Reproducibility of kinematic measures of the thoracic spine, lumbar spine and pelvis during fast running

• Good between-day reproducibility of thoracic spine with respect to pelvis in 3 planes.
• Good between-day reproducibility of lumbar spine with respect to pelvis in 3 planes.
• Good between-day reproducibility of thorax in lab coordinate frame in 3 planes.
• Little difference between 6DOF and GO approaches for spine with respect to pelvis.
• Motion of spine and pelvis in lab similarly reproduced in 6DOF and GO approaches.

This study evaluated the reproducibility of the angular rotations of the thoracic spine, lumbar spine, pelvis and lower extremity during running. In addition, the study compared kinematic reproducibility between two methods for calculating kinematic trajectories: a six degrees of freedom (6DOF) approach and a global optimisation (GO) approach. With the first approach segments were treated independently, however with GO approach joint constraints were imposed to stop translation of adjacent segments. A total of 12 athletes were tested on two separate days whilst running over ground at a speed of 5.6 ms−1. The results demonstrated good between-day reproducibility for most kinematic parameters in the frontal and transverse planes with typical angular errors of 1.4–3°. Acceptable repeatability was also found in the sagittal plane. However, in this plane, although kinematic waveform shape was preserved between testing session, there were sometimes shifts in curve offset which lead to slightly higher angular errors, typically ranging from 1.9° to 3.5°. In general, the results demonstrated similar levels of reproducibility for both computational approaches (6DOF and, GO) and therefore suggest that GO may not lead to improved kinematic reproducibility during running.