Biomechanical analysis of the stance phase during barefoot and shod running

Abstract

This study investigated spatio-temporal variables, ground reaction forces and sagittal and frontal plane kinematics during the stance phase of nine trained subjects running barefoot and shod at three different velocities (3.5, 4.5, 5.5 m s^-1). Differences between conditions were detected with the general linear method (factorial model). Barefoot running is characterized by a significantly larger external loading rate than the shod condition. The flatter foot placement at touchdown is prepared in free flight, implying an actively induced adaptation strategy. In the barefoot condition, plantar pressure measurements reveal a flatter foot placement to correlate with lower peak heel pressures. Therefore, it is assumed that runners adopt this different touchdown geometry in barefoot running in an attempt to limit the local pressure underneath the heel. A significantly higher leg stiffness during the stance phase was found for the barefoot condition. The sagittal kinematic adaptations between conditions were found in the same way for all subjects and at the three running velocities. However, large individual variations were observed between the runners for the rearfoot kinematics.

Introduction

Nowadays running can be considered one of the most important recreational activities. Since most people are running shod, many scientific studies investigated the influence of alterations in the properties of the shoe on the running style. Ground reaction forces and kinematic variables were found to vary with shoe hardness and shoe geometry (Nigg, 1986; Nigg and Morlock, 1987; Lees, 1988; Pratt, 1989; Edington et al., 1990; Van Woensel and Cavanagh, 1992; McNair and Marshall, 1994). The relationship between kinematic and external and internal kinetic variables was also studied using dynamic simulation models (Denoth, 1986; Gerritsen et al., 1995; Wright et al., 1998).

But there are still many aspects concerning the manner in which athletes adapt to different surfaces, shoes and other boundary conditions which are not well understood. This insight could be enhanced by studying the difference in kinematics between barefoot and shod running since in these situations boundary conditions influencing running kinematics are manipulated. Barefoot running can be seen as a running condition wherein external protection and shock reduction is minimal. So, alterations in running style are expected to be more pronounced than when comparing different shod conditions.

Until now, several authors studied barefoot running but conflicting results were presented in literature, probably because of limited samples. However, all studies agreed with the fact that the external loading rate is significantly larger in the barefoot condition (Dickinson et al., 1985; Komi et al., 1987; Lees, 1988; De Clercq et al., 1994). Concerning the sagittal plane kinematics a more extended body position and a smaller touchdown velocity of the foot were found during barefoot running (De Koning and Nigg, 1993).

The aim of the current study is to provide a comprehensive description of barefoot running using a statistical representative data set, and to compare barefoot with shod running. Therefore, spatio-temporal variables, ground reaction forces and sagittal and frontal plane kinematics of barefoot and shod running at three different velocities are analyzed and compared. In that way, systematic adaptations in the running style can be detected and hypotheses about the underlying mechanisms will be formulated.