COMPUTER KEYBOARD FORCE AND UPPER EXTREMITY SYMPTOMS

This case-control study assessed whether office workers who report mor e severe levels of musculoskeletal symptoms of the upper extremities d emonstrate higher levels of keyforce in comparison to controls with le ss severe symptoms. Office workers reporting working on computer keybo ards for four hours per day were classified as cases or controls based upon a median split on a Composite Symptom Severity score (cases 23, controls = 25). Keyboard force and keying rate lowe measured during a 15-minute keyboarding talk. Measures of task-related discomfort, muscu lar fatigue, pain, upper extremity symptoms, psychological distress an d force were collected at baseline, post-keyboard task and recovery. R atings of perceived effort and task credibility were also obtained. Me asures of work demands, perceived job stress, and upper extremity stre ngth and flexibility were also collected. The results indicated group equivalence on reported work demands and upper extremity strength. Cas es were more likely to receive a medical diagnosis of upper extremity cumulative trauma disorder, awaken from sleep due to symptoms, report higher levels of pain during work, experience greater impact of pain o n function, and report higher workload pressure and lower support. Cas es generated significantly higher keyboarding forces than controls, al though both groups produced forces well above that required to operate the keyboard (4-5 times activation force). Cases reported higher leve ls of upper extremity symptoms and discomfort than controls, and these measures were highest after the keyboarding task for both groups. No significant correlation between keyforce and key rate was observed in either group. Results suggest that generation of excessive force while working for a computer keyboard may contribute to the severity of upp er extremity symptoms. Clinically, the findings suggest that evaluatin g how an individual worker performs keyboarding tasks, or his or her w orkstyle, may be helpful in the management of these symptoms and disor ders.