Gerr 2005

Methods	RCT. Randomisation occurred following evaluation of workplace and ergonomic variables. The use of a random number table assured that each subject entering the study had an equal probability of being assigned to each of the 3 groups. Randomisation was done in blocks of 6 to assure equal numbers of participants in each of the study groups
Participants	A person eligible for inclusion in this study was: a newly hired worker who: anticipated using a single computer workstation for 15 hours or more per week and anticipated using a computer workstation for at least as many hours per week as in his/her previous job working at insurance and financial companies, food product producers, and universities in metropolitan Atlanta, GA, US who had reported experiencing arm or hand symptoms during the week prior to intervention Of the 447 eligible for health screening, a total of 379 individuals were eligible for inclusion into 1 or both cohorts (those who did not report experiencing arm or hand pain and neck or shoulder pain during the week prior to the study. 375 people were randomised into the arm and hand cohort and 356 were randomised into the neck and shoulder cohort
Interventions	The study compared alternate intervention, conventional intervention, and no intervention A study staff member reconfigured the subject's workstation if the subject was randomly assigned to either the alternative or conventional interventions (groups A or B) Verbal and written instructions describing the desired posture were provided to all group A and B participants At 3 days and 1 week after the intervention, study staff returned to the participant's workplace to check on continued maintenance of the posture. If the posture had changed from the intervention, additional workstation changes were made and additional instruction given Group A: alternate intervention: the workstation was adjusted according to the following configuration: Head tilt angle ≤ 3º (head tilt angle is defined as the angle formed between a line defined by the tragion of the ear and the infraorbitale of the eye and the horizon. To clarify the meaning of head tilt angle values, increasing neck extension results in larger values for head tilt angle and increasing neck flexion results in smaller (including negative) values) head rotation < 15º in either direction (L/R) J key at least 2 cm below elbow height keyboard inner elbow angle of > 120º J key at least 12.5 cm from edge of desk or work surface keyboard wrist ulnar deviation of 0º to 220º (i.e. up to 20º radial deviation) armrest present keyboard wrist rest present mouse wrist ulnar deviation of 25º to 5º mouse wrist extension of 20º to 30º mouse next to keyboard high‐quality chair present. Characteristics of high‐quality chair: easily (pneumatically) adjustable for height, adjustable height backrest, full contoured backrest, adjustable seat pan angle, round waterfall seat pan edge, 5‐legged base Group B: conventional intervention: the workstation was adjusted according to the following configuration: eye height level with top of monitor screen head rotation < 15º in either direction (L/R) J key at least 3 cm above elbow height keyboard shoulder flexion of 210º to 20º keyboard shoulder abduction of 210º to 20º keyboard inner elbow angle of 80º to 100º keyboard wrist ulnar deviation of 210º to 10º keyboard wrist extension of 210º to 10º keyboard wrist rest present mouse wrist ulnar deviation of 210º to 10º mouse wrist extension of 210º to 10º armrest present high‐quality chair present Group C: no intervention: instructed to continue keying in their usual posture and no changes were made to their workstations
Outcomes	Primary outcome: Time to event: symptoms of pain or discomfort ‐ participants were classified as having experienced musculoskeletal symptoms if they (1) reported musculoskeletal discomfort on any day of the week with a severity of ≥ 6 on the 0 to 10 VAS or (2) reported musculoskeletal discomfort on any day of the week for which they took medication (over‐the‐counter or prescription). Study participants were followed for each outcome separately until they became symptomatic (censored). Development of a symptom in 1 anatomic area did not stop the collection of data for the other anatomic area. 2 separate, overlapping cohorts were then defined to examine separately the risks of neck or shoulder symptoms and the risks of arm or hand symptoms Secondary outcome: Compliance: using a standard checklist, each workstation was evaluated for presence of specific items (e.g. mouse or other pointing device), and the adjustability of specific equipment. Following completion of the checklist, dimensional and angular measurements (e.g. seated elbow height, table surface height, keyboard inner elbow angle) were recorded
Notes	Gerr 2005 consists of 2 overlapping cohorts. The effect of the intervention was assessed as arm/hand and neck/shoulder pain
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	The use of a random number table assured that each subject entering the study had an equal probability of being assigned to each of the 3 groups. Randomisation was done in blocks of 6 to assure equal numbers of participants in each of the study groups
Allocation concealment (selection bias)	Unclear risk	No information on allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	High risk	There was no mention of blinding and the methods of intervention consisted of 2 distinct workstation and postural interventions
Blinding of outcome assessment (detection bias) Musculoskeletal disorders	High risk	Outcomes consisted of subjective symptoms measured with a check‐list
Incomplete outcome data (attrition bias) All outcomes	Low risk	Participants contributed data to their assigned intervention group regardless of compliance (i.e. data were analysed by ITT)
Selective reporting (reporting bias)	Low risk	Key findings: there were no significant differences in the incidence of musculoskeletal symptoms among the 3 intervention groups
Other bias	High risk	Large number of drop‐outs. "There were a large number of drop‐out/lost to follow‐up in arm/hand cohort – 147 (41% of those followed) were lost during the six month follow up period … No differences were observed in dropout rates (i.e. incomplete follow‐up) across the three intervention groups". Although the drop‐out rates were similar across the 3 randomised groups, there were a large number of drops‐outs in each group (36 to 42 across all 6 groups) for which the authors did not provide a reason