hig.sePublications
Change search
Link to record
Permanent link

Direct link
BETA
Waleh Åström, AmandaORCID iD iconorcid.org/0000-0002-6561-5423
Publications (4 of 4) Show all publications
Jackson, J., Forsman, M., Heiden, M., Waleh Åström, A. & Mathiassen, S. E. (2018). Symposium: Measuring posture in working life: Observation or inclinometry? [Mätning av arbetsställningar: observation eller inklinometri?]. In: Lindberg, Per (Ed.), FALF KONFERENS 2018 Arbetet – problem eller potential för en hållbar livsmiljö?   10-12 juni 2018 Gävle: Program och abstracts. Paper presented at FALF 2018 konferens 'Arbetet - problem eller potential för en hållbar livsmiljö?', 10-12 juni 2018, Gävle (pp. 38-40). Gävle: Gävle University Press
Open this publication in new window or tab >>Symposium: Measuring posture in working life: Observation or inclinometry? [Mätning av arbetsställningar: observation eller inklinometri?]
Show others...
2018 (Swedish)In: FALF KONFERENS 2018 Arbetet – problem eller potential för en hållbar livsmiljö?   10-12 juni 2018 Gävle: Program och abstracts / [ed] Lindberg, Per, Gävle: Gävle University Press , 2018, p. 38-40Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Quantifying postures during work is a key aspect of understanding the physical loads experienced by the body at work. Two commonly used tools to assess posture are observation and inclinometry. Observation can be performed in many ways, from real-time observations made at the worksite assessing gross body postures, to estimates of individual joint angles made by observers assessing still images taken from video recorded at the work site. Inclinometry is a direct technical measurement tool which typically uses tri-axial accelerometers to determine angles of specific body segments with respect to the line of gravity. Regardless of which tool is used, it will introduce some variability between repeated measurements of a same posture – this is called method-logical variability. Over the past ten years we have worked extensively in our Cost-efficient measurement of physical exposures research program to quantify the magnitude of error resulting from different measurement strategies – both in terms of bias (that is, the difference between the truth and the measured values) and precision (that is, how different repeated estimates of a same posture are). Further, we have compared the monetary costs and relative performances (in terms of measurement quality) of different measurement strategies. From these studies we have developed a set of recommendations to guide effective posture assessment.

We assessed bias in both observation and inclinometry to determine how close posture estimates were to the true body segment angles. Under ideal observation conditions, observers were not biased in estimating upper arm elevation angles (1). Conversely, we found a systematic underestimation of upper arm elevation angles made using inclino-metry, particularly for angles at or above 60° (2). We developed a simple, on-body incli-nometry calibration procedure, and determined it was effective at reducing inclinometer bias (2).

We investigated how data sampling should be distributed within and across days, and how much data was required to obtain a specific level of precision. Regardless of the tool, we found that efficiency was improved by distributing shorter sampling periods using a fixed-interval strategy across an entire day or days rather than collecting one longer period (3,4). Precision of inclinometer data is high and thus a single measurement of an event is sufficient. In contrast, observation requires repeated estimates of an image, even under ideal conditions (1, 5). For observation of still images from videos, we determined that efficiency was improved by assessing images extracted at set intervals across the recorded data (i.e. a work sampling approach) rather than making estimates based on continuously viewed intervals of video data (5). Further, repeated observations by one or more observers of a smaller number of frames of data improved the precision of angle estimates compared with a single observer rating a larger number of frames (6). In the case that a worker is obstructed from the camera view, additional frame analysis may be required and the uncertainty of the angle estimate may increase (7).

We developed models to assess the net cost of each method, including equipment acquisition, data collection and data analysis. While the initial expense may seem higher for inclinometers, cost gains are made during collection and analysis stages compared to the work-intensive post-collection efforts required for observation. We found that inclinometry was more cost efficient than observation in certain settings (8), but that uncertainty exists even in cost assessment models and thus that cost-efficiency is situation-dependent (9).

There are strengths and weaknesses to both tools and one must evaluate the goals of each data collection and the relative merits of each tool when determining the appropriate assessment method. Observation may be preferable for studies seeking a general impression of a working day, identifying the tasks comprising a working day, assessing twisting during work, or assessing whether anatomical segments are loaded or supported during work. Inclinometers may be preferred for studies requiring full day or multi-day assessments, a high degree of accuracy and precision in angle estimates, information on segmental movement velocities, and/or studies where workers cannot be adequately filmed. Rapid advances in inclinometer technology and smart phone analogues will serve to further minimise set-up times and acquisition costs, making direct technical measurement increasingly feasible.

