to ]
Quote | Reply
synthetic wrote:
There are many power points needed for data collection... the shoulders and arms, quad, calf (for high kick back), top of foot. As that one mount point will report only 240watts just like a bike... but here there are more moving parts the influence power that really the person is probably at 340w

The wattage will always be an estimate because you're measuring acceleration, not force. The contribution of the arms would partially show in the acceleration, but there's probably some reasonable assumptions to be made. Those with good leg mechanics, probably tend to have equally good arm mechanics.

The point isn't that the wattage value is accurate, it's that it's repeatable and represents your output in a more precise way than GPS data and you don't need a measured route and stopwatch.


TrainingBible Coaching
http://www.trainingbible.com
Quote Reply
Re: DCRainmaker preview of Stryd running power meter [motoguy128] [ In reply to ]
Quote | Reply
motoguy128 wrote:
synthetic wrote:
There are many power points needed for data collection... the shoulders and arms, quad, calf (for high kick back), top of foot. As that one mount point will report only 240watts just like a bike... but here there are more moving parts the influence power that really the person is probably at 340w


The wattage will always be an estimate because you're measuring acceleration, not force. The contribution of the arms would partially show in the acceleration, but there's probably some reasonable assumptions to be made. Those with good leg mechanics, probably tend to have equally good arm mechanics.

The point isn't that the wattage value is accurate, it's that it's repeatable and represents your output in a more precise way than GPS data and you don't need a measured route and stopwatch.


Out of interest, how accurately do running GPS devices measure speed?

Would they be accurate to 0.1 mph? The study below is a bit mixed and I'm not sure they tested the sort of device commonly available to runners.

http://www.ncbi.nlm.nih.gov/pubmed/25254901
Last edited by: Trev: Feb 8, 15 1:49
Quote Reply
Re: DCRainmaker preview of Stryd running power meter [Trev] [ In reply to ]
Quote | Reply
Trev wrote:
Out of interest, how accurately do running GPS devices measure speed?

Would they be accurate to 0.1 mph? The study below is a bit mixed and I'm not sure they tested the sort of device commonly available to runners.

http://www.ncbi.nlm.nih.gov/pubmed/25254901

Accuracy depends on all sorts of factors. Speed and direction of movement, location (forest, mountains, city, open field, etc), type of gps, is a differential gps used, etc. Walking at 5kph in a straight line on open roads, probably very accurate. Running on a soccer field with quick changes of speed and direction, probably not so accurate.

Team sports have switched to local positioning systems for accurate measurement of speed and acceleration.
Quote Reply
Re: DCRainmaker preview of Stryd running power meter [motoguy128] [ In reply to ]
Quote | Reply
motoguy128 wrote:
synthetic wrote:
There are many power points needed for data collection... the shoulders and arms, quad, calf (for high kick back), top of foot. As that one mount point will report only 240watts just like a bike... but here there are more moving parts the influence power that really the person is probably at 340w


The wattage will always be an estimate because you're measuring acceleration, not force. The contribution of the arms would partially show in the acceleration, but there's probably some reasonable assumptions to be made. Those with good leg mechanics, probably tend to have equally good arm mechanics.

The point isn't that the wattage value is accurate, it's that it's repeatable and represents your output in a more precise way than GPS data and you don't need a measured route and stopwatch.

yes well in the end it is to be used for personal improvement, not comparing vs other people like you can with a bike.

http://www.coupleofathletes.com
Quote Reply
Re: DCRainmaker preview of Stryd running power meter [Tom Fort] [ In reply to ]
Quote | Reply
Talking with the Stryd folks this Friday to present them with feedback/questions. While my own curiosity, DC Rainmaker's feedback and posts already in this thread provide some great areas for conversation, let me know what questions/feedback you have....

Thanks!

___________________________________
milesthedog on strava
Quote Reply
Re: DCRainmaker preview of Stryd running power meter [Trev] [ In reply to ]
Quote | Reply
Trev wrote:
motoguy128 wrote:
synthetic wrote:
There are many power points needed for data collection... the shoulders and arms, quad, calf (for high kick back), top of foot. As that one mount point will report only 240watts just like a bike... but here there are more moving parts the influence power that really the person is probably at 340w


The wattage will always be an estimate because you're measuring acceleration, not force. The contribution of the arms would partially show in the acceleration, but there's probably some reasonable assumptions to be made. Those with good leg mechanics, probably tend to have equally good arm mechanics.

