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Efficacy of exercise therapy in workers with rotator cuff tendinopathy: a systematic review.

OBJECTIVE
To perform a systematic review of randomized controlled trials (RCTs) on the efficacy of therapeutic exercises for workers suffering from rotator cuff (RC) tendinopathy.


METHODS
A literature search in four bibliographical databases (Pubmed, CINAHL, EMBASE, and PEDro) was conducted from inception up to February 2015. RCTs were included if participants were workers suffering from RC tendinopathy, the outcome measures included work-related outcomes, and at least one of the interventions under study included exercises. The methodological quality of the studies was evaluated with the Cochrane Risk of Bias Assessment tool.


RESULTS
The mean methodological score of the ten included studies was 54.4%±17.2%. Types of workers included were often not defined, and work-related outcome measures were heterogeneous and often not validated. Three RCTs of moderate methodological quality concluded that exercises were superior to a placebo or no intervention in terms of function and return-to-work outcomes. No significant difference was found between surgery and exercises based on the results of two studies of low to moderate methodological quality. One study of low methodological quality, comparing a workplace-based exercise program focusing on the participants' work demands to an exercise program delivered in a clinical setting, concluded that the work-based intervention was superior in terms of function and return-to-work outcomes.


CONCLUSION
There is low to moderate-grade evidence that therapeutic exercises provided in a clinical setting are an effective modality to treat workers suffering from RC tendinopathy and to promote return-to-work. Further high quality studies comparing different rehabilitation programs including exercises in different settings with defined workers populations are needed to draw firm conclusions on the optimal program to treat workers.


Introduction
Shoulder pain affects a substantial number of adults, with a prevalence rate that has been reported to stand between 9% to 26% in the general population of Western countries 1) . Shoulder pain is the third most common musculoskeletal symptom 2,3 ) and the most common cause of shoulder pain in adults is rotator cuff (RC) tendinopathy 4) . RC tendinopathy is an umbrella term that includes different shoulder conditions affecting subacromial structures, such as long head of the biceps tendinopathy, subacromial bursitis, and shoulder impingement syndrome (SIS) 5) .
RC tendinopathy is particularly prevalent in workers and can cause work absenteeism and loss of productivity leading to important societal economic costs 6) . Rehabilitation of workers with RC tendinopathy may be challeng- ing, particularly when exposure to risk factors of shoulder-related pain and disability, such as working with arms above shoulder level, carrying loads, and use of vibrating tools, is common [7][8][9][10] .
Generally, prescription of non-steroidal anti-inflammatory drugs (NSAIDs), exercises, and surgery are common treatment options in the management of RC tendinopathy in workers. No consensus, however, exists on the best approach needed for workers. Furthermore, it has never been established if work-related interventions are required and if interventions for workers need to include workrelated functional exercises 11) . Evidence regarding the efficacy of exercises in adults is substantial, and exercise has been advocated as a cost-effective treatment for RC tendinopathy 12) . Two recent systematic reviews were published on the efficacy of physiotherapy exercises for adults with SIS and RC tendinopathy 13,14) . The authors of both reviews concluded that therapeutic exercises are effective in the management of patients suffering from RC tendinopathy. Their conclusions were, however, limited to general adults, and no specific conclusions for workers or information on work-related outcomes were presented. Thus, the effectiveness of exercises in workers remains unelucidated. Considering the high prevalence of RC tendinopathy in workers, there is a need to further investigate the specific efficacy of exercises for this population. The aim of this review was to evaluate the published literature concerning the efficacy of therapeutic exercises for workers suffering from RC tendinopathy.

Methods
This systematic review conforms to the PRISMA methodological guidelines 15) .

Literature search and study identification
A literature search in four bibliographical databases was conducted ( Pubmed, CINAHL, EMBASE, and PEDro ) using a combination of keywords and MESH terms (Fig. 1). All databases were searched from their date of inception to February 2015. Previous published reviews were also reviewed, and study reference lists were retrieved and searched for additional relevant studies.

