QUANTIFYING WORK LOAD IN NECK, SHOULDERS AND WRISTS IN FEMALE DENTISTS

Objective: To assess the work load in neck and upper limbs of dentists . Methods: Twelve right-handed female dentists (six with and six witho ut a history of definite neck/shoulder disorders, pair-wise matched fo r age) were studied when performing authentic dental work. Electromyog raphy (EMG) was used to quantify the muscular load of the shoulders bi laterally and of the right forearm. Positions and movements of the hea d and wrists were measured, using inclinometers and electrogoniometers . Results: During work, the median load for the right upper trapezius muscle was 8.4% of the maximal voluntary EMG activity (MVE); during 90 % of the time the load was greater than or equal to 3.3% MVE (''static '' load). The figures were somewhat lower on the left side (7.0% and 2 .5% MVE, respectively). Subjects with disorders had over all lower loa d levels for the trapezius muscles, although not statistically signifi cant at <0.05, than those without disorders. During a standardized ref erence contraction for the trapezius, the load was 17% MVE, and the qu otient between MVE and torque [normalized to maximal voluntary torque (MVC)] was 0.5. These figures may be used for transformations. The mus cular load on the right forearm was similar to the loads on the trapez ius. The head was, on average, forward tilted greater than or equal to 39 degrees, and during 10% of the time greater than or equal to 49 de grees. The left hand was held in more static positions, with palmar fl exion and ulnar deviation, also reflected by lower angular velocities and repetitiveness, as compared with the right one, which was dorsifle xed. Conclusions: Dentists are exposed to high load on the trapezius m uscles bilaterally, and steep, prolonged forward bending of the head. Further, for the wrists the postures were constrained, but the dynamic demands were low.