The point isn't that the wattage value is accurate, it's that it's repeatable and represents your output in a more precise way than GPS data and you don't need a measured route and stopwatch.


Out of interest, how accurately do running GPS devices measure speed?

Would they be accurate to 0.1 mph? The study below is a bit mixed and I'm not sure they tested the sort of device commonly available to runners.

http://www.ncbi.nlm.nih.gov/pubmed/25254901

Sampling rate is important and something that study identified (at least from a read of the abstract). Most commercial sport GPS devices currently available sample at best at 1Hz. Accuracy (or precision) is very definitely going to be directly related to sampling rate.

Garmin suggest GPS accuracy of 15m is not unreasonable for commercial devices. In practice I've seen better than 5m in clear sky conditions but GPS is very susceptible to overhead conditions affecting line-of-sight to satellites as well as a number of other factors.

Trust me I’m a doctor!
Well, I have a PhD :-)
Quote Reply
Re: DCRainmaker preview of Stryd running power meter [PhilipShambrook] [ In reply to ]
Quote | Reply
PhilipShambrook wrote:
Sampling rate is important and something that study identified (at least from a read of the abstract). Most commercial sport GPS devices currently available sample at best at 1Hz. Accuracy (or precision) is very definitely going to be directly related to sampling rate.

Garmin suggest GPS accuracy of 15m is not unreasonable for commercial devices. In practice I've seen better than 5m in clear sky conditions but GPS is very susceptible to overhead conditions affecting line-of-sight to satellites as well as a number of other factors.

Odd that they used the devices that they did, since those aren't used by anyone in the running community (except for perhaps, studies like this)*. I suppose I could pay for another study, but we all know how that turned out last time...

(*I don't know anything about those specific devices, other than that they aren't used by consumers. They could be and likely are perfectly fine.)


-
My tiny little slice of the internets: dcrainmaker.com
Quote Reply
Re: DCRainmaker preview of Stryd running power meter [SwimGreg3] [ In reply to ]
Quote | Reply
I've been thinking about this thread a bit. First - thanks to @robert-stryd for his contributions from the mfr POV - excellent (and welcome to ST). Now, I think that @SwimGreg3 is onto something here wrt the phase of the run when you're not touching the ground. There are a number of ways to achieve the same run pace against and with the wind. Let's consider one possibility - the turnover and stride length are identical. In this case, the initial push off must be a higher acceleration into the wind vs with the wind, since this hypothetical runner is covering the same distance per stride either way, but we can agree (I think) that she would travel further with the wind than against when not in contact with the ground. So, there must be compensation in the ground contact phase of the cycles - into the wind, push off harder and then slow more while not touching the ground vs against the wind, pushing off less hard and slowing less while not touching the ground to make the total cycle time and total cycle distance identical. Even *I* could do the signal processing on that one to assess into the wind vs with the wind from an accelerometer POV. Now, what about the *many* other cases? Cadence and stride length can change with and against wind, for example. But I'll bet that the accelerometer data during the non-ground contact time is pretty clearly different into and with the wind regardless of changes in cadence. Could this be converted into accurate power for all (or most) conditions? I duuno. But can the accelerometers sense the difference between running into the wind vs against the wind. My guess is - you betcha. And *that* is the start of a signal processing algorithm that might provide a useful estimate of power that reflects the relative wind vector and speed vs the run vector and speed. I think that the objectives of Stryd are a challenge, but not impossible, based on what I assess the physics of running and measurement capabilities of the accelerometers to be. Might appear to be magical to some, but just straight up physics to the rest of us!
Quote Reply
Re: DCRainmaker preview of Stryd running power meter [milesthedog] [ In reply to ]
Quote | Reply
I am most interested in if they can/will collaborate with other companies with their intellectual property. I've got a Wahoo Tickr X and would love to experiment with power using their algorithms. Can/would they use data from other sensors and make their money from selling their app or licensing their algorithms the other companies?
Quote Reply
Re: DCRainmaker preview of Stryd running power meter [Tom Fort] [ In reply to ]
Quote | Reply
Right. I've been thinking about this as well.