Data extraction and quality assessment Study selection
Two evaluators independently reviewed the title and abstract of each article to determine whether it met the following inclusion criteria: 1) Participants suffered from RC tendinopathy or other related diagnostics, such as impingement syndrome, subacromial bursitis, or bicipital tendinitis. 2) Participants were adults (! 18 years).
3) The majority of participants were workers or specific workrelated outcome measures were used. The main outcomes of interest were work-related, but other clinical outcomes were also considered, such as pain and disability. 4) At least one of the interventions under study included exercises for the shoulder and could also include the upper quadrant. 5) Study design was a randomized controlled trials (RCTs). 6) The language of articles was either English or French. Studies that included participants suffering from shoulder pain were also eligible, as long as it could be determined that the majority of the study participants were suffering from RC tendinopathy. Studies were excluded if they had recruited patients with full thickness RC rupture, capsulitis, or post-surgery.

Data extraction
One evaluator extracted characteristics of the included studies with a standardized form that covered: characteristics of participants (mean age, gender, and duration of symptoms), occupation, type of interventions, outcome measures, follow-up period, and main results. Data extraction was later verified by a second independent evaluator.

Risk of bias tool
The risk of bias of the included studies was assessed with the Cochrane risk of bias tool 16) . This instrument is a well-known and validated assessment tool used to assess the risk of bias in RCTs. This tool appraised the risk of bias of a study in six methodological domains: sequence generation, allocation concealment, blinding (participants, provider, and assessor), incomplete outcome data, selective outcome data reporting, and other sources of bias 16 ) . Each item is appraised independently by two evaluators regarding its risk of potential bias: "unclear" indicates an unclear or unknown risk of bias based on the information presented in the study, "yes" indicates low risk of bias, and "no" indicates high risk of bias. For each methodological item, we also attributed a numerical score: a score of 2 was given if a low risk of bias was present, a score of 1 was given if the risk of bias was unclear or unknown, and a score of 0 was given if a high risk of bias was found to be present. A total score (out of 16) was then calculated and converted to a percentage to give an overview of the methodological quality and risk of bias of the included RCTs; higher scores signaled better methodological quality. Studies were rank ordered based on their quality, but there was no formal mechanism to exclude studies according to their quality. A pair of raters met to compare ratings and resolve disparities after the independent evaluation of each study. A structured consensus approach was used that involved: 1) re-review of the articles, 2) discussion of the adherence to standards, and 3) use of an independent third evaluator if consensus was not achieved.

