The Impact of Physiological and Psychological Fatigue on Work Efficiency: A Case Study of Parcel Sorting Work

Abstract

The popularity of online shopping in China has increased significantly, creating new development opportunities for the express delivery industry. However, the rapid expansion of the express industry has also created challenges in the parcel sorting process. The demanding nature of parcel sorting work, which is characterized by intense and prolonged repetitive tasks, makes individuals particularly vulnerable to the effects of fatigue. Fatigue is a complex condition that encompasses both physiological and psychological exhaustion. It often results in reduced energy levels and diminished functionality, significantly impacting an individual's performance at work and their overall well-being. This study aimed to investigate how physiological and psychological fatigue affects sorting efficiency and to identify appropriate rest periods that will allow employees to maintain their performance levels. The research involved fifteen participants who took part in a 60 min continuous sorting experiment and a similar experiment with scheduled breaks. During both trials, we collected data on participants' electromyography (EMG) and electrodermal activity (EDA), as well as subjective fatigue ratings (RPE). Signal features such as the median frequency (MF) of EMG and the skin conductance level (SCL) were analyzed to assess physiological and psychological fatigue, respectively. The results show that physiological fatigue mainly affects sorting efficiency in the first 30 min, while psychological fatigue becomes more influential in the following half-hour period. In addition, subjective fatigue levels during the first 30 min are primarily determined by psychological factors, while beyond that point, both physiological and psychological fatigue contribute to subjective fatigue. Rest periods of 415-460 s, based on EDA recovery times, effectively support sorting efficiency and participants' recovery. This study highlights the complex ways in which fatigue affects parcel sorting performance and provides valuable theoretical and practical insights for establishing labor quotas and optimizing work schedules in the parcel sorting industry.

Keywords: electrodermal activity (EDA); electromyography (EMG); intermittent rest; labor quota; parcel sorting; physiological fatigue; psychological fatigue; work efficiency.

Figure 1

The parcel sorting experiment employed three distinct types of boxes, which were labelled A, B, and C to represent the small, medium, and large sizes, respectively.

Figure 2

The experimental setup, which shows the environment and tasks. The three blue sorting bins, labelled A, B, and C, are the designated areas for different types of parcels.

Figure 3

Photo of electrode placement. The photo on the left illustrates the placement of electrodes for the collection of EMG data, while the photo on the right shows the positioning of the EDA data electrodes.

Figure 4

Illustration of physiological signal stabilization, with EMG on the top and EDA on the bottom. EMG1 Raw Data: The original raw EMG data; EMG1 Processed: The filtered and normalized EMG data; EDA1 Raw Data: The original raw EDA data; SC: Skin conductance level; Tonic Data: The tonic component of the EDA.

Figure 5

Sorting count over time.

Figure 6

Correlation matrices for different experiments. Only significant correlations are displayed. The numbers in the matrices represent the Pearson correlation coefficients. The figure is organized vertically with Experiment A on top and Experiment B below. The data for each experiment are divided into three segments horizontally, from left to right: total duration, the first 30 min, and the last 30 min.

Figure 7

The EMG illustrates the change in movement patterns of the participants during a work task. The corresponding video snapshots from the experiment provide visual evidence of the changes in movement patterns at the highlighted times. A Before change. B After change.