Sympathetic nervous activity contributes to the maintenance of muscle oxygenation. However, patients with chronic pain may suffer from autonomic dysfunction. Furthermore, insufficient muscle oxygenation is observed among workers with chronic neck and shoulder pain. The aim of our study was to investigate how muscle load tasks affect sympathetic nervous activity and changes in oxygenation of the trapezius muscles in subjects with chronic neck and shoulder pain. Thirty females were assigned to two groups: a pain group consisting of subjects with chronic neck and shoulder pain and a control group consisting of asymptomatic subjects. The participants performed three sets of isometric exercise in an upright position; they contracted their trapezius muscles with maximum effort and let the muscles relax (Relax). Autonomic nervous activity and oxygenation of the trapezius muscles were measured by heart rate variability (HRV) and Near-Infrared Spectroscopy. Oxyhemoglobin and total hemoglobin of the trapezius muscles in the pain group were lower during the Relax period compared with the control group. In addition, the low frequency / high frequency (LF/HF) ratio of HRV significantly increased during isometric exercise in the control group, whereas there were no significant changes in the pain group. Subjects with neck and shoulder pain showed lower oxygenation and blood flow of the trapezius muscles responding to isometric exercise, compared with asymptomatic subjects. Subjects with neck and shoulder pain also showed no significant changes in the LF/HF ratio of HRV responding to isometric exercise, which would imply a reduction in sympathetic nervous activity.

Objective. Virtual reality (VR) is an advanced technology that can be used to attenuate pain. The present study aimed to investigate which method was more effective for pain management: VR combined with exercise imagery or VR distraction. Methods. Fifty-two healthy students participated in this randomized cross-over controlled trial. One VR-based task aimed to passively use the imagery of driving a car as a distraction intervention (the driving group), whereas the other VR-based task aimed to use exercise imagery (running) to actively engage the participants in movement (the running group). The mechanical pressure pain thresholds of the quadriceps and forearm and the heat pain threshold of the hand of each subject were measured before, during, and after each VR task. The differences between the values at each time point and the differences between the groups were analyzed. Results. The pressure and heat pain thresholds were significantly greater during VR task than those before VR task in both driving and running groups. The changes in the pressure pain thresholds that occurred during VR task were significantly higher in the running group than in the driving group. The difference between groups gradually declined after VR task. Conversely, there was no significant difference in the changes in the heat pain thresholds between the groups both during VR task and after VR task. Conclusions. VR combined with exercise imagery has a greater effect on pressure pain thresholds, but not heat pain thresholds, than VR distraction.

Background. Conditioned pain modulation (CPM), a phenomenon also known as diffuse noxious inhibitory control, is thought to be affected by various factors, including sex and level of physical activity. However, the involvement of these factors in CPM remains unclear. Methods. Eighty-six healthy young subjects (M/F, 43/43) participated in this study. Participants were assessed on the basis of their mechanical pressure pain threshold (PPT), CPM response, body mass index (BMI), basal metabolic rate (BMR), and duration of moderate-to-vigorous physical activity (MVPA) over a week, using a motion counter. Response to CPM was evaluated as PPT during painful cold stimulation relative to baseline PPT. Results. Men showed significantly higher baseline PPT than women; however, this difference was no longer significant after controlling for confounders. Stepwise multiple linear regression analyses revealed BMR to be a significant contributor towards baseline PPT in the entire study population. In contrast, although there were no significant contributors to CPM response among men and in the overall study group, MVPA was positively associated with CPM response among women (β = 0.397). Conclusions. These results suggest that, among healthy young individuals, CPM response may be associated with moderate-to-vigorous physical activity in women but not in men.

Anesthesiology and Pain Medicine

Introduction Multidisciplinary pain management programs incorporating a cognitive-behavioral therapy (CBT) approach have been reported to be helpful for elderly people with chronic pain. However, it is unclear whether the same program for elderly people with chronic pain would translate to different cultures. This study investigated whether a multidisciplinary program based on that of Nicholas et al. (Pain 154(6):824–835, 2013) in Australia would be effective for elderly people with chronic pain in Japan. Methods Twenty-seven community-dwelling elderly people with chronic pain were enrolled to confirm changes (effect size d = 0.5) in pain disability, which were previously reported by Nicholas et al. The multidisciplinary program consisted of eight sessions (2 sessions a week for 4 weeks). Pain disability was assessed using the Pain Disability Assessment Scale (PDAS) as the primary outcome at the baseline, the beginning and the end of the program, and the 1- and 3-month (final) follow-up. We also assessed the pain severity, catastrophizing, pain self-efficacy, and physical function with the Timed Up and Go test (TUG) and the two-step test as secondary outcomes. Results PDAS, pain catastrophizing, and pain self-efficacy were significantly improved immediately after the program compared with baseline, and these effects were maintained at 3-month follow-up. The effect size (d) for the PDAS score was a medium size (0.54) from baseline to 3-month follow-up. Those who showed improvements in TUG immediately after the program tended to report improved psychometric measures at 3-month follow-up. Conclusion These results suggest that the Japanese multidisciplinary program has a similar effect on pain disability as that reported by Nicholas et al. This finding has important implications for the development of pain services in community-dwelling elderly Japanese.

Purpose: The purpose of the present study was to investigate the visual attentional behavior towards a pain-affected area and face/body images using eye tracking in complex regional pain syndrome (CRPS) patients. Moreover, we investigated the relationship between visual attentional behavior and clinical symptoms. Patients and methods: Eight female patients with CRPS type 1 in their upper limbs and 8 healthy adult women participated in this study. First, the participants were asked to watch videoclips in a relaxed manner (Videoclip 1 featured young adults who introduced themselves; Videoclip 2 featured young adults touching the hand of the other person sitting across from them with their hand.) Eye movement data were tracked with eye-tracking glasses. Results: In video clip 1, the fixation duration (FD) and fixation count (FC) on faces tended to be lower in CRPS patients than in healthy controls. This tendency was found in patients with low body cognitive distortions. In video clip 2, CRPS patients displayed significantly lower FD and FC on the unaffected hand while watching a video of the unaffected hand being touched compared with healthy controls. Moreover, patients with low body cognitive distortion displayed significantly longer FD on the affected hand. Conclusion: Some CRPS patients differed in visual attentional behavior toward the face and body compared with healthy controls. In addition, our findings suggest that patients with lower body cognitive distortion may have a high visual attention for the affected hand, while patients with higher distortion may be neglecting the affected hand.