In a study of sewing machine operators, showed that operators with a history of carpal tunnel syndrome used pinch grips more frequently and that the force used during these pinch grip exertions was greater than that employed by the control group (women performing the same jobs at the time that the case group members reported their symptoms). The effects of pinch grip exertions on the intrinsic muscles of the hand were considered in a study of employees in a garment shop. They found a positive correlation between pinch grip duration and hand pain in this population.
Emanoil (2000), discusses research that found that subjects using the vertical split keyboard kept their wrist angles and forearm movements in the lowest risk zone for carpal tunnel syndrome 71% and 78% of the time, respectively. When typing on traditional keyboards, subjects were in the lowest risk zone only 44 and 25% of the time. Wrists were in the highest risk zone only 2% of the time when using the vertical split keyboard compared with 12% with the traditional keyboard. (p. 13) Increased extensor activity, combined with wrist extension, may also increase carpal tunnel pressures. This may be intensified given the flexor tendon loading to depress the keys and increasing the carpal tunnel pressure as well. (Keir & Wells, 2002) research suggest that the specific interaction between a worker's body and tool use may be important, since pressure on the carpal tunnel from work tools is affected by this interaction " (Messing, Lippel, Demers & Mergler, 2000, p. 31)
Another study that Emanoil discussed compared an oversized, flat, and adjustable computer mouse with a built-in palm support with a smaller, contoured mouse device. Researchers measured the wrist extensions and hand movements of 24 men and women while they used the different mouse devices to move the cursor position and to scroll on the computer. Subjects also rated the smaller and larger mouse devices for comfort. The researchers found that the larger mouse reduced wrist extension by an average of more than eight degrees. At high levels, wrist extension can lead to carpal tunnel syndrome. The adjustability of the larger mouse also kept subjects from making small hand movements, such as flicking their wrists, which could increase their risk of injury. (Emanoil, 2000, p. 13)
The aim of this study was to perform a comprehensive investigation to document wrist and forearm postures of users of conventional computer keyboards. Researchers instrumented 90 healthy, experienced clerical workers with electromechanical goniometers to measure wrist and forearm position and range of motion for both upper extremities while typing. For an alphabetic typing task, the left wrist showed significantly greater (p [less than].01) mean ulnar deviation (15.0[degrees] [plus or minus] 7.7[degrees]) and extension (21.2[degrees] [plus or minus] 8.8[degrees]) than the right wrist (10.1[degrees] [plus or minus] 7.2[degrees] and 17.0[degrees] [plus or minus] 7.4[degrees] for ulnar deviation and extension, respectively). On the other hand, the right forearm had greater mean pronation (65.6[degrees] [plus or minus] 8.3[degrees]) than the left forearm (62.2[degrees] [plus or minus] 10.6[degrees]). Researchers further noted minimal functional differences in the postures of the wrists and forearms between alphabetic and alphanumeric typing tasks. Ergonomists should consider the statistically significant and probable practical difference in wrist and forearm posture between the left and right hand in ergonomic interventions in the office and in the design of computer keyboards. Actual or potential applications of this research include guiding the design of...
(Simoneau, Marklin & Monroe, 1999, p. 413)
Considering previous research conducted, it appears that deviated wrist posture in the flexion/extension plane is implicated in the etiology of work-related musculoskeletal disorders (WMSDs) of the wrist. Studies measuring carpal tunnel pressure have shown that carpal tunnel pressure decreases as the wrist moves toward a neutral posture in the flexion/extension plane. Less pressure in the carpal tunnel is beneficial because the median nerve, which passes through the carpal tunnel, is under less compression and is less likely to show the symptoms of carpal tunnel syndrome. In theory if a typist were to type on a negatively sloped keyboard with a wrist extension angle closer to a neutral posture than the approximately 200 extension with a conventional keyboard, then the typist would be less susceptible to WMSDs. (Simoneau & Marklin, 2001, p. 287)
Copies of 300+ questionnaires.16 each @ $48.00
Folding of 300+ copies.03 each @ $09.00
30# paper @ 300 sheets.03 each @ $9.00
Compensation for interview time (per employee) the rate of 1 hour sessions @85 participants
35.00 each @ $2,975.00
Compensation for evaluator time (per employee) during interview process @85 participants
35.00 [email protected] $2,975.00
Various supplies to include writing instruments, etc.
Compensation for evaluation of -- each @ $150.00
TOTAL ESTIMATED EXPENSE
Current job function:
Do you use a computer regularly?
Do you use the handrest provided by the company regularly?
How many hour non-stop do you use your hand rest in conjunction with computer use?
Do you have frequent burning, tingling, weakness, or numbness in the palm of the hand and the fingers? (especially the thumb and the index and middle fingers)
Do you fingers feel swollen?
If you have experienced burning, tingling etc. when did symptoms first occur?
Have you ever awaken in the middle of the night with numbness or pain in the wrist and hand?
Have you experienced a decrease in ability to grip objects, or perform labor-intensive tasks?
Have you lost the ability to decipher between varying temperatures of hot and cold?
Have you experienced numbness or pain in your hand, forearm, or wrist that awakens you at night?
Occasional tingling, numbness, "pins-and-needles" sensation, or pain. The feeling is similar to your hand "falling asleep."
Numbness or pain that gets worse while you are using your hand or wrist, especially when gripping an object with your hand or bending (flexing) your wrist.
Occasional aching pain in your forearm between your elbow and wrist.
Have you had stiffness in your fingers when you get up in the morning?
Do simple hand movements, such as brushing your teeth or holding a fork give you difficulty and pain in the wrist and hands?
Is it difficult to pinch items between your thumb and pointer finger?
Is it difficult to use your thumb while doing simple tasks such as opening a jar or using a hammer or screwdriver?
Carayon, P., Smith, M.J., & Haims, M.C. (1999). Work Organization, Job Stress and Work-Related Musculoskeletal Disorders. Human Factors, 41(4), 644.
Emanoil, P. (2000). Ergonomics Then and Now. Human Ecology, 28(2), 13.
Keir, P.J., & Wells, R.P. (2002). The Effect of Typing Posture on Wrist Extensor Muscle Loading. Human Factors, 44(3), 392+.
Marras, W.S., Marklin, R.W., Greenspan, G.J., & Lehman, K.R. (1995). Quantification of Wrist Motions during Scanning. Human Factors, 37(2), 412+.
Messing, K., Lippel, K., Demers, D., & Mergler, D. (2000). Equality and Difference in the Workplace: Physical Job Demands, Occupational Illnesses, and Sex Differences. NWSA Journal, 12(3), 21-49.
Posavac, E.J., & Carey, R.G. (2003). Program evaluation: Methods and case studies (6th ed.). Upper…
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