| 1. |
- Srinivasan, Divya, et al.
(författare)
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Between- and within-subject variance of motor variability metrics in females performing repetitive upper-extremity precision work
- 2015
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Ingår i: Journal of Electromyography & Kinesiology. - : Elsevier. - 1050-6411 .- 1873-5711. ; 25:1, s. 121-129
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Tidskriftsartikel (refereegranskat)abstract
- Kinematic motor variability is extensively studied in occupational, clinical and sports biomechanics, but the consistency of most motor variability metrics have never been reported. In this study, fourteen subjects performed a repetitive pipetting task on three separate days. Movements of hand, arm and pipette tip were recorded in 3D and used to compute shoulder elevation, elbow flexion and shoulder-arm coordination angles, as well as pipette-tip endpoint precision. Cycle-to-cycle motor variability was quantified using linear dispersion measures of standard kinematics properties such as peak velocity, range of motion, and inter-segmental relative phase. Between- and within-subject consistencies of these variability metrics were quantified by variance components estimated using a nested random effects model. For most metrics, the variance between subjects was larger than that between days and cycles. Entering the variance components in statistical power equations showed that for most metrics, a total of 80-100 subjects will be required to detect a 20% difference between two groups with sufficient power, while this difference can typically be detected in repeated-measures (paired) designs using 25 subjects. The reported between- and within-subject variance components can be used as a data base to facilitate efficient designs of future studies of kinematic motor variability.
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| 2. |
- Sandlund, Jonas, et al.
(författare)
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Consistency of individual motor variability patterns in repetitive precision work
- 2015
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Ingår i: Physiotherapy. - : Elsevier BV. - 0031-9406 .- 1873-1465. ; 101:Suppl. 1, s. e1334-e1335
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Background:A longstanding hypothesis in physical therapy and occupational research is that workers repeating a task very stereotypically will be more prone to develop musculoskeletal disorders than workers that manage to vary postures and loads. Increased movement variability (MV), presumably, modify tissue loads, distribute stresses more equally, and thus reduce the cumulative load on any particular tissue. A handful of studies of MV have indicated less overuse injuries and faster recovery from musculoskeletal pain disorders. Even when repeating strictly controlled tasks individuals may differ in motor consistency, some showing higher levels of MV than others. However, whether the extent of MV is indeed a consistent individual trait across different tasks and different days is not known.Purpose:To investigate whether individual profiles of MV is stabile between days, the consistency of MV patterns from kinematic recordings, repeated across three days, was studied when performing repetitive upper-extremity precision work.Methods:A laboratory-based simulation of precision work; a 'pipetting' task paradigm, was developed in which liquid was repeatedly transferred from one tube to another, with a cycle time of 2.8s. Fourteen healthy female subjects, aged 20-45 years, right-handed and with experience in pipetting participated on 3 different days under identical conditions. Kinematic data were obtained using an electromagnetic motion capture system (FASTRAK). MV in shoulder elevation, elbow flexion and shoulder-elbow coordination were operationalized using cycle-to-cycle standard deviations across 20 pipetting cycles of kinematics parameters including joint range of motion, average and peak velocities, time to peak velocities, average angle and phase. Multivariate analysis was conducted using principal component analysis (PCA) (SIMCA+P, 12.0) to analyze relationships among variables and individual patterns in the data matrix of the recordings from day1. Thereafter, in order to confirm the observed structure of inter-individual MV patterns, classification of the data from day2 and day3 was performed using the parameters of the model from day1.Results:Four PCA components (Eigenvalues>1) accounted for 80 percent of the total variance in the model for day1. In the subsequent prediction model where data from day2 and 3 were projected into the model of day1, all subject observations except one could be predicted with 95% confidence (Hotelling T2). And individual data scores from all three days were clustered in relative proximity to each other, indicating consistency in MV between days.Conclusion(s):The findings indicate, even in this small and homogenous sample of young healthy females, that there may indeed be consistent individual traits in motor variability. A next step would be to answer whether these traits remain consistent if work factors such as work pace or precision are altered, and whether individual profiles of MV are associated with physiological responses related to risk for developing musculoskeletal disorders.Implications:Consistency of individual MV patterns substantiate previous notions that some people appear prone to repeat themselves while others tend to vary their motor behavior when performing the same task. Assessment of MV by physical therapists in research and practice could be valuable to further explore and address the relation of MV and musculoskeletal health.
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| 3. |
- Sandlund, Jonas, et al.