Data analyses
The kappa statistic was used to calculate pre-consensus inter-rater agreement on individual methodological items, and an intraclass correlation coefficient (ICC) was calculated to evaluate inter-rater reliability of the total methodological scores using Statistical Package for Social Sciences (IBM SPSS Statistics 21, Chicago, USA). Studies that compared similar interventions with comparable outcome measures were identified for possible metaanalysis. The statistical significance was set at α=0.05.
Three RCTs compared therapeutic exercises to no intervention or to a placebo 17,18,25,26 ) , two studies compared therapeutic exercises to arthroscopic subacromial decompression 17,18,21,22 ) , one study compared two exercise programs of different intensities 28,29) and one RCT compared two different exercises programs 27 ) . Another study compared two exercise programs performed in different environments ( clinical setting or in the worker's environment) 19) , one RCT compared exercises to radial extracorporeal shockwave therapy (ECSWT) 20 ) , one study compared therapeutic exercises to a naturopathic intervention 30) , and one study compared an exercise program to individualized manual therapy in conjunction with an exercise program 23,24) . Samples of workers included construction journeymen, postal employees, and nurses 26,27,30) ; however, the other studies did not mention the type of work performed by participants or define their work-related environment or work demands.  We planned to pool results from multiple studies to perform a meta-analysis, but the only two studies that compared exercises to a placebo 25,26) and exercises to subacromial decompression 17,18,21,22) did not use the same outcome measures, thus rending any pooling of results meaningless.
Four out of nine studies described in detail their exercise program 20,23,25,26 ) , and three RCTs referred to previously published exercise protocols 17,18,27,30 ) . The active treatment period differed across studies, from eight to twelve weeks, and in two studies, participants were encouraged to pursue the program for a longer time [21][22][23][24] . Lengths of follow-up were heterogeneous across studies, with five RCTs that followed participants for eight to twelve weeks 19,[25][26][27]30 ) while the other five studies had a longer follow-up, ranging from 6 months to 8 years 17,18,[20][21][22][23][24]28,29) . In terms of work outcomes, studies were very heterogeneous. Four studies reported the percentage of patients that returned to work [17][18][19][20]28,29 ) , one study reported the number of sick days 23,24 ) , and three studies reported work function with different scales 21,22,25,26 ) . Two studies did not report on any specific work outcomes, but the study population included postal employees 30 ) and nurses 27) . Efficacy of therapeutic exercises compared to a placebo or to no intervention Two RCTs (n=127) of moderate methodological quality compared an exercise regimen to no intervention 25,26 ) , and one RCT (n=125) of moderate methodological quality compared therapeutic exercises to a placebo laser intervention 17,18) . In the study by Ludewig et al., participants were adults working as construction journeymen with at least 30% of their work tasks performed in overhead positions 26) . The exercise program aimed at restoring scapular control and was performed by the participants three times per week for ten weeks. Physiotherapists supervised two sessions with the participants, and the remaining time, the exercise program was performed at home. The control group received no intervention. In this study, the exercise group was found to be superior to the control group in terms of work-related disability ( 1-10 scale ) for postintervention scores (p<0.05), with a mean of 2.5 0.29 for the exercise group and of 3.7 0.29 for the control group after ten weeks 26) . In terms of work-related pain (1-10 scale), a statistically significant difference for postintervention score was observed (p<0.05), with a mean of 2.8 0.29 for the exercise group compared to a mean of 4.1 0.29 for the control group 26) .
In the study by Lombardi et al., participants ( exact work not specified) were involved in a repetitive maximum exercise regimen using a multi-pulley system with maximum bearable weight for four shoulder movements; the program duration was eight weeks 25 ) . The control group received no intervention, but both experimental and control groups were asked to take acetaminophen when experiencing pain. The authors used the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire to assess the work-related disability and general pain and function. In terms of work disability, the exercise group showed statistically significant improvement compared to the control group for inter-group comparison (p=0.001) 25) .
