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| 2. |
- Bosch, Tim, et al.
(författare)
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Temporal strategy and performance during a fatiguing short-cycle repetitive task
- 2012
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Ingår i: Ergonomics. - : Informa UK Limited. - 0014-0139 .- 1366-5847. ; 55, s. 863-873
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated temporal changes in movement strategy and performance during fatiguing short-cycle work. Eighteen participants performed six 7-minutes work blocks with repetitive reaching movements at 0.5 Hz, each followed by a 5.5-minute rest break for a total duration of one hour. Electromyography (EMG) was collected continuously from the upper trapezius muscle, the temporal movement strategy and timing errors were obtained on a cycle-to-cycle basis, and perceived fatigue was rated before and after each work block. Clear signs of fatigue according to subjective ratings and EMG manifestations developed within each work block, as well as during the entire hour. For most participants, timing errors gradually increased, as did the waiting time at the near target. Changes in temporal movement strategy were negatively correlated with changes in the level and variability of EMG, suggesting that an adaptive temporal strategy offset the development of unstable motor solutions in this fatiguing, short-cycle work
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| 3. |
- Bosch, Tim, et al.
(författare)
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The effect of work pace on workload, motor variability and fatigue during simulated light assembly work
- 2011
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Ingår i: Ergonomics. - : Informa UK Limited. - 0014-0139 .- 1366-5847. ; 54:2, s. 154-168
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated the effect of work pace on workload, motor variability and fatigue during light assembly work. Upper extremity kinematics and electromyography (EMG) were obtained on a cycle-to-cycle basis for eight participants during two conditions, corresponding to "normal" and "high" work pace according to a predetermined time system for engineering. Indicators of fatigue, pain sensitivity and performance were recorded before, during and after the task. The level and variability of muscle activity did not differ according to work pace, and manifestations of muscle fatigue or changed pain sensitivity were not observed. In the high work pace, however, participants moved more efficiently, they showed more variability in wrist speed and acceleration, but they also made more errors. These results suggest that an increased work pace, within the range addressed here, will not have any substantial adverse effects on acute motor performance and fatigue in light, cyclic assembly work. STATEMENT OF RELEVANCE: In the manufacturing industry, work pace is a key issue in production system design and hence of interest to ergonomists as well as engineers. In this laboratory study, increasing the work pace did not show adverse effects in terms of biomechanical exposures and muscle fatigue, but it did lead to more errors. For the industrial engineer, this observation suggests that an increase in work pace might diminish production quality, even without any noticeable fatigue being experienced by the operators.
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| 4. |
- Luger, Tessy, et al.
(författare)
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Changing variation by work station design
- 2017
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Ingår i: Industrial and Systems Engineering at Work. - 2168-9210. ; 49:8, s. 53-54
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 5. |
- Luger, Tessy, et al.
(författare)
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Influence of posture variation in a repetitive manual task on maximal acceptable work pace and perceived exertion
- 2016
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Konferensbidrag (refereegranskat)abstract
- Background. It is generally agreed that constrained postures during assembly work can lead to musculoskeletal disorders in the neck and shoulders. In a controlled experiment, we investigated the extent to which more variation of upper arm postures in a one-hour repetitive task influences maximal acceptable work pace (MAWP), perceived exertion (RPE), kinematics and muscle activity.Methods. 13 participants (6 females, 7 males; age 26 (SD 3) years) performed a pick-and-place task for one hour, using their dominant hand to movie pins between two targets. We compared three conditions in which the hand was moved: (1) horizontally, at an intended upper arm elevation of 30°; (2) obliquely, at an upper arm elevation between 20° and 40°; and (3) vertically, at an upper arm elevation between 10° and 50°. Using a psychophysical approach — with imposed work paces changing every two minutes (7-13 cycles/min) — we arrived at the MAWP of each participant. Postures of the arm, trunk and shoulder were recorded throughout, as was the activity of selected muscles (not reported here). Participants reported their RPE (Borg CR-10) at baseline and at MAWP.Results. The kinematics data confirmed that the conditions had similar average upper arm elevations (32.3° (SD 1.0°) but differed in variation (arm elevation SD: 5.2°, 8.1°, 10.9°). Increased posture variation did not lead to changes in MAWP (10.7, 10.6, 10.8 cycles/min), though it did lead to slightly lower RPE values (average increase from baseline: 5.4, 4.8, 4.7).Discussion.Increased biomechanical variation has been suggested to reduce the risk of developing musculoskeletal disorders. Even though our data suggest that there may be a trend towards a positive effect of variation on work perception, the increase in posture variation imposed here was not sufficient to influence performance. Further analyses of arm, shoulder and trunk kinematics and muscle activity patterns may reveal biomechani-cal differences of interest between the protocols.
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| 6. |
- Luger, Tessy, et al.
