Pain Tolerance Research Articles

Impact of COVID-19 Vaccination on Menstrual Cycle, Quality of Life and Perception on Fertility: A Mixed Methods Study of Women in Delhi-NCR

The COVID-19 pandemic presented extraordinary challenges which led individuals to make global efforts to develop a vaccine that could help battle the spread of the infection. The COVID-19 vaccine came as a sigh of relief for the world, but whilst we assess the positives, we must consider looking into the potential impacts it has had on aspects of health, including female reproductive health. The current study aimed at assessing the potential impacts that COVID-19 vaccination had on menstrual cycles and the perception of women about fertility-related issues following the jab through a comprehensive mixed methods design. A structured survey, using the Menstrual Symptom Questionnaire (MSQ) and WHO Quality of life scale was carried out with a diverse sample (n=500) of women (18-40 years) in the Delhi-NCR region, collecting data on menstrual cycle changes post receiving the Vaccine. Additionally, semi-structured interviews were conducted with a subset of the participants (n=15) to understand the perceptions of women about fertility-related issues following the Vaccine. The study suggests that most of the participants reported facing menstrual concerns such as missed periods, menstrual irregularities, excessive menstrual bleeding and increased cramping on the first day of their period. Through semi-structured interviews, the themes that emerged were fear regarding conception, early menopause, infertility, mood changes, anxiety, fatigue, less pain tolerance and problems with menstrual flow. Alongside, many had low scores on the quality-of-life questionnaire which was understood better through semi-structured interviews. Cognitive distortions were observed among participants while they explained their perceptions of the whole scenario. The study seeks to address a critical topic and fill knowledge gaps to understand the possible health impacts the COVID-19 vaccine has on women’s reproductive health. The study would contribute to creating scientific evidence and valuable insights for the health industry to understand any potential side effects the vaccine could have.

A Comparative Analysis of Pain Assessment Methods in the Initial Postoperative Phase Following Different Pilonidal Cyst Surgeries.

Background and Objectives: In this study, we aimed to evaluate pain intensity in patients after pilonidal disease surgeries of varying extent using pressure algometry and the visual analog scale and to explore potential correlations between these methods. Materials and Methods: A total of 78 adult patients with symptomatic pilonidal cysts were enrolled in this study. The patients were divided into two groups based on the type of surgery assigned to each patient at the pre-hospital consultation: pit-picking surgery (n = 39) and radical excision (n = 39). The pain levels at the surgical site were assessed and compared using the visual analog scale (VAS) and pressure algometry the morning before surgery and the day after the operation. Results: There was no statistically significant difference (p > 0.05) in VAS measurement results between surgical groups when comparing pain intensity experienced by patients before, during, and after surgery. Notably, specific pressure algometry variables (pressure pain tolerance left 2.05 ± 1.46 compared to 1.42 ± 0.73 kg/cm2, p = 0.02; maximum pressure pain tolerance left 2.91 ± 1.33 compared to 2.32 ± 1.14 kg/cm2, p = 0.04; maximum pressure pain tolerance center 2.51 ± 1.07 compared to 1.91 ± 0.91 kg/cm2, p = 0.01; interval of pressure pain tolerance center 0.98 ± 0.62 compared to 0.59 ± 0.39 kg/cm2, p = 0.00) on the first postoperative day were significantly lower in the "pit-picking" group compared to the excision group. Furthermore, no statistically significant correlation was found between VAS and pressure algometry measurements either before surgery or on the first postoperative day. Conclusions: In the early postoperative period following pilonidal disease surgery of varying extents, pain measured with the VAS does not differ. In contrast, the pressure algometry method showed greater pain in the minimally invasive surgery cohort on the first postoperative day. However, further larger studies are needed to compare these pain assessment methods in reporting pain intensity experienced during patient movement.

Pain tolerance and the thresholds of human sensory and motor axons to single and repetitive bursts of kilohertz-frequency stimulation.

