Display Level Influences Muscles

The researchers cited computer screen displays positioned at mid-level as causing less musculoskeletal strain than high- and book-level displays. The rapid increase in computer use by children over the past few years, say the authors, "has outpaced the development of knowledge about the ramifications for the health of children."

Children are physically and behaviorally different from adults; for example, children’s heads are proportionately larger than those of adults. This makes research conducted on adults inadequate to address computer-related discomfort in children.

Because research on what constitutes the optimal display height for children is limited, Leon Straker and colleagues conducted a study in which they presented an interactive task to 24 children of normal height age 10 to 12. The children's movements were recorded with an optical capture system while they read from a book and wrote on paper or read from a computer display and used a mouse and keyboard to enter data. The researchers measured 3-D posture and muscle activity in the neck and upper limb for the high-, mid-, and book-level displays. The authors state that the study is unique in that it captures 3-D posture and muscle activity under conditions that are commonly observed in schools.

The high display resulted in mainly upward bending of the upper neck. As the visual target was lowered, head and neck downward bending increased. The mid-level display was found to promote a more upright and symmetrical posture and lower average muscle activity than either the high- or the book-level position. Of the three positions, the low (book-level) display was found to cause the most strain on muscles and joints. Despite some limitations of their study, they believe the findings can aid in the development of guidelines for computer use by children.

MEDICA.de; Source: Human Factors and Ergonomics Society