Chronic Pain Patients Research Articles

Pains Revisited.

The management of pain patients has not evolved as rapidly as envisioned when IASP was founded almost 50 years ago. We sought to identify factors that could contribute to this situation, with a focus on concepts of pain and the education of pain physicians. Relevant literature describing new strategies for diagnosing and managing patients with high-impact chronic pain was reviewed. It appears that the acute-chronic dichotomy has outlived its usefulness and pains should be identified as of peripheral origin or due to central processing errors. Pains of peripheral origin and those of central processing errors require different diagnostic and therapeutic strategies. Peripheral treatments and opioids are not effective for central pains. When the cause of the pain lies in the central nervous system, a more centrally focused approach is needed to minimize wasteful pursuit of peripheral causes. The education and training of pain physicians should reflect the skills needed to address these 2 very different clinical problems.

Epidemiological Features of Chronic Low-Back Pain

Introduction: Chronic low back pain (LBP) is a major cause of abstinence from work in the world. Objective: The aim of the present study was to assess the epidemiological features of chronic low back pain patients in tertiary care teaching hospital. Materials and Methods: A descriptive cross sectional study was conducted from January 2018 to June 2018 among 70 patients attending at Physical Medicine and Rehabilitation outpatient department of the Shaheed Suhrawardy Medical College and Hospital after obtaining requisite consent from the patients. Data were collected through interviewing of the patients. The collected data were entered into the computer and analyzed by using SPSS (version 20.1) to assess the epidemiological features of chronic low back pain patients. Results: In a pool of 70 patients, most of the patients (n=34, 48.5%) belong to 31-40 year age group. In a pool of 70 patients, Male patients (52.85%) were more than the female patients (47.14%) at the Shaheed Suhrawardy Medical College and Hospital. In occupational status, most of the patients were Housewife (n=19, 27.14%) followed by service-holder (n=17, 24.28%). In a pool of 70 patients, most of the patients BMI were normal (n=49, 70%). Conclusion: Epidemiological features were characterized by male patients, as from the 31-40 years of life and housewife. Physical functional profile was primarily characterized by patients with normal BMI and overweight. Medicine Today 2024, Vol.36 (2): 107-109

Pain Sensitivity Questionnaire: Cross-cultural adaptation and validation of the Greek version.

The Pain Sensitivity Questionnaire (PSQ) was developed to assess general pain sensitivity. This study aimed to validate the Greek version of PSQ. The questionnaire was translated into Greek (PSQ-GR) and piloted in a small sample of patients with chronic pain (n=35). A total of 146 chronic pain patients and healthy volunteers completed the PSQ-GR, the Pain Catastrophizing Scale (PCS), Hospital Anxiety and Depression Scale (HADS) and Central Sensitization Inventory (CSI). To evaluate the test-retest reliability, 36 volunteers completed the PSQ-GR twice over 7±2days. Internal consistency was excellent (Cronbach's alpha 0.90-0.96) for PSQ-total, PSQ-minor, and PSQ-moderate. The Intraclass Correlation Coefficient was estimated at 0.90-0.96 for PSQ-total, PSQ-minor and PSQ-moderate and the SEM was 0.59-0.90 for PSQ-total, PSQ-minor and PSQ-moderate approximately. The smallest detectable change was 0.48 for PSQ-total, 0.47 for PSQ-minor and 0.44 for PSQ-moderate. Positive and significant correlations were observed between PSQ-GR and HADS (r=0.38, p<0.01), PCS (r=0.41, p<0.01) and CSI (r=0.30, p<0.01). Statistically significant differences in PSQ-GR scores were identified between the healthy volunteers and the chronic pain patients. The PSQ-GR is a reliable and valid tool that can assess pain sensitivity in healthy individuals and chronic musculoskeletal pain patients.

Exploring Pain Reduction through Physical Activity: A Case Study of Seven Fibromyalgia Patients.

Fibromyalgia is a chronic disease that affects a considerable fraction of the global population, primarily women. Physical activity is often recommended as a tool to manage the symptoms. In this study, we tried to replicate a positive result of pain reduction through physical activity. After collecting pain and physical activity data from seven women with fibromyalgia, one patient experienced a considerable reduction in pain intensity. According to the patient, the improvement was related to physical activity. Our study was conducted to investigate the replicability of this result through personalized activity recommendations. Out of the other six patients, three experienced a reduction in pain. The remaining three patients did not experience any pain relief. Our results show that two of these were not able to follow the activity recommendations. These results indicate that physical activity may have a positive effect on chronic pain patients. To estimate how effective physical activity can be for this patient group, an intervention with longer follow-ups and larger sample sizes needs to be performed in the future.

