OBJECTIVE: To measure the angle of applied manual force during assessment of posteroanterior stiffness in the lumbosacral spine.

DESIGN: Ten physiotherapists with bachelor's degrees in physiotherapy and postgraduate qualifications in manipulative physiotherapy assessed stiffness at 6 lumbosacral vertebral levels in a controlled order. Two pain free subjects acted as patients.

SETTING: A university biomechanics laboratory.

INTERVENTIONS: None.

MAIN OUTCOME MEASURES: Applied force vector angles in the sagittal plane.

RESULTS: The physiotherapists all varied the direction of the force they applied so that it was directed slightly toward the feet at the lower vertebral levels and more toward the head as they moved up the spine. There was a significant difference between the direction of the applied force vector angles at each vertebral level (p < .0001). The direction of force used was also significantly different for the two patients (p = .0067). The forces used by the physiotherapists were applied in directions more vertical than if forces had been applied in directions perpendicular to the surface curves of the two patients.

CONCLUSION: The direction of the force applied by the physiotherapists in this study when assessing posteroanterior stiffness varied significantly between vertebral levels and seemed to take into account the individual shape of the lumbosacral curve of each patient.

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