Although pain-related fear and catastrophizing are predictors of disability in low back pain (LBP), their relationship with guarded motor behavior is unclear. The aim of this meta-analysis was to determine the relationship between pain-related threat (via pain-related fear and catastrophizing) and motor behavior during functional tasks in adults with LBP. This review followed PRISMA guidelines. MEDLINE, Embase, PsychINFO, and CINAHL databases were searched to April 2021. Included studies measured the association between pain-related fear or pain catastrophizing and motor behavior (spinal range of motion, trunk coordination and variability, muscle activity) during movement in adults with nonspecific LBP. Studies were excluded if participants were postsurgery or diagnosed with specific LBP. Two independent reviewers extracted all data. The Newcastle-Ottawa Scale was used to assess for risk of bias. Correlation coefficients were pooled using the random-effects model. Reduced spinal range of motion during flexion tasks was weakly related to pain-related fear (15 studies, r = −0.21, 95% CI = −0.31 to −0.11) and pain catastrophizing (7 studies, r = −0.24, 95% CI = −0.38 to −0.087). Pain-related fear was unrelated to spinal extension (3 studies, r = −0.16, 95% CI = −0.33 to 0.026). Greater trunk extensor muscle activity during bending was moderately related to pain-related fear (2 studies, r = −0.40, 95% CI = −0.55 to −0.23). Pain catastrophizing, but not fear, was related to higher trunk activity during gait (2 studies, r = 0.25, 95% CI = 0.063 to 0.42). Methodological differences and missing data limited robust syntheses of studies examining muscle activity, so these findings should be interpreted carefully. This study found a weak to moderate relationship between pain-related threat and guarded motor behavior during flexion-based tasks, but not consistently during other movements. These findings provide a jumping-off point for future clinical research to explore the advantages of integrated treatment strategies that target both psychological and motor behavior processes compared with traditional approaches.

Background: Trunk co‐contraction during lifting may reflect a guarded motor response to a threatening task. This work estimated the impact of pain catastrophizing on trunk co‐contraction during lifting, in people with and without low back pain.Methods: Adults with high pain catastrophizing (back pain: n = 29, healthy: n = 7) and low pain catastrophizing (back pain: n = 20, healthy: n = 11), performed 10 repetitions of a lifting task. Electromyography data of rectus abdominis, erector spinae and external oblique muscles were collected, bilaterally. Co‐contraction indices were determined for rectus abdominis/erector spinae and external oblique/erector spinae pairings, bilaterally. Pain catastrophizing was measured using the pain catastrophizing scale and task‐specific fear using the Photograph series of daily activities scale. Three‐way mixed ANOVAs tested the effects of group (back pain vs. healthy), pain catastrophizing (high vs. low), lifting phase (lifting vs. replacing) and their interactions.Results: There were no main effects of pain catastrophizing, lifting phase, nor any interactions (p > 0.05). Group effects revealed greater co‐contraction for bilateral erector spinae/rectus abdominis pairings (but not erector spinae‐external oblique pairings) in people with back pain, compared to healthy participants, independent of pain catastrophizing and lifting phase (p < 0.05). Spearman correlations associated greater task‐specific fear and greater erector spinae‐left external oblique co‐contraction, only in people with back pain (p < 0.05).Conclusions: Greater co‐contraction in the back pain group occurred independent of pain catastrophizing, as measured with a general questionnaire. A task‐specific measure of threat may be more sensitive to detecting relationships between threat and co‐contraction.Significance Statement: This work contributes evidence that people with back pain commonly exhibit trunk co‐contraction when lifting. The lack of a relationship between pain catastrophizing and trunk co‐contraction, however, challenges evidence linking psychological factors and guarded motor behaviour in this group. Together, this suggests that other factors may be stronger determinants of co‐contraction in people with LBP or that a general construct like pain catastrophizing may not accurately represent this relationship.