Objectives This study concerned the influence of 6 positions of the computer mouse on the work table on posture, muscular load, and perceived exertion during text editing. Methods An optoelectronic 3-dimensional motion analysis system was used to register the postures of 10 men and 10 women using video display units. Muscular load was also registered (with electromyography), as was perceived exertion (with rating scales). Results A neutral posture with a relaxed and supported arm showed the least perceived exertion, and the electromyographic results showed low activity in both trapezius muscles in this position. Short operators (all women) showed a numerically higher activity in the 4 examined muscles than the tall operators (all men, except 1). This finding could be related to lower muscle force among women and to anthropometric differences, which also influence biomechanic load moments. Narrow-shouldered operators (8 women and 1 man) and short operators worked with larger outward rotation and abduction of the shoulder in a position of the mouse lateral to the keyboard than the broad-shouldered (7 men and 2 women) and tall operators did. Alm support markedly reduced muscle load in the neck-shoulder region among the operators. C O~~C~U S~O~~S The operators using video display units in this study prefell-ed to use the mouse on a table in a close to relaxed, neutral posture of the arm in combination with arm support. Short and narrow-shouldered operators worked in more strenuous postures of the arm when the mouse was located lateral to the keyboard.Key terms arm support, electromyography, input device, MacReflex motion analysis system, subjective ratings, upper limb, video display unit.In recent years, the occurrence of cumulative trauma disorders such as carpal tunnel syndrome and tendinitis has increased dramatically in the United States, and these diseases account for over 60% of occupational illnesses (1). Video display terminal users have reported musculoskeletal symptoms primarily in the upper limbs, neck, and shoulders (2, 3). Health problems during work with video display terminals have been reported also in Sweden (4,5).The computer mouse and other nonkeyboard input devices supplement the keyboard in many visual display unit (VDU) workstations. The mouse technique changes posture and movements compared with keyboard use without the mouse (6). Franzblau et a1 (7) found the incidence of cavpal tunnel syndrome to be related to the pattern of mouse usage in a medical illustration department.Associations between self-reported neck and upper-limb symptoms and physical exposure factors at VDU workstations have recently been investigated (8). The study showed that long hours of work with the mouse, as well as work with the mouse nonoptimally located on the table, seem to be risk factors for upper-limb symptoms.Several significant relationships between the design of workstations or postures on one hand and the incidence of complaints or medical findings on the other have been discovered among VDU operators using a...
The purpose of the study was to determine the level of energy expenditure and exposure to air pollution for bicycle messengers. Relationships between heart rate (HR) and oxygen uptake, and between HR and pulmonary ventilation (VE) for each participant were established in laboratory tests. Air pollution and HR were measured during one working day. The total oxygen uptake was then described as the total energy expenditure in Joule (J) and in multiples of the energy expenditure at rest (MET). The mean energy expenditure during a working day (8 h) was 12 MJ, (4.8 MET). The level of air pollution exposure when cycling seemed to be comparable with the levels of exposure when sitting inside a vehicle. The VE during cycling was four times higher than resting value. Increased VE led to increased exposure to air pollution.
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