QUANTIFICATION OF TRUNK MOTION IN RESPONSE TO COMPLEX PLATFORM PERTURBATIONS WHILE HOLDING WEIGHTS IN AN UPRIGHT POSTURE

Abstract

This experiment investigated the role of the lumbar region in a simple load-holding situation for three asymmetric (0, 45 and 90 deg) platform perturbations for 18 normal, college age males. The platform perturbations included horizontal translation and rotation in addition to stable condition. The weight was 20% of the subjects' body weight. The Balance System (Chattecx Co.) was used to monitor balance performance while the Lumbar Motion Monitor was used to quantify low-back kinematics. The platform perturbation significantly affected both the lumbar motion parameters and the dispersion, an index of postural sway. The asymmetry of direction of perturbation also significantly affected both the postural sway and the lumbar motion involvement. Given the large mass of the spine, corrective/reactive fast movements to maintain the balance due to the unexpected perturbation to the base of support may lead to impulsive loading of the spine which is associated with the low back injuries. The study of postural stability, whilst an additional manual material handling task is being performed presents a more realistic and functional test than the traditional protocols used presently in Balance Clinics. This type of functional dual tasking is a rich paradigm that requires more research investigations.