[The ergonomic analysis of different holding gun methods for standing guard soldiers]

Objective: To study the effects of different holding gun methods and gun weight on health when standing guard, and propose a way to support the health of long-term standing guard soldiers. Methods: We created different percentile mannequins by Classic JACK, and adjusted the standing guard posture based on its standards for soldiers. The pressure on lumbar L4/L5 and moment on ankles and knees were analysied for different holding gun methods and gun weight. Then the mathematical models of joint load, gun weight and body mass index were studied by multiple regression analysis. Results: Holding gun methods and gun weight influence the force characteristics on ankles, knees and lumbar L4/L5. Holding gun with a brace and hands applying downward force -2 kgf could significantly reduce lumbar L4/L5 pressure. When the hand force is -5, -3, -4, -3, -2, -1, 0, 1, 2 kgf, and the weight of the gun is 0, Lumbar vertebrae L4/L5 joint pressure of people with different body mass index(P(1), P(5), P(55), P(95), P(99)) are the smallest, respectively 269, 281, 321, 408, 444 N, and the same change trend occurs when the weight of the gun is 2, 4, and 8 kg.The moment on ankles and knees were less with the same holding gun method and the hands downward force ranged from 0 to -4 kgf, and the higher the body mass index is, the more the hands downward force needed to make the moment on ankles and knees zero. That is, the moment on ankles could be zero when the hands downward force ranged from -1 to -3 kgf, the moment on knees could be zero when the hands downward force ranged from -1.1 to -3.7 kgf. Conclusion: To reduce the pressure on lumbar L4/L5 and moment on ankles and knees, so as to cut down occupational risk of long-standing operation, we advise the long-term standing guard soldiers holding gun with a brace and hands applying downward force -2 kgf.