In this study the ability of inertial and magnetic sensors (TechMCS, Technaid SL, Madrid, Spain) to accurately track 3D motion is evaluated. An effort is made to decompose the accumulated error present in complex motion capture in order to better understand the strengths, weaknesses and fields of improvement of these sensors. A series of tests were conducted in static, quasi-static and pendulum-dynamic conditions. No significant influence of magnetic field distortion or accelerometer drift was observed. Our data suggests that the drift present after integrating the gyroscope data is a function of motion complexity, with an additional random component. Accurate calibration of gyroscopes and improved drift models are expected to further increase performance of wearable motion capture systems. A maximal discrepancy of almost 4° was observed under ideal testing conditions.