Pressure Pain Tolerance Thresholds Research Articles

Transcranial Direct Current Stimulation Reduces Pressure Pain Sensitivity in Patients with Non-Malignant Chronic Pain

Objectives: Non-malignant chronic pain is a clinical challenge because pharmacological treatment often fails to relieve pain. Transcranial direct current stimulation (tDCS) is a treatment that could have the potential for pain relief and improvement in quality of life. However, there is a lack of clinical trials evaluating the effects of tDCS on the pain system. The aim of the present study was to evaluate the effect of 5 days of anodal tDCS treatment on the pain system in chronic non-malignant pain patients using quantitative sensory testing (QST) and quality of life questionnaires: (1) Brief Pain Inventory-short form (BPI-sf), (2) European Organization for Research and Treatment of Life Questionnaire (EORTC-C30), and (3) Hospital Anxiety Depression Scale (HADS). Methods: Eleven non-malignant chronic pain patients (51±13.6 years old, 5M) participated in the study. Anodal tDCS was applied for five consecutive days, followed by sham stimulation after a washout period of at least two weeks. Pressure pain thresholds (PPT) and pain tolerance thresholds (PTT) were assessed in different body regions on days 1 and 5. Results: Anodal tDCS appeared to maintain PTT at C5 (clavicle) on day 5, but sham stimulation decreased PTT (P=0.007). Additionally, anodal tDCS increased PTT compared to sham at day 5 at Th10 ventral dermatomes (P=0.014). Both anodal and sham tDCS decreased the BPI-sf total and interference scores, and the EORTC-C30 fatigue score, but no interaction effect was observed. Discussion: This study adds to the evidence in the literature that tDCS may be a potential therapeutic tool for the management of non-malignant chronic pain.

Enhancing treatment of lumbar disc herniation with Erxian decoction and auricular acupoint pressure: A randomized controlled trial.

The incidence of lumbar disc herniation (LDH) is on the rise annually, with an emerging trend of affecting younger age groups. This study aims to investigate the clinical effectiveness of combining Erxian decoction with auricular acupoint pressure therapy in treating LDH. Our objective is to furnish evidence supporting the incorporation of traditional Chinese medicine (TCM) rehabilitation techniques in clinical settings. This randomized controlled trial enrolled 102 patients diagnosed with LDH and allocated them into Control and Intervention groups. The Control group underwent a 2-week rehabilitation regimen, whereas the Intervention group received an augmented treatment comprising Erxian decoction along with auricular acupoint pressure therapy based on the Control group. Main outcome measures included 3 scales - visual analog scale (VAS), Japanese Orthopedic Association (JOA), and Oswestry Disability Index - as well as 3 inflammatory markers: C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α). Additionally, pressure pain threshold and pain tolerance threshold values were evaluated. Participants were assessed at baseline, on 14-day, and on 28-day posttreatment. After 2 weeks of treatment, both the Control and Intervention groups exhibited significant improvements in the VAS, JOA, ODI, CRP, IL-6, TNF-α, pressure pain threshold, and pain tolerance threshold (P < .05). These improvements persisted at the 28-day in the VAS, JOA, and ODI scores (P < .05). On 14-day, the Intervention group showed significantly better outcomes compared to the Control group in terms of the VAS, JOA, ODI, CRP, TNF-α, and pressure pain threshold (P < .05). Compared to conventional rehabilitation therapy, the combination of Erxian decoction and auricular acupoint pressure therapy demonstrates clear benefits in alleviating symptoms in patients with LDH. This approach offers fresh perspectives and substantiates evidence for future treatment strategies in managing LDH.

Effects of an afforestation activity on thermal and mechanical pain mechanisms: A clinical trial

