Immediate Effects of a Textured Insole on Running Biomechanics in Rearfoot Strikers

Abstract

Running biomechanics are influenced by footwear and insole properties. The sensorimotor system, specifically subcutaneous plantar receptors, play a role in initiating adaptive gait mechanics. Designed to increase afferent signaling via plantar surface deformation, an insole inlaid with a textured heel-plate (TI) is proposed to precipitate gait changes during running. PURPOSE: To compare biomechanical patterns during over-ground running between the TI and a non-textured insole (NI). METHODS: Nineteen rearfoot strike runners (24.9 +/- 5.7 yo; 6 M, 13 F) performed twenty, 35-meter running trials under TI and NI conditions. Insole conditions were counter-balanced, and velocity was controlled (±5%). Plantar sensation was assessed using a 3.61g monofilament applied to seven standardized sites. Thirty-six reflective markers (dia.=16-20 cm), affixed bilaterally to lower extremity bony landmarks, were tracked via a 10-camera motion analysis system (120 Hz), and ground reaction forces were collected (1200 Hz). Visual3D and a custom Matlab script were used to determine lower extremity kinematics and kinetic variables. Perceived insole comfort was scored with a visual analogue scale. Dependent variables were analyzed using paired-samples t-tests; for data that violated assumptions, a Wilcoxon signed-rank test was utilized. RESULTS: Kinetic measures did not differ significantly between insole conditions; impact peak (NI=1.46±0.58 BW, TI=1.50±0.44 BW, p=.74), active peak (NI=2.37±0.16 BW, TI=2.35±0.15 BW, p=.28), loading rate (NI=35.9±12.2 BW/s, TI=34.0±13.2 BW/s, p=.26), peak braking (NI=-.31±.03 BW, TI=-.32±.06 BW, p=.69) and peak propulsion (NI=.27±.05 BW, TI=.27±.04 BW, p=.28). A significant increase in ankle internal rotation angle at initial contact was observed in the TI versus NI (NI=5.9 ± 5.9o; TI=7.3 ± 5.9o; p=.01, d=.24), however, no other significant kinematic differences were detected. NI (mdn=9.0) was rated as significantly more comfortable than TI (mdn=8.0) (z=-2.026 p=.04). CONCLUSION: Because kinematic and kinetic variables did not vary significantly between the TI and NI, the efficacy of the TI as a method of immediately altering running mechanics in a population of rear foot strikers should be further investigated. Insoles provided by: ShoeCue Inc (ShoeCue, Orleans, MA)