Morken 2002a

Methods	The study is designed as a cluster‐randomised controlled trial consisting of three intervention groups and two control groups. One control group (group B) was not randomised. The study was performed for a period of 16 months, from 1998‐2000 in eight aluminium plants in Norway.
Participants	For intervention group 1, 2, 3 and control group A, the inclusion criterion was workers who could shift groups of operators in the production line. Exclusion criterion was other functions/types of jobs. The excluded participants constituted control group B. All employees in the eight aluminium plants were recruited by participating in the baseline survey, where 92% (N=5654) filled out the questionnaire satisfactorily. Among them 67% were operators, 20% were office workers and 8% were managers. Mean age was 40 years with a range from 18‐69 years. Eighty‐six per cent were men and 14% were women. Mean duration of employment at the plant was 16 years. Of those completing the post intervention questionnaire (N=5143, 94% of all workers), 3321 participants were so‐called matched individuals with completed questionnaire in 1998 and 2000. Of those matched participants, 837 were operators in the production line which were randomised on group level to three intervention groups and control group A. The rest (N= 1344) constituted control group B. A number of 414 participants received the intervention. In intervention group 1 operators and supervisors participated (20 shift groups, N=132). In intervention group 2 operators only participated (18 shift groups, N=135). In intervention group 3, two groups of supervisors and managers and ten groups of operators participated (N= 147). A total number of 423 workers from the production line were in control group A. At 16 months follow‐up there were 2181 participants left. The production line was chosen for intervention due to high prevalence of MSD, well‐known risk factors and similar and comparable job content. Work in the production line was physically demanding. At baseline 94 had experienced pain in one of more of body parts the last 12 months (range 87‐95%). The prevalence of participants with neck pain was 68%.
Interventions	The intervention groups:The intervention was developed specifically for the needs of the aluminium industry. The intervention was similar in the three intervention groups. The reason for three groups receiving the same intervention was to examine the potential differing results according to who participated in the process; the operators and their supervisors (group 1), the operators only (group 2) or the managers and supervisors only (group 3). The company physiotherapists were the providers of the intervention, which included ten meetings aimed at coping with MSD at the workplace. Important components were learning by conversation and acting within the context of the environment. Each session had different topics. They lasted 2 hours; 1 hour and 15 minutes of didactics about knowledge from the topics and 45 minutes of discussion about solutions of work environment problems. Changes in the working environment were implemented after the sessions. The control groups: The control groups did not receive any special attention or information.
Outcomes	Measurements were made at baseline (1998) and 16 months after, with the following three main outcomes: Musculoskeletal symptoms (included musculoskeletal discomfort): The prevalence of musculoskeletal symptoms was assessed using Standard Nordic Questionnaire (SNQ) with modifications. Musculoskeletal symptoms were described as pain, discomfort or reduced mobility. The body parts examined were neck, shoulders, elbows, hands, upper neck, lower back, hips, knees and feet. Furthermore,  the body part “head” was specially added to the bodily items. A five‐point scale (from 'never' to 'very often',  instead of 'yes' and 'no') was used. Coping with musculoskeletal symptoms: An index of eleven coping strategy items was used. The questions concerned what the participants did when they experienced troublesome bodily pain or stiffness. The index had a three‐point scale ranging from 1 'seldom or never' to 3 'often'. The eleven scores were summarised to one score. Psychosocial work factors: A job content questionnaire (JCQ) was used to test psychosocial work factors such as job demands, job control and social support. It was a short Swedish version of the questionnaire, which was translated to Norwegian. The questionnaire consisted of 17 questions scored on a four‐point scale.
Notes	The project was initiated by the involved companies and funded by them. The planners, providers and assessors were having the same employer as the participants in the study. Additional information about the trial was found in two other publications (Morken 2000; Morken 2002b).  First author was contacted for missing information and responded.
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Low risk	Quote: “All the shift groups were randomised at the group level into three types of intervention groups or control group A". According to first author randomisation was performed by drawing of lots, which is an adequate method of randomisation. However, control group B was not randomised. Despite this we score 'yes' since we are disregarding control group B in further analyses.
Allocation concealment?	Low risk	According to author the allocation to the different groups was performed prior to the intervention by researchers who did not know the workers in the aluminium plants. The researchers had no knowledge of the health condition or work conditions in the different shifts. In other words, they had no possibility to lead the shifts into groups that "fitted". Based on information from author, even if some details are lacking, we choose to consider the allocation adequately concealed.
Blinding? All outcomes ‐ participants?	High risk	It was not possible to blind the intervention to the participants.
Blinding? All outcomes ‐ providers?	High risk	Companies' physiotherapists, planned the study, developed the program, and provided the intervention. Hence, the personnel were not blinded.
Blinding? All outcomes ‐ outcome assessors?	High risk	Quote: “Physiotherapists from the occupational health services distributed and collected the questionnaires in special meetings at the plants”.                           Outcome assessors were most likely not blinded.
Incomplete outcome data addressed? All outcomes ‐ drop‐outs?	Low risk	Quote: “Many of the respondents were lost due to the matching procedure when matching the data of the pre‐intervention and the post‐intervention survey”.                                  A number of 804 participants were lost to follow‐up, of which 713 were lost due problems with the matching procedure. This represents a drop‐out rate of 32‐ 39%, which is too high. However, additional analyses demonstrated that the lack of data from unmatched participants did not introduce any major bias. Hence, the score is 'yes'.
Incomplete outcome data addressed? All outcomes ‐ ITT analysis?	Low risk	Information provided by author confirms that all randomised participants were analysed in the group to which they were allocated.
Free of selective reporting?	Low risk	The results are reported and the findings were not in favour of the intervention. Based on an overall impression we score 'yes' here.
Similarity of baseline characteristics?	Low risk	Control group B had a significant higher control and coping at baseline. They also had higher age, and more years of experience. However, since we are disregarding control group B we score 'yes' here.
Co‐interventions avoided or similar?	Low risk	Possible co‐interventions were similar in index groups and control groups.
Compliance acceptable?	Low risk	Quote: ”The participation in the session for each groups varied from 70% to 100%”. Compliance was acceptable.
Timing outcome assessments similar?	Low risk	Author has confirmed that the timing of the outcome assessment was similar in all groups.