Sensory stimulation has shown the capacity to modulate pain mechanisms. Yet, the optimal methods of sensory stimulation remain uncertain. Afforestation activities stand out as a potential stimulation method, as they allow individuals to interact with multisensory stimuli produced in green environments. Exposure to natural multisensory stimuli has been shown to induce neurobiological activations in pain-related brain areas in healthy populations. However, the possible impact of the natural multisensory stimuli on the pain mechanisms themselves is yet to be explored. This study aimed to investigate the potential effects of sensory stimulation experienced during participation in an afforestation program on thermal and mechanical pain mechanisms. A single-group, pretest-posttest clinical trial was used. Forty-seven healthy adults performed an afforestation activity for 90 minutes. Measurements included cold pain detection and tolerance thresholds via the Cold Pressor Test, wind-up and mechanical pain sensitivity through a pinprick stimulator, and pressure pain detection and tolerance thresholds utilizing pressure algometry. For both thermal and mechanical pain thresholds, pain intensity was assessed using the 101-point Numeric Rating Scale. The results showed significant reductions in the cold pain intensity at the moment of detection (p = .046), mechanical pain sensitivity (p ≤ .014), and increases in the thresholds of pressure pain detection (p = .005) and tolerance (p ≤ .046). Therefore, the interaction with natural multisensory stimuli could be a possible therapeutic strategy to positively modulate mechanical pain sensitivity and pressure pain thresholds.

Effects of virtual reality on psychophysical measures of pain: superiority to imagination and nonimmersive conditions.

Virtual reality (VR) has been shown to be effective in pain management. However, to date, little is known about the mechanisms by which immersive experiences influence pain processing. The aim of this study was to investigate the direct effects of an immersive VR environment on the perception of experimental pain in individuals with chronic pain and pain-free controls. The immersion in a VR landscape was compared with mental imagery and a nonimmersive control condition. Using a randomized within-crossover design, pressure pain detection and tolerance thresholds, spatial and temporal summation (SSP, TSP), and conditioned pain modulation (CPM) were measured in 28 individuals with chronic pain and 31 pain-free controls using phasic cuff pressure on the legs. Direct comparison between the groups showed that although individuals with pain had significantly lower pain thresholds, reduced CPM effects, and increased TSP, the VR condition had the same pain-inhibitory effect on pain thresholds as in pain-free controls. Conditioned pain modulation effects were reduced by all conditions compared with baseline. There were no significant differences between conditions and baseline for TSP and SSP. Overall, pain modulatory effects were largest for VR and smallest for imagery. These results demonstrate that immersion in a VR environment has an increasing effect on pain thresholds, reduces pain inhibition in a CPM paradigm, and has no effects on TSP. This applies for participants with chronic pain and pain-free controls. These VR effects exceeded the effects of mental imagery on the nonimmersive control condition. This indicates that VR effectively modulates pain perception in both patients and controls irrespective of differences in pain perception.

Influence of genetic variants on remifentanil sensitivity in Chinese women.

Significant individual differences have been observed in pain sensitivity and analgesic effect of opioids. Previous studies have shown that genetic factors contributed to analgesics requirement obviously. Therefore, we investigated the role of genetic polymorphisms in the sensitivity to the analgesic effect of remifentanil in this study. One hundred thirty-seven patients undergoing gynaecological surgery were observed. Before procedures, we measured the basal pain threshold of each patient, including the pressure pain threshold and pressure pain tolerance threshold. Subsequently, patients received a continuous remifentanil infusion for 15 min at a constant rate of 0.2μg/(kg min). The pain thresholds were measured again after the remifentanil infusion. Moreover, respiratory depression was estimated using oxygen saturation during infusion. DNA was extracted from peripheral venous blood and genotyped using SNaPshot technology. Polymorphisms were found in genes associated with the individual variation in analgesia. Participants carrying OPRM1 rs9397685 AA, ADRB1 rs1801253 CC, and GCH1 rs8007267 CC polymorphisms showed higher sensitivity to analgesic effect induced by remifentanil, and the participants carrying the OPRD1 rs2234918 TT showed lower sensitivity to remifentanil-related respiratory depression. Moreover, individual susceptibility to remifentanil increases with age. Gene variation in OPRM1 rs9397685 AA, ADRB1 rs1801253 CC, GCH1 rs8007267 CC, and OPRD1 rs2234918 TT were related to the conspicuous interindividual differences in the analgesia and respiratory depression of remifentanil, mainly by affecting the target protein receptors and relative metabolic enzymes.

