Biomechanical load on human lumbar spine in palletizing tasks with restriction to access and varying headroom

• Published in: International journal of industrial ergonomics Vol. 23; no. 4; pp. 349 - 358
• Main Author: Kumar, Shrawan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.03.1999
• Subjects: Biomechanical analysis; Biomechanics; Disc compressive forces; Disc shear forces; Lifting; Materials handling; Mathematical models; Musculoskeletal system; Occupational diseases; Palletizing; Risk assessment; Stress analysis; Palletizing; Biomechanical analysis; Disc compressive forces; Lifting; Disc shear forces
• ISSN: 0169-8141; 1872-8219
• DOI: 10.1016/S0169-8141(98)00051-1

The objective of the study was to determine if restriction to access, asymmetry of posture, and reduced headroom in lifting and palletizing tasks affect biomechanical stresses on the lumbar spine significantly. Eleven male blue collar workers with a mean age of 29.1 yr, mean weight of 67.6 kg, and mean height of 174.1 cm with no musculoskeletal disorders were required to lift a 22 kg weight box measuring 46×30×30 cm to a shelf 125 cm high which allowed either 5 or 10 mm clearance for the weight box. The lifts were performed in sagitally symmetrical and 45° asymmetric planes under headroom adjusted to 80% and 90% of the subject's stature and unrestricted headroom. The 12 tasks were randomized and each task was performed three times. During these 12 tasks the xyz coordinates at 15 nodal points were recorded and were inputted to a biomechanical model. The disc compressive and shear forces, and the muscle forces for spinal and abdominal muscles were computed for six lumbar intervertebral discs for six stages of the lift. The results indicated that the take-off stage was most stressful followed by to- the-shelf stage. The multivariate analysis of variance revealed that the headroom affected the biomechanical loads significantly ( p<0.004). Symmetry affected the disc compressive load during take-off only ( p<0.01). The clearance had no impact on the biomechanical loading. Relevance to industry Lifting and palletizing are very common industrial activities. By breaking down the components of tasks and variables affecting them one can determine more clearly the effect of each of these variables. This will help in managing the risk at workplace.