Quick answer
No. Garmin watches do not measure leg spring stiffness, and there is no Garmin leg spring stiffness metric. It comes from Stryd. If you pair a Stryd foot pod with your Garmin, Stryd’s value is written into the FIT file, but it is still Stryd’s number. From Garmin data alone you can only make a rough model estimate, not a measurement.
What leg spring stiffness is
When you run, your leg behaves a bit like a spring. It compresses as you land and pushes you back up as you leave the ground. Stryd describes leg spring stiffness as a model of the elastic energy in your leg, calculated as the maximum vertical force in a step divided by how far you compress during ground contact. A stiffer spring compresses less for the same force.
Stiffness is expressed in kilonewtons per metre (kN/m). It depends on your body weight, your speed and how you land, so compare your own values at similar paces rather than with other runners.
What each source records
With a compatible watch or sensor: ground contact time, cadence, vertical oscillation, vertical ratio and stride length. No leg spring stiffness.
A paired Stryd pod adds its own fields to the Garmin FIT file, including leg spring stiffness and impact loading rate.
A published spring-mass model can turn contact time, cadence and pace into a stiffness estimate. It is not a measurement and not a Garmin metric.
Can you estimate it from Garmin data?
Only roughly. Morin and colleagues (2005) published a spring-mass model that estimates running stiffness from contact time, flight time, body mass, speed and leg length. It was developed with force-plate measurements, not with watch data, and Run-It has not checked it against Garmin runs. Treat any number it gives as a model estimate, not as your leg spring stiffness. The steps are:
Flight time. Step time is 60 divided by your cadence in steps per minute. Subtract ground contact time to get flight time.
Peak force. Fmax = body mass × 9.81 × π/2 × (flight time / contact time + 1).
Compression. The drop of your centre of mass during contact is Fmax × contact time² / (mass × π²) − 9.81 × contact time² / 8. Vertical stiffness is Fmax divided by that drop.
Leg stiffness. Leg compression adds the leg’s sweep: leg length − √(leg length² − (speed × contact time / 2)²) + the drop above. Leg length is often approximated as 0.53 × your height. Leg stiffness is Fmax divided by leg compression.
What the model gives, not what your Garmin measures
For 70 kg, 1.78 m, 5:00 per km, cadence 170 and 250 ms contact time, the model gives a leg stiffness of about 9.6 kN/m and a vertical stiffness of about 24.9 kN/m. Small errors in contact time move these numbers a lot, so compare only your own runs at similar paces, and only as a rough trend.
Do not use Garmin’s vertical oscillation as the compression. It measures how far you rise and fall over the whole step, including flight, not how far the leg compresses while your foot is on the ground. Use a lap or a steady section of a run rather than single seconds, because contact time is noisy.
If you use the estimate anyway
- It is not a measurement. The model assumes a simple spring and was not built for watch data. A Stryd value and a model estimate are not interchangeable.
- It changes with pace. Compare runs at similar speeds, or the difference will mostly be the pace.
- Stiffer is not always better. It describes your running pattern. Do not try to force a stiffer stride.
- Watch it as you tire. A drop late in a long run can show your form changing with fatigue.
How Run-It uses leg spring stiffness
Run-It shows leg spring stiffness as Leg spring, “how much spring your legs give back”, for runs from Stryd. It is part of the running form scores and the shoe comparison for Stryd runs, next to impact loading rate and vertical ratio.
Garmin runs are scored on Garmin’s own running dynamics instead: Loading Pattern Index, duty factor and vertical ratio. Run-It does not mix a paired Stryd pod’s values into a Garmin analysis, so each source stays consistent. If you run with both, connect Stryd to see Leg spring. Read more in how to compare running shoes with Garmin and Stryd data.
FAQ
Does Garmin measure leg spring stiffness?
No. Garmin running dynamics include ground contact time, cadence, vertical oscillation, vertical ratio and stride length, but not leg spring stiffness. A paired Stryd pod can write Stryd’s own value into your Garmin FIT file.
Can I calculate leg spring stiffness from Garmin data?
Only as a rough model estimate with the Morin spring-mass method. It is not a measurement and was not built for watch data, so use it at most as a trend across your own runs at similar paces.
What is a good leg spring stiffness?
There is no single good value. It depends on body weight, speed and running style, so compare your own runs at the same pace rather than with other runners.
Why is my Stryd leg spring stiffness 0?
Stryd says this can happen when your height is set incorrectly. Update your height in the Stryd app and check the next run.
Sources
- Morin JB, Dalleau G, Kyröläinen H, Jeannin T, Belli A. A simple method for measuring stiffness during running. Journal of Applied Biomechanics, 2005;21(2):167–180.
- Stryd, Stryd Duo balance metrics (definition of leg spring stiffness), accessed 2 November 2026.
- Stryd Help Center, Why is my leg spring stiffness 0?, accessed 2 November 2026.
