Effects of Temporary Order Pickers’ Physical Fatigue on Work-Break Schedules and Workforce Size in Warehouses

E-commerce companies often prioritize operational efficiency in workforce management, frequently overlooking worker safety and well-being. This study addresses this gap by focusing on night-shift picking operations in warehouses and proposing a methodology to mitigate physical fatigue among temporary order pickers. Unlike full-time employees, temporary pickers exhibit diverse age and experience levels, influencing their responses to fatigue. To address this variability, we categorize workers into four groups based on age and experience, quantitatively assessing their physical fatigue using a fatigue-recovery equation. We develop a mathematical model to design customized work-break schedules for each group, minimizing final fatigue levels. Moreover, a separate mathematical model determines the optimal workforce size by accounting for the impact of cumulative fatigue on work speed during picking operations. Simulation experiments assess the impact of integrating physical fatigue considerations into workforce management on reducing overwork and fatigue. Additional analyses explore varying worker group ratios and account for the unpredictability of temporary picker demographics. This study offers a practical tool and guidance to help companies foster human-centered warehouses.