Cabak 2017.

Study characteristics
Methods	Study design: RCT Setting: Poland, healthcare Exercise groups: 1 Comparison groups: 1
Participants	Number of participants: 68 (E1 = 22, C1 = 46) Chronic LBP duration: Not specified (not specified) Neurological/radicular symptoms: Not specified Mean age (years): 59 Sex (female): 72%
Interventions	Exercise Group 1 (E1): Physiotherapist teaches exercises movements and recommends 5 minutes of exercise each day at home; type = stretching; duration = 9 weeks; dose = low; design = standardised; delivery = independent with follow‐up; additional intervention = advice/education & psychological therapy & manual therapy & anti‐inflammatory/analgesics Comparison Group 1 (C1): Usual care/no treatment (waiting‐list group)
Outcomes	Core outcomes reported: Pain (Visual Analogue Scale); function (Roland‐Morris Disability Questionnaire); HRQoL (36‐Item Short Form Survey (Polish)) Follow‐up time periods available for syntheses: 9 weeks (short)
Notes	Conflicts of interest: Not reported Funding source: Not reported Other: SDs imputed
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Participants were "randomly assigned" to groups.
Allocation concealment (selection bias)	High risk	No information on treatment allocation concealment.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	1. Patients could not be blinded due to the nature of the treatment groups; 2. Unlikely that lack of patient blinding altered the intended intervention, as the treatments were entirely in control of care providers.
Blinding of care provider (performance bias)	Low risk	1. Care providers could not be blinded to allocation due to the nature of the treatments; 2. Unlikely that lack of care provider blinding altered intended intervention, as care providers had very little contact with control group.
Blinding of outcome assessment (detection bias) All outcomes	High risk	1. Outcome assessors in this study were patients, who could not be blinded due to the nature of the interventions; 2. Pain and functional questionnaires are subjective, and responses could be altered by awareness of intervention; 3. Reasonably likely that patients saw the experimental group as "better" than the control group (no intervention at all); all outcomes favoured the experimental group.
Incomplete outcome data (attrition bias) All outcomes	High risk	1. No description of dropout rate; 2. No evidence of missing data, much less of any biased analyses; 3. Impossible to guess whether an outcome value's missingness depended on its true value, as there was no information as to whether or not there was any missing data in the first place; 4. No evidence as to whether or not there was any missing data in each group; 5. It was impossible to guess whether an outcome value's missingness depended on its true value, as there was no information as to whether or not there was any missing data in the first place.
Participants analysed in group allocated (attrition bias)	Low risk	1. Appeared that all patients were analysed according to the treatment to which they were randomised.
Selective reporting (reporting bias)	Low risk	1. No linked protocol or statistical analysis plan found; within this publication all outcomes and analyses were fully reported.
Groups similar at baseline (selection bias)	High risk	While age and sex were reported and were similar between treatment groups, there was no report of baseline body mass index, pain, function or duration of symptoms.
Co‐interventions avoided or similar (performance bias)	Low risk	Intervention group could not use any additional therapies or medical consultations during the study period; control patients received usual care without any limitations.
Compliance acceptable in all groups (performance bias)	Low risk	It appeared that all participants in the intervention group attended all three mandated physiotherapy sessions (100% compliance).
Timing of outcome assessment similar in all groups (detection bias)	Low risk	1. All patients were assessed identically on outcomes, regardless of treatment group; 2. Visual Analogue Scale (for pain) and Roland‐Morris Disability Questionnaire (for function) are well‐validated tools in the low back pain context.
Other bias	Low risk	Appeared free from other sources of bias