A Reexamination of the Relationship between Foot Strike Angle and Early Stance Loading Variables during Running

Area of Science:

• Biomechanics
• Sports Science
• Running Dynamics

Background:

• Understanding the relationship between foot strike angle (FSA) and vertical loading rate (VLR) / vertical טibia acceleration (VTA) is crucial for injury prevention in runners.
• Previous models often assumed linear relationships, potentially oversimplifying complex biomechanical interactions.

Purpose of the Study:

• To compare nonlinear and piecewise linear models for representing the relationship between FSA and VLR/VTA during running.
• To investigate the influence of competitive running experience on these biomechanical parameters.

Main Methods:

• 475 U.S. Army trainees underwent running gait assessments on an instrumented treadmill.
• Vertical leg/tibia motion (VLR, VTA) and foot strike angle (FSA) were measured using force plates, accelerometers, and high-speed cameras.
• Multiple regression analysis, including nonlinear and piecewise terms, was employed, controlling for running experience.

Main Results:

• A significant nonlinear, quadratic relationship was observed between FSA and both VLR (R²=0.25) and VTA (R²=0.14).
• Running experience significantly impacted the models, with better predictive fit for experienced runners (VLR: R²=0.38; VTA: R²=0.16).
• Piecewise linear models yielded comparable results to quadratic models.

Conclusions:

• Nonlinear or piecewise linear models effectively represent the complex relationship between VALR/VTA and FSA.
• Both very low (forefoot) and very high (rearfoot) FSAs were associated with reduced VLR/VTA compared to moderate foot strike patterns.