Running power and the power index

[Joss Winn]

I'm trying to use GC with running power data from Garmin. However, in the running world, the way Power is measured is not uniform across different devices (Garmin/Stryd/Coros, etc). Garmin discuss this here: https://support.garmin.com/en-GB/?faq=vAzl2ne5dV6diuc2XbYZA6 

Basically, they say cycling is less efficient than running, so the power numbers will never be the same.

On the one hand, it doesn't matter if Garmin says my average power on a run is 350 and Stryd might say it's 262 because as long as I'm using Garmin, the power numbers are being calculated in the same way and are relative to one another. 

However, with GC and the Power Index in particular, I'm inputting run power data and it's being treated as if it were ride power data. See the attached screenshots. 

The file names indicate which is which. One shows Banister VDOT, and another Banister Run Power for every run I've recorded since Oct 2020. The third show the Banister Run Power since I've actually been recording running power (since June 10th 2022). 

The shape of my fitness and fatigue is the same across both charts since Oct 2020. The Performance looks right on the VDOT chart, too. The CP and Power Index lines from 2020 go in the opposite direction to what I'd expect, but I wasn't recording power until recently so I can ignore most of that. 

The third chart from the last 28 days does use Garmin power data and shows that most of my runs are above the average of 100. The peak towards the middle of that chart was a marathon with 2100m of elevation gain. CP = 423 watts, GOVSS = 288, Performance = 162 ml/min/kg. 

Btw, I'm a 48 year old male who has been running for less than two years and based on a month of power data, GC estimates my Peak CP = 388, Peak W' = 17.5 and current CP estimate = 379. I'm guessing that among you cyclists, those numbers look quite impressive?

As a new user to GC, it's fantastic software but I think that the modelling doesn't take into account the different ways that run power is being calculated by different devices and is therefore a bit misleading.

Any thoughts? 

[Joss Winn]

... I realise the problem is that the different competing companies don't agree how to calculate run power and that's not GC's problem. However, since that is what GC has to work with, might it be sensible to check which device the data came from and provide an option to normalise it in some way? How do triathletes work with the two different types of power?

[Ale Martinez]

El miércoles, 6 de julio de 2022 a la(s) 14:47:22 UTC-3, jo...@josswinn.org escribió:

... I realise the problem is that the different competing companies don't agree how to calculate run power and that's not GC's problem. However, since that is what GC has to work with, might it be sensible to check which device the data came from and provide an option to normalise it in some way?

I don't think so, but GC has tools to "massage" power data if you are interested enough.

 

How do triathletes work with the two different types of power?

In the same way they work with two different types of pace (?) 

[josswinn.org]

On 6 Jul 2022, at 19:53, Ale Martinez <amtri...@gmail.com> wrote:



Fair enough. 

I think the use of the Power Index in the Banister run power chart is misleading as it’s comparing run power against an index of bike power* and, at least from some devices, they are not the same. It’s a small observation but for runners coming to GC it’s confusing and from watching the video about that chart, the assumption seems to be that run and ride power can be treated as equal. 

Apologies if I’ve misunderstood. 

*from what I’ve read, the opendata project is ride data only? 

[Ale Martinez]

El miércoles, 6 de julio de 2022 a la(s) 19:43:48 UTC-3, jo...@josswinn.org escribió:

On 6 Jul 2022, at 19:53, Ale Martinez <amtri...@gmail.com> wrote:



El miércoles, 6 de julio de 2022 a la(s) 14:47:22 UTC-3, jo...@josswinn.org escribió:

... I realise the problem is that the different competing companies don't agree how to calculate run power and that's not GC's problem. However, since that is what GC has to work with, might it be sensible to check which device the data came from and provide an option to normalise it in some way?

I don't think so, but GC has tools to "massage" power data if you are interested enough.

 

How do triathletes work with the two different types of power?

In the same way they work with two different types of pace (?) 

Fair enough. 

I think the use of the Power Index in the Banister run power chart is misleading as it’s comparing run power against an index of bike power* 

Power Index for running is a pending task, it will be disabled in the release version since we don't have standard model parameters for running: https://github.com/GoldenCheetah/GoldenCheetah/commit/086be52ad9c422be2026b921bf54598ad11f7f20

[Joss Winn]

> On 7 Jul 2022, at 00:22, Ale Martinez <amtri...@gmail.com> wrote:
>
>


>
> Power Index for running is a pending task, it will be disabled in the release version since we don't have standard model parameters for running: https://github.com/GoldenCheetah/GoldenCheetah/commit/086be52ad9c422be2026b921bf54598ad11f7f20
>

This review offers a useful assessment of commercial sensors to measure running power.

Mechanical Power in Endurance Running: A Scoping Review on Sensors for Power Output Estimation during Running. https://www.mdpi.com/1424-8220/20/22/6482

"the aim of this scoping review was to critically examine the available running power meters and the current evidences about their use and application to endurance running performance.”

There’s a good discussion about the differences in measuring power in both cycling and running and the lack of a standardised model for estimating running power.

[Ale Martinez]

The article I linked in your other thread about running power refers to a previous one which, I think, explains the issues more clearly: https://www.outsideonline.com/health/running/what-running-power-anyway/. Personally, running on mostly flat courses, I have not found Power (Garmin 935+RD Pod) gives me any additional useful insight WRT pace.

[Joss Winn]

Yes, I read the article you linked to and found it helpful. Thank you.

I am interested to see whether training with power is useful for hill/mountain running. It makes sense to work with the concept of ‘power' because it accounts for elevation changes and environmental conditions, which would be useful to me.

With respect to GC, does it matter if one user inputs power data from Stryd and another inputs power data from Garmin - both using different definitions of power and how to calculate it? Or put another way, are there any assumptions built into GC about what power data is conceptually? Because in running, there is no conceptual agreement among the companies that produce the devices that record it.

Do the models in GC make assumptions about how the power data was calculated in the first place?

It seems that as long as I stick with the same device and don’t compare my data with other users, then the power data is reliable, even if it isn’t valid, because the ‘power’ data is a proprietary number that differs from device to device, unlike my HR or pace.

In the cycling world, do all power meters provide more or less the same data, based on the same understanding of ‘power’?

Sorry, lots of questions, but I think they are worthwhile questions to ask when starting to use GC with running power, which is becoming more widely available to users.

[Ale Martinez]

Yes, lots of questions going around basically the same issue.

To summarize: GC power related features were developed for cycling, where the concept is cristal clear and has been used for decades, afterwards most of them where allowed to be used for other sports, exceptions are those specific for cycling, with separate Power Zone parameters, but there’s no feature specific for running built in, much lees for specific running power meter. 

[Joss Winn]

On 8 Jul 2022, at 12:49, Ale Martinez <amtri...@gmail.com> wrote:

Yes, lots of questions going around basically the same issue.

To summarize: GC power related features were developed for cycling, where the concept is cristal clear and has been used for decades, afterwards most of them where allowed to be used for other sports, exceptions are those specific for cycling, with separate Power Zone parameters, but there’s no feature specific for running built in, much lees for specific running power meter. 

Thanks for your patience with my questions. I understand now.