Neuromechanics of the Hand: Functional Degrees of Freedom during Thumb Opposition

INTRODUCTION In classic mechanics, degrees of freedom (DOF) are defined as the minimum number of independent coordinates needed to describe a system’s position. The human musculoskeletal system has many mechanical DOF through which countless movements are accomplished. However, natural movements are characterized by the coordination of the DOF such that few vary independently. The concept of functional degrees of freedom (fDOF) is introduced to describe the very limited DOF of purposeful, coordinated movements (Li 2006). The purpose of this study was to examine the fDOF of thumb joints associated with opposition movement. It was hypothesized that thumb opposition would be characterized by widespread interand intra-joint coordination, leading to reduced fDOF from its mechanical DOF.