New Ultrasound-Guided Approach to Access to the Posterolateral Part of Intervertebral Lumbar Discs: A Cadaveric Study.

Background: Approximately 40% of chronic low back pain patients have a discogenic origin. In relation to intervertebral disc injuries, most of them are in the posterior and lateral zone of the disc, involving the anterior lumbar roots and the spinal cord. Objective: The objective was to analyze and describe the accuracy and safety of a new ultrasound-guided approach to target the posterolateral part of the intervertebral lumbar discs in cadaveric specimens. Methods: A cross-anatomical study on sixty cadaver intervertebral lumbar discs was performed. A needle was introduced in the posterolateral part of the discs using ultrasound guidance. A transducer was placed in the anterior abdomen to visualize the discs in cross-section as well. A dissection of the specimen was performed to visualize the final position of the needle tip and its distance from the main lumbar structures. The angulation, length, and distance of the needle from the vertebral spine, the relevant ultrasound anatomical references, and the accuracy of the procedure were evaluated. Results: The needle tip reached the posterolateral part of the discs in 93.3% of the attempts. The mean length of the needle inserted was 79 ± 15 mm, the angulation 129 ± 20.2°, the distance from the spinous process was 77 ± 19 mm, and the distance of the needle to the nerve roots was 2.0 ± 1.2 mm. No statistically significant differences between genders were found. Conclusions: An ultrasound-guided technique can be an accurate and safe technique to perform invasive procedures on the posterolateral part of the intervertebral lumbar discs.

Clinical results of ultrasound-guided intra-arterial embolization targeting abnormal neovessels for plantar fasciitis: 66 cases with up to 4 years of follow-up

BackgroundPlantar fasciitis (PF) is the most common cause of chronic heel pain, affecting young and older patients. MethodsThis retrospective study included patients with PF refractory to conservative treatment who underwent intra-arterial embolization of abnormal neovessels. All patients received temporary embolic material through a needle percutaneously inserted into the posterior tibial artery. The numeric rating scale (NRS) pain score, American Orthopaedic Foot and Ankle Society (AOFAS) score, and procedure-related adverse events were evaluated. ResultsBetween January 2020 and February 2022, 66 patients with PF were treated with intra-arterial embolization without major adverse events. The NRS pain score improved significantly, and the AOFAS score increased from 65.8 pre-treatment to 92.8 at 1 year post-treatment. The treatment effect was maintained until the final follow-up (mean duration: 30.9 months). ConclusionsUltrasound-guided intraarterial embolization using temporary embolic material may be effective for PF. Level of evidenceIV.

A Review of Remote Monitoring in Neuromodulation for Chronic Pain Management.

Neuromodulation techniques have emerged as promising strategies for managing chronic pain. These techniques encompass various modalities of nerve stimulation, including Spinal Cord Stimulation (SCS), Dorsal Root Ganglion Stimulation (DRG-S), and Peripheral Nerve Stimulation (PNS). Studies consistently demonstrate significant improvements in pain intensity, quality of life, and reduced opioid usage among patients treated with these modalities. However, neuromodulation presents challenges, such as the need for frequent in-person follow-up visits to ensure proper functionality of the implanted device. Our review explored factors impacting compliance in current neuromodulation users and examined how remote monitoring can mitigate some of these challenges. We also discuss outcomes of recent studies related to remote monitoring of neuromodulation. While remote monitoring capabilities for neuromodulation devices is an emerging development, there are promising results supporting its role in improving outcomes for chronic pain patients. Higher patient satisfaction, improved pain control, and reduced caretaker burdens have been observed with the use of remote monitoring. This review discusses the current challenges with neuromodulation therapy and highlights the role of remote monitoring. As the field continues to evolve, understanding the importance of remote monitoring for neuromodulation is crucial for optimizing pain management outcomes.