1. Jackson, J. A., Mathiassen, S. E. & Liv, P. Observer performance in estimating upper arm elevation angles under ideal viewing conditions when assisted by posture matching software. Appl. Ergon. 55, 208–215 (2016).

2. Jackson, J. A., Mathiassen, S. E., Wahlström, J., Liv, P. & Forsman, M. Is what you see what you get? Standard inclinometry of set upper arm elevation angles. Appl. Ergon. 47, 242–252 (2015).

3. Liv, P., Mathiassen, S. E. & Svendsen, S. W. Theoretical and empirical efficiency of sampling strategies for estimating upper arm elevation. Ann. Occup. Hyg. 55, 436–449 (2011).

4. Liv, P., Mathiassen, S. E. & Svendsen, S. W. Accuracy and precision of variance components in occupational posture recordings: A simulation study of different data collection strategies. BMC Med. Res. Methodol. 12, 58–68 (2012).

5. Rezagholi, M., Mathiassen, S. E. & Liv, P. Cost efficiency comparison of four video-based techniques for assessing upper arm postures. Ergonomics 55, 350–360 (2012).

6. Liv, P., Mathiassen, S. E. & Wahlström, J. Statistical power and measurement requirements in studies comparing observed postures between groups. (PhD Thesis, Umeå University, 2012).

7. Trask, C., Mathiassen, S. E., Rostami, M. & Heiden, M. Observer variability in posture assessment from video recordings: The effect of partly visible periods. Appl. Ergon. 60, 275–281 (2017).

8. Trask, C., Mathiassen, S. E., Jackson, J.A. & Wahlström, J. Data processing costs for three posture assessment methods. BMC Med. Res. Methodol. 13, 124–137 (2013).

9. Waleh Åström, A., Heiden, M., Mathiassen, S. E. & Strömberg, A. Uncertainty in monetary cost estimates for assessing working postures using inclinometry, observation or self-report. in review, (2018).

Place, publisher, year, edition, pages
Gävle: Gävle University Press, 2018
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:hig:diva-27077 (URN)978-91-88145-28-4 (ISBN)
Conference
FALF 2018 konferens 'Arbetet - problem eller potential för en hållbar livsmiljö?', 10-12 juni 2018, Gävle
Note

Symposium contributors:

1. How can we measure posture? An introduction to observation and inclinometry.Jennie Jackson and Mikael Forsman

2. Is what you see what you get? Assessing bias in observation and inclinometry.Jennie Jackson

3. How much, when and how often? Designing efficient data collections. Svend Erik Mathiassen

4. What will it cost? Modelling costs to determine efficient data collection strategies.Marina Heiden and Amanda Waleh Åström

5. Which tool should I use? The future of observation and inclinometry.Mikael Forsman, Jennie Jackson and Svend Erik Mathiassen

Available from: 2018-06-16 Created: 2018-06-16 Last updated: 2019-10-14Bibliographically approved
Waleh Åström, A., Heiden, M., Mathiassen, S. E. & Strömberg, A. (2018). Uncertainty in monetary cost estimates for assessing working postures using inclinometry, observation or self-report. Applied Ergonomics, 71, 73-77
Open this publication in new window or tab >>Uncertainty in monetary cost estimates for assessing working postures using inclinometry, observation or self-report
2018 (English)In: Applied Ergonomics, ISSN 0003-6870, E-ISSN 1872-9126, Vol. 71, p. 73-77Article in journal (Refereed) Published
Abstract [en]

Objective: To assess uncertainty in cost estimates for collecting posture data by inclinometry, observations and self-report.

Method: In a study addressing physical workloads at a paper mill, costs were calculated for measuring postures of twenty-eight workers during three shifts. Uncertainty in costs was assessed for all three methods as the range between an assumed best case (lowest cost) and worst case (highest cost) using scenario analysis.

Results: The cost for observation was larger, but also more uncertain (€16506 and €89552 in the best and worst case, respectively) than that of inclinometry (€7613 - €45896). Self-report costs were both lower and less uncertain (€3743 - €23368).

Conclusions: The extent of uncertainty in cost estimates implies that observation could be less expensive than inclinometry, e.g., in a scenario where experienced observers could use existing software, while inclinometers would have to be purchased. We propose adding uncertainty assessments to cost estimates when selecting a method for measuring working postures, and offer guidance in how to proceed in a specific setting.

