No abstract

Design engineers should avoid placing hand wheel valves at knee height or lower.

Maximum torque and electromyography (EMG) of muscle activity when turning an 18 inch dia. hand wheel valve was measured at 3 different heights to determine the biomechanical loading on a worker's body. Twenty-four electric utility plant mechanics and operators participated in this study. The major independent variables were valve height (overhead, chest, and knee level) and torque direction (right and left). The major dependent variables were maximum torque (ft-lbs) and maximum voluntary contraction (%MVC) of EMG. Subject's exerted an average of 111 ft-lbs counterclockwise torque, which was greater that the mean 104 ftlbs generated in the clockwise direction. Furthermore, participants exerted 13 to 16% greater torque at the overhead level than at chest level. When turning the valve counterclockwise (left), the %MVC of the left side muscles was greater than the right side muscles and vice versa for turning the valve clockwise (right).

No abstract

Electric utility power plant electricians use a conventional manual screwdriver to loosen and tighten small fasteners on a day-to-day basis, which may expose them to risk of musculoskeletal disorders (MSDs) affecting the wrist and upper extremity. Using a screwdriver handle that requires less muscle activity to exert the same level of torque can reduce the risk of MSDs. Maximal forearm torque in both supinating and pronating directions and at 3 forearm positions (supinated, neutral and pronated) were tested with 2 screwdrivers, a conventional straight-handled tool and pistol-grip screwdriver. Electromyography (EMG) of the finger flexor and extensor muscles and the biceps were monitored while performing maximal forearm torque exertions in the pronating and supinating directions at 3 forearm positions. The torque exerted while using the pistol-grip screwdriver was twice as great as with the straight handle (8.47 and 4.24 Nm, respectively). The turning direction affected maximal torque and interacted with position of the forearm. Normalizing maximal torque data to the muscle activity (Nm / %MVC EMG) revealed that the pistol-grip tool was much more efficient than the straight handle tool.