Muscular Not Skeletal Components Of Leg Stiffness Are Significantly Correlated With Associated Biomechanical Variables During Running

Abstract

Muscular (kMusc) and skeletal (kSkel) components of leg stiffness have been previously related to injury patterns in runners [1]. Though these components mirror proposed injury mechanisms in runners, their relationship to underlying biomechanical variables remains unclear. PURPOSE: to evaluate the association between components of leg stiffness (kMusc & kSkel) with common biomechanical variables of muscular (joint work) and skeletal loading (joint reaction forces) during a running task. METHODS: Thirteen recreational runners (8 male, 5 female) performed ten over ground running trials at 3.35 m/s (±5%) in each of four conditions with varying shoe and strike patterns. Kinematics and ground reaction forces (GRFs) were recorded using an 8-camera motion capture system (240 Hz, Qualisys) and force platform (1200 Hz, OR-7, AMTI). Visual3D (C-Motion) was used to calculate joint powers and compressive joint reaction forces (JRFs). MATLAB was used to calculate negative joint work values and stiffness variables. kMusc and kSkel were calculated as previously reported [1]. Prism 8.0 (GraphPad) was used to perform correlation analyses between muscular and skeletal contributions to load attenuation. RESULTS: kMusc had moderate and weak relationships with lower extremity work (p < 0.01; r = 0.55) and knee joint work (p = 0.01; r = 0.32). Weak correlations existed between kSkel and ankle (p = 0.25; r = -0.10), knee (p = 0.17; r = 0.14) and hip joint reaction forces (p = 0.46; r = 0.01). CONCLUSIONS: These data revealed moderate associations between kMusc and negative work values suggesting that kMusc is proportional to muscular contributions to load attenuation. JRFs had weak associations with kSkel, suggesting kSkel may not represent skeletal loading. These findings suggest this simplistic model may be insufficient to describe muscular and skeletal contributions to load attenuation. [1] Powell, Paquette & Williams, 2017.