Ergonomic interventions for work in a sitting position: an integrative review

The sitting position is one of the most common positions in the workplace and one that can contribute to overloading the musculoskeletal system. Ergonomics can play a significant role in ensuring an appropriate relationship between people and their work and in achieving better conditions for workers’ health. The objective of this study was to consult the available evidence on the results of different ergonomic interventions for the musculoskeletal systems of workers who perform their jobs in a sitting position. This was an integrative review, searching the LILACS, MEDLINE, PubMed, SciELO, and CINAHL electronic databases for articles published from 2010 to 2019. The following keywords were used: Trabalhadores OR Workers OR Trabajadores AND Dor OR Pain OR Dolor AND Postura Sentada OR Sitting Position OR Sedestación AND Ergonomia OR Ergonomics OR Ergonomía. A total of 183 articles were identified, 14 of which were selected for the review. For qualitative analysis, the articles were organized by author, year, sample/population, objective, analytical instrument, intervention and type of intervention: combinations of physical exercise programs and postural and ergonomic guidance; different types of guidance and facilitating instruments; or configuration of furniture and use of supporting devices. A quantitative analysis of study quality was conducted using the Physiotherapy Evidence Database, based on the Delphi list. The interventions contributed to improve physical conditions and the tasks being carried out, making them more appropriate for the workers.


INTRODUCTION
Musculoskeletal disorders that compromise occupational health can be caused by the type of work activity, by heavy and repetitive physical work, by unhealthy positions, by prolonged activities, and by irregular characteristics of the workplace. 1,2 The sitting position is one of the most common positions in the workplace, is a factor that causes disharmony between the body's mechanical components, and can contribute to overload of the musculoskeletal system. 3,4 Remaining sitting continually can cause muscle fatigue, reduce body proprioception, overload the body's structures, and injure workers. 5 As such, a healthy workplace should enable workers to vary their position. 6 To achieve this, it is important to recognize the workplace, identify its risk factors, use ergonomic resources to prevent occupational diseases, and provide treatment and rehabilitation for those already affected. 7,8 The objective of ergonomics is to improve working conditions through evaluation of tasks, projects, products, the working environment, and workers' skills and limitations, studying and assessing the workplace's limitations and the adaptations that can be made to it. 2,9 Ergonomic interventions are essential to ameliorate the effects of sitting for long periods while working, improving the environment, the way work is organized, the tasks performed while working, and, as a consequence, workers' comfort, safety, and wellbeing, making a positive contribution to their health. 5,9 As such, employers have a duty to seek ergonomic resources to improve working conditions. 10 The objective of this study was to consult the available evidence on the results of different ergonomic interventions for the musculoskeletal systems of workers who perform their jobs in a sitting position.

METHODS
An integrative review was conducted. This is a method for collecting, assessing, and synthesizing the results of research on a specific subject. The study comprised six steps: formulation of the research question; sampling or searching for studies in the literature; extraction of data; assessment of the selected studies; interpretation of the results; and presentation of the review. 11,12 The PICO (P: population; I: intervention; C: control or comparison; and O: outcome) strategy was employed to support formulation of the question and definition of the research problem, 13 where P is people who work sitting position, I is ergonomic interventions, C is the workplace, and O is publications in the literature dealing with the subject. The following research question was adopted: "What does the literature report about ergonomic interventions and which ones can yield improvements for the musculoskeletal system of people who work in a sitting position?" Searches were run on the following electronic databases for scientific studies published in Portuguese, English, or Spanish from 2010 to 2019: Literatura Latino-Americana e do Caribe em Ciências da Saúde (LILACS), Medical Literature Analysis and Retrieval System Online (MEDLINE), PubMed (both North-American), Biblioteca Eletrônica Científica On-line (SciELO), and Cumulative Index to Nursing and Allied Health Literature (CINAHL).
Inclusion criteria were articles published from 2010 to 2019 that investigated ergonomic interventions and used randomized clinical trial or quasi-experimental methodology. Exclusion criteria were articles and other publications that did not cover the chosen subject, review articles, duplicate articles, books, theses, dissertations, and undergraduate final-year projects.
Studies were classified during search, selection, and analysis by a single appraiser who conducted the electronic database searches independently. The studies identified were recorded and duplicates and those that did not meet the inclusion criteria were excluded.
Articles were selected in stages. First the titles were read, then the abstracts were read, and if they met the review objectives the full texts were then read. Data were analyzed with both quantitative and qualitative approaches.
Quantitative analysis of the methodological quality of articles was conducted using the Physiotherapy Evidence Database (PEDro) scale, which is based on the Delphi list. 14 Each article was analyzed for internal validity and statistical interpretation and scored on the scale up to a maximum of 10 points.
The Delphi list assesses the external validity and potential for generalization or applicability of clinical studies, but this criterion is not counted in the final score. High methodological quality is defined as scores greater than or equal to seven. To be awarded points, studies must describe the following: origin or the sample and inclusion criteria (item 1), random allocation of subjects (item 2), concealed allocation (item 3), paring of the sample (item 4), blinding of subjects, therapists, and evaluators (items 5, 6, and 7), key outcomes measured in 85% of the sample at different times (item 8), participants receiving treatment or a control condition (item 9), and intergroup comparisons (item 10). The results of intergroup statistical comparisons were described for at least one key outcome. 14 Studies were scored by two evaluators independently. Cases of disagreement were reassessed in conjunction until the evaluators reached a final consensus score.
The qualitative analysis comprised the following steps: 1) organization of articles by author, year, sample/population, objective, analytical instrument, intervention, and outcome; and 2) organization of articles according to the type of ergonomic intervention. In this step, for didactic reasons, the studies were allocated to different categories, depending on the type of intervention and considering the different options available for ergonomic intervention.

