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Zetterberg, C., Forsman, M. & Richter, H. O. (2017). Neck/shoulder discomfort due to visually demanding near work is influenced by previous neck pain, task duration, astigmatism, eye discomfort and accommodation. PLoS ONE, 12(8), Article ID e0182439.
Open this publication in new window or tab >>Neck/shoulder discomfort due to visually demanding near work is influenced by previous neck pain, task duration, astigmatism, eye discomfort and accommodation
2017 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, no 8, article id e0182439Article in journal (Refereed) Published
Abstract [en]

Visually demanding near work can cause eye discomfort, and eye and neck/shoulder discomfort during, e.g., computer work are associated. Here, to investigate direct effects of experimental near work on eye and neck/shoulder discomfort, 33 individuals with chronic neck pain and 33 healthy control subjects performed four visual tasks, rating eye and neck/shoulder discomfort at baseline and after each task. The cumulative performance time (reflected in the temporal order of the tasks), astigmatism, concurrent eye discomfort, and extent of accommodation all aggravated neck/shoulder discomfort. There was an interaction effect between the temporal order and eye discomfort: participants with a greater mean increase in eye discomfort also developed more neck/shoulder discomfort with time. Since moderate musculoskeletal symptoms are a risk factor for more severe symptoms, it is important to ensure a good visual environment in occupations involving visually demanding near work.

Keywords
astigmatism, computer vision syndrome, musculoskeletal disorder, oculomotor load, visual ergonomics
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:hig:diva-21513 (URN)10.1371/journal.pone.0182439 (DOI)000408355800023 ()28832612 (PubMedID)2-s2.0-85029224358 (Scopus ID)
Funder
Forte, Swedish Research Council for Health, Working Life and Welfare, 2005-0488Forte, Swedish Research Council for Health, Working Life and Welfare, 2009-1761
Available from: 2016-04-19 Created: 2016-05-20 Last updated: 2018-03-13Bibliographically approved
Domkin, D., Forsman, M. & Richter, H. (2016). Ciliary muscle contraction force and trapezius muscle activity during manual tracking of a moving visual target. Journal of Electromyography & Kinesiology, 28, 193-198
Open this publication in new window or tab >>Ciliary muscle contraction force and trapezius muscle activity during manual tracking of a moving visual target
2016 (English)In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 28, p. 193-198Article in journal (Refereed) Published
Abstract [en]

Previous studies have shown an association of visual demands during near work and increased activity of the trapezius muscle. Those studies were conducted under stationary postural conditions with fixed gaze and artificial visual load. The present study investigated the relationship between ciliary muscle contraction force and trapezius muscle activity across individuals during performance of a natural dynamic motor task under free gaze conditions. Participants (N = 11) tracked a moving visual target with a digital pen on a computer screen. Tracking performance, eye refraction and trapezius muscle activity were continuously measured. Ciliary muscle contraction force was computed from eye accommodative response. There was a significant Pearson correlation between ciliary muscle contraction force and trapezius muscle activity on the tracking side (0.78, p < 0.01) and passive side (0.64, p < 0.05). The study supports the hypothesis that high visual demands, leading to an increased ciliary muscle contraction during continuous eye–hand coordination, may increase trapezius muscle tension and thus contribute to the development of musculoskeletal complaints in the neck–shoulder area. Further experimental studies are required to clarify whether the relationship is valid within each individual or may represent a general personal trait, when individuals with higher eye accommodative response tend to have higher trapezius muscle activity.

Keywords
Ciliary muscle, Trapezius muscle, Near work
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:hig:diva-20299 (URN)10.1016/j.jelekin.2015.11.008 (DOI)000375923000025 ()26746010 (PubMedID)2-s2.0-84960859983 (Scopus ID)
Funder
Forte, Swedish Research Council for Health, Working Life and Welfare, 2005-0488Forte, Swedish Research Council for Health, Working Life and Welfare, 2009-1761
Available from: 2015-09-18 Created: 2015-09-18 Last updated: 2018-12-03Bibliographically approved
Wahlström, J., Bergsten, E., Trask, C., Mathiassen, S. E., Jackson, J. & Forsman, M. (2016). Full-shift trunk and upper arm postures and movements among aircraft baggage handlers. Annals of Occupational Hygiene, 60(8), 977-990
Open this publication in new window or tab >>Full-shift trunk and upper arm postures and movements among aircraft baggage handlers
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2016 (English)In: Annals of Occupational Hygiene, ISSN 0003-4878, E-ISSN 1475-3162, Vol. 60, no 8, p. 977-990Article in journal (Refereed) Published
Abstract [en]

Objectives: The present study assessed full shift trunk and upper arm postural exposure amplitudes, frequencies, and durations among Swedish airport baggage handlers, and aimed to determine whether exposures differ between workers at the ramp (loading and unloading aircraft) and baggage sorting areas.

