Cost-efficient observation of working postures from video recordings--more videos, more observers or more views per observer?

In ergonomics, assessing the working postures of an individual by observation is a very common practice. The present study investigated whether monetary resources devoted to an observational study should preferably be invested in collecting many video recordings of the work, or in having several observers estimate postures from available videos multiple times. On the basis of a data set of observed working postures among hairdressers, necessary information in terms of posture variability, observer variability, and costs for recording and observing videos was entered into equations providing the total cost of data collection and the precision (informative value) of the resulting estimates of two variables: percentages time with the arm elevated <15 degrees and >90 degrees. In all 160 data collection strategies, differing with respect to the number of video recordings and the number of repeated observations of each recording, were simulated and compared for cost and precision. For both posture variables, the most cost-efficient strategy for a given budget was to engage 4 observers to look at available video recordings, rather than to have one observer look at more recordings. Since the latter strategy is the more common in ergonomics practice, we recommend reconsidering standard practice in observational posture assessment.

[1]  G K Lemasters,et al.  Statistical methods for describing occupational exposure measurements. , 1985, American Industrial Hygiene Association journal.

[2]  A Burdorf,et al.  Group-based measurement strategies in exposure assessment explored by bootstrapping. , 2001, Scandinavian journal of work, environment & health.

[3]  Svend Erik Mathiassen,et al.  Optimizing cost-efficiency in mean exposure assessment - cost functions reconsidered , 2011, BMC medical research methodology.

[4]  P. Buckle,et al.  Current techniques for assessing physical exposure to work-related musculoskeletal risks, with emphasis on posture-based methods. , 1999, Ergonomics.

[5]  Alex Burdorf,et al.  Design of strategies to assess lumbar posture during work , 1996 .

[6]  Svend Erik Mathiassen,et al.  Observer reliability of industrial activity analysis based on video recordings , 2006 .

[7]  Svend Erik Mathiassen,et al.  Modeling costs of exposure assessment methods in industrial environments , 2012 .

[8]  Svend Erik Mathiassen,et al.  Methodological variance associated with normalization of trapezius EMG using submaximal reference contractions , 2006 .

[9]  Svend Erik Mathiassen,et al.  Theoretical and empirical efficiency of sampling strategies for estimating upper arm elevation. , 2011, The Annals of occupational hygiene.

[10]  Nathan B Fethke,et al.  Bootstrap exploration of the duration of surface electromyography sampling in relation to the precision of exposure estimation. , 2007, Scandinavian journal of work, environment & health.

[11]  S E Mathiassen,et al.  Precision of measurements of physical workload during standardised manual handling. Part II: Inclinometry of head, upper back, neck and upper arms. , 2006, Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology.

[12]  Svend Erik Mathiassen,et al.  Cost efficiency comparison of four video-based techniques for assessing upper arm postures , 2012, Ergonomics.

[13]  Chang-Chuan Chan,et al.  Sampling strategies for occupational exposure assessment under generalized linear model. , 2009, The Annals of occupational hygiene.

[14]  Svend Erik Mathiassen,et al.  Systematic evaluation of observational methods assessing biomechanical exposures at work. , 2010, Scandinavian journal of work, environment & health.

[15]  Svend Erik Mathiassen,et al.  Statistical power and measurement allocation in ergonomic intervention studies assessing upper trapezius EMG amplitude. A case study of assembly work. , 2002, Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology.

[16]  Svend Erik Mathiassen,et al.  Efficient one-day sampling of mechanical job exposure data--a study based on upper trapezius activity in cleaners and office workers. , 2003, AIHA journal : a journal for the science of occupational and environmental health and safety.

[17]  Svend Erik Mathiassen,et al.  Upper arm postures and movements in female hairdressers across four full working days. , 2010, The Annals of occupational hygiene.

[18]  James Morrison,et al.  How Long Is Long Enough? Evaluating Sampling Durations for Low Back EMG Assessment , 2008, Journal of occupational and environmental hygiene.

[19]  Svend Erik Mathiassen,et al.  The ability of limited exposure sampling to detect effects of interventions that reduce the occurrence of pronounced trunk inclination. , 2010, Applied ergonomics.

[20]  Monique Lortie,et al.  Observation Procedures Characterizing Occupational Physical Activities: Critical Review , 2000, International journal of occupational safety and ergonomics : JOSE.

[21]  Svend Erik Mathiassen,et al.  Variability in mechanical exposure within and between individuals performing a highly constrained industrial work task , 2003, Ergonomics.

[22]  Svend Erik Mathiassen,et al.  Cost-efficient design of occupational exposure assessment strategies--a review. , 2010, The Annals of occupational hygiene.

[23]  Barbara Silverstein,et al.  Interrater Reliability of Posture Observations , 2009, Hum. Factors.