Body image dissatisfaction and experimental pressure pain sensitivity in a cohort of 13-year-old adolescents

ObjectiveWe aimed to quantify the associations between body image (dis)satisfaction and pressure pain thresholds in adolescents, using data from Generation XXI, a population-based cohort study in Portugal. MethodsWe assessed 1785 13-year old adolescents cross-sectionally. Body image satisfaction was measured using the Children's Figure Rating Scale. Pain detection and tolerance thresholds were assessed using cuff pressure algometry. We quantified the associations between body image categories (satisfied, prefers slightly thinner, prefers much thinner, and prefers heavier) and pain detection and tolerance thresholds using linear and logistic regression for continuous and binary (odds of achieving the highest distribution quarter) outcomes, respectively. Models were adjusted to pubertal stage and body mass index. ResultsAdolescents who desired a heavier silhouette had lower pressure pain tolerance thresholds when compared to those who were satisfied (linear regression coefficient: −3.95; 95% confidence interval: −6.68, −1.21), which was more precise in boys (−3.51; −7.17, −0.08). Those adolescents also had lower odds of achieving the highest quarter of pressure pain tolerance threshold (odds ratio: 0.66; 0.48, 0.90), especially girls (0.58; 0.35, 0.98). Adolescents who desired much thinner silhouettes had lower odds of achieving the highest quarter of pressure pain tolerance (0.68; 0.46, 1.00), and this was clearer in girls (0.66; 0.48, 0.90). Pain detection thresholds did not show robust associations with body image dissatisfaction. ConclusionOur study suggests an association between satisfaction with one's silhouette and pain tolerance in adolescents from the general population, arguing for an integrated approach to the assessment of body image and pain sensitivity.

Sensitivity and pain in focal dystonia of the hand

IntroductionA growing body of evidence highlights the importance of understanding both the sensory and the motor pathophysiology of focal dystonia in order to improve its treatment. This study aims to evaluate somatosensory afferences in patients with focal or segmental dystonia affecting the upper limbs, to analyse whether the dominant limb is more frequently affected, to analyse pain tolerance, and to examine the potential association with pain perception in patients with hand dystonia. MethodsWe recruited 24 participants: 12 patients with focal hand dystonia and 12 individuals without dystonia. All participants were evaluated with a digital algometer (Somedic SenseLab AB®, Farsta, Sweden), a Semmes-Weinstein monofilament test, and the visual analogue scale for pain. ResultsAccording to our data, patients showed greater impairment in surface sensitivity than controls, both in the dominant and the non-dominant hands, as well as greater presence of pain (P > .001). Furthermore, the dystonia group showed a negative correlation between perceived pain and pressure pain tolerance threshold (rho = −0.83; P < .001). ConclusionsPatients with focal hand dystonia presented alterations in sensitivity and more severe perceived pain than individuals without dystonia. Future studies with larger samples should aim to analyse the clinical implications and everyday impact of both objective and subjective pain.

Immediate effect of quick massage on muscle tension and pressure pain threshold

ABSTRACT BACKGROUND AND OBJECTIVES: Massage is described as an effective complementary therapy for relieving muscle tension and pain. The aim of this study was to verify the benefits of quick massage on muscle tension and pressure pain tolerance threshold (PPT). METHODS: A randomized clinical study in which 40 professors participated and were randomly divided into control (CG) and experimental (EG) groups. They were assessed for the level of muscle tension in the shoulder and neck regions using the visual analogue scale (VAS). PPT was assessed through algometry at the upper trapezius and sternocleidomastoid muscles and at the following anatomical areas: base of the occipital, scapular spine, thoracic (T6-T7) and lumbar (L4-L5) regions. The EG received a single session of quick massage for 20 minutes on the shoulders, neck and spine. RESULTS: Regarding pain, a significant difference was observed only at the base of the occipital, the EG presented greater tolerance to pressure pain both before and after the intervention when compared to the CG. Regarding muscle tension, after the intervention, there was a reduction in the perception in the EG compared to the CG group. CONCLUSION: Quick massage was efficient to decrease the perception of muscle tension assessed by VAS, however, PPT did not increase after the intervention.

Comparison of the effect of two different types of dry-needling techniques on subacromial impingement syndrome

IntroductionInfraspinatus is one of the main muscles that is involved in the subacromial impingement syndrome. Dry needling and routine physical therapy can improve this syndrome. However, the dry needling technique is not well defined. Designrandomized controlled clinical trial, single-blind study. MethodSixty-six patients diagnosed with shoulder impingement syndrome were recruited and randomly divided into three groups. InterventionsIn 1st group; patients received deep dry needling technique in addition to routine physical therapy, in Hong's group; patients received Hong's dry needling technique in addition to routine physiotherapy and in third group; patient just received routine physical therapy. Main outcome measure(s)Before, immediately after and 4 weeks after the intervention, pain, disability and the pressure pain threshold were measured. ResultsThe findings of this study indicated that in DDN group, pain and disability reduction was significantly more than two other groups. Although, the pressure pain tolerance increased in all three groups after treatment, but the increase between groups was not significantly different. All study groups showed reduction in pain, while there was no significant difference between the three groups. ConclusionPain and disability reduction in the DDN group compared to the other two groups may reveal the treatment with deep dry needling technique along with routine physiotherapy is more effective than receiving dry needling with Hong's technique or routine physiotherapy alone. However, there was no significant difference between the three groups in pressure pain tolerance threshold and pain reduction.