Comparative Analysis of Efficacy of Endoscopic versus Open Carpal Tunnel Release

Objectives: To compare the efficacy between endoscopic and open carpal tunnel release procedures for carpal tunnel syndrome patients. Design and setting: Randomised control study in a single neurosurgery department Participants: 30 patients aged 35-69 years with clinically diagnosed carpal tunnel syndrome Main outcome measures: Primarily - operative duration, bleeding, pain score on day one, requirement of non-steroidal anti-inflammatory drugs (NSAIDs), time spent in hospital and days taken to return to work. Other outcomes include infection, wound status/cosmesis, injury to median nerve, chronic regional pain syndrome and patient satisfaction. Results: 15 patients were allocated to open surgery, and the other 15 for endoscopic. The average operative duration for open surgery was 9.9 minutes compared to 52 minutes spent for the endoscopic procedure. Cauterization had to be performed 4:1 times in endoscopic compared to open. Pain scores rated 3x higher after open surgery and resulted in increased NSAIDs use. Time spent in hospital after open surgery was 0.7 hours compared to 2.2 in endoscopic, however patients were able to return to work an average of 10.6 days earlier after endoscopic surgery. Conclusions: In carpal tunnel syndrome, endoscopic surgery allowed patients to experience less post-operative pain and return to work several days sooner than in open surgery.

The effect of cognitive functional therapy on the plantar pressure distribution symmetry in patients with chronic non-specific low back pain: A randomized controlled trial

ObjectiveThis study aimed to evaluate the effect of Cognitive functional therapy (CFT) on plantar pressure distribution symmetry in chronic non-specific low back pain (CNSLBP) patients. Methodforty females with NSCLBP (age range 30–50 years) were recruited for clinical trials. They were randomly divided into experimental and control groups (Each group had 20 patients). The patients in the experimental group received CFT for 8 weeks. The primary outcome was psychological variables inclusive of pain, kinesiophobia and disability. The secondary outcome was plantar pressure distribution symmetry which assessment in standing condition. The Covariance statistical method was used for data analysis. ResultsThe results of covariance analysis for primary outcome showed a significant difference (p < 0.05) with a reduction of 52 % in pain (p = 0.001), 12 % in kinesiophobia (p = 0.001) and 41% in disability (p = 0.001). Also, the results of covariance analysis for secondary outcome showed a significant difference in plantar pressure distribution symmetry of inter-limbs foot (p = 0.007), forward and backward in the right foot (p = 0.002) and forward and backward in the left foot (p = 0.001). ConclusionCFT reduces of pain, kinesiophobia and disability. In addition significant difference in the plantar pressure distribution symmetry was observed, which it is argued the plantar pressure asymmetric can be influenced by psychological factors.

Dysfunctional astrocyte glutamate uptake in the hypothalamic paraventricular nucleus contributes to visceral pain and anxiety-like behavior in mice with chronic pancreatitis.

Abdominal visceral pain is a predominant symptom in patients with chronic pancreatitis (CP); however, the underlying mechanism of pain in CP remains elusive. We hypothesized that astrocytes in the hypothalamic paraventricular nucleus (PVH) contribute to CP pain pathogenesis. A mouse model of CP was established by repeated intraperitoneal administration of caerulein to induce abdominal visceral pain. Abdominal mechanical stimulation, open field and elevated plus maze tests were performed to assess visceral pain and anxiety-like behavior. Fiber photometry, brain slice Ca2+ imaging, electrophysiology, and immunohistochemistry were used to investigate the underlying mechanisms. Mice with CP displayed long-term abdominal mechanical allodynia and comorbid anxiety, which was accompanied by astrocyte glial fibrillary acidic protein reactivity, elevated Ca2+ signaling, and astroglial glutamate transporter-1 (GLT-1) deficits in the PVH. Specifically, reducing astrocyte Ca2+ signaling in the PVH via chemogenetics significantly rescued GLT-1 deficits and alleviated mechanical allodynia and anxiety in mice with CP. Furthermore, we found that GLT-1 deficits directly contributed to the hyperexcitability of VGLUT2PVH neurons in mice with CP, and that pharmacological activation of GLT-1 alleviated the hyperexcitability of VGLUT2PVH neurons, abdominal visceral pain, and anxiety in these mice. Taken together, our data suggest that dysfunctional astrocyte glutamate uptake in the PVH contributes to visceral pain and anxiety in mice with CP, highlighting GLT-1 as a potential therapeutic target for chronic pain in patients experiencing CP.

Systematic Review of the Psychopathological Symptomatology and Neuropsychological Disorders of Chronic Primary Musculoskeletal Pain.

Chronic pain can develop without tissue damage, injury, or underlying illness. There are several intervening biological, psychological, and social factors involved in its appearance that significantly affect the activities of daily life. It is also associated with significant emotional anxiety and/or functional disability. This review systematically analyses works published in the last five years that evaluate the psychopathological symptomatology and neuropsychological disorders of chronic primary musculoskeletal pain (CPMP). A bibliographic search was carried out to identify articles published in English between January 2018 and March 2023 using the Medline, Scopus, PsycInfo, and Pubmed databases. Twenty articles were obtained using the PRISMA selection method. The main results of this study provided evidence of the presence of moderate and severe chronic pain in patients suffering from musculoskeletal pain. This increase in the intensity of pain correlates with greater psychopathological symptomatology, such as depression, anxiety, insomnia, lack of attention, and hyperactivity/impulsiveness, as well as the use of maladaptive coping strategies. Furthermore, there exists dysfunction in the cerebral structures related to attention and the processing of pain in patients with CPMP. This review may help to develop and optimise the multidisciplinary treatments adapted to the deficits caused by this illness.

Profile of chronic pain patients with opioid withdrawal syndrome according to psychological factors: a Latent Class Analysis.

Withdrawal syndrome stands out as the strongest risk factor for Prescription Opioid-Use Disorder (POUD) and is related to psychological and pain impairment in chronic pain population. This study aimed to identify profiles of chronic pain patients with opioid withdrawal based on psychological factors, and to explore the association between the classes and demographic, clinical, and substance use variables. This cross-sectional descriptive study involved 391 patients, 221 of them with interdose withdrawal (mean age=57.91±13.61 years; 68.3% female). Latent Class Analysis (LCA) and bivariate and logistic regression analyses were performed. Two latent classes were identified (BIC=4020.72, entropy=0.70, LRTs p<0.01): Withdrawal syndrome with No Psychological Distress (WNPD; 45.2%, n=100) and Withdrawal syndrome with Psychological Distress (WPD; 54.8%, n=121). The WPD class was more likely to experience craving, anxiety, and depression, and to report higher levels of pain intensity and interference (p<0.01). Patients in this class were younger, visited a higher number of specialists, and showed higher rates of high-dose opioid use, misuse, moderate-severe POUD, and tobacco and anxiolytics use (p<0.05). Only moderate-severe POUD (OR=2.64) and tobacco use (OR=2.28) increased the risk of WPD class membership. Although it is common for chronic pain patients to experience withdrawal symptoms during opioid treatment, more than a half of the participants reported concomitant psychological distress. Establishing differential profiles can help to improve withdrawal syndrome management during the treatment of chronic pain with opioids.

Immune response and cytokine profiles in post-laminectomy pain syndrome: comparative analysis after treatment with intrathecal opioids, oral opioids, and non-opioid therapies.

This study explores the interaction between cytokines, cell-mediated immunity (T cells, B cells, and NK cells), and prolonged morphine administration in chronic neuropathic pain patients without cancer-related issues. Despite evidence of opioid immunomodulation, few studies have compared these interactions. In a cross-sectional and comparative study, 50 patients with chronic low back radicular pain ("Failed Back Surgery Syndrome") were categorized into intrathecal morphine infusion (IT group, n = 18), oral morphine (PO group, n = 17), and non-opioid treatment (NO group, n = 15). Various parameters, including plasma and cerebrospinal fluid (CSF) cytokine concentrations, lymphocyte immunophenotyping, opioid escalation indices, cumulative morphine dose, and treatment duration, were assessed. CSF IL-8 and IL-1β concentrations exceeded plasma levels in all patients. No differences in T, B, and NK lymphocyte numbers were observed between morphine-treated and non-treated patients. Higher plasma IL-5 and GM-CSF concentrations were noted in IT and PO groups compared to NO. CSF IFNγ concentrations were higher in PO and NO than IT. Positive correlations included CD4 concentrations with opioid escalation indices, and negative correlations involved NK cell concentrations, CSF TNFα concentrations, and opioid escalation indices. Positive correlations were identified between certain cytokines and pain intensity in IT patients, and between NK cells and cumulative morphine dose. Negative correlations were observed between CSF IL-5 concentrations and pain intensity in IT and PO, and between opioid escalation indices and CSF cytokine concentrations in PO and IT. Associations between cytokines, cellular immunity, and prolonged morphine treatment, administered orally and intrathecally were identified.

