van Poppel 1998.

Methods	RCT
Participants	Subjects: 312 workers whose jobs included manual material handling. Workers who had a permanent partial work disability were excluded. Mean age 35.1. 172 subjects with previous LBP, 49 subjects with LBP at baseline.
Interventions	Preventive interventions: 1) Lumbar support (n=83), 6 months. 2) Lumbar support use at work plus education (n=70), 6 months. Control intervention: 3) Education: 5 hrs lifting instructions (n=82) 4) No intervention (n=77)
Outcomes	LBP incidence, sick leave due to back pain; no differences after 6 months.
Notes	A total of 312 workers were randomised of whom 282 were available for the 6‐month follow‐up. Compliance with wearing the lumbar support at least half of the time was 43%.
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Low risk
Allocation concealment?	Low risk	A ‐ Adequate
Blinding? All outcomes ‐ patients?	High risk
Blinding? All outcomes ‐ outcome assessor?	High risk
Incomplete outcome data addressed? All outcomes ‐ drop‐outs?	Low risk
Incomplete outcome data addressed? All outcomes ‐ ITT analysis?	Low risk
Similarity of baseline characteristics?	Low risk
Co‐interventions avoided or similar?	High risk
Compliance acceptable?	High risk	Compliance with wearing the lumbar support at least half of the time was 43%.
Timing outcome assessments similar?	Low risk