Background Individuals with chronic low back pain (CLBP) experience changes in gait control due to pain and/or fear. Although CLBP patients’ gait has been performed in laboratory environments, changes in gait control as an adaptation to unstructured daily living environments may be more pronounced than the corresponding changes in laboratory environments. We investigated the impacts of the environment and pathology on the trunk variability and stability of gait in CLBP patients. Methods CLBP patients (n=20) and healthy controls with no low-back pain history (n=20) were tasked with walking in a laboratory or daily-living environment while wearing an accelerometer on the low back. We calculated the stride-to-stride standard deviation and multiscale sample entropy as indices of “gait variability” and the maximum Lyapunov exponent as an index of “gait stability” in both the anterior-posterior and medial-lateral directions. The participants were assessed on the numerical rating scale for pain intensity, the Tampa Scale for Kinesiophobia, and the Roland–Morris Disability Questionnaire for quality of life (QOL). Results In a repeated-measures ANOVA, the standard deviation was affected by environment in the anterior-posterior direction and by group and environment in the medial-lateral direction. Multiscale sample entropy showed no effect in the anterior-posterior direction and showed both effects in the medial-lateral direction. Maximum Lyapunov exponents showed both effects in the anterior-posterior direction, but none in the medial-lateral direction. These changes of trunk motor control by CLBP patients were found to be related to pain intensity, fear of movement, and/or QOL in the daily-living environment but not in the laboratory environment. Conclusion These results revealed that CLBP patients exhibit changes in trunk variability and stability of gait depending on the environment, and they demonstrated that these changes are related to pain, fear, and QOL. We propose useful accelerometer-based assessments of qualitative gait in CLBP patients’ daily lives, as it would provide information not available in a general practice setting.

Background Pain-related fear influences impaired trunk movement (e.g., limited movement of range and velocity), but it is unclear how fear relates to trunk motor coordination (e.g., a more “in-phase” upper-lower trunk motion pattern). We conducted the present study to: (1) identify the motor coordination pattern of the in-phase upper-lower lumbar movements during the lifting, and (2) determine how pain-related fear is related to the trunk coordination pattern in workers with chronic low back pain (CLBP). Methods We examined 31 male workers with CLBP (CLBP group) and 20 healthy controls with no history of CLBP (HC group). The movement task was lifting a box, the weight of which was 10, 30%, or 50% of the subject’s body weight. We used a 3D motion capture system to calculate the mean absolute relative phase angle (MARP) angle as an index of coordination and the mean deviation phase (DP) as an index of variability. We used a numerical rating scale to assess the subjects’ task-specific fear. Results The MARP angle during trunk extension movement in the 50% condition was significantly decreased in the CLBP group compared to the HCs; i.e., the upper lumbar movement was more in-phase with the lower lumbar movement. The hierarchical multiple regression analysis results demonstrated that a decreased MARP angle was associated with high task-specific fear. Conclusions A more ‘in-phase’ upper-lower lumbar movement pattern was predicted by task-specific fear evoked when performing a work-related activity. Our findings suggest that an intervention for task-specific fear may be necessary to improve an individual’s impaired trunk motor coordination.

This study aimed to perform cluster analysis in patients with chronic pain to extract groups with similar circadian rhythms and compare neuropathic pain and psychological factors among these groups to identify differences in pain-related outcomes. A total of 63 community-dwellers with pain lasting at least 3 months and Numerical Rating Scale scores of ≥2 were recruited from 3 medical institutions. Their pain circadian rhythms were evaluated over 7 days by measuring pain intensity at 6-time points per day using a 10-cm visual analog scale. Cluster analysis was performed using 6 variables with standardized visual analog scale values at 6-time points for individual participants to extract groups with similar pain circadian rhythms. The results of the Neuropathic Pain Symptom Inventory and psychological evaluations in each group were compared using the Kruskal–Wallis test. The results revealed 3 clusters with different circadian rhythms of pain. The total and evoked pain subscale Neuropathic Pain Symptom Inventory scores differed among the 3 clusters. The results suggest that a thorough understanding of circadian pain rhythms in chronic pain patients may facilitate the performance of activities of daily living and physical exercise from the perspective of pain management.

Clinicians should consider the potential added value of task-specific fear assessment over the sole use of general kinesiophobia assessment.

Purpose To identify impaired trunk movement during work-related activity in individuals with low back pain (LBP) and investigate whether abnormalities were caused by generalized fear of movement-related pain. Methods This cross-sectional study was conducted at a hospital in Japan. We recruited 35 participants with LBP (LBP group; 26 males, 9 females) and 20 healthy controls (HC group) via posters at our hospital. The task required lifting an object. We used a 3D motion capture system to calculate the peak angular velocity of trunk flexion and extension during a lifting task. Pain-related factors for the LBP group were assessed using the visual analogue scale (VAS) for pain intensity over the past 4 weeks and during the task, the Tampa Scale for Kinesiophobia (TSK), the Pain Catastrophizing Scale (PCS), and the Pain Anxiety Symptoms Scale-20 (PASS-20). We compared kinematic variables between groups with a generalized linear mixed model and investigated the relationship between kinematic variables, VAS scores, and psychological factors by performing a mediation analysis. Results The peak angular velocity of trunk extension showed significant main effects on the group factors (LBP group vs. HC group) and their interactions; the value of the kinematic variable was lower at Trial 1 in the LBP group. No LBP participant reported pain during the experiment. The mediation analysis revealed that the relationship between the VAS score for pain intensity over the past 4 weeks and the peak angular velocity of trunk extension in the first trial was completely mediated by the TSK (complete mediation model, 95% bootstrapped CI: 0.07–0.56). Conclusion Individuals with LBP had reduced trunk extension during a lifting task. Generalized fear of movement-related pain may contribute to such impaired trunk movement. Our findings suggest that intervention to ameliorate fear of movement may be needed to improve LBP-associated disability.