(författare)
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Influence of posture variation on shoulder muscle activity, heart rate, and perceived exertion in a repetitive manual task
- 2017
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Ingår i: IISE Transactions on Occupational Ergonomics and Human Factors. - : Informa UK Limited. - 2472-5838 .- 2472-5846. ; 5, s. 47-64
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Tidskriftsartikel (refereegranskat)abstract
- Background: Repetitive light assembly work is associated with an increased risk for developing work-related musculoskeletal disorders. More exposure variation, for instance by redesigning the workstation, is generally proposed as an effective intervention. Purpose: We investigated the effect of upper arm posture variation in a one-hour repetitive pick-and-place task on shoulder muscle activity, heart rate and perceived exertion, measured on the Borg CR-10 scale and in terms of maximal acceptable work pace (MAWP). Methods: Thirteen healthy participants performed the task in three workstation designs where the hand was moved either horizontal (H30/30), diagonal (D20/40), or vertical (V10/50) with a mean upper arm elevation of ~30°. In a fourth design, the hand was moved horizontally at ~50° mean arm elevation (H50/50). Results: As intended, upper arm posture variation, measured by the upper arm elevation SD and range of motion, differed between H30/30, D20/40, and V10/50. However, MAWP (10.7 cycles·min-1 on average across conditions; determined using a psychophysical approach), average upper trapezius activity (54% reference voluntary exertion [RVE]), and heart rate (69 bpm) did not differ between these workstation designs. In H50/50, MAWP was lower (9.3 cycles·min-1), while trapezius activity (78% RVE) and perceived exertion (Borg CR-10) tended to be higher. Conclusions: Our results indicate that posture variation to the extent achieved in the current experiment leads to less effects on muscle activity and perceived exertion than a moderate change in working height.
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| 7. |
- Luger, Tessy, et al.
(författare)
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Influence of work pace on upper extremity kinematics and muscle activity in a short-cycle repetitive pick-and-place task
- 2017
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Ingår i: Annals of Work Exposures and Health. - : Oxford University Press (OUP). - 2398-7308 .- 2398-7316. ; 61:3, s. 356-368
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Tidskriftsartikel (refereegranskat)abstract
- Aim: This study investigated the extent to which controlled changes in work pace in a cyclic pick-and-place task influence upper extremity kinematics and muscle activity, and whether an effect depends on working height. Methods: Thirteen participants performed the task four minutes at each of five work paces ranging from 8 to 12 cycles·min-1 in each of two experimental conditions where the hand was moved horizontally with an average upper arm elevation of 30° and 50°, respectively. For each work cycle, we calculated the average and standard deviation of the upper arm elevation angle and the activity of the trapezius and deltoid muscles, as well as the angular peak velocity. We summarized these seven variables by calculating averages across cycles and cycle-to-cycle variabilities. Results: At 30° arm elevation, pace significantly influenced within-cycle angle variation, cycle-to-cycle variability of the average angle, angular peak velocity, and cycle-to-cycle variability of peak velocity. However, only angular peak velocity increased monotonically across all paces from 8 to 12 cycles·min-1). Average activity in the trapezius and the deltoid were the only muscle activity variables to increase consistently with pace. These effects of work pace did not change with working height. Conclusion: The present study did not find any consistent work pace effect on upper extremity kinematics and muscle activity, in spite of a comprehensive empirical basis compared to previous literature. While our results suggest that work pace may not be of critical concern in an occupational health context, we encourage further studies verifying or disproving this notion.
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| 8. |
- Luger, Tessy, et al.
(författare)
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Posture variation and maximal acceptable work pace during repetitive work
- 2016
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Konferensbidrag (refereegranskat)abstract
- Aim. It is generally agreed that work postures can lead to musculoskeletal disorders in the neck and shoulders. We investigated the extent to which more variation of upper arm postures in a repetitive task influences maximal acceptable work pace (MAWP), muscle activity, and perceived exertion.Methods. Thirteen healthy subjects (6F/7M; age 26 (SD 3) years) performed a repetitive pick-and-place task using their dominant hand in four one-hour conditions. In three conditions the average upper arm elevation was 30°, and the hand was moved (1) horizontally (H30), (2) diagonally with upper arm elevation between 20° and 40° (D20/40), (3) vertically, with upper arm elevation between 10° and 50° (V10/50). In the fourth condition, the hand was moved horizontally at 50° average upper arm elevation angle (H50). The travelled distance of the hand was the same for all conditions. Using a psychophysical approach with imposed work paces changing every two minutes (7-13 cycles/min), we arrived at the MAWP of each participant after 50 minutes. Postures of the arm were recorded throughout, as well as dominant upper trapezius muscle activity. Participants reported their perceived exertion (Borg CR-10) just after each protocol.Results. Kinematic analyses showed that we successfully designed protocols (Figure) differing in posture variation but not in average upper arm elevation angle (H30, D20/40, V10/50), and differing in average upper arm elevation angle but not in posture variation (H30, H50). MAWP was comparable in the conditions with differing posture variation (10.7 cycles/min), but lower in H50, although not significant (9.3 cycles/min). Subjects worked at MAWP with an upper trapezius activity level that did not significantly differ between experimental conditions (median 54% RVE). Dominant trapezius muscle activity at MAWP in H50 (78% RVE) was higher than in H30 (47% RVE), but not significant. Perceived exertion of the upper arm was higher in H50 (2.5) than H30 (1.5), but also not significant.Conclusion. Variation in upper arm elevation within the investigated limits did not affect MAWP although upper trapezius activity showed a tendency to increase with more variation. Increased working height tended to increase especially upper trapezius muscle activity and decrease MAWP. Thus, our results indicate that posture variation as applied in the current setting did not lead to significant differences in MAWP or muscle activity variables. More thorough workplace redesigns are apparently needed than those investigated by us to accomplish any major changes in psychophysical outcomes as measured by MAWP. Our results do show that engineers should pay attention to working height when advising companies on work pace.
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