Purpose <p>Evaluation of spinal mobility is essential for clinical assessment of spinal disorders and their treatment. Motion capture systems can offer intersegmental kinematic data for the spine, but results usually depend on marker placement, and the definition of reference frames can still pose a challenge for clinical relevance and data comparison. This pilot study aimed to propose a reduced marker set protocol to estimate thoracic, lumbar, and intervertebral ranges of motion (ROM) during functional trunk movements – flexion/extension (FE), lateral bending (LB), and axial rotation (AR).</p> Methods <p>Fifteen asymptomatic young adults performed standardised trunk tasks, while a twenty-one-marker configuration and motion-capture system were used to capture their 3D spinal motion. Anatomical coordinate systems were constructed for pelvis, thoracic, and lumbar regions. Three models of intervertebral kinematic constraints were compared, implementing different degrees of freedom between intervertebral segments, and different distribution of ROM to individual spinal levels. The agreement among models was assessed, and ROM was compared to literature data.</p> Results <p>Results showed large differences in ROM between kinematic models, as well as differences with reference data in the literature. Furthermore, differences between models were not consistent across all movements (FE, LB, AR).</p> Conclusions <p>This study highlights the need for in vivo data to reflect functional, coupled spinal motion. The choice of kinematic model had a large impact on ROM and segmental ROM. Nevertheless, the proposed recduced marker protocol combined with validated kinematic constraints could offer a feasible and anatomically plausible solution for clinical spine mobility assessment.</p>