(författare)
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Differences in motor variability among individuals performing a standardized short-cycle manual task
- 2017
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Ingår i: Human Movement Science. - : Elsevier BV. - 0167-9457 .- 1872-7646. ; 51, s. 17-26
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Tidskriftsartikel (refereegranskat)abstract
- Motor variability (MV) has been suggested to be a determinant of the risk for developing musculoskeletal disorders in repetitive work. In this study we examined whether individuals consistently differed in the extent of motor variability when performing a standardized short-cycle manual task. On three separate days, arm kinematics was recorded in 14 healthy subjects performing a pipetting task, transferring liquid from a pick-up tube to eight target tubes with a cycle time of 2.8 s. Cycle-to-cycle standard deviations (SD) of a large selection of shoulder and elbow kinematic variables, were processed using principal component analysis (PCA). Thereafter, between-subjects and between-days (within-subject) variance components were calculated using a random effects model for each of four extracted principal components. The results showed that MV differed consistently between subjects (95% confidence intervals of the between-subjects variances did not include zero) and that subjects differed consistently in MV between days. Thus, our results support the notion that MV may be a consistent personal trait, even though further research is needed to verify whether individuals rank consistently in MV even across tasks. If so, MV may be a candidate determinant of the risk of developing fatigue and musculoskeletal disorders in repetitive occupational work.
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| 4. |
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| 5. |
- Barbieri, Dechristian, et al.
(författare)
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Do sit-stand tables affect physical behavior and body composition similarly in normal-weight and overweight office workers? A pilot study
- 2023
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Ingår i: IISE Transactions on Occupational Ergonomics and Human Factors. - : Taylor & Francis. - 2472-5838. ; 11:3-4, s. 81-93
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Tidskriftsartikel (refereegranskat)abstract
- Background: A sit-stand table (SST) at work may help office workers shorten and break up sitting by periods of standing. However, it is not clear whether SST use influences sitting at and outside work to similar extents among normal-weight and overweight office workers, and whether it can change body composition.Purpose: To investigate if introducing SSTs affects physical behavior and body composition similarly in normal-weight and overweight office workers.Methods: In this pilot intervention study, physical behavior and body composition were evaluated and compared between normal-weight (n=8) and overweight (n=14) office workers, both before and after using a SST for 6 months. Time spent sitting, standing, and moving was recorded using a triaxial thigh accelerometer during work and leisure. Dual-energy x-ray absorptiometry was used to determine fat, lean, and bone mass. Physical behavior and body composition data were both processed using compositional data analysis.Results: The intervention was similarly effective for normal weight and overweight workers in changing physical behavior during work, mainly by reducing sitting time and increasing standing time, while no effects were seen during leisure. We found no effect of the intervention on body composition.Conclusion: A sit-stand table intervention for 6 months changed physical behaviors at work to a similar extent among normal weight and overweight office workers. No compensatory behaviors were observed during leisure, and the intervention had no significant effects on body composition.
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| 6. |
- Barbieri, Dechristian, et al.
(författare)
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Effects on variation in shoulder, forearm and low back muscle activity from combining seated computer work with other productive office tasks: Results from a simulation study
- 2022
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Ingår i: Ergonomics. - : Taylor & Francis. - 0014-0139 .- 1366-5847. ; 65:6, s. 815-827
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Tidskriftsartikel (refereegranskat)abstract
- The effect on muscle activity variation of combining different office tasks is not known. We recorded electromyography from the upper trapezius (UT), wrist extensor (WE) and lumbar erector spinae (LES) in 24 office workers during five productive tasks, and breaks. Minute-to-minute variance was then estimated, by simulations, in a reference ‘job’ consisting of 85% sitting computer work and 15% breaks, and in ‘jobs’ where sitting computer work was replaced by different proportions of the other office tasks and breaks. Replacing sitting computer work with sitting non-computer work increased estimated variance by, in median, 23% (UT), 19% (WE) and 0% (LES). Replacing it by other tasks, in particular standing computer work and non-desk work, was less effective in increasing variance. Thus, some combinations of office tasks have a slight potential to increase muscle activity variation in the shoulder and lower arm, but not the lumbar back, while others will be ineffective.
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| 7. |
- Barbieri, Dechristian Franca, et al.