Novel neurophysiological evidence for preserved pain habituation across chronic pain conditions

ObjectiveThe present study aimed to investigate whether subjective and objective measures of pain habituation can be used as potential markers for central sensitization across various chronic pain patients. MethodsTwo blocks of contact-heat stimuli were applied to a non-painful area in 93 chronic pain patients (low back pain, neuropathic pain, and complex regional pain syndrome) and 60 healthy controls (HC). Habituation of pain ratings, contact-heat evoked potentials (CHEP), and sympathetic skin responses (SSR) was measured. ResultsThere was no significant difference in any measure of pain habituation between patients and HC. Even patients with apparent clinical signs of central sensitization showed no reduced pain habituation. However, prolonged baseline CHEP and SSR latencies (stimulation block 1) were found in patients compared to HC (CHEP: Δ-latency = 23 ms, p = 0.012; SSR: Δ-latency = 100 ms, p = 0.022). ConclusionGiven the performed multimodal neurophysiological testing protocol, we provide evidence indicating that pain habituation may be preserved in patients with chronic pain and thereby be of limited use as a sensitive marker for central sensitization. These results are discussed within the framework of the complex interactions between pro- and antinociceptive mechanism as well as methodological issues. The prolonged latencies of CHEP and SSR after stimulation in non-painful areas may indicate subclinical changes in the integrity of thermo-nociceptive afferents, or a shift towards antinociceptive activity. This shift could potentially affect the relay of ascending signals. SignificanceOur findings challenge the prevailing views in the literature and may encourage further investigations into the peripheral and central components of pain habituation, using advanced multimodal neurophysiological techniques.

Minimal-invasive pain procedures are effective in different degenerative pain generators in CLBP: A prospective cohort study.

It is estimated that a significant number of spinal surgeries are performed, but many patients do not often benefit. Our aim was to determine how effective minimally invasive pain procedures (MIP) are in chronic low back pain (CLBP) patients with proven degenerative causes (specific low back pain). 386 eligible patients with CLBP/sciatica resistant to conservative therapy and scheduled for open surgery were screened, and 167 could be enrolled in this study. Indications for MIP in the remaining 150 individuals were made by one experienced spinal surgeon. Before and 6 months after the intervention, the numeric rating scale (NRS) and Oswestry Disability Index (ODI) were recorded. MIP was performed, such as radiofrequency of the facet and SI-joint, intradiscal electrothermal therapy in case of discogenic pain, as well as epidural neuroplasty in patients with disc herniation/epidural fibrosis. There was a statistically significant decrease in NRS (p< 0.05), as well as a significant increase in ODI (p< 0.001) 6 months after the procedures. This was also true for the results of all different pain generators and subsequent performed procedures alone. The indication of MIP should be routinely reviewed in patients with CLBP to avoid potentially open surgery and a burden on healthcare costs.

Posterior insula repetitive transcranial magnetic stimulation for chronic pain in patients with Parkinson disease – pain type matters: A double-blinded randomized sham-controlled trial

ObjectivesAltered somatosensory processing in the posterior insula may play a role in chronic pain development and contribute to Parkinson disease (PD)-related pain. Posterior-superior insula (PSI) repetitive transcranial magnetic stimulation (rTMS) has been demonstrated to have analgesic effects among patients with some chronic pain conditions. This study aimed at assessing the efficacy of PSI-rTMS for treating PD-related pain. MethodsThis was a double-blinded, randomized, sham-controlled, parallel-arm trial (NCT03504748). People with PD (PwP)-related chronic pain underwent five daily PSI-rTMS sessions for a week, followed by once weekly maintenance stimulations for seven weeks. rTMS was delivered at 10 Hz and 80% of the resting motor threshold. The primary outcome was a ≥ 30% pain intensity reduction at 8 weeks compared to baseline. Functionality, mood, cognitive, motor status, and somatosensory thresholds were also assessed. ResultsTwenty-five patients were enrolled. Mean age was 55.2 ± 9.5 years-old, and 56% were female. Nociceptive pain accounted for 60%, and neuropathic and nociplastic for 20% each. No significant difference was found for 30% pain reduction response rates between active (42.7%) and sham groups (14.6%, p = 0.26). Secondary clinical outcomes and sensory thresholds also did not differ significantly. In a post hoc analysis, PwP with nociceptive pain sub-type experienced more pain relief after active (85.7%) compared to sham PSI-rTMS (25%, p = 0.032). ConclusionOur preliminary results suggest that different types of PD-related pain may respond differently to treatment, and therefore people with PD may benefit from having PD-related pain well characterized in research trials and in clinical practice.