Transcutaneous electrical stimulation with repetitive bursts of a kilohertz carrier frequency is thought to be less painful than conventional pulsed currents by reducing the sensitivity of pain receptors. However, no purported benefit has been shown unequivocally. We compared the effects of carrier-frequency stimulation and conventional stimulation on pain tolerance and the thresholds for sensory and motor axons in twelve participants. The ulnar nerve was stimulated transcutaneously with a conventional single pulse and 5 and 10kHz carrier-frequency waveforms that had 5 and 10 pulses, respectively, when delivered in bursts of ∼1ms duration. Phase durations were adjusted across waveform types to match the total charge for a given current amplitude. Single bursts of stimulation were delivered from 1mA up until no longer tolerable. This was repeated with repetitive bursts of stimulation at 20Hz for 1s. Participants tolerated higher current amplitudes with both carrier-frequency waveforms than conventional stimulation, with repetitive bursts more painful than single bursts. However, compared to conventional stimulation, carrier-frequency waveforms required more current to produce sensory and motor-threshold responses and to obtain a maximal motor response (Mmax). When the current at pain tolerance was normalised to the current at Mmax, participants tolerated lower stimulus intensities with carrier-frequency waveforms than conventional stimulation. These findings indicate that there is little to no benefit in using carrier-frequency waveforms to minimise the discomfort from electrical stimulation as the increase in stimulus intensity at pain tolerance is more than offset by reduced effectiveness in the activation of sensory and motor axons. KEY POINTS: Transcutaneous electrical stimulation with repetitive bursts of a kilohertz carrier-frequency waveform is thought to be less painful than conventional pulsed currents. For ulnar nerve stimulation, when stimulus waveforms were matched for total phase charge, participants tolerated higher current amplitudes with carrier-frequency stimulation than conventional stimulation. However, compared to conventional stimulation, carrier-frequency waveforms required more current to produce a threshold response in both sensory and motor axons and to produce a maximal motor response (Mmax). When current at pain tolerance was normalised to current at Mmax, participants tolerated lower stimulus intensities with carrier-frequency waveforms than conventional stimulation. Carrier-frequency waveforms provide little to no benefit in minimising the discomfort from transcutaneous electrical stimulation as the increase in stimulus intensity at pain tolerance is more than offset by reduced effectiveness in activating sensory and motor axons.

Decoding pain: prediction under different emotional contexts through physiological signals

AbstractPain recognition is a challenging yet crucial problem. Common methods used to measure pain are based on self-reported tools; however, not every person can communicate it. Therefore, automatic pain detection methods have emerged. Since pain is related to the emotional state of an individual, this variable must be considered. Thus, this work proposes pain prediction under different emotional contexts. For this purpose, data were collected during a protocol designed for pain induction with previous emotional elicitation. Emotions were elicited through videos composed of excerpts of documentaries, horror and comedy films, while the pain was induced through a Cold Pressor Test. Physiological signals, such as electrocardiogram, electrodermal activity and surface electromyogram, were collected during the protocol. Furthermore, several questionnaires were answered and pain reports were also registered. Two problems were addressed: pain classification and estimation of the Pain Tolerance score. The algorithm with the best performance for each problem was found using only data from the neutral session and nested cross-validation strategy. Using only physiological data from the neutral session, a F1-score of 99.32% was obtained for pain recognition and a mean absolute error (MAE) of 0.29 was obtained for Pain Tolerance estimation. When considering all the emotional sessions, the physiological data were merged with scores of the Visual Analogue Scale questionnaire, achieving a F1-score of 98.60% and a MAE of 0.41, for the first and second problems, respectively. These results are promising and stress out the key role that the emotional context of the individuals plays in pain prediction.

