How Does the Dancer's Spine Move? Application of A Multisegmented Model.

PURPOSE: Historically, most biomechanical studies of the spine used a rigid single segment model. However, recent studies show that spinal segments do not move together predictably and that a multi-segmental model improves discrimination between patients and healthy controls. Although professional dancers experience low back pain equal to or more than the general and sporting population, to date, no study has described multi-segmented spinal motion of the dancer during any dance specific tasks which may place unique mechanical demands on the spine. The purpose of this study was to describe spinal motions of professional dancers during a common dance task, the arabesque, using a multi-segmented spinal model. METHODS: As part of larger study, 25 professional dancers (ages 24.8 +/-6.2; 5 males) performed two trials each of a right and left arabesque at their own pace while spinal kinematics were captured using a five-segment model (pelvis (PEL), lower lumbar (LL), upper lumbar (UL), lower thoracic (LT) and upper thoracic (UT). Motion was captured from initiation of vertical foot movement and ended at maximal foot height. Two trials were averaged and all values were time normalized. RESULTS: Means and standard deviations of motion in all segments in three planes were identified. In all three planes, the two upper segments (UT-LT and LT-UL) contributed 69-87% of the total spinal motion. In the coronal plane, side-bending of all segments occurred ipsilateral to the lifted leg with 54% of all motion occurring at a single segment (LT-UL). In the sagittal plane the spine generally extended, however the upper segment (UT-LT), began and remained in a flexed position throughout the motion, although it extended during the motion. In the transverse plane all segments rotated contralateral to the lifted leg. However, the lower two spinal segments contributed almost no motion. CONCLUSION: This study demonstrated that segmental motion was not uniform in degree or direction across multiple spine segments during an arabesque. Most spinal motion occurred in the upper spine. Using a multi-segmental model may improve understanding of the biomechanical stressors experienced by professional dancers.