REACTION TORQUES AND OPERATOR STRESS WHILE USING POWERED NUTRUNNERS

Reaction torque measures of six different nutrunners were correlated w ith EMG measures and subjective ratings of perceived exertion for diff erent work surface orientations, joint stiffnesses, rpm levels, air pr essure levels and handle configurations. Using an underpowered tool or using a softer joint resulted in larger impulses and worse ratings. A pulse-type shut-off mechanism produced the lowest reaction torque and the best rating. Overall, ratings correlated directly with the impuls e level. The subjects were good judges of stress levels, and subjectiv e ratings were valid measures of operator stress.