Angular motion of the thorax during the golf swing: a comparison of two orientation angle sequences

Orientation angles are commonly used to describe complex angular motions of the body. Selecting the most appropriate rotation sequence for a given segment's motion is crucial. The purpose of this study was to develop a set of generalisable, primary axis-centric sequence selection strategies and to compare the lean direction-lean-rotation (LDLR) sequence, selected for thoracic motion during golf driving based on the strategies, with the conventional rotation-bend-side bend (RBSB) sequence in assessing the level of inter-angle cross-talk. The RBSB method consistently revealed a higher level of inter-angle cross-talk, with substantially larger bi-angle ICC values across all angle combinations. The rotation-side bend and bend-side bend pairs in the RBSB method exhibited the largest ICC values (≥0.837). In contrast, the rotation-lean and lean direction-lean pairs in the LDLR method showed the smallest ICC values (≤0.063). The RBSB sequence demonstrated significantly larger RMS angle ranges (p < .001), indicating a deterioration of the major angle and inflation of the minor angles due to cross-talk. The LDLR sequence realistically portrayed the axial rotation-dominant thoracic motion during the golf drive. The strategies outlined in this study can serve as general guidelines and substantially enhance the applicability of the orientation angle method.