From Fellrnr.com, Running tips
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** For the first contact frame:
*** Measure the angle of the heel/forefoot line to estimate strike angle and therefore strike index. This can be categorized into FFS, MFS, RFS.
*** Find the horizontal distance from the middle of the foot to the hip to check for overstriding.
*** Look at the angle between the hip/knee and the knee/ankle to determine how straight the leg is. A straighter leg may indicate a higher impact force.
** Evaluate the frames between first and last contact: