Widespread Proprioceptive Acuity Impairment in Chronic Back Pain: A Cross-sectional Study.

OBJECTIVE: To investigate whether proprioceptive accuracy measured with the Joint Position Sense (JPS) in patients with chronic neck and low back pain is impaired exclusively in affected areas or also in distant areas, not affected by pain. DESIGN: Cross-sectional study. SETTING: Interdisciplinary outpatient rehabilitation clinic for back and neck pain. PARTICIPANTS: Patients with chronic neck pain (n=30), patients with chronic low back pain (n=30), and age- and sex-matched asymptomatic control subjects (n=30; N=90). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Patients and asymptomatic control subjects completed a test procedure for the JPS of the cervical spine, lumbar spine, and ankle in a randomized order. Between group differences were analyzed with the univariate analysis of variance and associations of the JPS with clinical features using the Pearson's correlation coefficient. RESULTS: Both patients with chronic neck pain (P<.001) and patients with chronic low back pain (P<.01) differed significantly from asymptomatic controls in the JPS of the cervical spine, lumbar spine and ankle joint, regardless of the painful area. No difference was shown between patient groups (P>.05). An association of the JPS with clinical characteristics, however, could not be shown. CONCLUSION: These results suggest widespread impairment of proprioceptive accuracy in patients with chronic and low back pain and a role for central sensorimotor processes in musculoskeletal pain conditions.

Objective Measurement of Subjective Pain Perception with Autonomic Body Reactions in Healthy Subjects and Chronic Back Pain Patients: An Experimental Heat Pain Study.

Multiple attempts to quantify pain objectively using single measures of physiological body responses have been performed in the past, but the variability across participants reduces the usefulness of such methods. Therefore, this study aims to evaluate whether combining multiple autonomic parameters is more appropriate to quantify the perceived pain intensity of healthy subjects (HSs) and chronic back pain patients (CBPPs) during experimental heat pain stimulation. HS and CBPP received different heat pain stimuli adjusted for individual pain tolerance via a CE-certified thermode. Different sensors measured physiological responses. Machine learning models were trained to evaluate performance in distinguishing pain levels and identify key sensors and features for the classification task. The results show that distinguishing between no and severe pain is significantly easier than discriminating lower pain levels. Electrodermal activity is the best marker for distinguishing between low and high pain levels. However, recursive feature elimination showed that an optimal subset of features for all modalities includes characteristics retrieved from several modalities. Moreover, the study's findings indicate that differences in physiological responses to pain in HS and CBPP remain small.

Explainable Artificial Intelligence (XAI) in Pain Research: Understanding the Role of Electrodermal Activity for Automated Pain Recognition.

Artificial intelligence and especially deep learning methods have achieved outstanding results for various applications in the past few years. Pain recognition is one of them, as various models have been proposed to replace the previous gold standard with an automated and objective assessment. While the accuracy of such models could be increased incrementally, the understandability and transparency of these systems have not been the main focus of the research community thus far. Thus, in this work, several outcomes and insights of explainable artificial intelligence applied to the electrodermal activity sensor data of the PainMonit and BioVid Heat Pain Database are presented. For this purpose, the importance of hand-crafted features is evaluated using recursive feature elimination based on impurity scores in Random Forest (RF) models. Additionally, Gradient-weighted class activation mapping is applied to highlight the most impactful features learned by deep learning models. Our studies highlight the following insights: (1) Very simple hand-crafted features can yield comparative performances to deep learning models for pain recognition, especially when properly selected with recursive feature elimination. Thus, the use of complex neural networks should be questioned in pain recognition, especially considering their computational costs; and (2) both traditional feature engineering and deep feature learning approaches rely on simple characteristics of the input time-series data to make their decision in the context of automated pain recognition.

Translation, cross-cultural adaptation and measurement proprieties of the German version of the Allodynia Symptom Checklist (ASC-12).

