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How much do we know about the effectiveness of warm-up intervention on work related musculoskeletal disorders, physical and psychosocial functions: protocol for a systematic review

Introduction Work-related musculoskeletal disorders (WMSDs) are a growing worldwide burden and effective interventions to prevent them are needed. Physical activity at the workplace is now recognised as a relevant component of WMSDs prevention. Along these lines, warm-up interventions are now offered in a large number of companies to manage WMSDs. Although benefits of warm-up have been previously documented in sports context, to the best of our knowledge, the effectiveness of such intervention in workplaces still remains to be established. Within this context, the aim of the present review is to identify from published literature the available evidence regarding the effects of warm-up on WMSDs and physical and psychosocial functions. Methods The following electronic databases will be searched (from inception onwards to June 2020): Cochrane Central Register of Controlled Trials, PubMed (Medline), Web of Science and Physiotherapy Evidence Database. Randomised and non-randomised controlled studies will be included in this review. Participants should be adult employees without specific comorbidities. Interventions should include a warm-up physical intervention in real-workplaces. The primary outcomes will be pain, discomfort or fatigue. The secondary outcomes will be job control or motivation at work. This review will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and two team members will independently screen all citations, full-text articles and abstract data. A systematic narrative synthesis will be provided with information presented in the text and tables to summarise the characteristics and findings of the included studies. Ethics and dissemination The approval of an ethical committee is not required. All the included studies will comply with the current ethical standards. The results of this review will summarise the effects of warm-up intervention on WMSDs, physical or psychosocial functions. This information could help professionals in decision making related to the use of these interventions to prevent WMSDs. Findings will be disseminated to academic audiences through peer-reviewed publications, as well as to policy-makers. PROSPERO registration number CRD42019137211.


INTRODUCTION
Work-related musculoskeletal disorders (WMSDs) are conditions affecting muscles, tendons, nerves, ligaments, joints or spinal discs. 1 They are now considered as a public health problem all over the world since their adverse consequences on quality of life and work participation are important. [2][3][4][5][6] This underlines the importance of finding effective prevention or curative strategies/interventions. In the last two decades, numerous researchers have identified the workplace as an ideal setting to support the promotion of healthier lifestyle and to prevent WMSDs. [7][8][9] Hence, the use of workplace physical activity interventions for the management of WMSDs is now well supported by scientific evidence. [10][11][12][13][14][15][16] Interestingly, WMSDs are conditions commonly characterised by the presence of pain or decreased function. 9 Therefore, workplace physical activity interventions often focus on numerous outcomes related to the individual such as pain, discomfort or fatigue, 10 15-17 physical function such

Strengths and limitations of this study
► This study will be to the best of our knowledge the first review to critically appraise the effectiveness of warm-up exercises to prevent work-related musculoskeletal disorders in workplaces. ► Reporting in accordance with the Preferred Reporting Items for Systematic Reviews and Meta Analyses statement. ► This study will include both randomised controlled trial (RCT) and non-RCT. ► A low number of studies and significant heterogeneity is expected that might prevent performing a meta-analysis of the results.
Open access as strength, flexibility or endurance 8 and psychosocial function such as quality of life, job satisfaction or wellbeing. 18 19 In theory, the workplace environment does offer the possibility to reach and to raise awareness of a large number of workers. 20 However, workplace physical activity programmes are less often offered and performed by those at risk of developing WMSDs (ie, low status, low income and blue-collar workers). 7 21 22 Furthermore, a 40%-60% compliance is commonly observed whatever the duration of the programmes. [23][24][25][26][27][28] It is presumable that these observations could partly stem from 'practical' barriers to offer physical activity at the workplace, such as time constraints, time of the day and duration of the training sessions. [29][30][31][32][33] In other words, programmes should be easy to implement in the daily routine of the employees as well as of the employers. This application recommendation is supported by scientific results that shown that short bouts of exercises are easier to fit in organisational routines than long sessions. 34 35 For instance, Andersen et al 34 in a 10-week workplace physical activity programme among office-workers, have compared the effects of a same weekly training volume, that is, 1 hour performed with different training frequencies (from one session per week to nine sessions per week) on training adherence. These authors have reported that adherence among office workers was significantly higher when the training volume was divided at least into 3 weekly training sessions.
In the last few years, the implementation of physical warm-up prior the beginning of the working days is increasingly adopted in companies to manage WMSDs (INRS 2018). In these companies, it is common to observe warm-up lasting between 5 and 15 min a day as well supervised by professionals such as sport trainer or physiotherapist as trained employees. 36 Previous reviews have found positive effects of warm-up on performance 37 and injury prevention in sports. [37][38][39][40][41] However, it is surprising that data on the effects of warm-up on WMSD are scarce and, when available, lead to rather conflicting/inconclusive results. [42][43][44] Within this context, the aim of this systematic review will be to evaluate the effectiveness of workplace warm-up interventions on WMSDs and physical and psychosocial functions among workers.

