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- Forsman, Mikael, Professor, et al.
(författare)
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Co-variation in time between near-far accommodation of the lens and trapezius muscle activity
- 2012
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Ingår i: Work. - Reading, MA, USA : Andover Medical Publishers. - 1051-9815 .- 1875-9270. ; 41:Suppl. 1, s. 3393-3397
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Tidskriftsartikel (refereegranskat)abstract
- Visual strain and discomfort may contribute to the generation of work-related musculoskeletal disorders among e.g. computer workers. A positive correlation on a group level between eye-lens accommodation and trapezius muscle activity has been reported. In this study we investigated the possibility of a direct, fast, connection between lens accommodation and trapezius muscles activity. The subjects focused alternately on Near and Far targets, with a mean switch time of 5 s, through four different lenses. The cross-correlation, R(tau) was computed, between the time signals of accommodation and electromyography (EMG) from 23 subjects. In the overall mean R(tau) of 736 curves, a small but significant correlation peak (0.019) with a delay (of the EMG signal) of about 0.3 s, revealed a small common component in the two signals. Among the lenses, the positive lens (3.5 D), showed the highest correlation peak (0.040). The correlation may be caused by a direct “hard-wired” connection between the ciliary and trapezius muscles. But it could also be caused indirectly by the subject’s need for a more stable head in a more demanding visual task. The latter is supported by the result that the correlation was the highest in the positive lens condition. The present correlation is however weak and it has probably a low practical importance.
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| 2. |
- Lodin, Camilla, 1970-, et al.
(författare)
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Eye- and neck/shoulder-discomfort during visually demanding experimental near work
- 2012
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Ingår i: Work. - : IOS Press. - 1051-9815 .- 1875-9270. ; 41:Suppl. 1, s. 3388-3392
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Tidskriftsartikel (refereegranskat)abstract
- Frequent use of digital information technology has an impact on eye- and neck/shoulder-discomfort. Studies with cross sectional and intervention design indicate an association between the two symptom categories. Still, whether visually demanding near work, per se, contributes to increased neck/shoulder discomfort remains a question of debate. The aim of this laboratory study was to assess if visually demanding experimental near work affects eye- and neck/shoulder-discomfort when the posture was adjusted for comfort and no movements were allowed. Thirty-three healthy subjects performed a visually demanding computer screen task (viewing task) under four different optical lens conditions: binocular -3.5 D and monocular -3.5 D, +3.5 D and ±0 D. During the experiment subjects were seated in an office chair (with neck support) that was individually adjusted for comfort. At baseline and after each viewing task, subjects reported their perceived eye- and neck/shoulderdiscomfort on Borg’s CR-10 scale. Results show a significant increase of eye discomfort between baseline and the first viewing task, and a significant increase in neck/shoulder discomfort from baseline throughout the first three viewing tasks. Further analysis is required to determent whether the neck/shoulder discomfort was induced by the demanding near work or the static posture, or a combination.
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| 3. |
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| 4. |
- Lodin, Camilla, 1970-, et al.
(författare)
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Sustained periods of binocular load may affect trapezius muscle activity
- 2011
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Ingår i: Wellbeing and innovations through ergonomics. - Oulu, Finland : Nordic Ergonomics Society. - 9789514295416 - 9789514295348 ; , s. 158-163
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Konferensbidrag (refereegranskat)abstract
- The relationship between activity in ocular muscles and activity in neck and scapular muscles that stabilizes gaze is well known. However, it is uncertain if ocular load per se contributes to increased muscle activity in the neck and scapular area. Sixty-six participants performed a fixation task under three different conditions: binocular with minus lenses (-3.5D) and monocular with minus lens (-3.5D) and neutral lens (±0D). Ocular accommodation and trapezius muscle EMG were measured. Multiple regression analysis showed that response diopters accounted for 11.6% (p=0.009) of the variance in EMG in the binocular condition. In the monocular conditions, there were no significant relationships.
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