This would also be the business model for Bioshift's automatic shifting algorithm. It would seem they need sell the algorithm directly to hardware manufacturers to include the algorithm as OEM. Selling directly to consumers brings with it the chance of pirated algorithms; unless Stryd will be selling a proprietary pod bundled with the algorithm download (don't know how Bioshift can sell their algorithm to consumers without proprietary hardware - btw, wireless sram seems to be a great opportunity for their product).

___________________________________
milesthedog on strava
Quote Reply
Re: DCRainmaker preview of Stryd running power meter [milesthedog] [ In reply to ]
Quote | Reply
Good conversation with Phoenix, a physics phd student at CU, who helped designed Stryd's algorithm. Here are some points I remember from this morning's conversation - if I'm wrong on any of these points, please let me know and I'll edit this post:

  • It's a proprietary motion sensor pod, much more advanced than Garmin's/Polar's/Wahoo's accelerometers. So, it will not be an algorithm that can be paired with the Wahoo Tickr-x. From Stryd: It is a more advanced accelerometer, however Stryd goes beyond just "motion sensing", we measure both "motion and the environment"

    • If synced with a phone beforehand, a runner can run with only the pod and the pod will record the activity, with auto-stop as a default feature, and will then automatically upload once back in range of the phone.
    • At this point in time, it does not measure speed, but works with GPS devices to record speed.
    • Wind, from Stryd: It measures acceleration and calculates force from the acceleration. If one change running form when encountering wind, which will register as a change in acceleration, then we can account for that perspective of wind impact. But we CANNOT measure every aspect that wind effect has on a runner currently. We have a plan to properly account for the impact of changes in wind speed but we don't have solid testing results on this now. We'll follow up here, and on our blog (http://blog.stryd.com), when we have more news on this.
    • When they launch, they will have ensured that their data will appear when uploaded to all major platforms: TP, Strava, Garmin Connect, RunKeeper. From Stryd: Our own website will always support the data. With open source API such as Strava, we can make sure that our data will be supported. As far as TrainingPeaks' and Garmin Connect's API, we are trying as hard as we can to get our data on their platform and we are quite confident that things will work out, but again it is impossible to promise we will be able to reach all major platforms.
    • It is their goal for it to be used as a cycling power meter is currently used, with the emphasis being more in line with how triathletes and TT cyclist ride: maintaining an even power and maximizing efficiency.


    ___________________________________
    milesthedog on strava
    Last edited by: milesthedog: Feb 16, 15 11:31
    Quote Reply
    Re: DCRainmaker preview of Stryd running power meter [milesthedog] [ In reply to ]
    Quote | Reply
    I made some edits in my above post relaying on my conversation with Stryd

    ___________________________________
    milesthedog on strava
    Quote Reply
    Re: DCRainmaker preview of Stryd running power meter [milesthedog] [ In reply to ]
    Quote | Reply
    milesthedog wrote:
  • It is their goal for it to be used as a cycling power meter is currently used, with the emphasis being more in line with how triathletes and TT cyclist ride: maintaining an even power and maximizing economy.

  • Not to be pedantic, but:

    http://forum.slowtwitch.com/...post=5425148#5425148
    Last edited by: Andrew Coggan: Feb 16, 15 11:06
    Quote Reply
    Re: DCRainmaker preview of Stryd running power meter [Andrew Coggan] [ In reply to ]
    Quote | Reply
    changed it to "efficiency" - the idea being to run at a faster pace producing less power - this reduction in power possibly indicating more efficient movement. I'm sure there will be some interesting research that can come from this if the device truly does correspond strongly with the data provided by a force-plate treadmill.