METHODS
The present review protocol is being reported in accordance with the reporting guidance the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA-P) statement 45 (see PRISMA-P checklist, online supplemental additional file 1). This review will be reported in accordance with the PRISMA statement.
Criteria for considering studies for this review Type of studies Original quantitative research studies that assessed the effect of a warm-up intervention in a workplace setting aiming at preventing WMSDs or musculoskeletal pain or discomfort or fatigue in the worker will be included in the review.
As correctly argued, randomised controlled trials (RCTs) are considered as the gold standard to assess the effectiveness of an intervention. 46 However, its implementation in occupational setting may not always be feasible and its implementation is called into question. 1 47-51 In that specific case, recent studies have suggested that non-RCT may maximise the body of evidence and have suggested including non-RCT in systematic-reviews. [52][53][54] For these reasons and as previously done in recent systematic reviews covering the scope of the present review, 10 49 both randomised and non-randomised controlled studies will be included. Therefore, quasi-RCTs (participants not randomly allocated), cluster randomised trials (ie, randomisation of a group of people, eg, randomisation at a company level), preference trials (patients can choose their treatment) and before-and-after study are design which will be included.
Period of studies publication was defined from inception onwards to June 2020. Finally, to be eligible for inclusion, studies had to be published in English in peerreviewed scientific journals. 19 49 As only studies in English will be included and may lead to reporting bias, we will report potentially eligible studies in other languages.
The following types of studies will be ineligible: case reports, abstracts, editorials, conference abstracts, letters to the editor, reviews and meta-analysis. Studies will be also excluded if the intervention was partially or totally implemented outside of the workplace, for example, in a clinical setting and if the intervention was implemented in combination with another intervention, for example, ergonomics. Therefore, studies will be excluded when differences can not only be attributed only to the warm-up intervention.

Types of participants
This review will include adult employees (18 years of age or older) and will exclude adults with specific comorbidities or diseases (such as diabetes, arthritis, cancer, stroke) and/or special populations (pregnant, severe or rare physical disability or cognitive disability).

Types of intervention
This review will include studies which have implemented warm-up interventions in real workplaces. To facilitate the comprehension of a warm-up intervention, we will use the definition given by McCrary et al 37 that is, 'a warm-up is a protocol specifically undertaken to prepare the onset of subsequent physical activity', in our case a working activity.
As recently used in a systematic review by Luger et al 55 to describe work-break programmes and a study by Slade and Keating 56 about exercise prescription, we will characterise the warm-up intervention with the following four components: 1. Duration: warm-up may last from 5 min to 1 hour. 2. Frequency: warm-up may differ in number.
3. Type: warm-up may be stretching as well as cardiotraining exercises or combination of strengthening exercises. 4. Intensity: warm-up may be performed with/without load or performed at a low or high percentage of the maximum heart rate. Studies will be excluded from this review if the warm-up intervention was partially or totally implemented outside of the workplace, for example, in a clinical setting or under laboratory conditions and if the warm-up intervention was implemented in combination with another intervention, for example, ergonomics.

Comparator
Inclusion criteria: We will consider studies that compared the warm-up intervention with a non-treatment control group (eg, no intervention or usual activity or another type of workplace physical activity) or a non-active comparator (eg, leaflets on benefits of physical activity).
Exclusion criteria: Studies with no comparison measures.

Main outcomes
WMSDs are defined as a group of conditions or health problems affecting the locomotor apparatus. These conditions are characterised by pain, impaired function, overall fatigue and stress. 9 57 Therefore, among primary outcomes we will include all the outcomes associated with work related musculoskeletal issues that are (1) participant's musculoskeletal pain through the use of pain scales (eg, Numeric Rating Scale or Visual Analogue Scale) or questionnaire (eg, McGill pain questionnaire) 55 and (2) participant discomfort or fatigue 10 55 through validated scales and (3) physical function as measured or estimated by questionnaires, scales, performances and/or specific tests. Dichotomous data such as presence/absence of symptoms will be also considered.

Secondary outcomes
For the prevention of the consequences of WMSDs we will include-if possible-and as secondary outcomes, all the outcomes associated with psychosocial function such as the measure of quality of life, job satisfaction, job control or motivation at work. In this review job control is considered as an indicator of psychosocial stress at work. 58 This indicator is often measured with the job demand-control support model developed by Karasek et al. 59 Information sources and search strategy Four electronic databases-Cochrane Central Register of Controlled Trials, PubMed (Medline), Web of Science and Physiotherapy Evidence Database-will be searched systematically from inception onwards to identify studies satisfying the search criteria. Note that these databases have previously used in published reviews covering the scope of this review. 49 55 60 61 The proposed search strategy terms for Medline are listed in table 1 and will be modified to fit the index system of other databases.

