Situation: The occupational health nurse of a private garment factory with 800 workers, including a fabric-dyeing area, is reviewing the workplace health and safety program. A survey of three sewing lines, which make the same garments at the same pace, shows: Line 1 — night shift; fixed-height tables; two rest breaks per shift; neck or back pain in 22 of 50 operators Line 2 — day shift; height-adjustable tables; two rest breaks per shift; neck or back pain in 6 of 50 operators Line 3 — night shift; height-adjustable tables; two rest breaks per shift; neck or back pain in 7 of 50 operators Which measure should the nurse recommend to reduce neck and back pain on Line 1?

Line 1 differs from Line 2 in two factors, shift and tables (44%, 22 ÷ 50, against 12%, 6 ÷ 50). Line 3 works nights like Line 1 but has adjustable tables, and its rate (14%, 7 ÷ 50) is close to Line 2's, so the night shift does not explain Line 1's excess; the fixed tables do. Adjustable tables remove the awkward posture at its source, an engineering control and primary prevention of work-related musculoskeletal disorders.

The question asks you to identify the most appropriate measure to reduce neck and back pain among operators on Line 1. The key is to compare the three lines and isolate the variable responsible for the higher pain rate.

Step 1: Compare the lines to find the difference

Line 1 and Line 2 differ in two ways: shift (night vs. day) and table type (fixed-height vs. height-adjustable). Line 1 has a pain rate of 44% (22/50), while Line 2 has 12% (6/50). That is a large difference, but it does not tell you which factor is responsible.

Line 3 is the critical comparison. Line 3 works the same night shift as Line 1, but uses height-adjustable tables. Its pain rate is 14% (7/50), which is nearly identical to Line 2’s daytime rate. Because Line 3 shares the night shift with Line 1 yet does not share the high pain rate, the night shift cannot explain the excess neck and back pain on Line 1. The remaining difference is the fixed-height table.

Step 2: Understand the mechanism of injury

Fixed-height tables force operators to maintain a static, awkward posture for prolonged periods. In sewing work, this often means sustained neck flexion, shoulder elevation, and forward trunk lean. These postures create continuous low-level loading on the cervical and lumbar paraspinal muscles, reduce blood flow, and increase intramuscular pressure, which over time produces fatigue and pain. Height-adjustable tables allow each worker to set the work surface to match their own anthropometrics, so the neck and trunk can remain closer to neutral alignment.

This is consistent with the ergonomic literature. A systematic review and meta-analysis by Agarwal et al. found that sit-stand workstations, which are a form of height-adjustable work surface, were associated with reduced low back discomfort among office workers ^[2]. Similarly, van Niekerk et al. noted that workstation modifications addressing adjustability to match user anthropometrics are among the most commonly recommended interventions for preventing musculoskeletal pain ^[3]. Thorp et al. also demonstrated that using a height-adjustable workstation to alternate between sitting and standing reduced musculoskeletal discomfort compared with seated-only work ^[1]. Although these studies involved office workers rather than sewing operators, the underlying principle is the same: adjusting the work surface to fit the worker reduces sustained awkward postures, which is the direct source of the strain.

Step 3: Why the other options are less appropriate

Option	Why it is not the best answer
1. Move Line 1 operators to the day shift	Line 3 shows that night shift alone does not produce high pain rates when adjustable tables are used. Shift change addresses the wrong variable.
2. Add a third rest break	Rest breaks provide temporary relief but do not remove the awkward posture during the many hours of actual work. This is a secondary, not primary, control.
4. Issue back-support belts	Back belts do not correct the workstation mismatch. Evidence does not support belts as an effective primary prevention for work-related musculoskeletal disorders.

Step 4: Classification of the intervention

Installing height-adjustable tables is an engineering control. In the hierarchy of occupational hazard controls, engineering controls are preferred over administrative controls (such as rest breaks or shift rotation) and personal protective equipment (such as back belts) because they remove the hazard at its source rather than relying on worker behavior. By changing the workstation so that neutral posture is possible, the nurse addresses the root cause of the musculoskeletal strain.

Key point! When comparing groups in an occupational health scenario, always look for the variable that differs between the high-problem group and the low-problem group. Line 3 is the control that rules out night shift as the cause.

Watch out! Do not confuse rest breaks or shift changes with true ergonomic correction. They may reduce exposure time but do not eliminate the awkward posture itself. The strongest recommendation is the one that modifies the workstation.