en Occupational Health Original Article <div style="text-align: justify;"><span style="font-family:Arial;"><span style="font-size:11pt"><span style="line-height:150%"><b><span style="font-size:10.0pt"><span style="line-height:150%"><span style="color:black">Background: </span></span></span></b><span style="font-size:10.0pt"><span style="line-height:150%"><span style="color:black">Cumulative effects of biomechanical risk factors on rotator cuff tendinopathy have not yet been determined. Accordingly, this study aimed to investigate cumulative effects of biomechanical risk factors on rotator cuff tendinopathy among workers.</span></span></span></span></span><br> <span style="font-size:11pt"><span style="line-height:150%"><b><span style="font-size:10.0pt"><span style="line-height:150%"><span style="color:black">Materials & Methods:</span></span></span></b><span style="font-size:10.0pt"><span style="line-height:150%"><span style="color:black"> This descriptive study was conducted on 470 patients suspected of rotator cuff tendinopathy, who referred to the radiology department of Rasool-e-Akram Hospital in Tehran, Iran (July 2018-March 2019). To this end, ergonomic risk factors, including excessive hand raising, repetitive tasks, upper arm flexion, grip force, awkward posture, vibration, abduction, and rotation were evaluated. The subjects were divided into four categories, according to the number of affecting risk factors. Next, univariate and multivariate analyses were performed to identify predictors of rotator cuff tendinopathy. The study data were analyzed by SPSS V24.0. </span></span></span></span></span><br> <span style="font-size:11pt"><span style="line-height:150%"><b><span style="font-size:10.0pt"><span style="line-height:150%"><span style="color:black">Results:</span></span></span></b><span style="font-size:10.0pt"><span style="line-height:150%"><span style="color:black"> Risk factors, such as excessive hand raising, repetitive tasks, upper arm flexion, and awkward posture had a significant association with the frequency of rotator cuff tendinopathy (p < 0.05). Our study showed that shoulder tendinopathy had a statistically significant association with having at least one affecting risk factor (OR=3.96 95%CI: 2.26-6.96), two affecting risk factors (OR=6.82 95%CI: 4.13-11.26), three affecting risk factors (OR=10.25 95%CI: 4.35-24.14), and four affecting risk factors (OR=12.61 95%CI: 1.69-93.63).</span></span></span></span></span><br> <span style="font-size:11pt"><span style="line-height:150%"><b><span style="font-size:10.0pt"><span style="line-height:150%"><span style="color:black">Conclusion:</span></span></span></b><span style="font-size:10.0pt"><span style="line-height:150%"><span style="color:black"> The existence of more than one mechanical risk factor in the workplace is associated with a greater increase in the possibility of rotator cuff tendinopathy. In most workplaces, there is usually more than one mechanical risk factor, so it is necessary to pay attention to cumulative effects of all of them.</span></span></span></span></span></span><br> &nbsp;</div> Shoulder Pain,Posture,Risk Factors,Workplace,Workers, 223 230 http://johe.rums.ac.ir/browse.php?a_code=A-10-489-1&slc_lang=en&sid=1 Saber Mohammadi mohamadi.s@iums.ac.ir 22400319475328460011401 22400319475328460011401 No Professor, Dept. of Occupational Medicine, School of Medicine, Iran University of Medical Sciences, Tehran, Iran. Iran University of Medical Sciences Fatemeh Shidfar tshidfar@yahoo.com 22400319475328460011402 22400319475328460011402 No MD, Dept. of Occupational Medicine, School of Medicine, Iran University of Medical Sciences, Tehran, Iran. Iran University of Medical Sciences Seyed Reza Saadat Mostafavi saadat.sr@iums.ac.ir 22400319475328460011403 22400319475328460011403 No Assistant Prof., Dept. of Radiology, School of Medicine, Hazrat-e Rasool General Hospital, Iran University of Medical Sciences, Tehran, Iran. Iran University of Medical Sciences Reza Salehi rez_salehi55@yahoo.com 22400319475328460011404 22400319475328460011404 No MD, Dept. of Radiology, Fayazbaksh Hospital, Tehran, Iran. Fayazbaksh Hospital, Tehran Afshin Zarafshar afshin.zarafshar@gmail.com 22400319475328460011405 22400319475328460011405 No MD, Dept. Occupational Medicine, School of Medicine, Iran University of Medical Sciences, Tehran, Iran. Iran University of Medical Sciences Elaheh Kabir Mokamelkhah dr_kabir.@yahoo.com 22400319475328460011406 22400319475328460011406 Yes Associated Prof., Occupational Medicine Research Center (OMRC), Dept. of Occupational Medicine, School of Medicine, Iran University of Medical Sciences, Tehran, Iran. Iran University of Medical Sciences