Assessment and testing of movement analysis systems: spot checks

Effective clinical application of movement analysis depends on the reliability of relevant results. The routine assessment of the errors (spot check) associated with the used instrumentation and experimental methodology is, therefore, extremely important both for the experimenter who produces the results and for a remote user of them in a data-sharing context. With the expression spot checks, reference is made to this assessment carried out at the beginning of each experimental session.This paper deals with instrumental errors and their effect on the errors which affect the reconstruction of the location in space of generic body landmarks and bone embedded frames, and the relative position of these with respect to reaction force vectors. These errors are analysed with the purpose of outlining their relative importance with respect to other errors more strictly related to a particular experimental protocol. A separate analysis is made of the low- and high-frequency components of the photogrammetric errors.Simple tests and relevant analytical procedures are described which allow the user of a movement analysis laboratory to carry out an effective spot check.