Analysis of 15 different pelvis marker protocols during sit-to-stand

Sit-to-stand (STS) is a common transition movement needed to perform daily tasks. Previously, the kinematics of the STS movement has been investigated using optical motion capture. This method uses cameras and reflective markers on the body to capture movements. During STS, these markers can be difficult to measure due to blocked vision from the chair's arm- and backrest. This can result in poor data quality. The aim of this study was to investigate 15 different marker protocols and compare them in terms of visibility and selected outcome measures: hip flexion mean angle and range of motion (ROM). Fourteen healthy subjects completed five successful trials of STS. Marker protocols consisted of three anterior marker protocols and five posterior marker protocols, combined into a total of 15 marker protocols. For visibility, the traditional pelvis marker protocol proved unsuitable for STS tracking. Marker pins or additional markers anteriorly, and sacrum markers posteriorly, proved to be more suitable alternatives. For hip flexion mean angle and ROM, the estimates had similar tendencies. Hence, marker protocols were not outcome measure specific. Anteriorly, marker pins resulted in similar estimates as the traditional pelvis marker protocol. Posteriorly, sacrum markers estimated a smaller hip flexion angle, compared to the traditional pelvis marker protocol. In conclusion, marker pins can be used instead of regular ASIS markers at anterior pelvis. Posteriorly, sacrum markers can be used instead of PSIS markers.