    ___________________________________
    milesthedog on strava
    Last edited by: milesthedog: Feb 16, 15 11:35
    Quote Reply
    Re: DCRainmaker preview of Stryd running power meter [milesthedog] [ In reply to ]
    Quote | Reply
    milesthedog wrote:
    changed it to "efficiency" - the idea being to run at a faster pace producing less power

    That's not correct either - efficiency is energy out/energy in x 100%.
    Quote Reply
    Re: DCRainmaker preview of Stryd running power meter [Andrew Coggan] [ In reply to ]
    Quote | Reply
    With power being a proxy for caloric utilization, if a runner maintained their speed at a lesser wattage (flat surface, no wind), one possibility could be that the movement pattern of the runner's limbs had become more efficient in either or both their swing phases and/or their foot strike. No?

    ___________________________________
    milesthedog on strava
    Last edited by: milesthedog: Feb 16, 15 12:14
    Quote Reply
    Re: DCRainmaker preview of Stryd running power meter [milesthedog] [ In reply to ]
    Quote | Reply
    milesthedog wrote:
    With power being a proxy for caloric utilization, if a runner maintained their speed at a lesser wattage (flat surface, no wind), one possibility could be that the movement pattern of the runner's limbs had become more efficient

    That's circular logic.
    Quote Reply
    Re: DCRainmaker preview of Stryd running power meter [Andrew Coggan] [ In reply to ]
    Quote | Reply
    Andrew Coggan wrote:
    I can't see a running power meter having a significant impact on how people actually train and perform.

    In an IM race, I know...

    I should target a NP of 68-70% of my FTP
    I should target a VI of around 1.05
    I should keep MaxP ~ FTP

    Intuitively, all of these same concepts of optimal average and maximum power production, and variance, seem like they would apply to running as well.

    Specifically, it would stand to reason that a robust running power meter would answer the question of how fast an IM racer should run up a hill, just as a power meter already does for the same athlete on his bike. Since there is an optimal power output when climbing a hill on the bike course, surely there is a corollary for climbing a hill on the run course.

    Given that, I don't at all understand why you don't see value in a device that would provide athletes the same data on the run as they use (often to the exclusion of all else) on the bike. Naturally the target ranges would need to be recalibrated for running, but the underlying principles would be the same -- average X watts, don't exceed Y watts. Why don't you see that as an improvement on things like pace, HR, RPE?
    Quote Reply
    Re: DCRainmaker preview of Stryd running power meter [Trev] [ In reply to ]
    Quote | Reply
    Trev wrote:
    I can see a running power meter changing the way people train - but would it be a change for the better.

    I can see a massive market for online power based training plans and software, it will go the way cycling has. In no time runners will be assuming you can't train effectively without a running power meter and will be going out training tying to stay in zones and worrying about if they have their FTP set correctly and how many TSS they score.

    This, definitely 100%. Agreed it's close to using pace/HRM but using power is just plain superior. Time will tell ...
    Quote Reply
    Re: DCRainmaker preview of Stryd running power meter [howlingmadbenji] [ In reply to ]
    Quote | Reply
    In cyclimg power is particularly useful because an increase in speed as a percentage requires a far greater percentage imcrease in power.

    Back in 1996 I got a Concept 2 Rowing Machine, which accurately gives pace and power.

    All the rowing training books talked about pace and there was no mention of power, but it became obvious to me it is so much simpler to train with power.

    200 watts is 500m / 2min pace. But to increase pace to only 1min 58sec pace a mere 3% faster, requires 10% more power.

    So for working out improvement, working out % of FTP to train at, quantifying work done etc, pace / speed can be very misleading.

    But I understand running pace is a function of power. Does this mean a 10% increase in pace requires 10% more power?


    If this is the case I can see Dr Coggan's point of view.
    Last edited by: Trev: Feb 17, 15 2:35
    Quote Reply
    Re: DCRainmaker preview of Stryd running power meter [Trev] [ In reply to ]
    Quote | Reply
    Trev wrote:
    But I understand running pace is a function of power. Does this mean a 10% increase in pace requires 10% more power?
    If this is the case I can see Dr Coggan's point of view.

    This is pretty much the case especially at the speeds triathletes typically run which I believe has been Andy's main point all along.

    Hugh

    Genetics load the gun, lifestyle pulls the trigger.
    Quote Reply

    Prev Next