Pain Provocation With Progressive Loading Is the Most Common Diagnostic Method for Achilles Tendinopathy: An International Cross-Sectional Study of 1048 Physiotherapists

OBJECTIVE: To explore and define the diagnostic criteria and practices employed by physiotherapists worldwide for Achilles tendinopathy. DESIGN: A cross-sectional study using an anonymous online survey distributed to physiotherapists internationally. The survey captured diagnostic criteria, use of objective tests, and imaging techniques in the management of Achilles tendinopathy. METHODS: The survey, collaboratively designed by experts in Achilles tendinopathy, comprised 27 questions covering demographic information, diagnostic practices, and the use of imaging. The survey was disseminated through various social media platforms and professional events. All data were collected via REDCap. RESULTS: One thousand and forty-eight physiotherapists completed the survey. Physiotherapists reported that symptom response to a series of progressive Achilles loadings tests (92%), pain tolerance palpating the Achilles tendon (79.8%) and visual comparison of the Achilles tendon (63.8%) were helpful objective tests to establish a diagnosis of Achilles tendinopathy. The most commonly referred form of imaging was ultrasound at radiology clinics (n =460, 63.3%). CONCLUSION: This global survey provides clinical perspective of physiotherapists diagnosing Achilles tendinopathy Although using a progressive loading protocol to form a clinical diagnosis, physiotherapists were also using pain elicited on palpation 79.8% to further establish diagnosis of Achilles tendinopathy, despite recent studies that have demonstrated Achilles palpation pain is present in a variety of posterior ankle conditions and that there is no standardised pressure for palpation.

Prefrontal oxygenation during experimental pain in adolescents engaging in non-suicidal self-injury

BackgroundThe intricate role of pain in non-suicidal self-injury (NSSI) makes the investigation of alterations in brain function during pain processing a critical yet underexplored topic. The aim of this study was to investigate fNIRS correlates of experimental pain and how these differed between adolescent patients engaging in NSSI and healthy controls. Methods154 adolescent patients with NSSI and 48 healthy controls underwent a heat pain stimulation with linearly increasing temperature from 32 °C to max. 50 °C, during which fNIRS activity was recorded. Associations between fNIRS activity and pain perception (i.e. pain threshold, pain tolerance and pain intensity) were examined using linear mixed models and linear regression analyses. ResultsAcross groups, we found a decrease in prefrontal oxygenation during increasing pain stimulation: Oxygenated hemoglobin was higher during baseline than during pain threshold (b = −0.36, p < .001) and higher during pain threshold than during pain tolerance (b = −0.10, p < .001). We did not find differential patterns of prefrontal oxygenation across the pain assessment between patients and healthy controls. Also, no association between pain intensity and fNIRS activity was found. LimitationsfNIRS was only recorded in prefrontal regions and our design did not include a non-painful stimulation as a control condition. ConclusionWhile our study adds to the understanding of prefrontal hemodynamic changes associated with pain processing, it did not contribute further evidence to the few existing findings regarding altered neural processing of pain in adolescents engaging in NSSI.

Neurovascular Shifts, Sensory Sensitivity, and PMDD in Autistic Women: Exploring Blood Flow Redirection, Mood Dysregulation, and Pain Tolerance during Menstruation

This article examines the relationship between Premenstrual Dysphoric Disorder (PMDD), neurovascular dynamics, and sensory sensitivities in autistic women during menstruation. The redirection of blood flow to the uterus during the menstrual cycle has been found to exacerbate cerebral perfusion deficits in neurodivergent individuals, particularly in the Prefrontal Cortex (PFC), which contributes to the mood dysregulation and emotional instability characteristic of PMDD. Autistic women, who often exhibit heightened sensory sensitivities, experience intensified discomfort during menstruation, as sensory overload and altered pain perception compound the emotional challenges of PMDD. These findings emphasize the need for neurodivergent-friendly menstrual products that mitigate both physical and emotional discomfort. Additionally, innovations using biodegradable materials, smart fabrics, and custom-fit menstrual solutions are discussed as potential breakthroughs to improve the quality of life for autistic women managing PMDD. This research highlights the importance of addressing both neurobiological and sensory aspects when designing interventions for PMDD in neurodivergent populations.

