Stryd Duo and Footpath Initial Impressions

Having used Stryd for running, training, and racing with power for more than eight years, I was excited when they announced a major new product update: the Stryd Duo and Stryd Footpath. Naturally, I was first in line to test out these new features, so here are my Stryd Duo and Footpath initial impressions.

First, adding this new functionality was very easy. I simply procured a second Stryd pod, added it to my right foot (The original is on my left foot.), added it to my Stryd Android app, and added it to my Garmin Forerunner 955 Solar. The two pods are essentially treated as a single device by Garmin.

The biggest change for me was moving from the Stryd Workouts Garmin Connect IQ app to the Stryd Zones Garmin Connect data field. I had long resisted this change but, now that I did it, the new Zones are better and more functional than the old Workouts app, and I’m glad I switched.

New Data

First things, first: I went on a very quick, easy treadmill run, wearing ultra minimalist Vibram KSO Evos – basically barefoot. Stryd Duo compares data from your left and right feet, so it can provide new metrics about your left-right balance. My data showed some interesting insights:

1. Ground Contact Time (GCT) Balance: 49% Left / 51% Right. My left foot is making slightly shorter contact with the ground than my right.
2. Vertical Ratio: 8%. I am bouncing up and down to the tune of 8% of my horizontal stride length. I’m not sure what a good benchmark for this should be.
3. Vertical Oscillation (VO) Balance: 51% Left / 49% Right. The left side of my body is bouncing up and down a little more than my right.
4. Leg Spring Stiffness (LSS) Balance: 51% Left / 49% Right. My left leg is giving a little more “pop” than my right – perhaps this is related to my increased bounce and decreased ground contact time on the left.
5. Impact Loading Rate (ILR) Balance: 53% Left / 47% Right. My left leg is enduring more strain than my right. I wonder if that has implications for recovery, stretching, etc.

We all have running asymmetries, and mine seem pretty modest, but I still wonder what interventions I might consider to achieve more balance.

Footpath Visualization

Enough with the treadmill, though; I was eager to take the Stryd Duo outside and test it on a wide variety of running surfaces. Wearing Vibram Spyridon Evo trail shoes, I struck out to North Boulder Park. My first run was an easy jog on pavement (mix of sidewalk and asphalt) around the perimeter of the park – running anticlockwise. The new Footpath feature gives me a 3-D visualization of the path that each of my feet takes while running; this is the view from the back:

Very interesting: it seems that my left foot follows a more “compact” route in each stride, not lifting as high as my right. But could that be an artifact of my anticlockwise loop? I ran a second loop, retracing the same round clockwise. Stryd Footpath allows me to compare data from two runs, so here are both loops superimposed, anticlockwise in the solid lines vs clockwise in the dashed:

Interesting! Running clockwise shifted both of my feet a little to the left. However, again, my left foot doesn’t rise quite as high. For both loops, my Stryd Duo Metrics were nearly identical to those from my treadmill test, so the picture of slight asymmetry/imbalance was becoming more robust.

Comparing Different Surfaces

Next, I wondered how my stride might differ on different surfaces. I ran the same anticlockwise and clockwise loops around the park, but this time on the grass just beside the sidewalk. Below is a comparison of my anticlockwise stride from the side view, grass in solid lines and pavement in dashed:

Wow, very interesting! My stride length is about the same, but my foot travels much higher in the grass than on pavement – which makes sense as I try to clear the blades of grass. Also, it seems that my foot doesn’t come quite as far forward, but pushes further backward on grass vs pavement.

Comparing Different Intensities

Now for the most interesting test: running at different intensities! I did two 100m striders on grass and two on pavement. Below is a comparison of my stride (side view) during the earlier easy jogs (272W) in solid lines vs the striders (613W) in dashed:

Wow, what a difference! My strider stride length is more than 1m vs my easy jog, which is much more compact at 66cm. My strider back kick is 40cm off the ground vs 10cm for my jog. These differences are intuitive, but it’s illuminating to see the visualization.

Let’s look at the same two run comparisons from a different vantage point – overhead:

Wow again! Here I can see a pretty standard pattern for my easy jog (solid lines), and the same longer stride seen above for my striders (dashed lines). However, the overhead view reveals something novel about my strider form: my strides are diverging from the centerline, likely supinating each foot. This will be a coaching point to work on: keeping my higher intensity strides going forward and backward so as not to waste power side to side.

Finally, below is a comparison of the same two runs, but this time viewed from the back:

I don’t even know what to say about those wild shapes of my striders (dashed lines), except that they likely correspond with the supinating pattern seen above. My biggest concern here is the asymmetry – again, something to work on.

So What?

Stryd’s new features are really cool for a data nerd like me. However, the question for new data and new tools is always, “So what?” How can I use this to improve my running, train smarter, reduce injury, etc?

A couple of areas for me to look into are my left/right imbalance when jogging – specifically lifting my left foot higher – and staying in the forward/backward plane when striding/sprinting. It’s hard to know what to make of these observations, though, without benchmarks or best practices to target.

Stryd’s new features would be most beneficial with coaching. I wonder if they might consider adding a remote/virtual coaching service and/or training to third party coaches on how to use/interpret these new data, and how to prescribe interventions based on them.

Final Thoughts

I still have a lot more testing to do (Today: hill sprints; this weekend: the track!), but Stryd’s new Duo and Footpath features are a quantum leap forward, likely the greatest single advance that I’ve seen from them since their launch eight years ago. These new features provide a great deal of the benefit traditionally reserved for complex/expensive camera, force plate, and sensor systems. Moreover, these benefits are not just accessible in the lab; they are “always on” whenever you are running. Kudos to the Stryd team (my neighbors in Boulder!) for introducing new innovations that have re-energized my enthusiasm for and use of their product – keep the innovations coming!