Work schedule and task factors in upper-extremity fatigue

Area of Science:

• Ergonomics and Occupational Health
• Human Factors Engineering

Background:

• Understanding the impact of work schedules on physical fatigue is crucial for preventing workplace injuries.
• Previous research often used simplified work durations, not reflecting real-world complexities.

Purpose of the Study:

• To investigate the combined effects of shift duration (8-h vs. 12-h) and task demands on upper-extremity fatigue.
• To determine how work schedule and task factors interact to influence fatigue onset and severity.

Main Methods:

• Laboratory simulation of a manual assembly task under varying repetition rates and torque loads.
• Participants self-adjusted work cycle durations to maintain moderate fatigue levels across different shift schedules.
• Monitoring fatigue progression over 8-h and 12-h day and night shift conditions.

Main Results:

• Increased repetition rates and torque loads reduced work cycle durations.
• Fatigue onset was accelerated by longer time on shift and night shifts compared to day shifts.
• The highest fatigue levels occurred during 12-h night shifts; 8-h night and 12-h day shifts showed similar fatigue by week's end.
• Work schedule effects on fatigue were more pronounced at lower workloads.

Conclusions:

• Shift length and timing significantly influence upper-extremity fatigue, particularly at lighter workloads.
• Findings support the development of evidence-based work-rest schedules for manual tasks to mitigate fatigue and enhance safety.
• Realistic, longer work schedules resulted in shorter work cycle durations compared to short-term studies.