Reproducibility of Range of Motion Measurements of the Spine with the Cybex

Range of motion (ROM) measurements of joints are often used in physiotherapy for diagnosis and for the selection of an appropriate intervention. In addition, it makes it feasible to quantify the effect of the intervention on the ROM. In this study we investigate the reproducibility (precision or reliability) of ROM measurements of the spine with the CYBEX Electronic Digital Inclinometer (EDI) 320. A further aim of the study is to estimate the minimum effect that can be detected in a clinical trial as a function of group size. In other words, this article deals with random variability in ROM measurements of the spine with the EDI 320. As is explained elsewhere in this volume, lack of random error is one of the main desiderata for an effect parameter (Bouter et al., 1990). We considered reproducibility as the degree in which repeated measurements on the same subjects provide the same results. This can be disturbed by intra-individual variability and measurement error.