BACKGROUND: Cutaneous allodynia is highly prevalent among migraineurs and is associated with a poor prognosis. The Allodynia Symptom Checklist (ASC-12) is a comprehensive questionnaire to identify the presence and severity of allodynia. Our aim was to translate and adapt the ASC-12 to German and evaluate its measurement properties. METHODS: Following the COSMIN guidelines, 80 migraine patients were enrolled in the study to evaluate the stages of translation (n=30) and measurement propriety assessment (n=50), respectively. After reaching a final version, the German ASC-12 was assessed for structural validity, internal consistency, test-retest reliability, construct validity and absolute agreement, using mechanical and thermal pain thresholds as reference method. RESULTS: The German version of the ASC-12 presented an adequate structural validity compatible with the original version of the questionnaire. Its internal consistency ranged from 0.70 to 0.80 considering the total score and the thermic, static and dynamic mechanic subdomains. The total score presented excellent reliability (ICC: 0.85) with a standard error of measurement of 1.15 points and smallest detectable change of 3.40 points. ASC-12 total scores were correlated with headache intensity (r=0.38, p=0.004), headache disability (r=0.37, p=0.004) and cold pain thresholds (r=0.28, p=0.025). The thermic allodynia ASC-12 scores were correlated with cold (r=0.36, p=0.005) and heat (r=-0.30, p=0.010) pain thresholds, while the static mechanical allodynia ASC-12 scores correlated with mechanical pain threshold (r=0.29, p=0.019) and with mechanical pain sensitivity (r=0.24 to 0.28, p< 0.045). Despite no significant bias between methods, quantitative sensory testing (QST) results and ASC-12 scores tend to disagree. CONCLUSION: The German version of the ASC-12 is available for research and clinical settings and presented adequate measurement proprieties, as the original version. Despite the correlation between the ASC-12 and QST, one method cannot be replaced by the other.

Psychophysical testing in chronic migraine and chronic tension type headache: An observational study.

BACKGROUND: Clinical presentation is the key to the diagnosis of patients with migraine and tension-type headache, but features may overlap when both become chronic. Psychophysical parameters may distinguish both conditions. We aimed to compare psychophysical aspects of patients with chronic migraine, chronic tension-type headache and headache-free controls, and to determine whether these can predict headache frequency. METHODS: An examiner blinded to the diagnosis assessed 100 participants (chronic migraine (n = 38), chronic tension-type headache (n = 31) and controls (n = 31)). Assessed variables included painful area, pressure pain thresholds, temporal summation, cervical range of motion, neck posture, headache and neck impact, quality of life, and kinesiophobia. Comparison between groups was performed with one-way ANOVA and multiple linear regression was used to assess the headache frequency predictors. RESULTS: We found differences of both headache groups compared to controls (p < 0.01), but not between headache groups. Neck disability was a significant predictor of headache frequency for chronic tension-type headache (adjusted R2 = 0.14; ß = 0.43; p = 0.03) and chronic migraine (adjusted R2 = 0.18; ß = 0.51; p < 0.01). CONCLUSIONS: Chronic tension-type headache and chronic migraine showed similar psychophysical results, but were significantly worse when compared to controls. The psychophysical examination did not discriminate between headache types. The variable best explaining headache frequency for both headache types was neck disability.

Postural control impairment in patients with headaches-A systematic review and meta-analysis.

