Rotation during lifting tasks: effects of rotation frequency and task order on localized muscle fatigue and performance

New work situations call for familiar work design methods: Effects of task rotation and how they are mediated in a technology-supported workplace

New digital assistive technologies strive to alleviate the completion of work tasks but thereby often threaten to make jobs increasingly monotonous. To counteract jobs becoming more and more monotonous, task rotation might be an appropriate technology feature. However, it is uncertain whether task rotation has unique positive effects, why it works, and whether there are any boundary conditions. To investigate this, we conducted two experimental vignette studies. In Study 1 (N₁ = 135), we drew on the job characteristics model and self-determination theory to examine perceived task variety, skill variety, and task identity, and expected satisfaction of the need for competence as mediators of the effect of task rotation on anticipated employee attitudes (job satisfaction, intrinsic work motivation), behavior (subjective performance), and well-being (positive and negative affect). The investigated vignette described a job where a digital assistance system either indicated the task rotation or only supported work steps. Regression analyses showed direct effects of task rotation on expected job satisfaction, intrinsic motivation, and positive affect. There were indirect effects of task rotation on all outcomes except expected negative affect. We used Study 2 (N₂ = 159) as an exact replication of Study 1. Additionally, to investigate the boundary conditions of task rotation effects, we drew on person-job fit theory and investigated openness to experience as a moderator of the effects of task and skill variety on the outcomes. Regression analyses showed direct effects of task rotation on expected job satisfaction, subjective performance, and positive affect. There were indirect effects of task rotation on all outcomes except expected negative affect and intrinsic motivation. Thus, the results of Study 1 could only be partly replicated. Openness to experience did not moderate the effects of task and skill variety on the outcomes. The results support the relevance of task rotation as a technology feature and indicate that rotations should offer especially skill variety and task identity, as these were the strongest mediators in our studies.

Effects of Vertical Lifting Distance on Upper-Body Muscle Fatigue

Manual material handling (MMH) is commonly demanded in the manufacturing industry. Occupational muscle fatigue of the arm, shoulder, and back, which arise from MMH tasks, can cause work absences and low efficiency. The available literature presents the lack of the fatigue comparison between targeted muscles, on the same part or on different parts. The main aim of the present study was to evaluate and compare the fatigue of upper-body muscles during repetitive bending tasks, an experiment involving 12 male subjects has been conducted to simulate material handling during furniture board drilling. The vertical lifting distance was chosen to be the single independent variable, and the three levels were 0, 250, and 500 mm. Surface electromyography (sEMG) was used to measure the muscle fatigue of the biceps brachii, upper trapezius, and multifidus, while the sEMG parameters, including the normalized electromyographic amplitude (Normalized EA) and mean power frequency (MPF), of the target muscles were analyzed. The experimental results reveal that during the manual handling tasks, the biceps brachii was the most relaxed muscle, contributing the least muscle tension, while the multifidus was the most easily fatigued muscle. Furthermore, the EMG MPF fatigue threshold (MPFFT) of multifidus muscle tension was tested to estimate its maximum workload in the long-term muscle contraction. In conclusion, bending angle should be maintained to a small range or bending should even be avoided during material-handling tasks.

More Hype Than Substance? A Meta-Analysis on Job and Task Rotation

Although there exist numerous publications on job and task rotation from various disciplines, there is no consistent evidence of their effectiveness. Drawing on theories from industrial and organizational psychology, knowledge management, ergonomics, and management science, we meta-analytically investigated relationships between job/task rotation and employee attitudes, learning and development, psychological and physical health, and organizational performance. Due to a conceptual overlap and frequent confusion of terminology, we analyzed the design of the rotation (job rotation vs. task rotation) as a possible moderator. The three-level meta-analysis on 56 studies (N = 284,086) showed that rotation was significantly associated with job satisfaction (r = 0.27), organizational commitment (r = 0.16), career success (r = 0.31), labor flexibility (r = 0.32), general psychological health (r = 0.20), stress/burnout (r = -0.13), individual performance (r = 0.13), and productivity (r = 0.13). Positive relationships between rotation and physical health could only be found when rotation was compared to high-intensity work. Task rotation yielded stronger relationships with attitudinal outcomes, job rotation with learning and development, psychological health, and organizational performance outcomes. Further moderator analyses showed that individualism decreased relationships between task rotation and attitudes, and correlations with organizational performance and physical health were stronger for subjective measures. The findings indicate that many expectations toward job and task rotation are not fully supported.

Postural and muscular adaptations to repetitive simulated work

Complex repetitive tasks are common in the workplace and have been associated with upper extremity disorders. The purpose of this study was to examine the progressive effects of highly repetitive work on joint kinematics and muscle activity of the trunk and upper extremity. Fifteen healthy men performed 60 one-minute cycles of 4 simulated automotive-related tasks. Electromyography of eight muscles and kinematics of the trunk and right upper extremity were collected. Data were analysed at 12-min intervals and divided into a complete work cycle. The time to complete the work cycle decreased by 6.3 s over the trials. Peak shoulder flexion decreased and peak elbow flexion increased during the work cycle. Muscle activity magnitude and variability was influenced by time during the repetitive tasks. This study found adaptations to highly repetitive but light work in only 1 h; redistributing muscle demands within the shoulder over time may reduce muscle fatigue development. Practitioner Summary: While the work was not strenuous, we were able to demonstrate muscular and postural adaptations in a single hour of simulated work. By evaluating both the whole work cycle and the sub-tasks, we aim to develop new methods for evaluating the risk of complex tasks in prolonged repetitive work.