Mouse versus keyboard use: A comparison of shoulder muscle load

Use of the computer mouse as an input device at visual display units is increasing, yet few studies could be found that directly addressed related musculoskeletal problems. Tasks similar to mousing, such as keyboarding, have been shown to result in static muscle loading of the shoulder, therefore the potential may also exist for increased neck and upper limb disorder with mouse use. The major aim of this pilot study was to compare the dominant shoulder muscle load from upper trapezius and anterior deltoid, gross postures and discomfort during mousing and keyboarding. This was performed in an effort to investigate whether use of the computer mouse is likely to be a risk factor for neck and upper limb disorders and the extent of this risk compared to keyboarding. Eight subjects performed a 10 min computer task with both mouse and keyboard input. Electromyographs of anterior deltoid and upper trapezius muscles, observations of posture and ratings of discomfort were collected. Group differences suggested increased anterior deltoid loads with mouse use and decreased trapezius loads. Also evident was the considerable inter-individual variation in muscle loads. This may help explain the pattern of work-related neck and upper limb disorders.