Introduction 1 3 4 5 6 7 8 5 9 8 r r 8 10 11 8 10 11 12 6 r r 6 r 12 Aim of this study was to further analyze the relationships between pain intensity and pain-related fear on the one hand, and avoidance behaviors on the other hand. Two studies were performed with separate samples of patients with CLBP. Pain related fears were operationally defined as the score on the TSK in study 1, and the Fear Avoidance Beliefs Questionnaire (FABQ) in study 2. Avoidance behavior was in both studies operationally defined as the unwillingness to engage in high intensity performance levels of three different FCE tests: high intensity lifting, prolonged standing in a forward bend position, and fast repetitive bending at the waist. Non-significant or weak relationships were considered falsifications of the hypotheses that pain and pain-related fears would have clinically relevant impact on FCE performances in patients with CLBP. Materials and methods Patients 13 Procedures 7 8 14 15 Measures 14 14 16 8 8 8 10 15 17 18 19 20 21 22 24 25 22 22 26 27 Analysis 28 Results 1 Table 1 Age, pain intensity, self-reported disability, pain related fear (TSK or FABQ), and performance variables of 2 samples of patients with chronic low back pain  n n  n n n n  Mean (SD) Mean (SD) Mean (SD) Mean (SD) Age (years) 37.8 (9.0) 37.8 (8.8) 40.4(8.6) 35.6 (8.3) Pain intensity (NRS; 0–10) 4.7 (2.3) 5.0 (1.6) 4.5 (2.4) 4.9 (2.2) Self-reported disability (RMDQ; 0–24) 12.5 (4.4) 12.4 (4.7) 11.6 (4.4) 11.2 (5.9) TSK (17–68) 37.5 (5.3) 36.0 (5.6) N/A N/A FABQ activity scale (0–24) N/A N/A 13.4 (4.1) 13.2 (5.6) FABQ work scale (0–36) N/A N/A 19.3 (9.5) 15.1 (11.6) * 31.7 (14.7) 18.9 (8.1) 32.3 (3.8) 20.5 (6.3) Lifting maximum heart rate (BPM) 126.7 (15.8) 129.7 (23.5) 128.2 (14.5) 128.8 (19.3) Static forward bend (sec) 187.4 (148.9) 230.6 (146.3) 188.0 (115.8) 237.3 (154.8) Dynamic forward bend (sec/rep) 2.8 (0.7) 3.2 (1.3) 3.2 (1.6) 2.9 (0.8) * p Note p 2 r r r r Table 2 n n  Study 1 Study 2  Pain TSK Pain FABQ activity scale FABQ work scale Lifting performance males (kg) −0.26 (−0.57 to 0.11) −0.12 (−0.46 to 0.25) * −0.13 (−0.43 to 0.19) * Lifting performance females (kg) −0.06 (−0.34 to 0.23) −0.17 (−0.43 to 0.12) 0.09 (−0.52 to 0.38) −0.07 (−0.51 to 0.40) −0.03 (−0.48 to 0.43) Lifting maximum heart rate (BPM) 0.05 (−0.17 to 0.27) −0.10 (−0.31 to 0.12) * −0.24 (−0.47 to 0.02) −0.24 (−0.47 to 0.02) Static forward bend (sec) 0.18 (−0.04 to 0.39) * * * −0.25 (−0.48 to 0.01) Dynamic forward bend (sec/rep) −0.10 (−0.31 to 0.12) 0.14 (−0.08 to 0.35) 0.03 (−0.23 to 0.29) 0.07 (−0.19 to 0.32) * Note * p n n n n r r r r 1 Fig. 1 Plot of maximum lifting performance and scores on the Tampa Scale for Kinesiophobia (TSK) in 79 patients with chronic low back pain  Table 3 Multivariate linear regression models predicting variance in performance in patients with chronic low back pain  β (95% CI) Beta p r 2 r 2 n      Dependent variable: lifting       •Gender (female = 0, male = 1) 14.45 (7.36 to 21.54) 0.48 <0.001 0.23 0.28  •Constant 17.01 (−9.60 to 43.62) – 0.205 –  Dependent variable: static forward bend      r 2      Dependent variable: dynamic forward bend      r 2      n      Dependent variable: lifting       •Gender (female = 0, male = 1) 14.94 (6.15 to 23.73) 0.48 0.001 0.23 0.37  •Pain intensity −1.83 (−3.65 to −0.01) −0.29 0.049 0.08   •Constant (kg) 45.70 (25.67 to 65.73) – <0.001 –  Dependent variable: static forward bend       •Constant (sec) 549.15 (336.09 to 762.21) – <0.001 – 0.27  •None of the other independent variables contributed significantly to the regression equation      Dependent variable: dynamic forward bend      r 2      3 r r r Discussion 2 r r r 2 1 12 There may be several explanations for the weakness or non-existence of the associations between pain intensity and pain related fears on the one hand, and avoidance behaviors on the other hand. Pain intensity and pain related fears might have been inappropriately operationally defined by the NRS, the TSK and the FABQ, avoidance behavior might have been inappropriately operationally defined by the three performance measures, our study samples differ from samples reported elsewhere, or the variables were appropriately operationally defined, but the relationship was mediated by one or more currently unknown variables. Additionally, a combination of the above may explain our findings. 8 9 12 20 8 10 29 30 29 31 32 33 30 34 35 36 36 37 38 39 25 8 40 41