Additional intended information sources
To be sure not to miss relevant studies for the review, the reference list of for all eligible articles will be checked. Then, a grey literature search will be performed on ClinicalTrials. gov. Finally, experts in this domain will be contacted to collect information on unknown or ongoing studies.

Data collection
Study selection process All studies that met inclusion criteria passed through a data extraction and quality assessment process performed by two independent reviewers. A third reviewer will be requested to resolve disagreement when consensus could not be reached. Reviewers will not be blinded to study author(s) or journal title. At stage 1, two independent reviewers will screen abstract and titles identified from the search strategy. At stage 2, the same two reviewers will screen the full-text articles for inclusion. At this stage, all reasons for exclusion of articles will be recorded and reported. Finally, the relevant studies, which respect eligibility criteria, will be screened by a senior review team member (NV) to be included in the systematic review.

Data extraction and management
First a data extraction form will be created and validated by the three team members. This data collection form will Open access be fulfilled by one team member (NL) and corrected by another team member (RB). Any disagreement between the two reviewers will be resolved by consensus or discussion with the senior review team member (NV). This extraction form could be modified from the information collected in the eligible studies but should at least specify the following information 60

Risk of bias (quality) assessment
Two team members (NL and RB) will independently assess the risk of bias for each included study. Any disagreement between team members will be solved by consensus or discussion with the third team member. As both randomised and non-randomised controlled studies will be included in this review, two risk of bias tools will be used.

For RCT
The Cochrane tool for assessing risk of bias from the Cochrane Handbook for Systematic Reviews of Interventions will be used to assess potential biases of the included studies. This tool is a well-known and validated instrument to assess the risk of bias in RCTs. 64 This tool has been revised in 2019 65 and has now five domains to assess bias arising from: (1) randomisation process, (2) deviation from the intended intervention, (3) missing outcome data, (4) measurement of the outcome and (5) selection of the reported result. Each domain will be scored as follow (see table 2): 'high risk of bias', 'low risk of bias' and 'some concerns'.

For non-RCT
The Risk Of Bias In Non-randomised Studies-of Interventions (ROBINS-I) will be used to asses potential biases of the included non-RCT. 66 This tool has seven domains to assess bias arising from (1) confounding, (2) selection of participants, (3) classification of the intervention, (4) deviations from the intended intervention, (5) missing data, (6) measurement of outcomes and (7) selection of the reported result.

Measures of treatment effect
For studies using continuous data, treatment effect will be reported as mean difference with 95% CI. In case the studies evaluate the same outcome with different scales, standardised mean difference with 95% CI will be calculated. Regarding dichotomous/categorical variables, the treatment effect will be calculated using the relative risk (RR) with 95% CI. [67][68][69][70] Since the number of included studies is greater than 5 68 and when these studies are considered as sufficiently homogeneous, outcome data will be synthesised using a random effect meta-analysis. 55 69 71 72 If meta-analysis is not possible due to heterogeneity or if the outcomes cannot be pooled, a narrative synthesis will be performed using text and table formats. Results will be also presented in forest plots.

Assessment of statistical heterogeneity
Statistical heterogeneity, defined as variability in the intervention effects will be estimated using the χ 2 test, with χ 2 p>0.10 provides significant evidence of heterogeneity. χ 2 assesses whether heterogeneity is only due to chance. To ensure a right comprehension of heterogeneity, χ 2 will be completed with I² statistics particularly relevant when studies have small sample size or are few in numbers. Heterogeneity will be categorised as follows 72 : ► 0%-40%: not be important. ► 30%-60%: moderate heterogeneity. ► 50%-90% substantial heterogeneity. ► 75%-100%: considerable heterogeneity.
Quality assessment and strategy for data synthesis To assess quality of evidence of the included studies the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach 73 will be used. This approach grades studies as followed: very low, low, moderate and high. As suggested by Bordado et al 19 the quality assessment will be based on the findings in data extraction, and will follow the domains of quality evaluation in the GRADE approach: risk of bias, inconsistency,

Overall risk of bias judgement Criteria
Low risk of bias The study is judged to be at low risk of bias for all domains for this result Some concerns The study is judged to be at high risk of bias in at least one domain for this result, but not to be at high risk of bias for any domain. High risk of bias The study is judged to be at high risk of bias in at least one domain for this result Or The study is judged to have some concerns for multiple domains in a way that substantially lowers confidence in the result.
Open access indirectness and imprecision. Two team members (NL and RB) will independently assess the quality of evidence of the included studies with the GRADE approach.