OBJECTIVE: To summarize the evidence regarding static and dynamic balance alterations among patients with headache. METHODS: Electronic databases (PubMed, CINAHL, and Web of Science) were searched by two researchers independently up to September 2021. Two reviewers selected eligible studies, extracted the data, and assessed the quality of evidence using the Downs and Black checklist. Case-control studies were included if they involved balance assessment of any kind of headache, including objective outcome measures of dynamic and static tests such as body sway displacement, limits of stability (LOS), gait, and tandem walk tests. A meta-analysis and post hoc sensitivity analyses were performed when possible. RESULTS: Twenty-two studies (1202 patients with headache and 597 controls) were included in this review and 16 of them in the meta-analysis. Risk of bias ranged from low to moderate among all studies. Greater sway area in static posturography was shown by patients with migraine in comparison to controls, with more consistent differences in more challenging test conditions, such as over a foam surface with eyes closed (difference of 4.8 cm2 , 95% CI: 3.8-5.9). Lower performance of patients with migraine during the tandem walk test (difference of -7.8 cm/s, 95% CI: -9.0 to -6.5) and slower reaction time in the LOS test (difference of 0.3 s, 95% CI: 0.2-0.4) were also verified. There is no evidence of altered sway velocity and length in static posturography among patients with migraine (p > 0.05). The level of evidence is very low for balance alteration of any kind among patients with tension-type and cervicogenic headache owing to the limited number of studies and high heterogeneity. CONCLUSION: This review confirmed the presence of static and dynamic balance alterations among patients with migraine. Future studies with low risk of bias are needed to decrease heterogeneity in methodology and explore the role of subdiagnosis on the balance of patients with headache.

Offset analgesia is increased intra-orally.

BACKGROUND: Offset analgesia (OA) is commonly used to quantify endogenous pain inhibition. However, the potential role of afferent inputs and the subsequent peripheral factors from different body areas on the underlying mechanisms are still unclear. OBJECTIVES: The aim of this cross-sectional study was to compare the magnitude of OA in four different body areas representing (a) glabrous and non-glabrous skin, (b) trigeminal and extra-trigeminal areas, and (c) intra- and extra-oral tissue. METHODS: OA was assessed at the oral mucosa of the lower lip, the skin of the cheek, the forearm and the palm of the hand in 32 healthy and pain-free participants. OA testing included two trials: (1) a constant trial (30 s of constant heat stimulation at an individualised temperature of Pain50 [pain intensity of 50 out of 100]) and (2) an offset trial (10 s of individualised Pain50 , followed by 5 s at Pain50 + 1°C and 15 s at Pain50 ). Participants continuously rated their pain during each trial with a computerised visual analogue scale. RESULTS: A significant OA response was recorded at the oral mucosa (p < .001, d = 1.24), the cheek (p < .001, d = 0.84) and the forearm (p < .001, d = 1.04), but not at the palm (p = .19, d = 0.24). Significant differences were shown for OA recorded at the cheek versus the mucosa (p = .02), and between palm and mucosa (p = .007), but not between the remaining areas (p > .05). CONCLUSION: This study suggests that intra-oral endogenous pain inhibition assessed with OA is enhanced and supports the role of peripheral mechanisms contributing to the OA response.

Muscle endurance training of the neck triggers migraine attacks.

BACKGROUND: Most migraine patients report neck pain as part of their migraine symptomatology, but it is unknown whether triggering neck pain would induce migraine attacks. Our aim was to assess the occurrence of headache and/or neck pain after an endurance test of the neck muscles among migraineurs and controls. METHODS: Sixty-five patients with migraine and 32 headache-free participants underwent a manual examination of the cervical spine by an assessor blinded towards the diagnosis and were sub-classified according to the appearance or absence of neck pain. Subsequently, the endurance of the neck flexors and extensors was tested three times, in a random order. The maximum sustained duration was recorded and the test was terminated when the subject was unable to maintain the position or reported pain. On the day after the assessment, participants were asked to report the potential occurrence of headache or neck symptoms. RESULTS: None of the controls reported headache after assessment, while migraine-like headache was reported by 42% of the patients with migraine (p < 0.001) after 15.8 h (SD: 10.0). Neck pain was more prevalent in migraineurs compared to controls (45% vs. 16%, p = 0.006). When considering the neck pain subtype, there were no differences among the three profiles regarding neck pain but participants with referred pain to the head reported a migraine attack more often (45%, p = 0.03). CONCLUSION: Patients with migraine are more likely to report neck pain and migraine attacks following a neck muscle endurance test. Participants with neck pain referred to the head during manual examination had a greater prevalence of migraine attacks than those without or with only local pain.

Investigation of Correlations Between Pain Modulation Paradigms.

