Differences in Kinematic Correlates of Impact Loading Between Rearfoot and Non-Rearfoot Strikers in Running

Abstract

Impact loading (in particular, average vertical loading rate (AVLR)) has been implicated in the development of several running-related injuries (RRIs). Some researchers have also suggested that overstriding (landing with the foot too far in front of the centre of mass (COM)) may be linked to increased loading rates and RRI. There is no clear method for measuring overstriding. PURPOSE: To establish the relationship between kinetic outcomes (vertical impact peak (VIP), instantaneous vertical loading rate (IVLR), and AVLR) and five kinematic measures of overstriding (angle of shank at initial contact (IC); horizontal distance from heel to COM at IC; horizontal distance from centre of pressure (COP) to COM at IC; angle between COP, COM, and vertical projection of the COM; percent of step length anterior to COM). METHODS: 18 healthy female recreational runners (12 rearfoot strikers (RFS), 6 non-rearfoot strikers (NRFS)) ran at their preferred speed on an instrumented treadmill (Treadmetrix) while ground reaction force data and 3D joint kinematics were collected using a motion capture system (Qualisys). Data were analyzed using Visual3D software (C-Motion). Pearson’s correlation coefficients were used to assess the relationship between the kinetic and kinematic variables. RESULTS: RFS and NRFS displayed opposing relationships between the kinematic measures of overstriding and kinetic outcomes. RFS showed a moderate positive correlation between AVLR and horizontal distance from heel to COM at IC (r=0.62, p=0.037). Conversely, NRFS displayed moderate to strong negative correlations between kinetic outcomes and several kinematic measures, with percent of step length anterior to COM showing the strongest association (AVLR r=-0.56, p=0.031; IVLR r=-0.65, p=0.009; VIP r=-0.80, p=0.016). CONCLUSIONS: Findings from this study suggest RFS and NRFS demonstrate moderate to strong, but opposing relationships between kinematic measures of overstriding and kinetic outcomes associated with RRI. Two potential measures of overstriding are associated with increased loading rates, but are dependent on classification of foot strike. Prospective studies are warranted to determine whether these overstriding measures also result in increased injury incidence. Supported by a Mitacs Accelerate Graduate Research Award.