Interpersonal and individual effects of an app-based Christian and Islamic heart meditation intervention in healthy adults: protocol of a stratified randomised controlled trial

BackgroundThe academic development and widespread adoption of meditation practices for well-being and therapy have predominantly focused on secularised adaptations of Buddhist and Hindu techniques. This study aims to expand the field by investigating Christian and Islamic meditation that emphasize the spiritual significance of the heart through elements of visualisation and recitation. It compares the effects of spiritual heart-centred meditation with mindfulness meditation and a waitlist control, focusing on dimensions of social functioning, psychophysiology, cognition, and mental health.MethodThis study employs a stratified 3-arm randomised controlled method with mixed-method repeated measures across three assessment time points: before intervention (T1), after an 8-week intervention (T2), and at a 3-month follow up (T3). The three conditions include spiritual meditation (either Christian or Islamic), mindfulness meditation (Mindfulness-Based Stress Reduction – MBSR), and a waitlist. Participants will be stratified into Christian and Muslim samples and randomly allocated to the spiritual meditation, MBSR, or waitlist control conditions. Importantly, participants assigned to the spiritual meditation condition will be matched to the spiritual meditation program corresponding to their religion. The intervention will be administered through a mobile phone app with daily 20-minute guided meditation sessions for eight weeks. Primary outcomes pertain to the domain of interpersonal functioning, focusing on prosociality, forgiveness, empathy, and perspective taking. Secondary outcomes include physiology: pain tolerance, pain intensity, stress reactivity assessed via heart rate (HR) and heart rate variability (HRV), psychophysiological reactivity associated with a forgiveness task as measured through HR and HRV, attention (alerting, orienting, and executive attention networks), and mental health (stress, depression, anxiety, subjective well-being, positive and negative affect).DiscussionThis trial aims to test the effects of an app-based Christian and Islamic meditation, compared to secular mindfulness and a waitlist, using a randomised controlled trial. If the results yield positive outcomes, this study will support the efficacy of these contemplations, offering practitioners a way to enhance their well-being within their religious framework.Trial registrationClinicalTrials.gov, NCT06136676. Registered on 18 November 2023.https://clinicaltrials.gov/study/NCT06136676.

The impact of different music genres on pain tolerance: emphasizing the significance of individual music genre preferences

Music is a promising (adjunctive) treatment for both acute and chronic pain, reducing the need for pharmacological analgesics and their side effects. Yet, little is known about the effect of different types of music. Hence, we investigated the efficacy of five music genres (Urban, Electronic, Classical, Rock and Pop) on pain tolerance. In this parallel randomized experimental study, we conducted a cold pressor test in healthy volunteers (n = 548). The primary outcome was pain tolerance, measured in seconds. No objective (tolerance time) or subjective (pain intensity and unpleasantness) differences were found among the five genres. Multinomial logistic regression showed that overall genre preference positively influenced pain tolerance. In contrast, the music genres that participants thought would help for pain relief did not. Our study was the first to investigate pain tolerance at genre level and in the context of genre preference without self-selecting music. In conclusion, this study provides evidence that listening to a favored music genre has a significant positive influence on pain tolerance, irrespective of the kind of genre. Our results emphasize the importance of individual music (genre) preference when looking at the analgesic benefits of music. This should be considered when implementing music in the clinical setting.

Psychophysical changes after total sleep deprivation and experimental muscle pain.

Sleep disturbances exacerbate chronic pain, increase psychological load, and increase inflammation. Delayed onset muscle soreness (DOMS) mimics aspects of chronic pain, predominantly affecting peripheral pain mechanisms, while experimental sleep provocations have been shown to impact central pain mechanisms. This study aimed to combine a DOMS model with total sleep deprivation (TSD) to create a novel model affecting both peripheral and central pain mechanisms. A total of 30 healthy participants attended two sessions (baseline and follow-up) separated by 24 h of TSD and a home rating after 48 h. Assessments of interleukin 6 (IL-6) levels, sleep quality, pain catastrophising, affect, and symptoms of depression and anxiety were included in the baseline and follow-up sessions. Additionally, pressure pain and tolerance thresholds, temporal summation, and conditioned pain modulation (CPM) were assessed using cuff-pressure algometry in the baseline and follow-up sessions. DOMS was induced with eccentric calf raises during the baseline session followed by 24 h of TSD. At follow-up pain tolerance (p = 0.012) was significantly reduced, and CPM (p = 0.036) was significantly impaired compared to baseline. Psychological changes included decreases in pain catastrophising (p = 0.027), positive affect (p < 0.001), negative affect (p = 0.003), and anxiety (p = 0.012). Explorative regression models predicted 58% and 68% of DOMS pain intensity after 24 and 48 h, respectively, based on baseline body mass index, pain thresholds, psychological measures, and IL-6 (p < 0.01). Combining DOMS with 1 night of TSD induced pain hypersensitivity, impaired CPM, and altered psychological states. A combination of baseline inflammation, psychological measures, and pain sensitivity significantly predicted DOMS pain intensity after 24 and 48 h.

Diminished pain sensitivity mediates the relationship between psychopathic traits and reduced learning from pain

Individuals with elevated psychopathic traits exhibit decision-making deficits linked to a failure to learn from negative outcomes. We investigated how reduced pain sensitivity affects reinforcement-based decision-making in individuals with varying levels of psychopathic traits, as measured by the Self-Report Psychopathy Scale-Short Form. Using computational modelling, we estimated the latent cognitive processes in a community non-offender sample (n = 111) that completed a task with choices leading to painful and non-painful outcomes. Higher psychopathic traits were associated with reduced pain sensitivity and disturbances in reinforcement learning from painful outcomes. In a Structural Equation Model, a superordinate psychopathy factor was associated with a faster return to original stimulus-outcome associations as pain tolerance increased. This provides evidence directly linking reduced pain sensitivity and learning from painful outcomes with elevated psychopathic traits. Our results offer insights into the computational mechanisms of maladaptive decision-making in psychopathy and antisocial behavior.

Racial Disparities in Anesthesia Care: A Systematic Review of Pain Management and Patient Outcomes.

Racial disparities in healthcare are a prominent issue that needs to be addressed to improve the quality of care for all patients. There are several disparities and biases related to the perceived pain tolerance people of color (POC) patients have and their need for analgesics. These biases lead to inadequate pain management and decreased health outcomes. Our study aims to highlight these disparities and how they impact the care patients receive, specifically in the field of anesthesia. To conduct this study, a comprehensive systematic literature search was performed, articles were included and removed according to specific inclusion and exclusion criteria, and a systematic review was performed. Sixteen papers that met the inclusion and exclusion criteria were selected, and after data collection, correlations between POC and pain tolerance were assessed throughout the articles. The studies reviewed showed that there may be some correlation between racial background and perceived pain tolerance. While some studies found that racial disparities may negatively impact the care POC patients receive, others found that there was no correlation at all. Regardless, more studies need to be conducted to assess the factors influencing the treatment of POC in anesthesia.

Randomized, placebo-controlled study on the effects of intravenous GSK3858279 (anti-CCL17) on a battery of evoked pain tests in healthy participants.

C-C Motif Chemokine Ligand 17 (CCL17) is a chemokine that binds and signals through the G-protein coupled CC-chemokine receptor 4 and has been implicated in the development of inflammatory and arthritic pain. GSK3858279 is a high-affinity, first-in-class, monoclonal antibody, binding specifically to CCL17 and inhibiting downstream signaling. In this phase I, randomized, single-center, double-blind, placebo-controlled, three-period, incomplete-block crossover study (NCT04114656), the analgesic effects and safety of intravenous GSK3858279 were assessed in a battery of evoked acute pain assessments on healthy, adult (aged ≥18 years), male participants. Participants were randomized 1:1 to receive either one placebo (0.9% w/v NaCl) dose followed by two GSK3858279 doses (PAA treatment sequence), or one GSK3858279 dose followed by two placebo doses (APP treatment sequence). The co-primary end points were ultraviolet B heat pain detection threshold (°C), cold pressor time to pain tolerance threshold (PTT, sec), and electrical PTT (mA, single stimulus). Twenty-one participants were enrolled (PAA = 11; APP = 10). Mean age (standard deviation) was 29.3 (7.9) years for PAA, 31.1 (7.7) years for APP. No significant differences were observed in the analgesic effect between GSK3858279 and placebo for any end point. Exposure to GSK3858279 was similar between Period 1 (APP sequence), and Periods 2 and 3 (PAA sequence), with some GSK3858279 carry-over. Changes in serum CCL17 levels were consistent with the expected GSK3858279 activity. All drug-related adverse events were mild in intensity and caused no discontinuations. The absence of an efficacy signal in this acute pain model does not preclude efficacy in chronic pain states.

