Kinematics of trunk movements: protocol design and application in obese females

Purpose: Whether kinematic analysis of the trunk can provide useful clinical insight into the relationship between function and various spinal conditions is still under debate. The aim of this study was to develop a clinical protocol and an associated biomechanical model to characterize quantitatively the trunk movements in obese subjects. Methods: Twenty (10 obese, 10 control) female subjects were evaluated with an optoelectronic system and passive markers attached to the spine during forward flexion, lateral bending, and rotation of the trunk. Results: We found a systematic error due to skin artifacts of less than 5 degrees in both groups. Intra- and inter-subject standard deviation was less than 6 degrees. Obese subjects demonstrated a significantly reduced motion in the thoracic spine associated with an increased pelvic tilt angle as compared to controls. Conclusions: Our protocol was able to characterize trunk mobility in obese and normal subjects suggesting that kinematics could represent, even in an obese population, a promising method to investigate subclinical spinal disorders and to assess the effectiveness of rehabilitation programs. (Journal of Applied Biomaterials & Biomechanics 2008; 6: 178-85)