The effect of typing frequency and speed on the incidence of upper extremity cumulative trauma disorder

Typing in the work setting, with its emphasis on speed, force and repetitive movements and its tendency to be performed under less than optimum conditions has been one of the major causes of upper extremity cumulative trauma disorder (CTD). This disorder, also known as overuse syndrome, is a chronic condition believed to result from habitual overuse of the digits, hands or arms. The objective of this study was to examine the relationship between typing habits, specifically the influence of typing frequency, speed and style, on the incidence of injury. One hundred Israeli female typists aged between 20 and 60 years with no prior history of orthopedic or neurological disease participated in the study. Data collection took place at the work setting and consisted of a clinical evaluation of the upper extremities and trunk, a typing test, and a questionnaire which included questions concerning demographic information, occupational history, and upper extremity usage in the home and at work. Subjects were asked whether they had suffered from pain or other symptoms in the upper extremity (shoulder, arm, forearm, elbow or hand) on more than three occasions in the last year or on one occasion lasting more than a week. Subjects who answered no to this question were designated as ‘non-sufferers’. Those who answered yes to the question were designated ‘sufferers’. The 100 women who participated in the study represented a wide range of ages and educational levels. The variables describing on-the-job performance showed a wide range of values. Similar variability was found in the anthropometric variables. On the basis of the subjective criterion, 40 of the women belonged to the group labeled ‘sufferers’. The remaining 60 subjects belonged to the group of ‘non-sufferers’. The Odd's ratio test (OR), a common statistical procedure for risk factor estimation, was used to determine threshold levels associated with the development of CTD. Age, hours worked per week, typing speed, and years worked as a typist were variables in which at least one cut-off value generated a significant OR. The delineation of factors associated with typists who are classified as ‘sufferers’ establishes a portrait of the typical worker at risk for the development of CTD and provides insight into ways in which employers, clinicians and workers themselves could reduce the risk of CTD.