AN ERGONOMIC COMPARISON OF INDUSTRIAL SPRAY PAINT GUNS

Two spray guns were used by 10 subjects in a laboratory. One gun was a 'traditional' spray gun. The other was the OMX gun which had 'ergonom ic' features including reduced gun and hose weight and two triggers (o ne for horizontal surfaces and one for vertical). The 10 subjects (5 e xperienced industrial spray painters and 5 inexperienced students) use d each gun for 4 h. The criteria used to evaluate the two guns were: ( 1) Wrist deviation in all three axes, (2) EMG frequency shift of 3 sho ulder muscles over the test period, (3) integrated EMG activity of the forearm flexors, and (4) body discomfort ratings. It was found that t he OMX gun resulted in significantly less radial/ulnar deviation in th e wrist, and moderately increased flexion/extension and pronation/supi nation deviations from neutral. During the painting period, up to 50% less fatigue in the shoulder muscles was found for the OMX gun. Additi onally, the triggering activation levels for sustained grip contractio ns were found to be acceptable for the OMX gun when using the short tr igger. Finally, the amount of discomfort reported by the subjects was statistically lower in the shoulder, upper back, arm, elbow, forearm, wrist, and hand with the OMX gun design. Collectively, these results i ndicate that the OMX gun would be expected to reduce exposure to occup ational risk factors for workers. This study demonstrated how the inco rporation of ergonomic design principles can be used to minimize occup ationally-related risk. Relevance to industry Cumulative trauma disord ers (CTDs) are soft tissue disorders resulting from repeated exertions and excessive movements of the body. Industrial spray painting fits t he profile of a highly repetitive task. Improving spray paint gun desi gn could potentially reduce the risk of CTDs in industrial spray paint ing tasks.