In the study by Brox et al., one group performed therapeutic exercises using a suspended sling for 1 h daily for three to 6 months in addition to ergonomic advice (anatomic and function learning) and was compared to a placebo group (detuned laser treatment) 17,18 ) . The type of work of the participants was not mentioned, but 48% of the participants were working with the hand above shoulder level, and, at baseline, 77% of them reported shoulder pain while working. A greater reduction in the proportion of participants reporting shoulder-related absence from work was observed in the therapeutic exercise group ( 23%) than in the placebo group ( 19%). However, no statistical testing was reported for this outcome 17,18) . Efficacy of therapeutic exercise vs. surgery Two RCTs compared subacromial surgical decompression to therapeutic exercises with a follow-up of 2.5 years in one study (n=125) 17 ) and of 4 to 8 years in the other study (n=84) 21 ) . The study by Haahr et al., of moderate methodological quality, included 84 subjects of whom 73% were on sick leave because of shoulder pain, and 70% previously had a potentially strenuous job, but the exact type of work was not reported. An exercise program aimed at recruiting periscapular muscles and strengthening the stabilizing muscles of the shoulder joint was supervised for 19 sessions and continued at home two to three times per week afterwards. No significant differences were found between groups in terms of sick leave associated with financial compensation (p<0.05) in the 4 years following treatment. At the end of follow-up, 53% of participants in the exercise group were working, and 51% of participants in the surgery group were working (p=0.88) 21) . Inter-group comparison did not reach statistical significance in terms of function assessed with the Constant-Murley Score (%) at 3, 6, and 12 months (p= 0.27, p=0.76, and p=0.38, respectively) 22 ) . In the longer timespan (four to eight years), more workers felt recovered or improved in the therapeutic exercises group (67.5%) than in the surgery group (60%) 21) .
In the study by Brox et al., a greater decrease in the proportion of participants with shoulder-related absence from work was observed at 2.5 years in the exercise group, with a mean decrease of 23%, whereas in the surgery group, the mean decrease was 12% 17 ) . However, no statistical testing was reported 18) . Different therapeutic exercise programs One study of low methodological quality by Osteras et al. (n=61 workers; type of work not reported) compared two different exercise regimens of twelve weeks duration with a follow-up of 6 months 28,29 ) . The exercise program was not only aimed at strengthening the shoulder but also at improving general health condition. The main differences between the two exercise regimens were time on bike, number of weight resisted exercises, and number of repetitions. The high-dosage group performed eight exercises (three sets of thirty repetitions), and the low-dosage group performed five exercises (two sets of ten repetitions ) 28,29 ) . At 6 months, inter-group comparison also showed a statistically significant difference (p<0.05) in favor of the high-dosage exercise group for mean reduction of 59.1% in the costs of sick leave compared to the low-dosage exercise group with a reduction of 42.3% . The mean difference of sick leave duration between the groups was 4.1 days per month, with the low-dosage group accounting for the longer sick leave periods 28) .
Mean change in pain (1-10 VAS) was statistically significant (p<0.05) at 6 months for between-group comparison, with a change of 4.3 cm (95% CI: 3.7 to 5.0) for the high-dosage group and 1.8 cm (95% CI: 0.7 to 2.7) for the low-dosage group 29) . This difference between groups of 2.5 cm 0.2 may be considered clinically important since it is over the minimal clinically important change on a VAS of 1.4 cm 31 ) . Authors also reported a significant difference (p<0.05) in the Shoulder Rating Questionnaire (SRQ) scores (range 17-90 ) at 6 months, with a mean improvement of 29.2 (95% CI: 21.7 to 36.0) for the high-dosage group and 7.3 (95% CI: 0.2 to 19.7) for the low-dosage group 29) . Again, the difference between groups is over the minimal clinically important change of 12 points for the SRQ 32) .
A study of low methodological quality by Cheng et al. compared a clinic-based intervention ( n = 48 ) to a workplace-based intervention ( n = 46 ) on workers performing various tasks of moderate physical demands 19 ) . Both groups received an exercise program including shoulder stretches and strengthening as well as scapular control exercises. The clinic-based group received work simulation in a clinical setting while the workplace-based group had a job coach assigned and received biomechanics and ergonomic education. At four weeks, a significantly higher percentage of workers returned to work in the work-based group (71.7%) than in the clinic-based group (37.5%), p=0.001 19 ) . The Shoulder Pain and Disability Index (SPADI; range 0-100) reached statistical significance for inter-group comparison (p=0.03) in favor of the workplace-based group. However, the difference between groups may not be considered clinically impor-tant 33) .