Sensibilidad y dolor en distonías focales de la mano

IntroductionA growing body of evidence highlights the importance of understanding both the sensory and the motor pathophysiology of focal dystonia in order to improve its treatment. This study aims to evaluate somatosensory afferences in patients with focal or segmental dystonia affecting the upper limbs, to analyse whether the dominant limb is more frequently affected, to analyse pain tolerance, and to examine the potential association with pain perception in patients with hand dystonia. MethodsWe recruited 24 participants: 12 patients with focal hand dystonia and 12 individuals without dystonia. All participants were evaluated with a digital algometer (Somedic SenseLab AB®, Farsta, Sweden), a Semmes-Weinstein monofilament test, and the visual analogue scale for pain. ResultsAccording to our data, patients showed greater impairment in surface sensitivity than controls, both in the dominant and the non-dominant hands, as well as greater presence of pain (P>.001). Furthermore, the dystonia group showed a negative correlation between perceived pain and pressure pain tolerance threshold (rho=−0.83; P<.001). ConclusionsPatients with focal hand dystonia presented alterations in sensitivity and more severe perceived pain than individuals without dystonia. Future studies with larger samples should aim to analyse the clinical implications and everyday impact of both objective and subjective pain.

Effects of cold versus hot compress on pain in university students with primary dysmenorrhea

BACKGROUND AND OBJECTIVES: Dysmenorrhea is the most common gynecological complaint among young women. Several therapeutic resources have been studied, aiming at reducing pain. The objective of this study was to identify the influence of cold or hot compresses on pain intensity and pressure pain tolerance thresholds in women with primary dysmenorrhea. METHODS: A single-blind randomized clinical study involving 40 young women divided into two groups: hot compress or cold compress, applied for 20 minutes on the lower abdomen and lower back regions. Pressure pain tolerance thresholds were evaluated by algometry in the vastus medialis, gluteus maximus, lumbar paravertebral muscles and supraspinatus ligaments L4-L5 and L5-S1. Pain intensity was assessed by the visual analog scale. RESULTS: No significant changes in pressure pain tolerance thresholds were observed immediately after the application of the compresses, nor 30 minutes later. The comparison of the variation in the effect of changes showed no differences between the intervention groups, either regarding the pressure pain tolerance thresholds or the visual analog scale. However, both groups had a significant reduction in the visual analog scale right after the application and 30 minutes after the end of the intervention. Nevertheless, right after the use of the compresses, as well as 30 minutes after its end, the group that received the cold compress had a more significant reduction in pain intensity (p=0.002 and p=0.004, respectively). CONCLUSION: Cold or hot compresses did not produce changes in pressure pain tolerance thresholds. However, pain perception was lower after this treatment, especially in the group using cold compresses.

Pain, disability and catastrophizing in individuals with knee osteoarthritis

ABSTRACT BACKGROUND AND OBJECTIVES: Knee osteoarthritis is among the leading sources of chronic disability and may lead to depression, anxiety and pain catastrophizing, enhancing perceived pain. This study aimed at investigating the influence of pain catastrophizing on attitudes and perception of pain, and in the functionality of individuals with knee osteoarthritis. METHODS: This observational study involved 18 patients, who were assessed for weight and height, and completed the Pain-related Catastrophizing Thoughts Scale (PCTS), Survey of Pain Attitudes (SPA), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the visual analog scale (VAS). Symptoms and disability were assessed by the Lequesne Index, functional mobility was evaluated by the Timed Up and Go (TUG) test. Pressure pain tolerance thresholds (PPT) were assessed by a digital algometer. RESULTS: Mean body mass index of the sample was classified as obese (32,2±4,3). When split by the median of PCTS, differences were observed in most domains of SPA. Patients with more catastrophic thoughts took longer to perform TUG and presented more pain, joint stiffness and worse functionality (WOMAC). Despite the tendency to report more pain (VAS) in patients above the median score of PCTS, no differences were observed between groups with higher or lower catastrophizing regarding PPT. Positive and significant associations between the Rumination factor of PCTS and WOMAC outcomes were observed, as well as between the Hopelessness factor and TUG, Lequesne and WOMAC. CONCLUSION: The higher the presence of catastrophic thoughts, the worse the attitudes towards pain and the physical functionality of knee osteoarthritis patients.

