A Re-Examination of the Relationship Between Foot Strike Angle and Early Stance Loading Variables during Running.

Abstract

Purpose: To compare nonlinear and piecewise linear models for FSA with VLR/VTA during running, controlling for competitive running experience.

Methods: 475 U.S. Army trainees completed surveys on their participation in sports and a running gait assessment on an instrumented treadmill while VLRs, VTAs, and FSAs were measured (via force plates, tibial-mounted accelerometers, and high-speed cameras, respectively). A 3-minute warm-up was given and then participants ran for one minute at 2.68-2.91 m/s, followed by 14 strides of data collection. Multiple regression was used to assess the prediction of VLR and VTA by FSA, including nonlinear/piecewise terms and controlling for competitive running experience.

Results: A nonlinear, quadratic relationship was found for FSA x VLR (R2= 0.25, p<0.001) and VTA (R2= 0.14, p<0.001), and with a significant effect of running experience (p<0.02). Models showed similar shapes but better fit for those with (VLR: R2=0.38, VTA: R2=0.16) versus without (VLR: R2=0.21, VTA: R2=0.11) competitive running experience. Finally, VLRs peaked at similar FSAs as in previous work (≈10-12° current vs 5-10° previous). Piecewise linear regression produced similar results to quadratic models (R2 Difference< 0.02).

Conclusions: Our results show that nonlinear or piecewise linear models can be used to represent the relationship between VALR/VTA and FSA. While VLRs/VTAs were lowest with the lowest FSAs (i.e, most forefoot), participants with the highest FSAs (i.e., most rearfoot) showed reduced values compared to FSAs typical of a more moderate/flatter rearfoot strike pattern.