The study by Martins et al. 27 ) , of low methodological quality, compared two different rehabilitation programs on a sample of nurses (n=18). The program was composed of stretching and strengthening exercises, with a progressive increase in resistance at every three sessions followed by ice application. In the experimental group, proprioceptive exercises, such as joint position, rhythmic stabilization, and repositioning of arm exercises as well as use of unstable base, proprioceptive neuromuscular facilitation and speed and accuracy exercises were added to the program performed by the control group. There was a significant reduction in pain for both groups (p<0.01), but no significant difference was found between groups ( p! 0.05 ) . In terms of change in function assessed by the Western Ontario Rotator Cuff Index (WORC), only the experimental group achieved statistically significant improvement in every domain of the questionnaire, including work domain (p=0.01). However, no statistical difference was found for inter-group comparison (p>0.05) 27) . Efficacy of therapeutic exercise vs. Radial Extracorporeal-Shock Wave Therapy (ECSWT) A study of moderate methodological quality by Engebretsen et al. compared a supervised exercise regimen to ECSWT on a sample of workers, but the type of work was not mentioned. At inclusion, 45% were on sick leave 20) . The exercise program was provided twice weekly for 45 minutes for a maximum of 12 weeks and was mainly aimed at regaining scapular motor control. The proportion of participants who returned to work in the exercise group reached 20% while the proportion was 13% in the ECSWT group (OR: 1.1; 95% CI: 1.0 to 1.2) 20) . In terms of pain (10-point scale), none of the groups showed statistically significant differences, with a mean difference between groups of 0.4 (95% CI: 0.7 to 0.3) for pain at rest and a mean difference of 0.4 ( 95% CI : 1.4 to 0.4) for pain during activity 20) . The SPADI score revealed statistically significant improvement for pre-post treatment comparison in both groups (p<0.001 for the exercise group and p=0.001 for the ECSWT group). However, no statistically significant difference was observed in inter-group comparison (mean change of 7.6% [95% CI: 16.6 to 0.5]). Therapeutic exercises vs. naturopathic treatment A study of moderate methodological quality by Szczurko et al. in 85 postal employees compared the efficacy of therapeutic exercises, including isometric strength and endurance exercises as well as passive, activeassisted, and active joint therapy, with the addition of placebo tablets to a combination of naturopathic treatment that included acupuncture, Phlogenzym supplements, and dietary counseling for 12 weeks 30 ) . Pain assessment at week 12 using an 8-point VAS scale revealed a statistically significant mean difference between groups in favor of the naturopathic treatments ( 1.7; 95% CI: 2.5 to 0.88 ) . The authors also reported the SPADI score (range: 0-100), with a mean difference between groups of 29.7 (95% CI: -42.4 to 17), which is clinically important 33 ) , again in favor of the naturopathic treatment group. No work-related outcomes were assessed in this study. Manual therapy and therapeutic exercise vs. therapeutic exercise alone A study of low methodological quality by Kromer et al. 23,24 ) compared the efficacy of therapeutic exercises alone to a combination of therapeutic exercises and manual therapy on 90 patients from which 78 were currently working (type of work not reported). Participants to the manual therapy group received two treatments a week for five weeks. The treatments consisted of manual mobilizations of the shoulder, cervical spine, and thoracic spine. The manual therapy group as well as the exercise only group received supervised sessions of stretching and strengthening exercises for the shoulder joint, and for the cervical spine, two times per week. They also had to do two to five training sessions per week at home. There was no statistically significant difference between groups in terms of days of sick leave (p=0.13), but both groups improved significantly in terms of function measured with the SPADI at 1 year; however, no significant differences were found between groups, with a change of 25.2% (95% CI: 18.7-31.7) for the group receiving manual therapy and exercise and a change of 31.5% (95% CI: 26.5-36.6) for the exercise group.