OBJECTIVE: Endogenous pain modulation can be quantified through the use of various paradigms. Commonly used paradigms include conditioned pain modulation (CPM), offset analgesia (OA), spatial summation of pain (SSP), and temporal summation of pain (TSP), which reflect spatial and temporal aspects of pro- and antinociceptive processing. Although these paradigms are regularly used and are of high clinical relevance, the underlying physiological mechanisms are not fully understood. DESIGN: The aim of this study is therefore to assess the association between these paradigms by using comparable protocols and methodological approaches. SETTING: University campus. SUBJECTS: Healthy and pain-free volunteers (n = 48) underwent psychophysical assessment of CPM, OA, SSP, and TSP (random order) at the same body area (volar nondominant forearm) with individualized noxious stimuli. METHODS: CPM included heat stimuli before, during, and after a noxious cold-water bath, whereas for OA, three heat stimuli were applied: baseline trial, offset trial, and constant trial. For the SSP paradigm, two differently sized heat stimulation areas were evaluated, whereas for TSP, the first and last stimulus of 10 consecutive short heat stimuli were assessed. A computerized visual analog scale was used to continuously evaluate pain intensity. The magnitudes of all associations between all paradigm pairs were analyzed with Spearman's correlation, and individual influencing factors were assessed with a multivariate linear regression model. RESULTS: Weak to moderate correlations among all four paradigms were found (P > 0.05), and no distinct influencing factors were identified. CONCLUSIONS: A limited association between pain modulation paradigms suggests that CPM, OA, SSP, and TSP assess distinct aspects of endogenous analgesia with different underlying physiological mechanisms.

Comparison of Feature Extraction Methods for Physiological Signals for Heat-Based Pain Recognition.

While even the most common definition of pain is under debate, pain assessment has remained the same for decades. But the paramount importance of precise pain management for successful healthcare has encouraged initiatives to improve the way pain is assessed. Recent approaches have proposed automatic pain evaluation systems using machine learning models trained with data coming from behavioural or physiological sensors. Although yielding promising results, machine learning studies for sensor-based pain recognition remain scattered and not necessarily easy to compare to each other. In particular, the important process of extracting features is usually optimised towards specific datasets. We thus introduce a comparison of feature extraction methods for pain recognition based on physiological sensors in this paper. In addition, the PainMonit Database (PMDB), a new dataset including both objective and subjective annotations for heat-induced pain in 52 subjects, is introduced. In total, five different approaches including techniques based on feature engineering and feature learning with deep learning are evaluated on the BioVid and PMDB datasets. Our studies highlight the following insights: (1) Simple feature engineering approaches can still compete with deep learning approaches in terms of performance. (2) More complex deep learning architectures do not yield better performance compared to simpler ones. (3) Subjective self-reports by subjects can be used instead of objective temperature-based annotations to build a robust pain recognition system.

Increased mechanosensivity of the greater occipital nerve in subjects with side-dominant head and neck pain - a diagnostic case-control study.

Objectives: To investigate differences in pressure pain thresholds (PPTs) and longitudinal mechanosensitivity of the greater occipital nerve (GON) between patients with side-dominant head and neck pain (SDHNP) and healthy controls. Evaluation of neural sensitivity is not a standard procedure in the physical examination of headache patients but may influence treatment decisions. Methods: Two blinded investigators evaluated PPTs on two different locations bilaterally over the GON as well as the occipitalis longsitting-slump (OLSS) in subjects with SDHNP (n = 38)) and healthy controls (n = 38). Results: Pressure pain sensitivity of the GON was lower at the occiput in patients compared to controls (p = 0.001). Differences in pressure sensitivity of the GON at the nucheal line, or between the dominant headache side and the non-dominant side were not found (p > 0.05). The OLSS showed significant higher pain intensity in SDHNP (p < 0.001). In comparison to the non-dominant side, the dominant side was significantly more sensitive (p = 0.004). Discussion: Palpation of the GON at the occiput and the OLSS may be potentially relevant tests in SDHNP. One explanation for an increased bilateral sensitivity may be sensitization mechanisms. Future research should investigate the efficacy of neurodynamic techniques directed at the GON. Level of Evidence: 3b.

