Effects of a leaf spring structured midsole on joint mechanics and lower limb muscle forces in running.

Tobias Wunsch,Thomas Stöggl,Hermann Schwameder,Nathalie Alexander,Josef Kröll,Steven Allen Gard

doi:10.1371/journal.pone.0172287

Abstract

To enhance running performance in heel-toe running, a leaf spring structured midsole shoe (LEAF) has recently been introduced. The purpose of this study was to investigate the effect of a LEAF compared to a standard foam midsole shoe (FOAM) on joint mechanics and lower limb muscle forces in overground running. Nine male long-distance heel strike runners ran on an indoor track at 3.0 ± 0.2 m/s with LEAF and FOAM shoes. Running kinematics and kinetics were recorded during the stance phase. Absorbed and generated energy (negative and positive work) of the hip, knee and ankle joint as well as muscle forces of selected lower limb muscles were determined using a musculoskeletal model. A significant reduction in energy absorption at the hip joint as well as energy generation at the ankle joint was found for LEAF compared to FOAM. The mean lower limb muscle forces of the m. soleus, m. gastrocnemius lateralis and m. gastrocnemius medialis were significantly reduced for LEAF compared to FOAM. Furthermore, m. biceps femoris showed a trend of reduction in running with LEAF. The remaining lower limb muscles analyzed (m. gluteus maximus, m. rectus femoris, m. vastus medialis, m. vastus lateralis, m. tibialis anterior) did not reveal significant differences between the shoe conditions. The findings of this study indicate that LEAF positively influenced the energy balance in running by reducing lower limb muscle forces compared to FOAM. In this way, LEAF could contribute to an overall increased running performance in heel-toe running.

Highlights

IntroductionThe mechanical energy generated by the muscles of the lower limb joints enables the runner to fulfil the movement task and determines running performance
From a biomechanical perspective, the mechanical energy generated by the muscles of the lower limb joints enables the runner to fulfil the movement task and determines running performance
A reduction of 32% in the peak power absorption (p < 0.001, dz = 2.50) and 11% in the energy absorption (p = 0.010, dz = 1.11) was found for leaf spring structured midsole shoe (LEAF) compared with foam midsole shoe (FOAM), whereas at the ankle joint, a reduction of 17% in peak power generation (p < 0.001, dz = 2.08) and 13% in the energy generation (p < 0.001, dz = 4.29) occurred (Table 1 and S1 File)

Summary

Introduction

The mechanical energy generated by the muscles of the lower limb joints enables the runner to fulfil the movement task and determines running performance. Three major strategies have been proposed to improve the mechanical energy cost in running to enhance running performance: (1) storage and return of energy (2) optimization of the muscle functions by enabling muscles to work at an optimal forcevelocity and force-length relationship, and (3) minimization of energy loss [1, 2]. Running shoe designs have had limited success in applying the concept of energy return [1, 3] and the concept of functional optimization of the musculoskeletal system lacks scientific. Structured midsole for running shoes the Open Access Publication Fund of the University of Salzburg

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