Fig. 2

Example of a lumbopelvic (FP-PL) segment angle-angle diagram from one subject. One segment’s angular displacement (x axis) in sagittal plane versus another segment’s angular displacement (y axis) in sagittal plane during forward bend. Altered lumbopelvic rhythm was defined as slope greater than 45° in the first 1/3rd of the movement. To quantify coordination changes observed in a segment angle-angle diagram, a coupling angle (insert), which is the angle between the vector formed between two adjacent data points relative to the right horizontal, coupling angle (θ) = atan [(Y _i + 1 –Y _i )/(X _i + 1 –X _i )], was used to standardize segment coordination across trials and subjects