Table 1 Methodological quality criteria

		Score
Internal validity (IV) criteria
A	Method of randomisation adequate (eg, random number table)?	1
B	Treatment allocation concealed?	1
C	Groups similar at baseline regarding age, gender, history of back pain, area of work, pregnancy, nurse grade and baseline measures?	1
D	Co-interventions avoided or similar?	1
E	i) Drop-out/withdrawal individuals adequately described?	0.5
E	ii) Drop-out rate acceptable (<20% for short-term and <30% for long-term follow-up)?	0.5
F	Intention to treat method of analysis (irrespective of compliance, change in group status)?	1
IV score		6

Descriptive quality (DQ) criteria
G	Eligibility criteria specified?	1
H	Index and control interventions explicitly described?	1
I	i) Short-term follow-up measurement (⩽3 months post initiation of intervention)?	0.5
I	ii) Long-term follow-up measurement (>3 months post initiation of intervention)?	0.5
J	Sample size for each group described at randomisation and all important outcome assessments?	1
K	Point estimates and measures of variability presented for primary and secondary outcome measures?	1
L	i) Sampling method adequate?	0.5
L	ii) Participation rate adequate (>80%)?	0.5
DQ score		6

Total score (IV+DQ scores)		12