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Forsman, Mikael, ProfessorORCID iD iconorcid.org/0000-0001-5777-4232
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Publications (10 of 26) Show all publications
Domkin, D., Forsman, M. & Richter, H. O. (2019). Effect of ciliary-muscle contraction force on trapezius muscle activity during computer mouse work. European Journal of Applied Physiology, 119(2), 389-397
Open this publication in new window or tab >>Effect of ciliary-muscle contraction force on trapezius muscle activity during computer mouse work
2019 (English)In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 119, no 2, p. 389-397Article in journal (Refereed) Published
Abstract [en]

The present study aimed to identify whether or not an increase in ciliary-muscle contraction force, when the eye-lens is adjusted for viewing at a near distance, result in an increase in trapezius muscle activity, while performing a natural work task. Twelve participants, ranging in age from 21 to 32 years, performed a computer-mouse work task during free gaze conditions. A moving visual target was tracked with a computer mouse on a screen placed at two different distances from the eyes, 25 cm and 50 cm. Tracking performance, eye accommodation, and bilateral trapezius muscle activity were measured continuously. Ciliary-muscle contraction force was computed according to a formula which takes into account the age-dependent, non-linear relationship between contraction force of the ciliary muscle and the produced level of eye accommodation. Generalized Estimating Equations analyses were performed. On the dominant hand side and for the nearest screen distance, there was a significant effect of ciliary-muscle contraction force on the trapezius muscle activity (p<0.001). No other effects were significant (p>0.05). The results support the hypothesis that high visual demands, during computer mouse work, increase ciliary muscle contraction force and contribute to a raise of the sustained level of trapezius muscle activity. The current study specifically clarifies the validity of the relationship between ciliary-muscle contraction force and trapezius muscle activity and demonstrates that this relationship is not due to a general personal trait. We conclude that a high level of ciliary muscle contraction force can contribute to a development of musculoskeletal complaints in the neck-shoulder area.

Keywords
Ciliary-muscle contraction force; Computer mouse work; Electromyography; Eye-accommodation; Trapezius muscle; Visual ergonomics
National Category
Occupational Health and Environmental Health
Research subject
Health-Promoting Work; Health-Promoting Work, Digital shapeshifting
Identifiers
urn:nbn:se:hig:diva-26194 (URN)10.1007/s00421-018-4031-8 (DOI)000457735500006 ()30430279 (PubMedID)2-s2.0-85056460114 (Scopus ID)
Funder
Forte, Swedish Research Council for Health, Working Life and Welfare, 2009-1761
Available from: 2018-03-01 Created: 2018-03-01 Last updated: 2023-08-29Bibliographically approved
Neumann, W. P., Winkel, J., Palmerud, G. & Forsman, M. (2018). Innovation and employee injury risk in automotive disassembly operations. International Journal of Production Research, 56(9), 3188-3203
Open this publication in new window or tab >>Innovation and employee injury risk in automotive disassembly operations
2018 (English)In: International Journal of Production Research, ISSN 0020-7543, E-ISSN 1366-588X, Vol. 56, no 9, p. 3188-3203Article in journal (Refereed) Published
Abstract [en]

Engineering innovations in car disassembly systems are studied for affects on system operators’ risk of repetitive strain injury (RSI). Objective instrumented measures of injury risk factors with synchronized video-based task analyses were used to examine changes in operators’ RSI risk during two cases of engineering innovation: 1) a shift in industrial model from traditional extracting saleable parts to line-based full material recovery, and 2) the prospective effects of a simulated “Lean” inspired process improvement in the line system.

Both cases of innovation showed significantly increased movement speeds and reduced muscular recovery opportunities, implying increased RSI risk. This case study reveals a mechanism by which innovation may increase RSI risks for operators. Managers responsible for engineering innovation should ensure their teams have the tools and mandate necessary to control injury hazards as part of the development and design process. These cases suggest how failure to manage RSI hazards in the innovation process may allow increases of injury risks that can compromise operational performance. This “innovation pitfall” has implications for operator health and organizational sustainability. Alternative pathways are discussed.

Place, publisher, year, edition, pages
Taylor & Francis, 2018
Keywords
Human Factors, Corporate Social Responsibility, Ergonomics, Disassembly, Design af Production Systems, Workload Control, Closed-loop Supply Chain
National Category
Occupational Health and Environmental Health
Research subject
Health-Promoting Work; Intelligent Industry
Identifiers
urn:nbn:se:hig:diva-26137 (URN)10.1080/00207543.2018.1432910 (DOI)000434401700010 ()2-s2.0-85042937746 (Scopus ID)
Available from: 2018-02-12 Created: 2018-02-12 Last updated: 2020-11-23Bibliographically approved
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, 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
Research subject
Health-Promoting Work
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: 2022-10-25Bibliographically 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: 2022-10-25Bibliographically approved
Wahlström, J., Bergsten, E. L., 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
Research subject
Health-Promoting Work
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: 2022-12-12Bibliographically 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: 2022-10-25Bibliographically 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: 2022-10-25Bibliographically approved
Zetterberg, C., Richter, H. & Forsman, M. (2015). Temporal co-variation between eye lens accommodation and trapezius muscle activity during a dynamic near-far visual task. PLOS ONE, 10(5), Article ID e0126578.
Open this publication in new window or tab >>Temporal co-variation between eye lens accommodation and trapezius muscle activity during a dynamic near-far visual task
2015 (English)In: PLOS ONE, E-ISSN 1932-6203, Vol. 10, no 5, article id e0126578Article in journal (Refereed) Published
Abstract [en]