5-10
Rev Quasi-experimental study To examine whether using a height-adjustable workstation can improve subjective levels of fatigue, musculoskeletal discomfort and work productivity relative to seated work.
A modified version of the questionnaire CIS20-R strength questionnaire and the MAF scale: to assess fatigue; NMQ: to assess musculoskeletal discomfort; modified version of the HWQ: to assess work productivity; 10 cm VAS: to assess acceptability of the adjustable workstation Use of an electric ergonomic workstation (sit-stand condition) or working in a sitting position (sit condition) Transitioning from sitting to standing every 30 minutes led to a significant reduction in fatigue levels and back discomfort in overweight workers, while maintaining work productivity.

Randomized controlled clinical trial
To investigate the effectiveness of a workstation ergonomic intervention for work-related posture and low back pain in video display terminal workers.
REBA: to assess posture, load or strength, repetitiveness and frequency of changing positions and drawing-based pain assessments (to indicate the extent of pain) Ergonomic assessment, changes to design of workstation and physiotherapy assessment The intervention improved work-related posture and was effective for reducing the prevalence of lumbar pain.

DISCUSSION
Considering the studies included in this review, it was observed that several different ergonomic interventions yielded satisfactory results for workers, both with regard to posture and to musculoskeletal symptoms. [15][16][17][18][19][20][21][22][23][24][25][26][27][28] Only one study was found that covered physical exercises with workers who work in a sitting position. However, its methodological quality was not high, although these practices are considered the gold standard intervention. This study found that after the after less than 2 months of the program of physical exercise and postural and ergonomic guidance, workers reported that pain and musculoskeletal discomfort had reduced, even among those without job satisfaction. 19 Job satisfaction is a complex factor involving psychosocial aspects and workers' mental health and wellbeing, 29 and should be cared for and assessed in depth.
One study observed that daily occupational gymnastics in the workplace can improve gains in flexibility, reduce rates of physician-certified sick leave for low back pain and other pains 30 and minimize reports and intensity of musculoskeletal pain. 31 It could be inferred that inclusion of physical exercises with instruction from trained professionals works to encourage workers to adopt healthy measures in the workplace, in addition to encouraging them to do the exercises daily. Another relevant question is whether employers can encourage these practices with group or individual activities, 32 contributing even more to improve physical condition and job satisfaction.
Four studies employed different types of guidance and instruments to facilitate adherence to the guidance, 16,17,20,21 two of which had high methodological quality, using electronic biofeedback devices and reported positive results with reduction of musculoskeletal symptoms 16,17 and improved posture among the workers. 16 Use of instruments, questionnaires, protocols, and sensors enables working conditions and repetitiveness of tasks and postures to be assessed, helping to improve the working environment and working conditions. 33 Along the same lines, a study that employed a biofeedback device with six individuals for a 5-hour period was able to demonstrate a contribution to maintenance of good posture while working on a computer. 34 Only two of the studies about furniture configuration had high methodological quality, both controlled and randomized clinical trials, 15,18 while all of the others scored below 7. [22][23][24] These interventions contribute to a healthier, more flexible, more comfortable, more productive, and more satisfactory workplace. 15,18,[22][23][24] It was possible to identify reductions in low back pain among workers who used sitting workstations, 23 after using sit-stand workstations, [18][19][20][21][22][23][24] and after adjustments and modifications to office furniture, 15 reporting improvements in postural aspects, reductions in musculoskeletal complaints, improved psychosocial conditions, and better disposition and interaction between workers in the work environment. 15,[22][23][24] All of the studies that employed auxiliary devices had methodological quality scores below 7. Use of these devices was effective for reduction of body discomfort, for improving posture, and for reducing musculoskeletal symptoms. 25,26 One of the studies that employed interventions using magnifying loupes to improve workers' vision identified significant reductions in discomfort involving the neck, shoulder, upper arm, elbows, lower arms, lower back, and whole body after the intervention and also improvements over time in cervical movement amplitude and in deep neck muscle resistance, although there were deteriorations in front head posture and cervical kinesthetic sensitivity, suggesting that the loupes have both positive and negative results for workers' physical wellbeing. 28 Workstations should be adaptable to each worker 35 to enable greater efficiency and better satisfaction for the users who work with these systems, 36 and ergonomic interventions can contribute to helping workers learn to adopt healthy postures when working 16 and when concentrating on their work. 23 The sitting position predominates in many types of jobs and remaining seated for prolonged periods can overload musculoskeletal structures and lead to development of symptoms such as pain and discomfort, since no posture is healthy if maintained for long periods and sitting should be a dynamic matter. 30 Therefore, ergonomic interventions work to change workplace situations, contributing to improve physical conditions and helping to improve the tasks being undertaken, making them more appropriate for the workers performing them. 28

CONCLUSIONS
The studies demonstrate that, in general, the different ergonomic interventions were effective for reducing musculoskeletal symptoms in workers who work in a sitting position.

Author contributions
CS was responsible for study conceptualization, data curation, formal analysis, investigation (including data collection), methodology, project administration, supervision, validation, visualization, writing -original draft, and writing -review & editing. SGNS was responsible for study conceptualization, data curation, formal analysis, investigation (including data collection), methodology, project administration, resources/materials, supervision, validation, visualization, writing -original draft, and writing -review & editing. PRM, LFRMF, and LLPTC were responsible for study conceptualization, investigation (including data collection), methodology, supervision, validation, writingoriginal draft, and writing -review & editing. IAPW was responsible for study conceptualization, data curation, formal analysis, investigation (including data collection), methodology, project administration, supervision, validation, visualization, writing -original draft, and writing -review & editing. All authors have read and approved the final version submitted and take public responsibility for all aspects of the work.