2.1 Study criteria
The studies were included if 1) they are published in the English
language; 2) they are randomised control trials (RCTs) or a secondary
analysis of RCTs; 3) report data from participants aged between 18 and
70 years; 4) only examine people with CLBP (≥ 12 weeks) or have a
subgroup for people with CLBP; 5) have at least one therapeutic
intervention which is not medication, surgery or an injection
intervention, with separate data for this intervention; 6) measure PEs
prior to the intervention; 7) examine the association between any type
of PEs and the outcomes; and 8) have at least one of the outcomes of
pain intensity, physical status and HRQOL.
The studies were excluded if 1) they have participants with other health
issues rather than LBP; 2) are a secondary analysis of an RCT study that
has already been included in this review; 3) have participants with back
pain without specifying its region to the lumber region; and 4) do not
state clearly that all participants (or 85% at least) had LBP.