Discussion
The aim of this review was to evaluate the current scientific literature with respect to the efficacy of therapeutic exercises in workers suffering from RC tendinopathy. Ten studies were included, and the mean methodological quality of trials was low to moderate with an average quality score of 54.4% 17.2. All studies lacked some information on blinding of participants and providers, which is understandable considering the nature of the interventions. The heterogeneity in terms of work-related outcome measures and follow-up periods was too important to perform a meta-analysis. Moreover, the majority of studies did not report the types of workers, the work environment, or work demands. Despite these limitations, we are able to draw some conclusions on the currently available evidence as to the efficacy of exercises for workers suffering from RC tendinopathy.
Previous reviews have shown moderate evidence that exercise therapy is an effective modality to treat RC tendinopathy in general adults [11][12][13][14]34,35 ) . However, there was a lack of evidence on the effectiveness of exercises for specific populations of workers. It is often believed that the rehabilitation of worker populations is more difficult and the outcomes could be poorer, at least for certain workers.
Based on three studies of moderate methodological quality, we conclude that there is moderate evidence that an exercise regimen in workers suffering from RC tendinopathy is an effective modality in terms of pain reduction, improvement in work-ability, and potential improvement for return-to-work when compared to a control intervention or to a placebo 17,18,25,26) . A statistically significant and clinically important improvement in the work module of the DASH score was shown in the study by Lombardi et al. In the study by Ludewig et al., participants in the exercise group had significantly better outcomes in terms of work-related pain and work-related disability after intervention. Interestingly, in this study, the exercise program was performed at home. In the study by Brox et al., although no statistical testing was performed, more participants returned to work in the exercise group (23% ) than in the placebo laser group (19%). These results are consistent with the results of the systematic review by Kuhn et al. that concluded that exercise is effective for the reduction of pain and function in general adults and that home exercise programs may be as effective as supervised exercises 11) .
When exercise therapy is compared to surgery, there is low to moderate evidence that both interventions are equally effective in workers in terms of pain relief, function, and return-to-work, and this conclusion is supported by two RCTs. In the study by Haahr et al., 53% of the subjects in the exercise group were working compared to 51% in the surgery group at 4-8 years follow-up. However, there was a greater decrease in the proportion of participants with shoulder-related absences from work in the exercise group (23%) than in the surgery group (12%) in the study by Brox et al. 17,18 ) , while none of the treatments showed a clear superiority in terms of pain and function. Regarding the costs of interventions, therapeutic exercises presented lower average costs, which were nearly half the surgical costs. Based on the results of these two RCTs, we can conclude that exercise could be recommended as a modality for workers suffering from RC tendinopathy prior to the surgical option for reduction in pain and improvement in function as well as for returnto-work. These recommendations are consistent with those of another systematic review on the efficacy of surgery for RC tendinopathy in adults, which concluded that there is no significant difference between exercise therapy and surgery as a treatment for adults suffering from a RC tendinopathy 40) .
Based on the studies included in this systematic review, we could not conclude on the optimal exercise program to treat workers suffering from RC tendinopathy. Moreover, the type of exercises in relation to a worker's environment or his or her work demands that is required to promote return-to-work is still unknown. In terms of intensity, the results from one study of low methodological quality showed that the exercise regimen with the higher dosage provided greater pain relief than the lower dosage exercise program, and there was a more important reduction in cost of sick leave in workers for the high-dosage exercise program (59.1%) than the low-dosage exercise regimen (42.3%). However, in terms of function, none of the groups showed statistically significant differences for inter-group comparisons 28,29 ) . In terms of types of exercises, adding proprioceptive exercises to the exercise program did not result in any added benefit compared to range-of-motion and strengthening exercises, according to one study of low methodological quality that included nurses 27) .
At the moment, there is no consensus on the optimal exercise treatment program for adults suffering from RC tendinopathy. Recent systematic reviews recommend that exercises should focus on strengthening the RC muscle and the scapular stabilizing muscles 13,35) .
In terms of treatment setting, one study of low methodological quality compared clinic-based interventions to workplace-based interventions 19) . There was a statistically significant change in favor of the workplace-based intervention for the SPADI score, but this difference was below the minimal clinically important difference 33 ) . However, significantly more participants returned to work in the workplace-based intervention ( 71.7% ) than in the clinic-based intervention (37.5%).
Based on the results of the current systematic review, we can conclude that there is clearly a need for RCTs of higher methodological quality regarding the optimal nature, intensity, and environment of exercise therapy programs for RC tendinopathy to draw firm conclusions on the benefit of a multimodal workplace-based intervention. The evidence concerning the best approach for workers in terms of type and intensity of exercises, as well as the environment in which they are provided, either in the work place, in a clinical setting, or at home, remains scarce 36 ) . This is an area of great interest as many worker programs focus on comprehensive rehabilitation programs that not only include clinical exercises but also work-related functional exercises and psychosocial intervention to address potential work-related stress factors [37][38][39] . It thus remains unclear what kind of intervention is the most effective and cost-effective for workers with RC tendinopathy and if different populations of workers need different approaches.
Three RCTs of low methodological quality compared therapeutic exercises to other interventions. When comparing supervised exercise therapy with radial extracorporeal shock-wave therapy (ECSWT), one RCT of moderate quality concluded that more participants in the exercise group returned to work ( 20.4% ) than in the ECSWT group (13%), but these results were not statistically significant 20) . One study of moderate methodological quality was conducted on postal employees and concluded that participants in both groups were improved in terms of pain and function, but there was a greater improvement in the naturopathic treatment group. However, the exercise program in this study consisted of active, active-assisted, and passive ROM exercises as well as isometric endurance and strength training exercises initially developed to treat patients with cervicobrachialgia, which could not be adequate to treat efficiently patients with RC tendinopathy 41,42) . Also, no outcomes in this study were specific to work 30 ) . Another study evaluated the benefit of adding manual therapy to an exercise program 23,24 ) . Both groups improved significantly, but there were no statistical differences between groups in the SPADI scores or in terms of days and costs of sick leave. Of note, a recent systematic review concluded that manual therapy, when added to an exercise program, could be beneficial in terms of pain and function in the management of adults suffering from RC tendinopathy 43) . There is, therefore, a need for further studies on the benefit of adding manual therapy to an exercise program in the treatment of workers suffering from RC tendinopathy.
In our review, only seven studies used specific workrelated outcomes. Work-related outcomes are often understudied even though authors have stressed that, for workers, these work-related outcomes can differ from pain and function outcomes in the general population 39 ) . Future studies will need to systematically assess workrelated outcomes and health care costs.

