Ergonomic evaluation of the operating characteristics of the 6MF-30 portable pneumatic extinguisher

• We measured HR, EMG and the degree of fatigue of 14 subjects operating the 6MF-30.
• The effects of carrying posture on HR and EMG data were significant.
• The effects of carrying posture on the degree of fatigue were significant.
• The strap of the 6MF-30 lessens physical stress.
• The optimal carrying posture adopted when using 6MF-30 includes the oblique strap.

The 6MF-30 portable pneumatic extinguisher, which is one of the most widely used pieces of equipment for fighting forest fires in China, can produce great physical discomfort for the wearer. To mitigate the physical discomfort associated with the use of the 6MF-30, the operating characteristics of this machine were ergonomically evaluated. Fourteen subjects were instructed to operate the 6MF-30 portable pneumatic extinguisher using three different carrying postures (oblique strap, vertical strap and no strap) two different motions (stationary and swinging) during a simulated firefighting task. Dependent measures included heart rate (HR), electromyography (EMG) data and a subjective assessment (measured as the degree of fatigue in the left arm, right arm and waist). The EMG data were acquired from the palmaris longus and the biceps brachii of the left arm of each subject. Variance analysis indicated that the effects of the carrying posture on the HR (p < 0.001), the EMG data of the left arm (the p value of the palmaris longus is 0.001 and the p value of the biceps brachii is 0.015), and the degree of fatigue of the left and right arms (p < 0.001) were significant, while the effects of motion on all of the dependent measures, and the effects of carrying posture on the degree of fatigue of the waist were not significant. The effect of an oblique strap on the whole-body load is minimal, and the use of the equipment without a strap produced significantly greater physical discomfort for the wearer than did the oblique strap and the vertical strap. The results suggest that the strap of the 6MF-30 can help Chinese forest firefighters to lessen physical stress when operating the 6MF-30, and the use of the oblique strap should be adopted as the standard position.