All posts by nakan

W’Bal Connect IQ app now stores data and make it available into Garmin Connect

The v2.0.0 of the W’Bal Connect IQ data field is now live and this new version now stores the W’Bal data into the fit file of the session, enabling Garmin connect to display the graph after the sync.

I still strongly recommend to use Golden Cheetah for post-activity analysis and W’Bal investigations, but as a lot of you asked for the data, and as it was technically pretty easy, I’ve worked on this.

After the session is synced to Garmin Connect, you will find the following graph on the web version:

And this one in Garmin Connect Mobile:

Note that this change will make the new fit file of the activity file a “2.0” fit version and it may not be supported in all platforms at this time.

How to manage the settings of the W’Bal app on ConnectIQ

You’re interested about the W’Bal app, and you have it installed on your Garmin device, but you don’t know how to change the default settings ? You’re at the right place !

You have two ways to change the parameters:

  • Using Garmin Express on a Mac or Windows computer
  • Using Garmin Connect Mobile on an iOS, Android or Windows Mobile smartphone or tablet.

Using Garmin Express

Once you have your Garmin device connected on your computer, Garmin Express will allow you to manage the applications you’ve installed.

On Express, choose your device and click on the “Manage apps” button. You will then see a list of installed or available apps:

apps_on_expressAt the right of the app name, you’ll find a “three dots” button. Click it to be able to change settings:

settings

Edit the settings to fit your values, save and you’re done !

Using the mobile app

You can change parameters on the Garmin Connect Mobile app. In the app menu, choose “Garmin Devices -> Your device”. The you will have a link to manage Connect IQ apps.

Choose to manage “Data fields” and then you should find “W’Bal” in the “installed” section. Tap the app and then choose the “Settings” button. You’ll be able to change settings:

android

Edit the settings to fit your values, save and you’re done !

What to do when my Edge won’t save the parameters ?

It seems like Garmin is experiencing problems with the parameters on the Edge 1000 or Edge 520 bike computers for Connect IQ data fields… It will be corrected soon (hopefully), but in the meantime, here is a workaround.

If you’re experiencing problem with the parameters on a Edge, you can try the following procedure. You will have to use Express on a Mac / Windows PC, I have not yet any solutions to provide with the Mobile app…

  • Connect the Edge to the computer, and launch Garmin Express.
  • Identify what is the filename of the W’Bal app name on the “Garmin/Apps/” folder on the Edge. In my case here, it’s “F2FEC2F7.PRG“. I don’t know if you will get the same name of a different one:

prg_file

  • Once you have identified the app name, go into the “Garmin/Apps/Settings/” folder on the Edge. If a file named like the app but with a extension exists, delete that file:

set_file

  • When the file is deleted, go back to Express and change the parameters as described above. This will create a new “.SET” file on the Garmin/apps/Settings folder on the Edge.
  • Disconnect the Edge, and check the parameters.

With the W’Bal app, you can easily check the settings as the field will display the parameters (i.e “250|20000” as “CP|WPRIME“) when the activity is not started. You can  also check the Method parameter as the field title will change from “% W’Bal (int)” for integral method, and “% W’Bal (diff)“.

I really hope you have now everything to change the settings of my app, but if for any reason you’re still in trouble, feel free to leave a comment below.

Enjoy your ride!

Everything about my W’ Bal (W Prime Balance) Connect IQ app

A few weeks ago, I released the first version of my W’ Bal datafield on Garmin Connect IQ. This app is designed to display the remaining value of W’ during a ride on the cyclist’s device. Let’s dig a bit into this interesting value…

garmin_iq_wprime_web

What is W’ Balance ?

To make it simple, assume that a cyclist have a given amount of energy at the beginning of a ride. This value, known as W’ (or W prime) is measured in joules.

While you’re riding at low intensity, W’ remains at it full level, and you can theoretically continue riding at this intensity for a while. But if you push harder, you will start using this energy. The limit at which you will start lowering the W’ is known as CP (Critical Power). At my level, I use to consider my CP and FTP as the same value.

So if you push on the pedals harder than CP, W’ will decrease. As soon as your watts get lower than CP, W’ will “regenerate”, and the value will increase again. So if you ride long enough below CP, W’ will be at 100% again.

All these variation in W’ are expressed as “W’ Bal” in the Dr. Skiba theory, and this value was then implemented on the GoldenCheetah software, on the “Charge” chart of a ride:

wprimebal

You can note on this chart the peaks above CP (the line is going down, as the amount of remaining W’ decrease), and the periods where power is below CP (the line is going up, as the amount of remaining W’ increase).

To be able to compute W’ Bal, we need two values:

  • CP: a given threshold (watts)
  • W’: a given amount of energy (joules)

How to get my CP and W’ values ?

To estimate your CP and W’ values (if you don’t already know them), GoldenCheetah provides a tool in the “Tools -> Estimate CP and W’” menu. Here you can enter you maximum amount of watts for a short effort (3-5min) and a long one (15-60 minutes). Based on that, it will give you an estimation of W’ and CP.

Of course, if you already know your FTP value, you can use it as CP.

Compute methods (the real maths behind the data)

Initially, the only known formula to get W’ Bal was the one from Dr Skiba. It was the one implemented in GoldenCheetah at the beginning. On my data field, it’s called “integral” and it’s the default method, just because I prefer it… This formula uses another parameter to define the speed at which W’ is regenerating when the power is below CP. This value is known as TAU, and it’s based on the activity history.

The second method, by Froncioni / Clarke only use current power to compute recovery, so with this formula, W’ Bal will usually regenerate faster, and decrease faster as well. It’s now the default method on GoldenCheetah. It’s known as “differential” and available starting from version 1.2 on my data field, but you have to configure “compute method” parameter to “differential” instead of “integral”.

What is the difference between the two formulas? This one:

wprime

The blue line is the differential formula (the one used by default in GoldenCheetah). The red is the integral formula of Dr. Skiba. Values here are for a mixed field test (5min VO2Max, 10 min recovery, 20 min FTP test).

The only advice I can give you is: try both formulas and choose the one you prefer. Science has not yet validated one against the other.

Where can I get this app ?

First, you will need to ensure your Garmin device is compatible with Connect IQ apps, and has an updated firmware. Compatible devices with powermeters and Connect IQ are, at the time of writing are:

  • Forerunner 920XT
  • Fenix 3 / Fenix 3 HR
  • Edge 1000
  • Edge 520
  • Epix

Then, go to the Connect IQ store on Garmin Connect Mobile, or directly at this page: https://apps.garmin.com/en-US/apps/6dcfffe5-cd3d-41f3-8ba3-13fa0647b003 and get the stuff.

You will have to change the three parameters to suit your values (CP, W’ and Method).

Can I get the sources ?

Yep, all the source code is available on Github here.

Anything else ?

Feel free to leave a comment to this entry for any feature request, bug, advice or question. Enjoy your ride!