Methods: Trunk and upper arm postures were measured using inclinometers during three full work shifts on each of 27, male baggage handlers working at a large Swedish airport. Sixteen of the baggage handlers worked on the ramp and 11 in the sorting area. Variables summarizing postures and movements were calculated, and mean values and variance components between subjects and within subject (between days) were estimated using restricted maximum likelihood algorithms in a one-way random effect model.

Results: In total, data from 79 full shifts (651 hours) were collected with a mean recording time of 495 minutes per shift (range 319-632). On average, baggage handlers worked with the right and left arm elevated >60° for 6.4% and 6.3% of the total workday, respectively. The 90th percentile trunk forward projection (FP) was 34.1° and the 50th percentile trunk movement velocity was 8°s-1. For most trunk (FP) and upper arm exposure variables, between-subject variability was considerable, suggesting that the flight baggage handlers were not a homogeneously exposed group. A notable between-days variability pointed to the contents of the job differing on different days. Peak exposures (>90°) were higher for ramp workers than for sorting area workers (trunk 0.6% ramp vs 0.3% sorting; right arm 1.3% ramp vs 0.7% sorting).

Conclusions: Trunk and upper arm postures and movements among flight baggage handlers measured by inclinometry were similar to those found in other jobs comprising manual material handling, known to be associated with increased risks for musculoskeletal disorders. The results showed that full-shift trunk (FP), and to some extent peak arm exposures, were higher for ramp workers compared to sorting workers.

Keywords
baggage handling, exposure variability; ergonomics, musculoskeletal disorders, epidemiology
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:hig:diva-20430 (URN)10.1093/annhyg/mew043 (DOI)000386017300007 ()27417186 (PubMedID)2-s2.0-84990985854 (Scopus ID)
Funder
AFA Insurance, 100071Forte, Swedish Research Council for Health, Working Life and Welfare, 2009-1761
Available from: 2015-10-16 Created: 2015-10-16 Last updated: 2018-03-13Bibliographically approved
Jackson, J., Mathiassen, S. E., Wahlström, J., Liv, P. & Forsman, M. (2015). Digging deeper into the assessment of upper arm elevation angles using standard inclinometry [Letter to the editor]. Applied Ergonomics, 51, 102-103
Open this publication in new window or tab >>Digging deeper into the assessment of upper arm elevation angles using standard inclinometry
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2015 (English)In: Applied Ergonomics, ISSN 0003-6870, E-ISSN 1872-9126, Vol. 51, p. 102-103Article in journal, Letter (Other academic) Published
Keywords
Validity, Bias, Posture assessment
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:hig:diva-19344 (URN)10.1016/j.apergo.2015.04.012 (DOI)000358389100012 ()26154209 (PubMedID)2-s2.0-84937416785 (Scopus ID)
Available from: 2015-05-20 Created: 2015-05-20 Last updated: 2018-03-13Bibliographically approved
Jackson, J., Mathiassen, S. E., Wahlström, J., Liv, P. & Forsman, M. (2015). Is what you see what you get? Standard inclinometry of set upper arm elevation angles. Applied Ergonomics, 47, 242-252
Open this publication in new window or tab >>Is what you see what you get? Standard inclinometry of set upper arm elevation angles
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2015 (English)In: Applied Ergonomics, ISSN 0003-6870, E-ISSN 1872-9126, Vol. 47, p. 242-252Article in journal (Refereed) Published
Abstract [en]

Previous research suggests inclinometers (INC) underestimate upper arm elevation. This study was designed to quantify possible bias in occupationally relevant postures, and test whether INC performance could be improved using calibration.

Participants were meticulously positioned in set arm flexion and abduction angles between 0° and 150°. Different subject-specific and group-level regression models comprising linear and quadratic components describing the relationship between set and INC-registered elevation were developed using subsets of data, and validated using additional data.

INC measured arm elevation showed a downward bias, particularly above 60°.  INC data adjusted using the regression models were superior to un-adjusted data; a subject-specific, two-point calibration based on measurements at 0° and 90° gave results closest to the ‘true’ set angles.

Thus, inclinometer measured arm elevation data required calibration to arrive at ‘true’ elevation angles. Calibration to a common measurement scale should be considered when comparing arm elevation data collected using different methods.

Keywords
measurement error, observation, working postures
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:hig:diva-16159 (URN)10.1016/j.apergo.2014.08.014 (DOI)000347663600028 ()25479994 (PubMedID)2-s2.0-84919663729 (Scopus ID)
Available from: 2014-01-24 Created: 2014-01-24 Last updated: 2018-03-13Bibliographically approved
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5777-4232

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