(författare)
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Comparison of sedentary behaviors in office workers using sit-stand tables with and without semi-automated position changes
- 2017
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Ingår i: Human Factors. - : SAGE Publications. - 0018-7208 .- 1547-8181. ; 59:5, s. 782-795
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Tidskriftsartikel (refereegranskat)abstract
- Objective: This study compared usage patterns of two different electronically controlled sit-stand tables during a 2-month intervention period among office workers.Background: Office workers spend most of their working time sitting, which is likely detrimental to health. Although the introduction of sit-stand tables has been suggested as an effective intervention to decrease sitting time, limited evidence is available on usage patterns of sit-stand tables, and whether patterns are influenced by table configuration.Methods: Twelve workers were provided with standard sit-stand tables (non-automated table group) and 12 with semi-automated sit-stand tables programmed to change table position according to a pre-set pattern, if the user agreed to the system-generated prompt (semi-automated table group). Table position was monitored continuously for two months after introducing the tables, as a proxy for sit-stand behavior.Results: On average, the table was in a “sit” position for 85% of the work-day in both groups; this did not change significantly during the 2-month period. Switches in table position from sit to stand were, however, more frequent in the semi-automated table group than in the non-automated table group (0.65 vs. 0.29 hr-1; p=0.001).Conclusion: Introducing a semi-automated sit-stand table appeared to be an attractive alternative to a standard sit-stand table, since it led to more posture variation.Application: A semi-automated sit-stand table may effectively contribute to making postures more variable among office workers, and thus aid in alleviating negative health effects of extensive sitting.
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| 8. |
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| 9. |
- Barbieri, Dechristian, et al.
(författare)
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Neck, trunk, and upper arm posture variation during computer work at a sit-stand table in a real work setting
- 2019
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Konferensbidrag (refereegranskat)abstract
- Background: Computer work is generally associated with constrained postures and sedentary behaviors. Sit-stand tables have been suggested as an effective intervention to promote changes in gross body posture, and thus reduce sitting. However, few studies have addressed to what extent sit-stand table usage affects posture variation in other body regions. The aim of this study was to examine neck, trunk and arm postures among office workers with access to sit-stand tables.Methods: Twenty-four office workers (16 females, 8 males; mean age 41 (SD9) years) participated. At entry, workers received sit-stand tables, which were then used for two months. Neck and trunk flexion, and right upper arm elevation (RUA) was recorded on three consecutive days, two hours/day, during the last week of table use. Minute-to-minute variability for the three postures during sitting (CWsit) and standing (CWstand) computer work was obtained for each participant. Job variance ratios (JVR) were calculated for the actual work, and for other combinations of CWsit and CWstand by simulation1.Results: CWsit and CWstand were performed for 72% and 28% of the time spent at the computer. Minute-to-minute variability was larger in CWsit than in CWstand for all three postures, and the difference CWsit-CWstand was largest for RUA [median 1.7 (IQR −0.2–1.7)º], followed by trunk [1.6 (0.9–3.0)º] and neck [0.9 (0.0–3.1)º]. During actual work, JVR was between 1 and 3 for most participants. Simulations suggested that maximum variability would occur at a combination of 40–80% CWsit and 20–60% CWstand.Conclusion: Neck, trunk and arm posture variation during computer work can be increased by manipulating proportions of time spent sitting and standing at a sit-stand table. The tentative “optimal” proportions reported here could be a benchmark for occupational health professionals.
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| 10. |
- Barbieri, Dechristian, et al.
(författare)
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Sit-stand tables with semi-automated position changes : a new interactive approach for reducing sitting in office work
- 2017
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Ingår i: IISE Transactions on Occupational Ergonomics and Human Factors. - : Informa UK Limited. - 2472-5838 .- 2472-5846. ; 5:1, s. 39-46
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Tidskriftsartikel (refereegranskat)abstract
- Background: Introduction of sit-stand tables has been proposed as an initiative to decrease sedentary behavior among office workers and thus reduce risks of negative cardiometabolic health effects. However, ensuring proper and sustainable use of such tables has remained a challenge for successful implementation. Objective: We developed a new system to promote and sustain the use of sit-stand tables. Methods: The system was programmed to change the position of the table between “sit” and “stand” positions according to a regular pre-set pattern, if the user agreed to the system-generated prompts prior to each change. The user could respond to the system-generated prompts by agreeing, refusing or delaying the changes by 2 minutes. We obtained user compliance data when this system was programmed to a schedule of 10 minutes of standing after every 50 minutes of sitting. Compliance was investigated in nine office workers who were offered the semi-automated sit-stand table for two months. Results: On average, the system issued 12-14 alerts per day throughout the period. Average acceptance rate ranged from 75.0-82.4%, and refusal rate ranged from 11.8-10.1% between the first and eighth weeks of intervention (difference not statistically significant). During the first week after introduction, the table was in a standing position for 75.2 min on average, increasing slightly to 77.5 min in the eighth week. Conclusion: Since the workers were essentially sitting down before the table was introduced, these results suggest that the system was accepted well, and led to an effective reduction of sitting during working hours. Users also reported that the system contributed positively to their health and wellbeing, without interrupt their regular work, and that they would like to continue using the sit-stand table even beyond the two-month period, as part of their regular work. Compliance beyond two months of use, however, needs to be verified.
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