Effective Designs of Non-Keyboard Computer Input Devices

With the prevalence of computer usage in society today, the incidence of work related musculoskeletal disorders (MSD) has correspondingly increased, particularly in the upper limbs including neck, shoulder, arms and wrists [20]. For computer workers, a myriad of possible contributing factors for these musculoskeletal injuries have been identified including seated work, awkward positions, static work, inactivity, overuse, lack of breaks, stress on bone and connective tissue, pressure on blood vessels and nerves, gender, age and psychological stress [20]. In a sense, a computer input device can be considered as an exercise machine. It stresses and strains certain muscles repeatedly. However, similar to exercise machines, overuse can lead to pain and even permanent injury. So what do these injuries tell us about the natural posture and movement of the human form? What are the limits to the stress applied to human muscles? And if we know these limits of muscles and form, can we design a computer input device that would cause less injury? This paper is a literature review of research that attempts to address such issues. Since there are so many different factors that potentially contribute to MSD of computer workers, this paper will narrow its scope to mainly non-keyboard input devices (NKID) which include the mouse, joystick, trackball, touchscreen and touchpad. However, it should be noted that most research lump keyboard and mouse into one object, the computer input device, since both constrain posture for static tasks. Thus research on just NKID specific injuries are sparse. In this paper, Section II gives an overview of MSD is and a brief overview of possible risk factors, which will be elaborated in Section IV with an emphasis on how it relates to NKID usage. Section III-A describes how common NKIDs are in use and III-B talks about the loads exerted on muscles and the posture users take. Section V describes some popular hypotheses relating some risk factors to MSD as well as experimental results to support them. Section VI compares the differences in NKID designs, mainly in how it affects wrist movement (lateral along direction of arm) and ulnar deviation (radial about the wrist.) Section VII gives design recommendations followed by conclusions in Section VIII.