The dynamical interaction between arms and trunk segments during walking

The focus of this dissertation research was to investigate the biomechanics underlying the emergence of coordination patterns during walking. Two experiments were conducted in which the movement of arms, thorax and pelvis were modeled mathematically to capture the coupling among these segments. Fourteen healthy young subjects were instructed to walk on the treadmill at various speeds and kinematic data were collected using 3D motion analysis system.; The purpose of the first experiment was on the mechanism for the concurrent transitions in the arm-leg frequency ratio from 1:1 to 2:1 and in the inter-arm phase relationship from out-of-phase to in-phase observed at slow walking speeds. A pair of passive pendulum excited at suspension point was adopted as a model. The acceleration at the shoulders consisted of in-phase at step frequency and out-of-phase stride frequency components. The change in magnitude ratio between two acceleration components was associated with the occurrence of the transitions. The results of mathematical simulations of transitions showed that the proximity of the frequency of acceleration at shoulder joint to the natural frequency of the arms influenced the occurrence of the transitions.; The purpose of the second experiment was to develop a torsional spring model to estimate the axial stiffness between thorax and pelvis, the amount of stored elastic energy, and to consider the role of axial stiffness on the dynamics of arm-trunk complex during walking. The axial stiffness was estimated from the angular displacements between trunk segments and the amount of axial torques due to the arm swing and the oscillation of thorax. The increase in the angular displacements with increasing speed was mainly due to increased amplitude of pelvic oscillation. The amplitude of thoracic oscillation remained low independent of changes in walking speeds, which was due to the counteraction between torques due to arm swing and the axial stiffness. Elastic energy in the trunk increased linearly with speed increases.; The results of these studies showcase the dynamical involvement of trunk movement to the emergence of inter-limb coordination during walking. This will expand our understanding of the relationship between biomechanical constraints and the emergence of coordination patterns.