Effects of keyboards, armrests, and alternating keying positions on subjective discomfort and preferences among data entry operators.

This dissertation presents three studies aimed at reducing the intensity or duration of static exertion to alleviate the musculoskeletal discomfort associated with intensive keying operations. The interventions included alternative keyboards, armrests, and sit-stand workstations. The first study compared two alternative keyboards---KB2 (straight, click-action keys) and KB3 (fixed-split, lateral-inclined geometry)---with an original keyboard (KB1: straight, soft-action keys). After using KB2 or KB3 for five weeks, KB2 and KB3 were rated significantly more desirable for daily use than KB1 (KB1 = 4.3 vs. KB2 = 2.3; KB1 = 4.6 vs. KB3 = 1.5; 0 = extremely desirable, 10 = extremely undesirable) and substantially reduced overall upper body discomfort (KB1 = 4.0 vs. KB2 = 2.4; KB1 = 3.9 vs. KB3 = 1.5; 0 = no discomfort, 10 = worst imaginable discomfort). The second study compared keying with two types of armrests---an articulating armrest (AA) and a chair armrest (CA)---with keying without an armrest. After using AA or CA for 13 weeks, subjects preferred both AA and CA over the no-armrest condition (AA = 1.2, CA = 3.2; 0 = strongly prefer test armrest, 10 = strongly prefer original) and overall upper body discomfort was significantly reduced (no-armrest = 3.9 vs. AA = 1.9; no-armrest = 3.7 vs. CA = 2.5). During keying, AA was used much longer than CA (AA: left/right = 90%/89% vs. CA: left/right = 69%/55%). The third study compared keying in alternating positions with a sit-only position. One group (Group I) used a workstation adjustable for sifting or standing. A second group (Group II) rotated between sifting and standing workstations. After keying in alternating positions for 13 weeks, both groups reported that keying in alternating positions was significantly more desirable (Group 1: sit-only = 5.1 vs. alternating = 2.4; Group II: sit-only = 4.6 vs. alternating = 2.7) and significantly reduced overall body discomfort (Group I: sit-only = 4.6 vs. alternating = 1.5; Group II: sit-only = 4.3 vs. alternating = 1.7). On average, subjects in both groups chose standing twice daily for 24--31 minutes each time. The study results show that musculoskeletal discomfort was associated with these interventions. No single piece of equipment was favored by everyone and the effectiveness of each varied among subjects; some reported a reduction in overall body discomfort up to eight points and some reported an increase up to 3.5 points. Keying in alternating positions was the most effective strategy in reducing discomfort and CA was the least effective piece of equipment. These interventions may be used to improve comfort and well-being for many computer users.Ph.D.Applied SciencesHealth and Environmental SciencesIndustrial engineeringOccupational safetyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/132161/2/9959784.pd