Strengths and limitations of the review
A complete literature search was performed by the authors using four databases. Inclusion criteria were specific to ensure that a majority of participants suffered from RC tendinopathy. RCT was the only research design included in the present review, which is the highest form of evidence for clinical trials. The inter-rater agreement was good to excellent for all the items of the risk of bias assessment tool.
Our study has some limitations that arise from the RCTs included in the review, which had small sample sizes and moderate to high risk of bias. Also, because of the heterogeneity of the results, we could not conduct meta-analyses. Some of the studies presented data about the return-to-work rate of workers, but the information was not available in all the trials. Moreover, the authors used non-validated and heterogeneous return-to-work outcomes.

Conclusions
Low to moderate-grade evidence exists that therapeutic exercises provided in a clinical setting are an effective modality to treat workers suffering from RC tendinopathy in terms of pain reduction, improvement in function, and return-to-work. Since exercise therapy is a simple and cost-effective approach to treat RC tendinopathy that seems to favor return-to-work, it should be considered first. However, the optimal intensity and context in which the therapeutic exercise program is provided remain unclear, as does whether other interventions would be useful. Further studies are needed, particularly trials that assess multimodal rehabilitation treatments with specific populations of workers and work-related outcomes to draw firm conclusions on the optimal exercise program to treat workers.

Type of contribution
FD participated in the design, coordination, led the interpretation of results and writing of the manuscript. JB performed the collection of data, statistical analyses, interpretation of results and drafted the manuscript. CED participated in the design, interpretation of results and writing of the manuscript. PF participated in the design, interpretation of results and writing of the manuscript. VL participated in the collection of data, statistical analyses, interpretation of results and drafted the manuscript. JCM participated in the design, interpretation of results and writing of the manuscript. JSR participated in the design, interpretation of results and writing of the manuscript. All authors read and approved the final version of the paper.