Clinical reasoning skills of German and Dutch manual therapists: a cross-sectional study.

INTRODUCTION: Reflective clinical reasoning (CR) is believed to play a crucial role in achieving an efficient therapy process, supported by evidence-based approaches that improve patient outcomes. The aim of this study was to evaluate the CR process of German manual therapists (MTs) using the CR skills of Dutch MTs as a reference. METHODS: This cross-sectional study evaluated the CR process and diagnostic ability of German MTs. Dutch MTs served as the reference standard due to their experience with direct access. The CR skills were assessed using the Diagnostic Thinking Inventory (DTI), a questionnaire measuring diagnostic competence. Descriptive and inferential statistics were conducted to compare the groups. Subgroup analyses were performed to analyze the influence of work experience (in years) and the level of education on CR. RESULTS: 396 manual therapists (229 German and 167 Dutch) completed the DTI. Dutch MTs revealed higher DTI sum-scores compared to German MTs (p < .001; Cohen´s d = .41). Subgroup analyses regarding professional education revealed no significant differences in DTI sum-scores within German MTs and between both groups. In the subgroup analyses regarding professional experience, differences of moderate effect size were reached between German and Dutch novice MTs (in favor of Dutch novice MTs; p = .001; Cohen´s d = .62), and between German novice MTs and experienced German MTs (in favor of experienced German MTs; p < .001; Cohen´s d = .6). CONCLUSION: The results suggest that academically educated German and Dutch MTs as well as experienced German and Dutch MTs are similar in terms of their hypothetical-deductive CR skills. In turn, German novice MTs seem to use hypothetical-deductive processing to a lesser extent compared to Dutch novice MTs and experienced German MTs, which in turn may support the hypothesis that the level of professional experience and education has a significant impact on the development of hypothetical-deductive CR skills.

Physical Therapist Interventions to Reduce Headache Intensity, Frequency, and Duration in Patients With Cervicogenic Headache: A Systematic Review and Network Meta-Analysis.

OBJECTIVE: The aim of this study was to assess the efficacy of physical therapist interventions on the intensity, frequency, and duration of headaches, as well as on the quality of life of patients with cervicogenic headache. METHODS: The following databases were searched up to October 2022: Physiotherapy Evidence Database, Web of Science, Pubmed, and Cochrane Library. Randomized controlled trials assessing the effect of physical therapist interventions on adults with cervicogenic headache were included. Quality appraisal was conducted using the Cochrane risk of bias 2.0 tool and the Confidence in Network Meta-analysis web app. Synthesis methods were conducted in accordance with the Cochrane Handbook. RESULTS: Of the 28 identified reports, 23 were included in the quantitative synthesis. Manipulation plus dry needling was the highest-ranked intervention to reduce the short-term headache intensity (mean difference [MD] = -4.87; 95% CI = -8.51 to -1.24) and frequency (MD = -3.09; 95% CI = -4.93 to -1.25) when compared to a control intervention. Other high-ranked and clinically effective interventions (when compared to a control intervention) were muscle-energy technique plus exercise (MD = 4.37; 95% CI = -8.01 to -0.74), as well as soft tissue techniques plus exercise (MD = -3.01; 95% CI = -5.1 to -0.92) to reduce short-term headache intensity, and dry needling plus exercise (MD = -2.92; 95% CI = -4.73 to -1.11) to reduce short-term headache frequency. These results were based on a low certainty of evidence. CONCLUSION: The 4 most highly ranked interventions can be considered in clinical practice. However, no conclusive recommendation can be made due to the low certainty of evidence. IMPACT: Combined interventions such as spinal joint manipulation plus dry needling and muscle-energy technique or soft tissue techniques or dry needling plus exercises seem to be the best interventions to reduce short-term cervicogenic headache intensity and/or frequency.

