The upshot of how STRYD works is that this all essentially means that it should be GREAT as a source of speed on treadmills. Handy for those winter indoor runs.
However STRYD’s post, below, also is interesting in that it shows and neatly summarises potential sources of error with treadmills .Well, I thought it was interesting!!
Info from STRYD Follows:
All foot pods on the market require pace calibration. But, one-point calibration only works at a chosen running speed, run form, etc. From day zero, we’ve aimed to build Stryd to be a calibrationless technology. While Stryd is accurate, with your data, we’re now more accurate than ever. Shown below is a large number of runs (orange dots) with verified distance and Stryd’s new pace algorithm. Now, we need you to test. Let us know if you see anything out of the ordinary so we can continue to make Stryd even better.
Thanks to all of YOU (and your excellent data) we are happy to announce the next firmware update for your Stryd foot pod power meter.
A new pace algorithm, with improved indoor and outdoor accuracy
Improved support for treadmills with heavy vibrational characteristics
Mysteriously Low Treadmill Pace
Many runners noticed that running on a treadmill feels differently when compared to running outdoors. Understanding this difference, may actually help improve our run training. After testing on multiple runners and treadmills, we think we have the answer now. The root cause is that treadmill speed is never constant. More specifically, when your body is in the air, the motor applies an extra speed recorded by the treadmill, but not applied to you.
Notice from the figure above, that
belt speed (in blue) reduces at each foot strike, and to compensate,
the treadmill the motor temporarily over speeds the belt (blue line above Avg belt speed) when the runner is in the air.
The extra distance traveled by the belt (shaded in red) does not cause any extra effort or metabolic cost to runners. Our study shows that such free distance accounts for 2% added distance across commercial grade treadmills with good calibration. (Note: some laboratory grade treadmills with specially designed flywheels are more resilient to such effects).
Let’s ALL Be More Accurate!
When performing our study, we found lots of treadmills which had off calibration, meaning the speed reporting is not accurate. ALL treadmills can be calibrated to an accurate speed without a professional’s help. Here’s how you can do it by yourself, and in only a few minutes.
Measure true belt length (Using a roll of sticky tape and a tape measure) Manually rotate the belt and place three pieces of tape at points evenly distributed across the belt. Measure the distance between the three and add them together.Measure true belt speed (Using a friend with a stopwatch app) Keep one piece of tape on the treadmill belt, and set the speed you wish to calibrate to. Have your friend watch you run, counting tape (belt) revolutions as they measure time. Stop the timer when you reach 100 revolutions.
True Belt Speed = Revolutions x True Belt Length / Time
Firmware Update Instructions
Make sure your Stryd mobile app is up-to-date! Check the version number in either Google Play Store (v3.9) or Apple App Store (v2.7). If you are out of date, upgrade to these versions.
Upgrade your firmware: Go to ‘Settings’ -> ’Software Update’ -> Press the ‘Upgrade’ button to upgrade.
Lastly, we need to emphasize two final and critical steps in order to allow you to connect via Bluetooth to Stryd again. After the firmware upgrade is completed, please:
Completely force the Stryd app to quit. To do that, double-click on the Home button to access the new app switcher or multitasking tray and then swipe up on the app that you want to close.
Turn off and then turn on the Bluetooth. To do that, bring up the Control Center by swiping up from bottom of your iPhone screen, find the bluetooth icon, click on it twice.
Once you are done with the 2 steps above, you are ready to use your Stryd device with the new firmware installed!