Impact of marker set configurations in the measurement of hip axial rotation in ballet turnout

Le résumé fourni par la source

The hip is the main contributor to turnout, a key element in classical ballet involving large external rotations of the lower limb. Measuring hip axial rotation during turnout using skin-markers is challenging due to substantial soft tissue artifacts in the thigh. These measurements depend on the chosen thigh marker set, and no consensus exists on the most suitable configuration for large hip motions. We hypothesized that soft tissue artifacts would significantly affect hip rotation measurements obtained by different marker-set protocols. This study compared three marker set protocols for assessing hip axial rotation during the Assemblé Dessus jump in 17 experienced ballet dancers. A rectangular rigid-cluster (CC) positioned in the thigh mid-lateral portion and a custom-designed wedge-shaped cluster (WC) positioned on the distal portion of the iliotibial band were compared to the Vicon’s Plug-in-Gait (PIG) markers’ protocol. Data was tracked via an 8-camera motion capture system, and Visual 3D was used to calculate hip rotation from the three marker sets. Statistical parametric mapping and one-way ANOVA were used to assess the effect of the marker set on hip rotations. The choice of marker set significantly affected hip axial rotation measurements. PIG provided less reliable estimates than CC and WC, and an offset between WC and CC measurements was observed which may be due to skin twisting caused by a constant torsional load on the thigh. Based on these findings, a rigid cluster protocol may be more suitable to assess larger hip axial rotations, such as in the ballet turnout. However, careful consideration should be given to the cluster proximal-distal location when comparing inter-session data. • The turnout is a key element of classical ballet technique, and involves a large external rotation of the lower limb with the hip as the main contributor. • Marker set configuration significantly affected hip axial rotation measurements in the ballet turnout. • Kinematic model based on Vicon’s Plug-in-Gait marker set protocol provided less reliable estimates of hip axial rotation than rigid-clusters protocols. • Hip-axial rotation measurements may be affected by the proximal-distal rigid cluster-location.

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