Computer mouse position as a determinant of posture, muscular load and perceived exertion

Abstract

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...

Concordance between VDU-users’ ratings of comfort and perceived exertion with experts’ observations of workplace layout and working postures

“…However, the results were consistent with previous studies on work using the computer mouse, both in the field and in experimental laboratory settings (Bystrom et al, 2002;Karlqvist et al, 1999;Karlqvist et al, 1998;Wahlstrom et al, 2000). Moreover, the results from study II showed that perceived emotional stress during the assessment period was associated with higher activity of the trapezius muscle on the side not operating the mouse.…”

“…the way in which a subject performs a computer work task. Earlier studies on working without supporting the forearms, a specific element of computer working technique, have shown a relationship with increased activity in the trapezius muscles (Aarås et al, 1997;Karlqvist et al, 1998). In a study of working methods among computer user two different ways in which trained computer users perform work, using the computer mouse, was identified through observation assessments: the arm-based method and the wrist-based method (Wahlström et al 2000).…”

“…Anthropometric measures such as differences in shoulder width and hand size have also been proposed as possible factors increasing the ris for women (Karlqvist et al, 1998;Tittiranonda et al, 1999). One study of risk factors among computer users indicated that pain in other body regions was a predictor of persistent arm pain (Lassen et al, 2005).…”

“…time, and weight (Toomingas et al, 1997a). The optimal method to use depends on the objectives of the study, and a recently published review showed that both observation assessments and self-reported data generally provide sufficient exactness to establish priorities for intervention at the occupational safety and health practitioners level (David, 2005).In connection with computer work ratings of perceived exertion, and perceived comfort have been frequently used in exposure assessment studies (Holte et al, 2003;Karlqvist et al, 1998;Tam and Yeung, 2006;Wahlstrom et al, 2004). In most studies self-ratings are used in connection with either observations or technical measurements in order to confirm that the objective findings correspond to the subjective perception.…”

“…The computer mouse is by far the most common nonkeyboard device. The introduction of alternative input devices has not been ver successful, although some studies have indicated that the use of such alternatives may reduce the risk of upper extremity symptoms (Fernstrom and Ericson, 1997;Karlqvist et al, 1999). Moreover, variations in the design of the traditional computer mouse have been evaluated with respect to carpal tunnel syndrom no major differences have been found between different designs in terms of wrist positions or carpal tunnel pressure during computer work (Keir et al, 1999).…”