Serious treatment-emergent adverse events in chronic low back pain patients treated with buprenorphine or oral opioids: a retrospective commercial claims analysis.

Aim: Explore the safety of Belbuca® (buprenorphine buccal film), buprenorphine transdermal patches and oral opioids for chronic low back pain (cLBP) treatment. Methods: The retrospective analysis of the MarketScan Commercial database (2018-2021) included treatment-naive cLBP adults. The first date of buprenorphine (Belbuca and transdermal patch) or opioid prescription was index date. Cohorts were defined based on the index medication. Observation included a 6-month pre-index period, while post-index lasted until the end of continuous insurance coverage. There were 44 relevant treatment-emergent adverse events (TEAEs) identified in the literature. Incidence rate ratio (IRR) and incidence rate difference (IRD) were used to compare serious TEAE rates (in 1000 person-years) between cohorts. Propensity-score matching minimized the selection bias. Results: Buprenorphine had lower rates of 15 serious TEAEs than oral opioids (all p≤0.037), while higher rates only for serious dizziness (IRR 2.44, p=0.011; driven by Belbuca), opioid abuse/dependence (IRR 3.13, p=0.004; driven by patches) and cholecystitis (IRD 20.25, p=0.044; an outlier). Additionally, a comparison between Belbuca and oral opioids showed lower rates of 13 serious TEAEs (all p≤0.024) and a higher serious dizziness rate (IRR 3.17, p=0.024). Although the rates of serious opioid abuse/dependence were similar (24.60 vs 26.93, p=0.921), all Belbuca patients and none of the opioid patients had a positive history of these events. Belbuca also had lower rates of five serious TEAEs than transdermal patches (all p≤0.018), including a serious opioid abuse/dependence (IRR 0.04, p<0.001), but higher rates of serious cholecystitis (IRD 52.17, p=0.035; an outlier) and suicidal ideation (IRD 156.50, p<0.001; an outlier). Conclusion: Buprenorphine had a better safety profile than oral opioids in cLBP treatment. Belbuca showed a more favorable TEAE profile than buprenorphine transdermal patches and oral opioids.

M98 - Comparisons Between Prescription Opioid Formulations and Risk for New-Onset Affective Disorders in Chronic Pain Patients

M98 - Comparisons Between Prescription Opioid Formulations and Risk for New-Onset Affective Disorders in Chronic Pain Patients

W78 - Nomi™ SMRxT Bottles Track Daily Medication Intake Patterns in Chronic Pain Patients Prescribed Opioids

W78 - Nomi™ SMRxT Bottles Track Daily Medication Intake Patterns in Chronic Pain Patients Prescribed Opioids

Understanding the flexion-relaxation phenomenon in non-specific chronic low back pain patients throught immersive virtual reality feedback approach

The flexion-relaxation phenomenon (FRP) is frequently absent among non-specific chronic low back pain (NSCLBP) patients. However, it is unknown whether this absence is intrinsic to their pathology or merely a consequence of reduced trunk flexion. Immersive virtual reality (IVR) can create a patient avatar whose range of motion can be modulated to differ from the real movement. The present study enrolled 15 NSCLBP patients and 15 asymptomatic participants with similar characteristics to disentangle the relationship between range of motion and the FRP in NSCLBP using IVR. Trunk kinematics and lumbar muscle electromyography were assessed. The IVR environment was combined with a motion capture system to create avatars that moved like each participant. The IVR display showed a closed room and a mirror reflecting the subject’s avatar with a target line to be reached by trunk flexion. The avatar’s trunk movements were modulated from reality, leading the participants to flex their trunk more than their voluntary maximum trunk flexion. Under IVR conditions, NSCLBP patients significantly increased their trunk flexion angle, which was coupled with a significant improvement in the FRP. The absence of the FRP among the NSCLBP population appeared to be primarily related to reduced trunk flexion.