Table 1 Relationship between markers and angles for spinal mobility

 β1

Pelvic obliquity at rest

Angle at rest between the pelvic axis (the vector LPSI-RPSI) and the horizontal plane.

 β2

Lumbar lateral flexion range

Angle between S1-L1 vector and the vertical pelvic axis through full range of lateral flexion.

 β3

Thoracic lateral flexion range

Angle between the T1-L1 vector and S1-L1 vector through full range of lateral flexion.

 β4

Shoulder range

Angle between the vector connecting both shoulders with the horizontal plane through full range of lateral flexion.

 βdc

Thoracic distal curvature range

Angle between vectors S1-L3 and L3-T6 through full range of lateral flexion.

 βpc

Thoracic proximal curvature range

Angle between vectors L3-T6 and T6-T1 through full range of lateral flexion.

 βlti

Full lateral trunk inclination range

Angle between the S1-T1 vector and the vertical axis through full range of lateral flexion.

 αkrest

Angle of thoracic kyphosis at rest

Angle at rest between the vectors L3 –T6 and T6-T1.

 α3

Thoracic range

Angle between the vector T1-L1 and the vector S1-L1 through the full range of flexion/extension.

 αfti

Full trunk flexion/extension range

Angle between the S1-T1 vector and the vertical axis in flexion/extension.

 Tr

Thoracic spinal rotation range

Angle between the vector from the line of the shoulders (LACR – RACR) and the vector defined by the line of the hips (LPSI - RPSI) throughout the full range of thoracic spinal rotation.