Stephen Burastero

Effect of four computer keyboards in computer users with upper extremity musculoskeletal disorders.

Eighty computer users with musculoskeletal disorders participated in a 6-month, randomized, placebo-controlled trial evaluating the effects of four computer keyboards on clinical findings, pain severity, functional hand status, and comfort. The alternative geometry keyboards tested were: the Apple Adjustable Keyboard [kb1], Comfort Keyboard System [kb2], Microsoft Natural Keyboard [kb3], and placebo. Compared to placebo, kb3 and to a lesser extent kb1 groups demonstrated an improving trend in pain severity and hand function following 6 months of keyboard use. However, there was no corresponding consistent improvement in clinical findings in the alternative geometry keyboard groups compared to the placebo group. Overall, there was a significant correlation between improvement of pain severity and greater satisfaction with the keyboards. These results provide evidence that keyboard users may experience a reduction in hand pain after several months of use of some alternative geometry keyboards.

Effect of keyboard keyswitch design on hand pain.

This randomized clinical trial evaluated the effects of keyboard keyswitch design on computer users with hand paresthesias. Twenty computer users were matched and randomly assigned to keyboard A (n = 10) or B (n = 10). The keyboards were of conventional layout and differed in keyswitch design. Various outcome measures were assessed during the 12 weeks of use. Subjects assigned keyboard A experienced a decrease in hand pain between weeks 6 and 12 when compared with keyboard B subjects (P = 0.05) and demonstrated an improvement in the Phalen test time (right hand, P = 0.006; left hand, P = 0.06). Keyboard assignment had no significant effect on change in hand function or median nerve latency. We conclude that use of keyboard A for 12 weeks led to a reduction in hand pain and an improved physical examination finding when compared with keyboard B. There was no corresponding improvement in hand function or median nerve latency.

Workplace Use of an Adjustable Keyboard: Adjustment Preferences and Effect on Wrist Posture

This study presents an evaluation of an adjustable keyboard based on subjective preference and wrist joint motion during typing. Thirty-five computer users used the adjustable split design keyboard for 7-14 days during their usual work and were instructed to adjust the keyboard to the opening angle they preferred. At the end of this period, three-dimensional motion analysis was performed to compare the distribution of wrist joint angles while subjects typed on a conventional keyboard and the adjustable keyboard adjusted to the subjects preferred angle. The mean preferred opening angle was 14 degrees +/- 10. The mean ulnar deviation of the subjects who selected the opening angles between 21 and 28 degrees (n = 12) decreased from 18 degrees +/- 5 on the flat to 14 degrees +/- 5 on the adjustable (p < 0.05), while those who selected 0 to 10 degrees (n = 6) and 11 to 20 degrees (n = 17) split angles showed no significant differences in ulnar deviation. Mean wrist extension on the adjustable keyboard was 17 degrees +/- 5 and was significantly less than the 24 degrees +/- 5 observed on the conventional keyboard and most likely due to the presence of palm support. On average, subjects reported that the adjustable keyboard was more comfortable (0.5 +/- 0.5) (worse = -1, same = 0, better, = 1) in comparison with the conventional keyboard.

Effect of Four Computer Keyboards in Computer Users with Upper Extremity Musculoskeletal Disorders

Eighty computer users with musculoskeletal disorders participated in a six-month, randomized, placebo-controlled trial evaluating the effects of four computer keyboards on clinical findings, pain severity, functional hand status, and comfort. The alternative geometry keyboards tested were: the Apple Adjustable Keyboard™ [kb1], Comfort Keyboard System™ [kb2], Microsoft Natural Keyboard™ [kb3] and placebo. Compared to placebo, kb3 and to a lesser extent kb1 groups demonstrated an improving trend in pain severity and hand function following six months of keyboard use. However, there was no corresponding consistent improvement in clinical findings in the alternative geometry keyboard groups compared to the placebo group. Overall, there was a significant correlation between improvement of pain severity and greater satisfaction with the keyboards. These results provide evidence that keyboard users may experience a reduction in hand pain after several months of use of some alternative geometry keyboards.

Ergonomic Analysis of Pallets and Drum Handling

This study investigates the effects of heavy pallet and drum handling on spinal loading at the L5/S1 region and surface electromyographic activity of the erector spinae muscles, and the associated risk of low back disorder (LBD). Ten field technicians at the Lawrence Livermore National Laboratory (LLNL) were asked to unstack plastic and metallic pallets and manipulate 55 gallon waste drums. Lifting the metallic and plastic pallets and lowering a 34 Kg drum induced the highest disc compression at the L5/S1 level, while manipulating the pallets and breaking up a 203 Kg drum induced the highest low back muscle activity. The major results showed that posture has a significant influence on disc compression force; however, the lowest muscle load may not be correlated with the lowest disc compression. The computed disc compression forces and EMG activities are most likely responsible for the elevated risk of back injury in waste management workers.

Comparison of Muscle Activity during Use of Computer Pointing Devices in Cad Operators

This study examined the use of four different computer pointing devices on surface electromyographic activity of the index finger, forearm and shoulder/neck muscles among CAD operators in the workplace. Subjects were randomly assigned to use their own mouse, a trackball, a joystick mouse or an experimental mouse. Results showed that there was a statistically significant difference in muscle load for the upper trapezius, extensor indicis proprius, and extensor carpi ulnaris across pointing devices for CAD operations. The flexor digitorum superficialis muscle load remained relatively constant when all pointing devices were compared.

An ergonomic analysis of waste container handling: Part II

This study examined the effects of waste container handling on surface electromyographic activity of the erector spinae, infraspinatus and upper trapezius muscles, trunk kinematics (position, velocity and acceleration) measured in three planes (lateral, sagittal and transverse), spinal loading at the L5/S1 region and low back disorder (LBD) risk. Eleven field technicians at the Lawrence Livermore National Laboratory (LLNL) were asked to manipulate 30 and 55 gallon waste drums and carry a 5 gallon carboys in their workplace. Results showed that there was a statistically significant difference in muscle load on the erector spinae during drum handling activities. Loading and unloading the 55-gallon drums required more force from all muscle groups than the 35-gallon drums. Muscle peak load did not show a significant difference between 35 and 55 gallon drum rolling. For carboy transport, peak muscle activity is greater for all muscle groups with the two carboy carry. The calculated LBD risk also recognized the same activities as being most “at risk.” This data was used by the participatory team to focus their interventions and determine handling limits.