Influence of three principles of pacing on the temporal organisation of work during cyclic assembly and disassembly tasks (original) (raw)
Related papers
Applied Ergonomics, 2020
Current industrial production systems allow assembly of customised products which include additional elements distinguishing them from a reference model. This customisation can result in significant additional time constraints which compel workers to complete their tasks faster, which may pose problems for older workers. The objective of this laboratory study was to investigate the impact of restrictive or flexible pacing during assembly of customised products among groups of younger and older participants. The data gathered were used to analyse cycle-time, assembly performance, muscular load, and kinematic adaptations. The flexible pacing condition was found to improve production performance, increasing customised assembly cycle-time and reducing biomechanical load, for both young and older participants. However, as the task required fine manual dexterity, older participants were subjected to a higher biomechanical load, even in the flexible pacing scenario. These results should encourage assembly-line designers to allow flexible time constraints as much as possible and to be particularly attentive to the needs of older workers. Highlights: Temporal leeway reduces biomechanical load (muscular and kinematic). A flexible pacing rhythm improves work performance. Even with flexible pacing, older participants present higher levels of muscular activity than younger participants.
Applied Ergonomics, 2020
Research suggests an association between motor variability (MV) during repetitive work and work-related musculoskeletal disorders (MSDs). However, whether MV is a consistent individual trait, even across working conditions or tasks, remains unknown. This study assessed whether individual MV traits were consistent during complex work performed under different temporal conditions. Fifteen women performed cyclic assembly under four conditions differing in pace and organisation (line-type, batch-type). MV of trapezius muscle activity and upper arm elevation was quantified and partitioned into variance components. For all MV metrics, a non-zero between-subjects variance was found, indicating consistent individual MV traits across conditions. Variance between subjects was higher for electromyography (EMG) MV metrics compared with kinematic metrics. Our results showed individuals exhibited consistent MV traits across working conditions differing in pace and production process. Further research is needed to understand whether MV is an individual predictive factor for MSD onset or progression.
International Archives of Occupational and Environmental Health, 1996
An industrial assembly task known to imply a high risk for shoulder-neck disorders was simulated in the laboratory Eight females (aged 22-32 years) were trained to manage industrial work pace (120 according to the methods-time measurement system, MTM) They carried out seven work protocols at different days with different combinations of work pace (120 or 100 MTM), break allowance (20 min of active or passive breaks added every 2 h), and duration of the working day (2, 4 or 6 h) During 6 h of work at 120 MTM the electromyographic (EMG) amplitude from the upper trapezius muscle increased by about 11 %, the EMG zero crossing rate decreased by about 2.5 %, and perceived fatigue increased by about 4 CR 10 scale units When work pace was reduced to 100 MTM, the upper trapezius EMG amplitude decreased by 20 % and became less variable Heart rate decreased by about 10 bpm, perceived fatigue decreased by about 1 CR 10 scale units, and shoulder tenderness was reduced by about 5 %. However, the work task could still not be performed in a physiological steady state Added breaks, whether active or passive, had no apparent effects on upper trapezius load during work or on physiological responses Recovery of EMG, maximal strength, heart rate and blood pressure sensitivity, and tenderness was complete 4 h after work, independent of the preceding work conditions These findings suggest that a limitation of the daily duration of assembly work may be more effective in limiting acute fatigue than reduced work pace or increased break allowance.
Time—A key issue for musculoskeletal health and manufacturing
Applied Ergonomics, 2007
Time is a key issue for both ergonomists and engineers when they engage in production system interventions. While not their primary purpose, the actions of engineers have major effects on biomechanical exposure; possibly of much greater magnitude than many ergonomics interventions. This paper summarises the aims, actions and tools of engineers and ergonomists, emphasising time-related outcomes. Activities of the two groups when attempting to manipulate time aspects of work may be contradictory; engineers wishing to improve production and ergonomists aiming at better health as well as contributing to production. Consequently, tools developed by ergonomists for assessing time aspects of work describe rest patterns, movement velocities or daily duration of exposures, while engineering tools emphasise time-efficient production. The paper identifies measures that could be used to communicate time-relevant information between engineers and ergonomists. Further cooperation between these two stakeholders as well as research on the topic are needed to enable ergonomists to have a larger impact on the design of production systems.
The importance of the work/rest pattern as a risk factor in repetitive monotonous work
International Journal of Industrial Ergonomics, 2000
The work cycle time is an important parameter in assessing the risk for development of musculoskeletal disorders caused by repetitive monotonous work. The work/rest pattern in the work cycle time may be an even more important factor. Based on the normalized work cycle time for 48 meat cutters, a`slowa group (121.0}138.9% of the mean work time) and a`fasta group (68.4}85.5% of the mean work time) were de"ned. During work, the mean muscle activity level for the wrist extensor was 20% of the reference value, and the #exor muscles were 40% of the reference value. No di!erences were observed between the`slowa and the`fasta group of meat cutters. Electrophysiological signs of muscle fatigue in the power spectrum analysis from the EMG signals registered during meat cutting showed no di!erences between the groups. Meat cutting work seems to be performed with a stereotyped muscle activity pattern with only small variations for the forearm muscles. Regardless of a rather large di!erence in the work/rest pattern between the two groups of meat cutters, no di!erences were found in any of the measured acute physiological responses. To evaluate the risk of the workload, more comprehensive variables must be included in addition to the work cycle time and the work/rest pattern.
2017
Ergonomics has positive effects on both physical health and productivity, but estimating productivity benefits is difficult at the task design/redesign stage. Rest allowance prediction models are not suitable for repetitive short cycle dynamic tasks and MTM techniques are limited in their suitability for considering ergonomics risk factors such as posture and force. The purpose of this study was to investigate the relationship between force and exertion duration on self selected duty cycle time and discomfort. Twenty one participants completed repetitive upper limb exertion treatments, each of duration ten minutes. Five levels of Force (10, 20, 40, 65 and 80% MVC) and Exertion period (1, 2, 4, 6.5 and 8 seconds) were investigated. The psychophysical adjustment method was used whereby participants self selected a work pace for the second half of each treatment. Duty cycle, derived from the self pace cycle time, was the measure of productivity effects in the experiment. ANOVA revealed...
Force, posture and repetition induced discomfort as a mediator in self-paced cycle time
International Journal of Industrial Ergonomics, 2010
Musculo Skeletal Disorders (MSDs) especially those of the upper limb are a highly prevalent occupational health problem in industry incurring substantial costs. A link has been shown between physical risk factors and the causation of MSDs, in particular, high levels of force, deviated postures and repetitive movements. These have each been associated with increased operator discomfort in industry and laboratory experiments. Ergonomic interventions reducing the effects of these risk factors have been demonstrated to lower discomfort but also increase productivity. There are many case studies which have reported on the relationship between physical risk factors, associated discomfort and productivity, but few attempts have been made to investigate the relationship and model it.