Dental and anesthesiology problems in nicotine dependents (literature review)

Nowadays, smoking is one of the significant factors for the development of inflammatory periodontal diseases. The effect of nicotine on the microcirculation is manifested in the deterioration of the trophic level of the gums and a decrease in their resistance to infection. Atrophy of acinar parts of small salivary glands develops and other morphological changes characteristic of progressive sialadenitis occur. A change in the microflora of the oral cavity was found depending on the duration of smoking. Epithelial dysplasia, which covers the entire thickness of the epithelium, but does not affect the connective tissue, is called carcinoma. Worldwide, more than 300 million people use smokeless tobacco. Malignant changes at the site of precancerous diseases occur after a couple of years of using the product. In smokers, nicotine blocks H-cholinergic receptors and reduces sensitivity to local anesthetics. Nicotine promotes the production of the CYP2E1 enzyme, which is responsible for the metabolism of halogen anesthetics: halothane, enflurane, diethyl ether, trichlorethylene, chloroform, isoflurane and methoxyflurane. Chronic smokers show reduced pain tolerance. Before morphine loading, the assessment of pain threshold in nicotine-dependent individuals was significantly lower than in non-smokers. Smokers require higher doses of opiates and benzodiazepines than nonsmokers. Smoking reduces the potency of aminosteroid muscle relaxants, the required doses of vecuronium and rocuronium in smokers were 25 % higher than in patients leading a healthy lifestyle. Smokers also need more frequent doses to maintain neuromuscular block. Quitting smoking 4–6 weeks (ideally 8 weeks) before general anesthesia reduces the frequency of peri- and postoperative complications.

Use of a surgical referral algorithm within a standardized shoulder physical therapy program to assist clinical decision-making

Purpose Determine (a) utility of a shoulder referral algorithm, (b) patients improving ≥15% on the Western Ontario Rotator Cuff(WORC) score with standardized Physical Therapy(PT) +home exercises, and (c) presenting characteristics among PT-Only, PT + Surgical Consult and Surgery participants. Materials and Methods Prospective cohort study of patients 30–65 years old with shoulder pain. A standardized PT program assessed pain, ROM, strength and exercise tolerance (i.e., referral algorithm) at 2-, 6- and 12-weeks to determine if a surgical consultation might be beneficial. A blinded research assessor evaluated pain, ROM, strength and WORC score at 6-, 12-weeks and 6-months. The proportion improving WORC scores ≥15% and group differences were also evaluated. Results 32/128 (25%) participants underwent consultation with 16 (12.5%) undergoing surgery. WORC scores improved ≥15% by 12-weeks in most PT-Only/PT + Surgical Consult participants (n = 77[70%]) and was maintained at 6-months. Surgery participants used more NSAIDs (p = 0.01), injections (p = 0.002) and trended to higher opioid use (p = 0.06). PT + Surgical Consult/Surgery participants (n = 16/32; 50%) knew diagnostic imaging results more than PT-Only (n = 26; 31%) (p = 0.02). Surgery participants presented with worse pain, ROM, strength and WORC scores than PT-Only (p < 0.05). Conclusions The algorithm identified those with worse symptomology (25%), 50% of whom underwent surgery. WORC scores improved ≥15% in most participants (70%). Presenting characteristics were significantly worse between PT-Only and Surgery participants.

Pressure algometry in the general adult population: Age and sex differences.

