Background:
In this week’s post, we review a recent research article on welding [1]. In this paper, the authors investigated physical outcomes associated with two different set-ups for welding equipment. They believed that an adapted system would reduce exposure to various risk factors when compared to the conventional design. This extends the ideas outlined in the previous post on welding exposures and offers some insights on a potential intervention/change that can reduce risk of injury among these professionals.
Article Review:
The study involved 10 stud welders at a construction site. Normally this job required employees to use an extremely forward bent posture to perform many of the tasks, but with an alternate design and additional equipment to help distribute materials, the authors believed there would be a reduction in physical exposures. They preformed a field-based assessment of back angles and back and neck muscle recruitment among iron workers using a conventional and an alternate stud welding system.
The alternate system had a significant reduction on back angles, with average forward bending decrease from 34 degrees to 9 degrees with the new design. In addition, the percentage of work time spent in forward bent postures of greater than 60 degrees (which is considered a significant risk factor for the back) was reduced from an average of 40 to an average of 4.7 percent with the new design. However, the upper trapezius (neck/shoulder muscle) results show that the new design increased overall activity and reduced the “rest” time for the muscle. No significant differences were found between the two conditions for back muscle activity. This does make sense because during deeper ranges of back bending, ligaments and non-muscular tissue, rather than active muscle, are placed under the greatest loading. Therefore, while muscle activity between upright and bent postures are not different, the postural demand of forward bending does create strain on other structures in the back.
The authors note that many epidemiological studies have noted increased back bending angles and time spent in bent postures are associated with development of lower back pain. With this in mind, the proposed system seems to provide a benefit and could help reduce the occurrence of lower back pain among welders. However, they note that the increased load on the neck/shoulder region, and by extension the upper limb, may cause increased risk of injury to these body regions. More work is needed to determine if the benefit to the lower back is offset by the increased risk to the upper limb.
EWI Works Comments:
This study was well designed with a good selection of physical exposure measures to determine differences between the traditional and adapted systems. The results provide some interesting outcomes that show the adapted system might be better suited to reduce lower back injury risk, but more work is needed to determine if the loading in the neck/shoulder negates the overall benefit.
We believe that one way this could be accomplished is through follow up with participants to gather their feedback on what they like and dislike about each system, where they feel fatigue and discomfort when using each system, and what changes might be made to further improve the adapted system. Perhaps, with a more investigation and adaptation the increased loading in the neck/shoulder could be avoided.
References:
1. Fethke, N.B., Gant, L.C., Gerr, F. (2011). Comparison of biomechanical loading during use of conventional stud welding equipment and an alternate system. Applied Ergonomics, 42, 725-734.
Comments?
Cheers!
David & Linda.
