Between-day reliability of three-dimensional motion analysis of the trunk: A comparison of marker based protocols.

Motion capture of the trunk using three-dimensional optoelectronic systems and skin markers placed on anatomical landmarks is prone to error due to marker placement, thus decreasing between-day reliability. The influence of these errors on angular output might be reduced by using an overdetermined number of markers and optimization algorithms, or by defining the neutral position using a reference trial. The purpose of this study was to quantify and compare the between-day reliability of trunk kinematics, when using these methods.