Keywords
Cost components, scenario analysis, exposure assessment
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:hig:diva-25532 (URN)10.1016/j.apergo.2018.04.005 (DOI)000437366400009 ()29764616 (PubMedID)2-s2.0-85046100007 (Scopus ID)
Funder
Forte, Swedish Research Council for Health, Working Life and Welfare, 2010-0748Forte, Swedish Research Council for Health, Working Life and Welfare, 2009-1761
Note

Erratum to "Uncertainty in monetary cost estimates for assessing working postures using inclinometry, observation or self-report" [Appl. Ergon. 71C (2018) 73-77].DOI: 10.1016/j.apergo.2018.10.002. ScopusId 2-s2.0-85055122791

Available from: 2017-11-15 Created: 2017-11-15 Last updated: 2019-01-28Bibliographically approved
Waleh Åström, A., Heiden, M., Mathiassen, S. E. & Strömberg, A. (2018). Uncertainty of cost components in assessments of working posture by different methods. In: : . Paper presented at 20th Congress International Ergonomics Association, 26-30 augusti, 2018, Florens, Italy.
Open this publication in new window or tab >>Uncertainty of cost components in assessments of working posture by different methods
2018 (English)Conference paper, Poster (with or without abstract) (Refereed)
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:hig:diva-27892 (URN)
Conference
20th Congress International Ergonomics Association, 26-30 augusti, 2018, Florens, Italy
Available from: 2018-09-11 Created: 2018-09-11 Last updated: 2019-05-03
Waleh Åström, A., Heiden, M., Mathiassen, S. E. & Strömberg, A. (2017). Uncertainty in monetary cost estimates for assessing working postures using inclinometry, observation or self-report. In: Anna-Lisa Osvalder, Mikael Blomé and Hajnalka Bodnar (Ed.), NES 2017 ”JOY AT WORK”: Conference Proceedings. Paper presented at Nordic Ergonomics and Human Factors Society Conference (NES2017) 'Joy at Work', 20-23 August 2017, Lund, Sweden (pp. 160-161).
Open this publication in new window or tab >>Uncertainty in monetary cost estimates for assessing working postures using inclinometry, observation or self-report
2017 (English)In: NES 2017 ”JOY AT WORK”: Conference Proceedings / [ed] Anna-Lisa Osvalder, Mikael Blomé and Hajnalka Bodnar, 2017, p. 160-161Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Background

In order to optimize cost-efficiency when collecting posture data in field studies, accurate cost data are needed. A few studies have assessed costs of different measurement methods, but they did not address the uncertainty of the cost estimates. Information on the uncertainty of cost estimates is key input when deciding which method to use.

Aim

This study aimed atassessingthe uncertainty in estimates of costs for collecting posture data by inclinometry, observations and self-report.

Method

The study wasbased on data collected at a Swedish paper mill (Heiden et al. 2017)1. Using a model developed by Trask et al. (2014)2, costs were calculatedfor measuring trunk and upperarm postures of twenty-eight workers during three full shifts using inclinometers, observations from recorded videos, and workers’ self-reports from a questionnaire. For each measurement method, the uncertainty of the actually observed total cost was assessed by determining the range of costs between an assumed best case (lowest cost) and worst case (highest cost) using scenario analysis.

Results

Observation was the most expensive method (€41499) and also showed a large uncertainty in the cost estimate (€19089–€87154). Self-reports had the lowest cost (€9156) with the smallest uncertainty (€3941–€27473). The overall cost for inclinometry was €16851 with best and worst cases €8567 and €60313, respectively. The actual costs of inclinometry and self-reports in the conducted study were reasonably close to the best case.

Discussion

In their study of flight baggage handling, Trask et al. (2014) concluded that inclinometry was more expensive than observation when measuring trunk and arm postures. In the present study, we found observation to be the more expensive. Given the uncertainty in cost estimates, both results are plausible. Notably, in Trask et al. (2014), video recordings were restricted to 4 hours, whereas in the present material, video recordings covered full 7 -to 12-hour shifts. The time allocated to collecting video material for observations will significantly affect the cost comparison of methods, and this may serve as an example that further investigations of separate cost components for each method are warranted.

Conclusions

Based on a meticulous cost assessment, we found that cost estimates for observation of working postures were the most uncertain, followed by inclinometry and self-reports. A better understanding of data collection costs and their uncertainty, and thus of how to properly identifyan optimal measurement method, requires a deeper analysis of the cost model, and of the contributions of separate cost components to the overall cost

1 https://doi.org/10.1093/annweh/wxw0262

2 https://doi.org/10.5271/sjweh.3416

Keywords
Scenario analysis, exposure assessment, method comparison, cost calculation
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:hig:diva-25314 (URN)978-91-7753-152-4 (ISBN)
Conference
Nordic Ergonomics and Human Factors Society Conference (NES2017) 'Joy at Work', 20-23 August 2017, Lund, Sweden
Available from: 2017-09-21 Created: 2017-09-21 Last updated: 2018-03-13Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6561-5423

Search in DiVA

Show all publications