Abstract
Rocker profile shoes with a proximally placed apex are currently one of the most prescribed shoe modifications for treatment and prevention of lower leg deficits. Three geometrical rocker design parameters apex position (AP), apex angle (AA) and rocker radius (RR) influence both plantar pressure redistribution and kinetic and kinematic alterations of the lower leg. In addition, longitudinal bending stiffness (LBS) of the outsole influences these parameters as well. This study aims to investigate the effects of the LBS in combination with different forefoot radii of rocker shoes on kinematics and kinetics of the lower limb. 10 participants walked in standard shoes and six experimental shoe conditions with high and low LBS and three different forefoot rocker radii with the same (proximal) AP and AA. Lower extremity kinematics and kinetics were collected while walking on an instrumented treadmill at preferred walking speed and analysed with a repeated measures ANOVA and Statistical Parametric Mapping (SPM) (α = .05; post hoc α = .05/6). SPM analyses revealed no significant differences for LBS and interaction LBS*RR for most research variables in terminal stance (ankle angle, ankle moment, ankle power, foot-to-horizontal angle, shank-to-vertical angle, external ankle moment, ground reaction force angle). A significant LBS effect was found for anterior-posterior position of the centre of pressure during pre-swing and peak ankle dorsiflexion angle. No relevant significant differences were found in spatio-temporal parameters and total work at the ankle between low and high LBS. This study showed that longitudinal bending stiffness does not affect the biomechanical working mechanism of rocker profile shoes as long as toe plantarflexion is restricted. Providing that the forefoot rocker radius supports at least a normal foot-to-horizontal angle at toe-off, there is no reason to increase sole stiffness to change ankle kinematics and kinetics.
Highlights
Rocker profile shoes with a proximally placed apex are currently one of the most prescribed shoe modifications for treatment and prevention of lower leg deficits
High longitudinal bending stiffness (LBS) shifts the application of the ground reaction force (GRF) more distally, resulting in an increased ankle plantarflexion moment (PFM) during terminal stance in running [7]
This study aims to inves tigate the effects of LBS and different forefoot radii of rocker shoes with the same proximal apex position (AP) and apex angle (AA) on kinematics and kinetics of the ankle (DF, PFM and power) and its underlying variables (FHA, shank-to-vertical angle, external ankle moment arm, anterior-posterior position of the centre of pressure (COP) and sagittal plane GRF vector angle)
Summary
Rocker profile shoes with a proximally placed apex are currently one of the most prescribed shoe modifications for treatment and prevention of lower leg deficits. Three geometrical rocker design parameters apex position (AP), apex angle (AA) and rocker radius (RR) influence both plantar pressure redistribution and kinetic and kinematic alterations of the lower leg. Changes in the geometrical forefoot rocker design parameters: apex position (AP) [1], apex angle (AA) and rocker radius (RR) [2] induce both plantar pressure redistributions [3] and lower limb kinetic and kinematic alterations [4,5]. Research in LBS of shoes is, as opposed to walking performance, more focussed on running performance where increase in power and positive work are the main goals [9,12] This contrasts with rocker profile shoes in a clinical setting where reducing PFM is often one of the main goals [5].
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