Performance and strain in short-cycled repetitive work

Work Rhythm and Breathing Rhythm in a Repetitive Perceptual–Motor Task: The Effects of Synchronization on Performance

A laboratory investigation was conducted to determine if synchronization between the work rhythm and the respiratory biorhythm benefits perceptual-motor performance. The effect of work-respiratory (W–R) synchronization on reaction time, error rate, and perceived difficulty was evaluated for a visual choice reaction time task. Interstimulus intervals were chosen to induce a work rhythm. Prior to the experiment, the task was performed in a self-paced mode so that a baseline work rate could be identified for each subject. Each subject (N=22) then performed the task at 3 machine-paced work rhythms; 1) equal to the work rhythm of the baseline work rate, 2) 33% faster than the work rhythm of the baseline work rate, and 3) 33% slower than the work rhythm of the baseline work rate. Each condition consisted of two, 4 min trials separated by a brief rest break. Work rate (in responses per minute) was held constant across conditions through adjustments in task structure. Regression analysis revealed that W–R synchronization was associated with a 1% reduction in error rate and a 15 msec reduction in reaction time. These results suggest that W–R synchronization benefits perceptual–motor performance of repetitive tasks.

Comparative study of upper limb load assessment and occurrence of musculoskeletal disorders at repetitive task workstations

This study explored the relationship between subjectively assessed complaints of pain in the arm, forearm and hand, and musculoskeletal load caused by repetitive tasks. Workers (n=942) were divided into 22 subgroups, according to the type of their workstations. They answered questions on perceived musculoskeletal pain of upper limbs. Basic and aggregate indices from a questionnaire on the prevalence, intensity and frequency of pain were compared with an upper limb load indicator (repetitive task index, RTI) calculated with the recently developed Upper Limb Risk Assessment (ULRA). There was relatively strong correlation of RTI and general intensity and frequency of pain in the arm, and general intensity and frequency of pain in the arm and forearm or prevalence of pain in the arm. Frequency and intensity of pain in the arm were weakly correlated. An aggregate indicator of evaluation of MSDs, which was calculated on the basis of the prevalence, intensity and frequency of pain, was to a higher degree associated with the musculoskeletal load of a task than basic evaluative parameters. Thus, such an aggregate indicator can be an alternative in comparing subjectively assessed MSDs with task-related musculoskeletal load and in establishing limit levels for that load.

Work-physiological synchronization as a determinant of performance in repetitive computer work

The present study tested the hypothesis that performance would improve when the work rhythm of a highly repetitive task was synchronous with a worker's internal physiological rhythms. Experienced office workers (n = 20) used video display terminals (VDTs) to perform a repetitive, self-paced data-entry task in a simulated office environment over a 2-day period. Each work day consisted of six 40-min work periods. Work rhythm changes were induced by varying input data field lengths (3-13 characters) across eleven of the twelve work periods. The degree of synchronization between the work and breathing rhythms, and also between the work rhythm and variations in the interbeat interval, was scored using cross-spectral analysis. Synchronization scores were then used to predict keying performance using multiple regression analysis. The degree of synchronization between the work and breathing rhythms was not predictive of performance. However, increased synchronization between the work and cardiac rhythms was predictive of (a) increased keystroke output, (b) lower error rate and (c) lower correction rate. The results suggest that performance in repetitive VDT work might improve if the task is designed to promote work-physiological synchronization.

Workplace ergonomic factors and the development of musculoskeletal disorders of the neck and upper limbs: a meta-analysis

In the past 10 years there has been growing awareness among occupational health professionals worldwide of the large burden of illness associated with musculoskeletal disorders of the neck and upper limbs. It has been suggested that these disorders are associated with highly repetitive work and are due, at least in part, to ergonomic factors. This review examines the epidemiologic evidence of the relationship between workplace ergonomic factors such as repetition, force, static muscle loading, and extreme joint position and the development of muscle, tendon, and nerve entrapment disorders of the neck and upper limbs of exposed workers. An extensive search for relevant studies was undertaken. Of 54 potentially relevant studies identified, three met the a priori inclusion criteria. The validity of these studies was assessed, and one study was found to have major flaws. Criteria to demonstrate causality were also applied and were met in the most rigorously conducted study. When the results of these studies are compared and aggregated where appropriate, they provide strong evidence of a causal relationship between repetitive, forceful work and the development of musculoskeletal disorders of the tendons and tendon sheaths in the hands and wrists and nerve entrapment of the median nerve at the carpal tunnel. The comparison of exposed to controls for hand/wrist tendinitis gives an unadjusted common odds ratio of 9.1 (95% CI 4.9-16.2). The adjusted odds ratio for carpal tunnel syndrome is 15.5 (95% CI 1.7-141.5) based on the most rigorous study.