Effects of armrests on workload with ten-key operation

Area of Science:

• Ergonomics
• Occupational Health
• Human-Computer Interaction

Background:

• Prolonged work with visual display terminals (VDTs) often involves constrained postures leading to static muscular fatigue.
• Data entry and similar tasks can exacerbate muscle strain in the arms and shoulders.
• Existing workstations may not accommodate individual ergonomic needs, particularly regarding desk height and arm support.

Purpose of the Study:

• To evaluate the effectiveness of adjustable armrests on a prototype VDT chair in reducing static muscular strain.
• To assess the impact of varying armrest heights and keyboard distances on muscle fatigue.
• To provide ergonomic recommendations for VDT workstation design.

Main Methods:

• An experiment was conducted with male subjects performing a data entry task using a prototype VDT chair with adjustable armrests (22-28 cm height).
• Surface electromyography (sEMG) was used to measure muscle strain in the arm and shoulder.
• Subjective feedback was collected through performance metrics, weight-loading assessments on armrests, and questionnaires.

Main Results:

• The use of armrests significantly alleviated muscle strain during one-handed keyboard operation.
• Adjustable armrests proved beneficial for operators working at unadjustable desk heights or lacking wrist support.
• Muscle strain reduction was observed with optimal armrest height and keyboard positioning.

Conclusions:

• Adjustable armrests are an effective ergonomic intervention for mitigating muscle fatigue in VDT users.
• A VDT chair with height-adjustable armrests is highly desirable for shared workspaces or multi-user environments.
• Implementing ergonomic features like adjustable armrests can improve worker comfort and potentially reduce the risk of musculoskeletal disorders.