Background and Aim of Study. Despite several hundred RCTs of exercise for persistent non-specific low back pain (NSLBP), the treatment targets of exercise are unclear. In a systematic review we observed 30 direct and indirect treatment targets of exercise described across 23 RCTs for persistent NSLBP. Since not all treatment targets and outcomes can be assessed in all RCTs, it is therefore important to prioritise these treatment targets through consensus from key stakeholders. These consensus workshops aimed to agree treatment targets for the use of exercise interventions in randomised controlled trials (RCTs) in persistent NSLBP using nominal group workshop (NGW) methodology. Methods and Results. The first UK workshop included people who had experience of exercise to manage their persistent NSLBP, clinicians who prescribe exercise for persistent NSLBP, and researchers who design exercise interventions tested in RCTs. The second workshop included participants attending an international back and neck pain research workshop. Twelve participants took part in the UK NGW and fifteen took part in the final ranking of the exercise treatment targets. In addition to the original list of 30 treatment targets, a further 26 ideas were generated. After grouping and voting, 18 treatment targets were prioritised. The top five ranked targets of exercise interventions for persistent NSLBP were: pain reduction, improvement in function, reduction of fear of movement, encouragement of normal movement and improvement of mobility. The results of the international NGW will also be presented. Conclusion. Future RCTs of exercise should consider more consistent assessment of these treatment targets. Sources of Funding: This PhD is funded by the Research Institute for Primary Care and Health Sciences, Keele University. Prof NE Foster is a UK National Institute for Health Research Senior Investigator, and was supported by a UK National Institute for Health Research Professorship (NIHR-RP-011-015). The views expressed in this publication are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health. Conflicts of Interest: No conflicts of interest

Background. Complex interventions, such as exercise for LBP, often have many treatment targets. Matching a primary outcome to the target(s) of exercise interventions may provide greater standardized mean differences (SMDs) than using an unmatched primary outcome. We aimed to explore whether the conclusions of exercise trials for LBP might differ with i) improved matching of outcomes to treatment targets and ii) the use of composite outcome measures. Methods and Results. We investigated i) matching in five trials (n=1033) that used an unmatched primary outcome but included some of their matched outcomes as secondary outcomes; ii) composite outcomes in four trials (n=864). The composite consisted of standardised averaged matched outcomes. All analyses replicated the primary outcome analysis, applied to the matched or composite outcome in each dataset. When not possible, SMDs were calculated for the primary and matched outcomes. i) Of five trials, three had greater SMDs and increased statistical significance with matched outcomes (pooled effect SMD 0.35 (95% CI 0.16, 0.54), p=0.0003) compared to an unmatched primary outcome (pooled effect SMD 0.13 (95% CI 0.04, 0.23) p=0.007). ii) Of four composite outcomes: two matched trials had greater SMDs and improved statistical precision in the primary outcome than the composite outcome; two unmatched trials had greater SMDs and improved statistical precision in the composite compared to the primary outcome. Conclusion. Using an outcome that matches exercise targets in LBP trials appears to produce greater SMDs than an unmatched primary outcome. Future trials should consider primary outcome selection aligned with exercise treatment targets. Sources of Funding: L Wood's PhD is funded by the Research Institute for Primary Care and Health Sciences, Keele University. Prof NE Foster is a UK National Institute for Health Research Senior Investigator, and was supported by a UK National Institute for Health Research Professorship (NIHR-RP-011-015). The views expressed in this publication are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health. Conflicts of interest: No conflicts of interest