Background Psychological features have been related to trunk muscle activation patterns in low back pain (LBP). properties (trunk stiffness and damping). Mechanical properties were also compared with t-tests between groups based on stratification according to high/low scores based on median values TAK-375 for each psychological measure. Results Fear of movement (TSK) was positively associated with trunk stiffness (but not damping) in response to a forward perturbation (r2?=?0.33, P?=?0.03), but not backward perturbation (r2?=?0.22, P?=?0.09). Other pain-related fear constructs (PHODA-SeV, FABQ, PCS) were not associated with trunk stiffness or damping. Trunk stiffness was greater for individuals with high kinesiophobia (TSK) for forward (P?=?0.03) perturbations, and greater with forward perturbation for those with high fear avoidance scores (FABQ-W, P?=?0.01). Conclusions Fear of movement is usually positively (but weakly) associated with trunk stiffness. This provides preliminary support an conversation between biological and psychological features of LBP, suggesting this condition may be best understood if these domains are not considered in isolation. Introduction People with low back pain (LBP) have changes in muscle mass activation [1], [2], trunk mechanical properties [3], [4]) and fear of pain [5], [6]. Although biological and psychological domains are often discussed in isolation, they are likely interdependent. Consistent with this view, studies have shown that adaptation in muscle mass activation depends on attitudes about pain [7], and compromise of the expected relaxation of the lumbar muscle tissue at trunk flexion end range in people with LBP correlates with high fear avoidance behaviour [8]. Although it is usually assumed changes in trunk muscle mass activation relates to differences in trunk mechanical properties, the association between variance in psychological presentation and trunk mechanical behaviour has not been tested. A relationship between psychological and mechanical features would support contemporary neurophysiology and psychology pain models, for example, the prediction of pain/threat of injury causes the body to protect the painful part in an effort to reduce pain [9], the fear-avoidance model [10], [11], and the diathesis-stress pain theory [12] (i.e., behaviours which provide short-term relief can have detrimental long-term effects if the behaviour RECA remains unchanged [13]). We considered simultaneous investigation of biological and psychological systems could help to better understand this relationship between mechanical and behavioural domains. Investigation of how biological and psychological features interact is usually of relevance because they both have the potential to influence the presentation and management of LBP. Motor control (i.e., trunk stiffness, relative tissue flexibility, preferred movement strategies) and psychological factors (i.e., emotions, cognitions, behaviours) are both likely to influence motor output and alter trunk mechanical behaviour. Depending upon the robustness of motor and psychological systems, it is probable the relationship is usually bi-directional in nature. Optimal trunk mechanical overall performance will vary depending upon the required task, and if a person with LBP cannot efficiently alter their mechanical response, it may have unfavorable long-term biopsychosocial effects (i.e., increased trunk TAK-375 load, reduced movement variability, reinforcement of maladaptive pain behaviour). Several psychological features have been explored in relation to LBP, most notably sizes related to the fear-avoidance model [14]. The three aspects of this model are fear of movement/re-injury, pain catastrophizing [15], and avoidance behaviour, all of which could relate to changes in trunk motor control. Questionnaires to assess these components have been developed [16]C[19]. There has also been a focus on distress [20], [21]. It remains unknown which psychological features, if any, are related to trunk mechanical properties. In this study we aimed to test the hypothesis that higher kinesiophobia relates to greater protection of the spine (increased trunk stiffness) by exploring TAK-375 the relationship between trunk mechanical properties and other aspects of the fear-avoidance model (pain catastrophizing thoughts, avoidance behaviour) as well as a component of the distress model (depressive disorder). Methods Participants Nineteen participants with LBP (6 male, 13 female; mean body mass index (BMI) 23.6 (SD 3.8); imply age 43 (range 26C65 years)) were recruited with the objective to include those with both high and low fear of pain. Participants were included if they scored at least a 10 out of 100 around the Quebec Back Pain Disability Level (QBPDS), reported a pain intensity of at least 1/10 at the time of participant screening (Numeric Pain Rating Level, NPRS), and a BMI of 31. Exclusion criteria were a history of malignancy, unexplained weight loss >4.5 kg in the past 6 months, neurologic disease, severe spinal structural deformity (e.g., >8 mm rib hump), loss of bowel or bladder control, major changes in walking balance or strength, numbness or altered sensation in the groin region, respiratory disease, hip or knee medical procedures or currently experienced a hip or knee injury, use of a walking aide, numbness in their lower extremities, or pregnancy. Participants were recruited via university or college and city newspaper advertisements. The Institutional Medical Ethics Committee at the University of.