Garmin Running Power

Garmin's Running Power Meter is a software download for their existing hardware, rather than a new hardware product. The software for Garmin Running Power (GRP) is their Connect IQ data field, but unfortunately, it won't run on any Connect IQ enabled Garmin watch. In fact, it will only run on the Garmin 935, Garmin Fenix 5X, and Garmin Chronos. (It supports the Fenix 5/5S, but those models appear to have hardware issues with sensors.) You also need a sensor that supports Garmin's Running Dynamics, which is available embedded in a heart rate strap or a clip-on pod. To get any meaningful data out of GRP, you'll also need a Footpod, preferably Stryd (more on that later.)

1 How It Works

Like any other running power meter, GRP estimates power primarily from your running pace and the slope. Running intensity is proportional to pace, and generally proportional to incline, but the relationship between intensity and running downhill is rather more complex. GRP claims to use three other factors:

• Vertical Oscillation. It seems intuitively obvious that the effort of bouncing up and down needs to be included in a running power, the science doesn't back this up. The relationship between vertical oscillation and effort (Running Economy) is not really valid. This is because the balance of a runner is more like bouncing a ball; there's some effort involved, but there's also a lot of elastic bounce as well.
• Breaking. Garmin referred to this as "horizontal oscillation" though most Running Sensors referred to this as the braking force. Strangely, Garmin's running dynamics system doesn't report on any braking force, though obviously it's able to detect horizontal acceleration.
• Wind. Generally, air resistance is incorporated through pace, but Garmin actually attempt to include wind speed. Their approach is to get with the data from a local weather station using the Bluetooth connection to a smart phone, and then use the heading to calculate your current windspeed. You'll need your smart phone with you, and it's possible that this approach might work in some very limited situations. You do need to be running in an environment where there's little or no shelter from the wind, such as trees or buildings, so that your subject to the prevailing winds. The wind would need to be steady in both direction and velocity. This combination of events seems to be so limited that I'm struggling to see any benefit. Luckily, you can turn this feature off.

2 Testing Results

I'm still testing GRP, but here are my initial thoughts.

• Getting your running pace from GPS is fairly useless, so it's not surprising that GRP's power estimate when using GPS as the speed source is pretty worthless. I typically see power estimates fluctuating by +/- 50 watts when maintaining an even effort.
• When I use Stryd as a Footpod to provide current pace, GRP provides a much better power estimate.
• I've not tested GRP with a Garmin Footpod, but this might be a more cost-effective approach then using Stryd. Of course, it will also require a lot more effort in terms of regularly recalibrating the Footpod, something you don't have to do with Stryd.
• The GRP estimate of power is much higher than the estimate I get from Stryd. Garmin claim that running power should be higher than cycling power for a given effort based on a number of research papers.