The original Stryd Pioneer is mounted on the chest and measures and records heart rate, cadence, ground contact time, vertical oscillation and, of course, power.
The new Stryd is worn on the shoe and measures distance, pace, cadence, ground contact time, power and two new efficiency metrics. The first is Form Power (FP). Form Power is a measurement of the amount of power that Is produced to maintain the runner’s individual form, but is not put towards the metabolic cost of running forward. The second is Leg Spring Stiffness (LSS). Leg Spring Stiffness is a measure of running efficiency and how well the runner recycles the energy that they apply to running. LSS has been shown to be correlated with running performance.
Both Stryd devices have been validated with 3D motion capture cameras, force-plate treadmills and VO2-Max testing.