PROCESS EVALUATION
The subject of process evaluations covers a broad range of topics, but the center of the issue is still simple. In each process, the individual must perform a task. The physical characteristics of the task, as well as the effort required by an individual performing the task, are quantifiable. Methods of quantification are grouped based on the type of data being collected: muscular effort, joint posture, physiological effort, and force application. After quantifying the task requirements and effort of the individual performing the task, results can be used in several ways:
- To benchmark findings against best practices, standards, or guidelines
- To recommend areas for improvement
- To justify recommendations for change
Case Study: Methods Assessment of Ergonomics Intervention
Background
Industrial assembly, VDT work, and inspection tasks often require awkward, static postures for the neck and shoulder. These postures have been associated with increased musculoskeletal discomfort and decreased productivity. Biomechanically, flexed neck postures increase the load on the neck or cervicobrachial region. Interventions designed to improve worker posture have had the effect of reducing the load on the trapezius muscles and contributed to reductions in sick leave. A funded project investigated the effect of such an ergonomic intervention on a simple assembly task. The intervention took the form of a periscope-style mirror set-up used to reduce the amount of time a worker spends with their neck bent to look at their work.
Approach
The project consisted of two studies. In the first study, twelve participants performed a simple, fifteen-minute assembly task driving screws into blocks. The task was performed with four workstation arrangements: (1) industrial standard configuration, (2) mirror configuration, (3) periscope configuration, and (4) pistol grip configuration. In the second study, eight participants performed the same task for four hours in the industrial standard and periscope configurations.
Posture (neck, shoulder, and elbow), muscle activity (bilateral trapezius, cervical and thorasic erector spinae, levator scapulae, and deltoid) productivity, and discomfort data was collected from each subject in each trial condition.
Finding
Study 1 results indicated that there were positive biomechanical impacts associated with the interventions. The trade off for these ergonomic improvements was a decrease in productivity during the fifteen-minute trials. Initially, performance is inhibited while using the periscope intervention. It was initially hypothesized that the initial performance decrement would be overcome and the subject would eventually reach the same (or surpass) productivity level when performing the simple task with no intervention. The basis for this hypothesis is grounded in the belief that an individual's productivity decreases with increased muscle fatigue. In this instance, the muscle fatigue would develop in the muscles in the cervical (neck) spinal region. In study 2, productivity in both conditions improved over the four-hour period. The improvements using the periscope were greater in the periscope configuration compared to the industry standard configuration. Three of the eight participant's productivity levels at the end of the sessions were the same regardless of the workstation configuration. It is suggested that the productivity decrements associated with the interventions can be mitigated via greater training and adaptation.
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