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OBJECTIVE	This study investigated long-term effects and implementation processes of workplace strength training for musculoskeletal disorders .
METHODS	333 and 140 laboratory technicians from private and public sector companies , respectively , replied to a 3-year follow-up questionnaire subsequent to a 1-year randomized controlled trial ( RCT ) with high-intensity strength training for prevention and treatment of neck , shoulder , and arm pain .
METHODS	Being a natural experiment , the two participating companies implemented and modified the initial training program in different ways during the subsequent 2 years after the RCT .
RESULTS	At 3-year follow-up the pain reduction in neck , shoulder , elbow , and wrist achieved during the first year was largely maintained at both companies .
RESULTS	However , the private sector company was rated significantly better than the public sector company in ( 1 ) training adherence , ( 2 ) training culture , that is , relatively more employees trained at the workplace and with colleagues , ( 3 ) self-reported health changes , and ( 4 ) prevention of neck and wrist pain development among initially pain-free employees .
CONCLUSIONS	This natural experiment shows that strength training can be implemented successfully at different companies during working hours on a long-term basis with lasting effects on pain in neck , shoulder , and arm .

