| Study characteristics |
| Methods |
Study design: RCT
Setting: Netherlands, occupational
Exercise groups: 2
Comparison groups: 1 |
| Participants |
Number of participants: 65 (E1 = 23, E2 = 21, C1 = 21)
Chronic LBP duration: Not specified (long)
Neurological/radicular symptoms: Not specified
Mean age (years): 42
Sex (female): 0% |
| Interventions |
Exercise Group 1 (E1): Progressive resistance exercises for the isolated lumbar extensor muscle groups (load set at 50% of maximal isometric extension strength of participant at baseline); type = strengthening; duration = 8 weeks; dose = low; design = partially individualised; delivery = individual; additional intervention = none
Exercise Group 2 (E2): Nonprogressive low‐intensity resistance exercise programme (load set at a maximum of 20% of the maximal isometric extension strength of participant at baseline); type = strengthening; duration = 8 weeks; dose = low; design = partially individualised; delivery = individual; additional intervention = none
Comparison Group 1 (C1): Usual care/no treatment (waiting‐list group) |
| Outcomes |
Core outcomes reported: Function (Roland‐Morris Disability Questionnaire); HRQoL (36‐Item Short Form Survey)
Follow‐up time periods available for syntheses: 8 weeks (short) |
| Notes |
Conflicts of interest: Not reported
Funding source: Not reported
Other: None |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Random sequence generation (selection bias) |
Low risk |
Concealed randomisation was performed by means of a computer‐generated table of random numbers with a block size of six. |
| Allocation concealment (selection bias) |
Low risk |
Randomised, three‐arm trial with concealed allocation, assessor blinding |
| Blinding of participants and personnel (performance bias)
All outcomes |
High risk |
Assumed not possible |
| Blinding of care provider (performance bias) |
High risk |
Assumed not possible |
| Blinding of outcome assessment (detection bias)
All outcomes |
Low risk |
Measurement of outcomes was carried out by the principal investigator or research assistants who were not aware of group allocation. |
| Incomplete outcome data (attrition bias)
All outcomes |
Low risk |
Six participants withdrew during the intervention period. |
| Participants analysed in group allocated (attrition bias) |
Unclear risk |
All analyses were carried out according to the intention‐to‐treat principle. |
| Selective reporting (reporting bias) |
Low risk |
Support for judgement was not available. |
| Groups similar at baseline (selection bias) |
Low risk |
There were only minor differences in demographic characteristics. |
| Co‐interventions avoided or similar (performance bias) |
Low risk |
No co‐interventions were reported during both the intervention and the waiting‐list period. |
| Compliance acceptable in all groups (performance bias) |
Low risk |
A total of 31 participants received the high‐intensity strengthening programme. |
| Timing of outcome assessment similar in all groups (detection bias) |
Low risk |
Support for judgement was not available. |