Body Image Measured via the Fremantle Awareness Questionnaire in Individuals With and Without Pain: A Systematic Review and Meta-Analysis.

Research suggests that pain negatively affects body image, and body image may also influence reported pain levels. This review aims to summarize the literature on differences in body image distortion between individuals with pain compared to pain-free individuals. The review was conducted according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses 2020 statement and an a priori preregistered protocol. The literature was searched using 5 electronic databases. Studies assessing body image with the Fremantle Awareness Questionnaire (FAQ) in individuals with and without pain were eligible for inclusion. Screening and selection of eligible studies were performed by independent reviewers. Methodological quality was assessed with the Joanna Briggs Institute critical appraisal tool. Meta-analyses, meta-correlations, and metamean analyses were performed using random-effect models. The primary outcome was the FAQ score; secondary outcomes were reported pain variables. Data from individuals with pain (n = 2277) and without pain (n = 615) were summarized. Significant body image distortions were found in individuals with pain compared to individuals without pain. Compared to pain-free individuals, the pain group rated significantly higher in the FAQ when experiencing back pain (standardized mean differences=1.33, 95% confidence interval=.88-1.77) or other body parts (standardized mean differences=1.25, 95% confidence interval=.51-1.99). The results of meta-correlation analyses confirmed the positive relationship between body image distortion and pain intensity (r = .31), pain at rest (r = .31), or pain during movement (r = .36), but not for pain duration. A difference in mean FAQ results was observed between individuals with pain in different areas (knee and back). PERSPECTIVE: This review confirms differences in body image distortion between pain and pain-free individuals. Pain intensity was correlated with altered body perception, but not pain duration. A moderate correlation was observed between body image distortion and reported pain variables. Body image was more impaired by knee pain than back pain. REGISTERED PROTOCOL AT PROSPERO: CRD42022309937; https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022309937.

Assessing the Influence of Nonischemic A-Fiber Conduction Blockade on Offset Analgesia: An Experimental Study.

Offset analgesia (OA) is believed to reflect the efficiency of the endogenous pain modulatory system. However, the underlying mechanisms are still being debated. Previous research suggested both, central and peripheral mechanisms, with the latter involving the influence of specific A-delta-fibers. Therefore, this study aimed to investigate the influence of a nonischemic A-fiber conduction blockade on the OA response in healthy participants. A total of 52 participants were recruited for an A-fiber conduction blockade via compression of the superficial radial nerve. To monitor fiber-specific peripheral nerve conduction capacity, quantitative sensory testing was performed continuously. Before, during, and after the A-fiber block, an individualized OA paradigm was applied to the dorsum of both hands (blocked and control sides were randomized). The pain intensity of each heat stimulus was evaluated by an electronic visual analog scale. A successful A-fiber conduction blockade was achieved in thirty participants. OA has been verified within time (before, during, and after blockade) and condition (blocked and control side) (P < .01, d > .5). Repeated measurements analysis of variance showed no significant interaction effects between OA within condition and time (P = .24, η²p = .05). Hence, no significant effect of A-fiber blockade was detected on OA during noxious heat stimulation. The results suggest that peripheral A-fiber afferents may play a minor role in OA compared with alternative central mechanisms or other fibers. However, further studies are needed to substantiate a central rather than peripheral influence on OA. PERSPECTIVE: This article presents the observation of OA before, during, and after a successful A-fiber conduction blockade in healthy volunteers. A better understanding of the mechanisms of OA and endogenous pain modulation, in general, may help to explain the underlying aspects of pain disorders.

Association between myofascial trigger point therapy and conditioned pain modulation.