Experimental pain studies have revealed inter-individual variations in pain perception that are influenced by age, sex, and country of origin. This study aimed to explore the age and sex differences in pressure pain thresholds within the Iranian general population. To assess the pressure pain thresholds, a handheld pressure algometer was applied bilaterally to the middle fingers of both hands. The participants also completed the short form of the McGill Pain Questionnaire to provide a clinical pain rating. This cross-sectional study included 1610 adult subjects (54.96% female, mean age 40.13 ± 10.18 years). The findings indicated that females generally exhibited lower pain thresholds than males when assessing pain detection and tolerance parameters (P < .001). Females also demonstrated a significant lower pressure thresholds and clinical pain ratings compared with men (P < .001). Additionally, significant differences were observed between age groups in terms of pain detection and tolerance thresholds (P = .02 and P = .03, respectively). However, the interaction between sex and age was not significant. No significant differences in pain detection thresholds were observed between the right and left hand (P = .11). This study underscores the potential utility of algometry as a valuable tool for objectifying pain in the Iranian population.

Hyperalgesia in Patients With a History of Opioid Use Disorder

Short-term and long-term opioid treatment have been associated with increased pain sensitivity (ie, opioid-induced hyperalgesia). Treatment of opioid use disorder (OUD) mainly involves maintenance with methadone and buprenorphine, and observations of heightened cold pain sensitivity among patients are often considered evidence of opioid-induced hyperalgesia. To critically examine the evidence that hyperalgesia in patients with OUD is related to opioid use. Web of Science, PubMed, and Embase between March 1, 2023, and April 12, 2024, were searched. Studies assessing cold pressor test (CPT) pain responses during treatment seeking, pharmacological treatment, or abstinence in patients with OUD history were included. Multilevel random-effects models with robust variance estimation were used for all analyses. Study quality was rated with the JBI checklist. Funnel plots and Egger regression tests were used to assess reporting bias. Main outcomes were pain threshold, tolerance, and intensity in patients and healthy controls, and unstandardized, standardized (Hedges g), and percentage differences (%Δ) in these measures between patients and controls. The association between pain sensitivity and opioid tolerance, withdrawal, and abstinence indices was tested with meta-regression. Thirty-nine studies (1385 patients, 741 controls) met the inclusion criteria. Most studies reported CPT data on patients undergoing opioid agonist treatment. These patients had a mean 2- to 3-seconds lower pain threshold (95% CI, -4 to -1; t test P = .01; %Δ, -22%; g = -0.5) and 29-seconds lower pain tolerance (95% CI, -39 to -18; t test P < .001; %Δ, -52%; g = -0.9) than controls. Egger tests suggested that these differences may be overestimated. There were some concerns of bias due to inadequate sample matching and participant dropout. Meta-regressions yielded no clear support for hyperalgesia being opioid related. Patients receiving opioid agonist treatment for OUD are hypersensitive to cold pain. It remains unclear whether hyperalgesia develops prior to, independent of, or as a result of long-term opioid treatment. Regardless, future studies should investigate the impact of hyperalgesia on patients' well-being and treatment outcomes.

Isokinetic Knee Strengthening Impact on Physical and Functional Performance, Pain Tolerance, and Quality of Life in Overweight/Obese Women with Patellofemoral Pain Syndrome.