Near work is associated with increased activity in the neck and shoulder muscles, but the underlying mechanism is still unknown. This study was designed to determine whether a dynamic change in focus, alternating between a nearby and a more distant visual target, produces a direct parallel change in trapezius muscle activity. Fourteen healthy controls and 12 patients with a history of visual and neck/shoulder symptoms performed a Near-Far visual task under three different viewing conditions; one neutral condition with no trial lenses, one condition with negative trial lenses to create increased accommodation, and one condition with positive trial lenses to create decreased accommodation. Eye lens accommodation and trapezius muscle activity were continuously recorded. The trapezius muscle activity was significantly higher during Near than during Far focusing periods for both groups within the neutral viewing condition, and there was a significant co-variation in time between accommodation and trapezius muscle activity within the neutral and positive viewing conditions for the control group. In conclusion, these results reveal a connection between Near focusing and increased muscle activity during dynamic changes in focus between a nearby and a far target. A direct link, from the accommodation/vergence system to the trapezius muscles cannot be ruled out, but the connection may also be explained by an increased need for eye-neck (head) stabilization when focusing on a nearby target as compared to a more distant target.

Keywords
Accommodation, Ciliary muscle, Computer work, Electromyography, Eye-neck (head) stabilization, Gaze stabilization, Visual ergonomics
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:hig:diva-16689 (URN)10.1371/journal.pone.0126578 (DOI)000354542500115 ()25961299 (PubMedID)2-s2.0-84930675377 (Scopus ID)
Funder
Forte, Swedish Research Council for Health, Working Life and Welfare, 2005-0488; 2009-1761
Available from: 2014-05-23 Created: 2014-05-23 Last updated: 2022-09-15Bibliographically approved
Richter, H., Zetterberg, C. & Forsman, M. (2015). Trapezius muscle activity increases during near work activity regardless of accommodation/vergence demand level. European Journal of Applied Physiology, 115(7), 1501-1512
Open this publication in new window or tab >>Trapezius muscle activity increases during near work activity regardless of accommodation/vergence demand level
2015 (English)In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 115, no 7, p. 1501-1512Article in journal (Refereed) Published
Abstract [en]

Aim

To investigate if trapezius muscle activity increases over time during visually demanding near work.

Methods

The vision task consisted of sustained focusing on a contrast-varying black and white Gabor grating. Sixty-six participants with a median age of 38 (range 19–47) fixated the grating from a distance of 65 cm (1.5 D) during four counterbalanced 7-min periods: binocularly through −3.5 D lenses, and monocularly through −3.5 D, 0 D and +3.5 D. Accommodation, heart rate variability and trapezius muscle activity were recorded in parallel.

Results

General estimating equation analyses showed that trapezius muscle activity increased significantly over time in all four lens conditions. A concurrent effect of accommodation response on trapezius muscle activity was observed with the minus lenses irrespective of whether incongruence between accommodation and convergence was present or not.

Conclusions

Trapezius muscle activity increased significantly over time during the near work task. The increase in muscle activity over time may be caused by an increased need of mental effort and visual attention to maintain performance during the visual tasks to counteract mental fatigue.

Keywords
Attention fatigue, Accommodation, Békésy test, Compensatory effort, Contrast threshold tracking, Electromyography, Visual ergonomics
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:hig:diva-18656 (URN)10.1007/s00421-015-3125-9 (DOI)000355872200011 ()25697148 (PubMedID)2-s2.0-84930575168 (Scopus ID)
Funder
Forte, Swedish Research Council for Health, Working Life and Welfare, 2005-0488; 2009-1761
Available from: 2015-01-01 Created: 2015-01-01 Last updated: 2022-09-15Bibliographically approved
Richter, H., Domkin, D. & Forsman, M. (2014). Ciliary muscle contraction force and trapezius muscle activity during manual tracking of visual targets. Investigative Ophthalmology and Visual Science, 55(13)
Open this publication in new window or tab >>Ciliary muscle contraction force and trapezius muscle activity during manual tracking of visual targets
2014 (English)In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 55, no 13Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2014
Keywords
464 clinical (human) or epidemiologic studies: risk factor assessment, 404 accommodation, 455 ciliary body
National Category
Health Sciences
Identifiers
urn:nbn:se:hig:diva-35793 (URN)000433203504110 ()
Available from: 2021-05-07 Created: 2021-05-07 Last updated: 2022-09-09Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5777-4232

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