INTRODUCTION: Myofascial trigger point therapy (MTrP) is a widely used therapeutic approach, although the underlying mechanisms remain unclear. Mechanisms discussed include peripheral involvement of muscles as well as central pain modulating processes such as the conditioned pain modulation (CPM). The aim of this study was to investigate whether the analgesic response of MTrP and the analgesic response of CPM correlate in asymptomatic participants in order to identify shared underlying mechanisms of MTrP and CPM. METHOD: Both, CPM and MTrP protocols consisted of heat-based test stimuli (heat pain thresholds before and after the intervention) and pressure-based (conditioning) stimuli. Asymptomatic participants (n = 94) were randomly assigned to receive either mild, intense or no pressure stimuli (between-group design) to both the fingernail and the MTrP of the infraspinatus muscle (within-group design). Pressure stimuli at both locations (fingernail, MTrP) were applied with a pressure algometer for 120 s and continuously adjusted to maintain a constant pain intensity of mild or intense pain. All thermal stimuli were applied on the lower leg with a thermal stimulator. RESULTS: A significant correlation was shown between the analgesic effect of CPM and MTrP therapy for mild (r = 0.53, p = 0.002) and intensive stimuli (r = 0.73, p < 0.001). 17.3% of the variance of the MTrP effect were explained by CPM after mild stimulation, and 47.1% after intense stimulation. Pain-related characteristics did not explain the variance within the analgesic response using a regression analysis. CONCLUSIONS: Between the analgesic responses following MTrP and CPM paradigms, a moderate to strong correlation was observed, suggesting shared underlying mechanisms.

Differential Effects of Thermal Stimuli in Eliciting Temporal Contrast Enhancement: A Psychophysical Study.

Offset analgesia (OA) is observed when pain relief is disproportional to the reduction of noxious input and is based on temporal contrast enhancement (TCE). This phenomenon is believed to reflect the function of the inhibitory pain modulatory system. However, the mechanisms contributing to this phenomenon remain poorly understood, with previous research focusing primarily on painful stimuli and not generalizing to nonpainful stimuli. Therefore, the aim of this study was to investigate whether TCE can be induced by noxious as well as innocuous heat and cold stimuli. Asymptomatic subjects (n = 50) were recruited to participate in 2 consecutive experiments. In the first pilot study (n = 17), the parameters of noxious and innocuous heat and cold stimuli were investigated in order to implement them in the main study. In the second (main) experiment, subjects (n = 33) participated in TCE paradigms consisting of 4 different modalities, including noxious heat (NH), innocuous heat (IH), noxious cold (NC), and innocuous cold (IC). The intensity of the sensations of each thermal modality was assessed using an electronic visual analog scale. TCE was confirmed for NH (P < .001), NC (P = .034), and IC (P = .002). Conversely, TCE could not be shown for IH (P = 1.00). No significant correlation between TCE modalities was found (r < .3, P > .05). The results suggest that TCE can be induced by both painful and nonpainful thermal stimulation but not by innocuous warm temperature. The exact underlying mechanisms need to be clarified. However, among other potential mechanisms, this may be explained by a thermo-specific activation of C-fiber afferents by IH and of A-fiber afferents by IC, suggesting the involvement of A-fibers rather than C-fibers in TCE. More research is needed to confirm a peripheral influence. PERSPECTIVE: This psychophysical study presents the observation of temporal contrast enhancement during NH, NC, and innocuous cold stimuli but not during stimulation with innocuous warm temperatures in healthy volunteers. A better understanding of endogenous pain modulation mechanisms might be helpful in explaining the underlying aspects of pain disorders.

Spatial summation of pain is associated with pain expectations: Results from a home-based paradigm.

The purpose of this study was to reproduce the previously observed spatial summation of pain effect (SSp) using non-laboratory procedures and commercial equipment. An additional aim was to explore the association between expectations and SSp. The Cold Pressor Task (CPT) was used to induce SSp. Healthy participants (N = 68) immersed their non-dominant hands (divided into 5 segments) into cold water (CPT). Two conditions were used 1) gradual hand immersion (ascending condition) and 2) gradual hand withdrawal (descending condition). Pain intensity was measured on a Visual Analogue Scale (VAS). Psychological factors, such as the participants' expectations of pain intensity were also measured on a VAS. Results showed significant SSp (χ2(4) = 116.90, p < 0.001), reproduced with non-laboratory equipment in a home-based set-up. Furthermore, two novel findings were observed: i) there was a significant correlation between expectations and perceived pain, indicating a link between pain expectations and SSp, ii) spatial summation increased with the increase in duration exposure to the noxious stimulus (Wald χ2(8) = 80.80, p < 0.001). This study suggests that SSp is associated with pain expectations and can be formed by a mixture of excitatory and inhibitory mechanisms potentially driven by temporal characteristics of neural excitation. Moreover, this study proposes a new feasible way to induce SSp using a home-based set-up.