Background/Objectives: Patellofemoral syndrome is a common osteoarticular condition that affects many individuals. Various treatment options are available, with a significant emphasis on targeted muscle-strengthening exercises. The purpose of this study was to investigate the effect of isokinetic muscle strengthening on muscle strength, joint range of motion, quality of life, physical performance, and pain tolerance in overweight/obese women with patellofemoral syndrome. Methods: Twenty-four overweight or obese women with patellofemoral syndrome participated in the study during September and October 2023 in a private medical facility for physical medicine and functional rehabilitation. They were randomly assigned to one of two groups for six weeks of isokinetic muscle strengthening. The first group (ISO.G) followed a rehabilitation program combined with isokinetic muscle strengthening. A second group (PCM.G) followed a rehabilitation program that includes an isokinetic protocol in passive compensation movement. The extensors' peak torque was measured before and after training. Results: The flexors' peak torque, stair climbing test, 10 m walk, chair lift, monopodal support, goniometric knee flexion test, heel-buttock distance measurement, pain, and quality of life scores improved significantly in both groups. The ISO.G, on the other hand, benefited from a significant increase in quadriceps muscle strength revealed by the extensors' peak torque. Conclusions: For the treatment of patellofemoral syndrome, isokinetic muscle strengthening in concentric mode appears to have a significant advantage over the classic rehabilitation program with isokinetic passive compensation, particularly in muscle strength gain, in addition to the improvement of joint range of motion, quality of life, physical performance, and pain tolerance. Isokinetic training may be recommended as a beneficial approach for the rehabilitative treatment of patellofemoral pain syndrome in overweight/obese women.

Acute analgesic effect of nicotine vaping using three experimental pain induction tasks: a randomized, placebo-controlled laboratory study.

Pain and nicotine use are co-occurring conditions with a significant impact on health. Experimental evidence supports an acute analgesic effect of nicotine which may reinforce nicotine use among those with chronic pain. Evidence for nicotine analgesia have primarily been gathered in combustible cigarette users and have not been extended to electronic nicotine delivery systems (ENDS or vaping). Furthermore, the mechanisms of nicotine analgesia in humans are not well understood. Assess the effect of acute vaped nicotine on subjective and behavioral indices of pain sensitivity using three tasks designed to probe distinct mechanisms of analgesia. This study recruited ENDS users (N = 86) to undergo a paced vaping protocol followed by pain tasks in counterbalanced order. Across four sessions, participants vaped e-liquid containing nicotine or placebo, and flavor or no-flavor in a 2 × 2 within-subject design. Assessments included cold pressor, submaximal effort tourniquet to induce ischemic pain, and temporal summation of heat pain, an index of central sensitization. Compared to placebo, nicotine increased cold pressor pain tolerance (ηp2 = 0.031), ischemic pain threshold (ηp2 = 0.073) and tolerance (ηp2 = 0.056) but had no effect on temporal summation of pain. Flavor did not affect pain sensitivity. Females reported greater ischemic pain sensitivity (ηp2 = 0.027) and greater reductions in craving (ηp2 = 0.086). Consistent with research from tobacco smoking, analgesia may be reinforcing and contribute to nicotine dependence among ENDS users. More research on sex differences is warranted.

A Mixed-Methods study of the impact of sex and situational pain catastrophizing on pain sensitivity.

It is well established that catastrophic thinking about pain modulates clinical pain severity, but it may also relate to interindividual differences in the pain experience during procedures. This mixed-methods study investigated the relationship between ratings of situational pain catastrophizing and reported pain sensitivity in the context of receiving a nerve block without sedation, and explored participants' experiences. Healthy volunteers (n = 42) completed baseline psychosocial questionnaires, underwent quantitative sensory testing, and received a lower extremity nerve block, followed by further psychosocial assessment and interviews. Associations of catastrophizing scores with pain sensitivity and procedural site pain were assessed using Spearman's correlations. Interviews were reviewed using an immersion/crystallization approach to identify emergent themes. Greater situational catastrophizing scores were associated with higher pain sensitivity, measured as lower pain threshold and tolerance. Although females exhibited greater pain sensitivity generally, moderation analysis revealed a significant association between situational catastrophizing scores and pain sensitivity only among male participants. Qualitative interviews revealed the importance of participants' emotional responses to pain, and a mismatch of expectation and experience with procedural pain. Males also reported more negative comments about procedural pain. Examination of the variable subjective experience while receiving a nerve block in this experimental lab-based study revealed an important relationship between situational pain catastrophizing scores and pain sensitivity, which was more prominent among male participants. These findings reinforce how insight into individual expectations, emotions, and thought processes may impact pain sensitivity during procedures, and may inform strategies to personalize care, improving patient satisfaction and procedural acceptance.