Analysis of subgroups or subsets
In case a sufficient number of studies are included in the review, a subgroup analysis will be performed. The latter will be carried out for each outcome and for the following factors: (1) participants' characteristics (eg, sex, age. If possible authors will compare participants aged 40 years and younger with participants aged 41 years and older), (2) WMSDs location (eg, neck vs low back vs upper extremities), (3) occupational activity (eg, active vs sedentary jobs), (4) length of intervention, (5) study design (eg, RCT vs non-RCT) and (6) comparison group type (eg, passive vs active control group) 55 70 and (7) implementation warm-up intervention (supervised vs non supervised). 74

Sensitivity analysis
The authors of the present systematic review planned to perform sensitivity analysis to determine whether our findings are affected by high risk of bias and baseline pain. They also planned to combine the outcomes concerning pain, discomfort or fatigue and physical function. To perform sensitivity analysis, studies will be considered to be at high risk of bias if one of the main biases would be rated unclear or high risk (ie, random sequence allocation, allocation concealment, incomplete outcome data or selective outcome reporting. 63 Concerning pain, the low-intensity pain threshold was defined as 3 out of 10 on a pain intensity scale. 75 76

ETHICS AND DISSEMINATION
No ethic committee was required to conduct this review. However, all included studies in this review will follow current ethical standard and will be in accordance with the Declaration of Helsinki. The results of this review will be submitted for publication to a peer-reviewed high-impact academic journal. Other dissemination may include presentations at international conferences, seminars and note to social media to influence decision-makers.

DISCUSSION
Workplace physical activity is now well recognised as a potential intervention to prevent WMSDs. 7 8 11-17 Although benefits of a warm-up have been previously documented in sports context, [37][38][39][40][41] to the best of our knowledge, the effectiveness of such intervention in workplaces remains to be established. Interestingly, the primary outcome analysed in this review will be associated with WMSDs such as pain, discomfort or fatigue. The secondary outcomes will be related to physical or psychosocial functions. All these outcomes recognised to be decreased in case of WMSDs are also the main outcomes reported in studies assessing the effects on an intervention on WMSDs. [10][11][12][13][14][15][16] For these reasons, these findings could constitute a solid starting point to help clinicians, researchers, companies and policy-makers trying to reduce the burden of WMSDs.

LIMITATIONS AND STRENGTHS
Our review presents several strengths. The major strength is the systematic procedure employed. In this sense, a large number of scientific databases will be searched. Then, two reviewers will independently screen articles, rate the quality of these studies and the risk of bias. Finally, the use of recommended standard reporting instruments such as PRISMA-P, ROBINS-I and GRADE will strengthen the recommendations that should be made at the end of the review. At this point, however, we are aware that the potential strength of this review could be reduced by the lack of high-quality trials and high heterogeneity. First, the recent scientific literature confirms that RCT in a workplace context are, of course possible but rare. 34 77-79 In this sense, numerous authors have concluded that considerable efforts had to be made to overcome difficulties to implement such study design, but also to recruit a large number of employees. 1 46-48 80 To deal with this heterogeneity, the authors have preplanned to perform a subgroup and a sensitivity analysis. This choice will allow knowing whether or not the intervention effects differ between trials. Then, we are also aware that including both RCT and non-RCT will therefore lead to downgrade the validity and strength of the review and will increase the risk of bias especially for the blinding and generation domains. 70 Second, a recent review of literature by Johnson et al 81 on how outcomes are measured in workplace physical activity interventions have reported heterogeneous measurement tools and data collection making comparisons between studies rather difficult. To conclude, although the researchers do not anticipate protocol amendments, issues that arise with the original protocol will be documented in the review paper under the methodology section.
Contributors All listed authors have contributed and will continue to contribute meaningfully to the protocol and proposed review. NL, RB and NV conceived the proposed review and developed the search strategy. NL and RB are the two title and abstract reviewers, and NL and RB arethe two full-text reviewers. NV will be the third reviewer that will help resolve any discrepancy. RB submitted the protocol to PROSPERO and is responsible for updating the registered protocol as needed. All authors read the final protocol manuscript and revised it forcontent; all also approved the final version.
Funding This review is part of a PhD thesis-project conducted in the University of Grenoble Alpes and Opti'Mouv. The research project is promoted by the University of Grenoble Alpes and partially financed by the 'Ministère de l'Enseignement Supérieur et de la Recherche' via the 'Association Nationale Recherche Technologie' (ANRT) by means of the 'Convention Industrielle de Formation par la Recherche' (CIFRE) grant (n 2019/0488). The founding source has no role in the study design, data collection, results interpretation or manuscript writing.
Competing interests Opti'Mouv is a company that provides workplace health promotion services as workplace physical activity programmes.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
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