Effectiveness of online teaching during the COVID-19 pandemic on practical manual therapy skills of undergraduate physiotherapy students.

OBJECTIVES: This study includes two separate parts: the objective for part A was to evaluate the practical manual therapy skills of undergraduate physiotherapy students who had learned manual therapy techniques either online or in classroom depending on the phases of the pandemic. The objective for part B was to evaluate in a randomized prospective design the effectiveness of video-based versus traditional teaching of a manual therapy technique. DESIGN: Cross-sectional cohort study (part A) and randomized controlled trial (part B). SETTING: University of Luebeck, undergraduate physiotherapy students in years 1-3. METHOD: In part A, physiotherapy students who had learned manual therapy either online (during the pandemic) or in classroom (prior to and after the lock down periods of the pandemic) were videotaped while performing two manual techniques on the knee joint and on the lumbar spine. Recordings were analyzed independently by two blinded raters according to a 10-item list of criteria. Inter-rater reliability was assessed using Cohen's kappa for each item. Performance across cohorts was analyzed using analysis of variance. In part B, students were randomized to learn a new technique on the cervical spine either from a lecturer or from the same lecturer on a video recording (independent variable). Practical performance of the technique was analyzed by two raters blinded to group allocation according to a 10-item list of criteria (dependent variable). Results were analyzed statistically by using ANCOVA with year of study as a covariate. RESULTS: Sixty-three and 56 students participated in part A and part B of the study, respectively. The inter-rater reliability for video analyses for both parts of the study was moderate (k = 0.402 to 0.441). In part A, there was no statistically significant difference across years of study for the practical performance of the technique on the back F(2,59) = 2.271; p = 0.112 or the knee joint F(2,59) = 3.028; p = 0.056. In part B, performance was significantly better when learned from a lecturer and practiced on a peer than when learned from a video and practiced on a rescue dummy (p < 0.001). CONCLUSION: Practical skill performance can be acquired from videos but immediate skill reproduction is significantly better when the technique is presented by a lecturer in classroom and practiced on peer students.

Psychological mechanisms of offset analgesia: The effect of expectancy manipulation.

A frequently used paradigm to quantify endogenous pain modulation is offset analgesia, which is defined as a disproportionate large reduction in pain following a small decrease in a heat stimulus. The aim of this study was to determine whether suggestion influences the magnitude of offset analgesia in healthy participants. A total of 97 participants were randomized into three groups (hypoalgesic group, hyperalgesic group, control group). All participants received four heat stimuli (two constant trials and two offset trials) to the ventral, non-dominant forearm while they were asked to rate their perceived pain using a computerized visual analogue scale. In addition, electrodermal activity was measured during each heat stimulus. Participants in both intervention groups were given a visual and verbal suggestion about the expected pain response in an hypoalgesic and hyperalgesic manner. The control group received no suggestion. In all groups, significant offset analgesia was provoked, indicated by reduced pain ratings (p < 0.001) and enhanced electrodermal activity level (p < 0.01). A significant group difference in the magnitude of offset analgesia was found between the three groups (F[2,94] = 4.81, p < 0.05). Participants in the hyperalgesic group perceived significantly more pain than the hypoalgesic group (p = 0.031) and the control group (p < 0.05). However, the electrodermal activity data did not replicate this trend (p > 0.05). The results of this study indicate that suggestion can be effective to reduce but not increase endogenous pain modulation quantified by offset analgesia in healthy participants.