Semester

Summer

Date of Graduation

2014

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Industrial and Managements Systems Engineering

Committee Chair

Xiaopeng Ning

Committee Co-Chair

Majid Jaridi

Committee Member

Ashish Nimbarte

Abstract

Back injury caused by sudden loading is a significant risk among workers who perform manual material handling tasks (MMH). Therefore, it is critical to understand the effects of influential factors on back injury risks during sudden loading, and to develop load handling strategies that can reduce the biomechanical impacts to the spine caused by sudden loading. In this study we explored the effects of foot placement, load handling position as well as uneven ground conditions on trunk biomechanical responses under sudden loading event.;In the first experiment we investigated the effects of different foot placements and load asymmetry on trunk biomechanics during sudden loading. Fifteen subjects experienced sudden release of a 6.8 kg external load from symmetric or asymmetric directions while maintaining four different foot placements. The results showed that subjects experienced on average 4.1 degrees less trunk flexion, 6.6 Nm less L5/S1 joint moment and 32.0 N less shear force when using staggered stance with right foot forward (the most preferred placement) in comparison to wide stance (the least preferred placement). Asymmetric load releasing position consistently resulted in smaller trunk biomechanical impact than symmetric position. The findings suggest that staggered stance and asymmetric load holding position can be used as a protective load handling posture against low back pain caused by sudden loading.;In the second experiment we investigated the effects of load handling position on trunk biomechanics during sudden loading. Eleven male subjects were exposed to a 6.8 kg sudden loading while standing upright and holding the load at three different vertical heights in the sagittal plane or 45 degree asymmetric to the sagittal plane. Results showed that subjects experienced smaller spinal compression with the decrease of load holding height; more specifically, at the 'Low (umbilicus level)' height condition, the peak L5/S1 joint compression force was 10.1% and 15.1% less than the 'Middle (shoulder level)' and 'High (eyebrow level)' conditions, respectively. Further, asymmetric posture resulted in 3.9% less compression force than symmetric posture. These findings suggest that handling loads in a lower position could work as a protective strategy when experiencing sudden loading.;In the third experiment we investigated the effects of uneven ground conditions on trunk biomechanical responses during sudden loading. Thirteen subjects experienced sudden loading with two different weights (3.4 kg and 6.8 kg) while standing on flat or laterally slanted ground conditions (0°, 15° and 30°). Our results showed that subjects experienced larger peak L5/S1 joint compression force with the increase of ground slanted angle. On average, the peak L5/S1 joint compression force generated in the 30° condition was 6% and 8% larger than 15° and 0° conditions, respectively. Furthermore, greater trunk biomechanical impact was constantly observed in the 3.4 kg weight condition compared with the 6.8 kg condition. Findings of this study suggest that standing on laterally slanted ground surface increases the risk of low back injury when experiencing sudden loading.

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