As a significant contributory factor to low back injury, sudden loading during manual material handling often occurs on uneven ground surfaces. The present study investigated the effects of laterally slanted grounds on trunk biomechanical responses during sudden external loading. 13 male subjects experienced sudden loading of 6.8 kg while standing on a laterally slanted ground of 0 degree, 15 degree and 30 degree. The results showed that peak L5/S1 joint compression forces in the 30 degree condition was 10.5% and 6.5% greater than the 0 degree and 15 degree conditions, respectively. In addition, 30 degree condition also generated 14.8% and 15.1% larger increase in trunk flexion angle compared with the 0 degree and 15 degree conditions, respectively. These findings suggest that standing on a laterally slanted ground could increase the risk of low back injury, and should therefore be avoided in a work place.
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