Intervertebral motion during vibration.

• Vibration exposure is widely recognized as a risk factor for low back pain. An experimental protocol was designed to quantify the intervertebral motion response in human subjects to sinusoidal vertical vibration at 5 and 8 Hz, and at a variety of acceleration levels. Intervertebral motion in the mid-sagittal plane was measured using a transducer linkage system attached to pins placed directly into the spinous processes of adjacent vertebrae. The postures of the subjects were carefully controlled. The effects of forward flexion, arm support, gravitational load, and sitting on a cushion were evaluated. The rigid body motion of the superior vertebra with respect to the inferior vertebra was expressed in terms of relative sagittal plane rotation, axial translation, and anterior-posterior shear translation. It was found that the lumbar motion segments exhibited coupled periodic behaviour in response to sinusoidal vertical vibration, with up to 1 mm peak-to-peak displacement in the axial direction. The greatest intervertebral motion occurred when the subject was exposed to 5 Hz vibration as compared to 8 Hz. For a constant frequency of 5 Hz excitation, the peak-to-peak amplitudes of the computed motions tended to increase as the acceleration level increased. In the flexed posture, with no arm support, the active trunk musculature helped reduce the intervertebral motion. Additional gravitational load on the shoulders caused increased relative axial displacement. A polyethylene foam cushion placed on the seat reduced vibration transmission at 5 Hz excitation and consequently decreased the intervertebral motion.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Kirurgi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Surgery (hsv//eng)

Nyckelord

Adult

Back Pain

etiology

Biomechanics

Female

Humans

Intervertebral Disk

physiology

Lumbar Vertebrae

physiology

Movement

physiology

Posture

physiology

Reference Values

Risk Factors

Vibration

adverse effects

Risk Factors

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)