A biomechanical assessment of running with hallux unstable shoes of different material stiffness.

ABSTRACT

PURPOSE: Functional footwear with different unstable profiles has been widely used to mimic barefoot condition and offload plantar loading for pathological or injury prevention. However, little research investigates the effect of unstable structure on particular foot functions. In this study, a prototype of unstable shoe design with unstable element of different stiffness placed at the hallux (a regionalized rocker) was used. The primary objective was to analyse the biomechanical performance of running with hallux unstable shoes, aiming to potentially stimulate and increase the toe gripping function. METHODS: The lower limb kinematics and plantar pressure distribution were measured to comparatively analyse the soft (SS) and hard (SH) unstable shoes with flat control shoes (CS). RESULTS: The SS showed increased big toe and reduced forefoot plantar pressure. The SS led to similar lower limb kinematics to baseline CS except for reduced hip abduction, increased rotation range of motion (ROM), increased peak ankle plantar flexion and ROM. The SH presented significantly altered lower limb kinematics across hip, knee and ankle, and laterally distributed plantar pressure. CONCLUSIONS: Unstable shoes with soft material led to reduced medial metatarsal loading by increasing the support area and modified joint kinematics minimally. Unstable shoes with stiffer material presented compensatory kinematic movements across all joints and laterally shifted plantar loading distribution. These findings may provide implications on toe grip function training for foot pressure off-loading.