Total sleep deprivation increases pain sensitivity, impairs conditioned pain modulation and facilitates temporal summation of pain in healthy participants.

Chronic pain patients often suffer from insomnia or impaired sleep which has been associated with increased pain sensitivity, but a limited amount of studies have investigated the effects of total sleep deprivation on central pain mechanisms. Therefore, the aim of this study was to determine the effects of total sleep deprivation on temporal summation, conditioned pain modulation, thermal and pressure pain sensitivity in healthy participants. Twenty-four healthy participants took part in this two-session trial. The measurements were conducted after a night of habitual sleep (baseline) and following 24 hours of total sleep deprivation. Detection thresholds for cold and warmth and pain thresholds for cold and heat were assessed. Cuff induced pressure pain detection and tolerance thresholds, temporal summation and conditioned pain modulation were assessed with user-independent, computer-controlled cuff algometry. Conditioned pain modulation was significantly impaired, temporal summation was significantly facilitated and pain sensitivity to pressure and cold pain were significantly increased at follow-up compared with baseline. In conclusion, this study found that one night of total sleep deprivation impaired descending pain pathways, facilitated spinal excitability and sensitized peripheral pathways to cold and pressure pain. Future studies are encouraged to investigate if sleep therapy might normalize pain sensitivity in sleep-deprived chronic pain patients.

Pain Tolerance: The Influence of Cold or Heat Therapy

ObjectivesResources of heat or cold therapies have been widely used for their low cost, analgesic action and for assisting the rehabilitation of acute or chronic injuries. The objective of this study was to search for associations between skin surface temperature and pressure pain tolerance thresholds (PPTs) of healthy individuals undergoing cryotherapy and thermotherapy. MethodsThis is an experimental clinical trial with 22 healthy university students aged between 18 and 35 years. Volunteers underwent thermography and algometry assessments at 6 points in both knees before, immediately after, and 20 minutes after the application of frozen (cryotherapy) or heated (thermotherapy) gel bags in the right knee for 20 minutes. Data were analyzed by 1-way analysis of variance, Student's t test, and Pearson or Spearman correlation tests. ResultsThere was a significant change in skin surface temperature after cryotherapy and thermotherapy, which was maintained after 20 minutes of withdrawal (P < .001). After the intervention, no significant differences were observed regarding the PPT compared to the baseline measurements, nor between the experimental and control knees. ConclusionCryotherapy and thermotherapy produced significant changes in the temperature of the evaluated points after their application. Despite this, no differences in pain tolerance were observed, and there was little association between skin surface temperature and PPT in the knees of healthy women after application of the resources.

Associations Between Skin Surface Temperature and Pressure Pain Tolerance Thresholds of Asymptomatic Individuals Exposed to Cryotherapy and Thermotherapy

ObjectiveThe purpose of this study was to evaluate associations between skin surface temperature and pressure pain tolerance thresholds (PPTs) of asymptomatic individuals exposed to cryotherapy and thermotherapy. MethodsTwenty-two asymptomatic female university students aged between 18 and 35 years underwent thermography and algometry assessments at 6 points in both knees before, immediately after, and 20 minutes after the application of frozen (cryotherapy) or heated (thermotherapy) gel bags in the right knee for 20 minutes. Data were analyzed by 1-way analysis of variance, Student t test, and Pearson or Spearman correlation tests. ResultsThere was a significant change in skin surface temperature after cryotherapy and thermotherapy, which was maintained after 20 minutes of withdrawal (P < .001). After the intervention, no significant differences were observed regarding PPT compared with the baseline measurements, nor between the experimental and control knees. ConclusionCryotherapy and thermotherapy produced significant changes in the temperature of the evaluated points after their application. No differences in pain tolerance were observed in these asymptomatic participants. There was little association between skin surface temperature and PPT in the knees of healthy women after application of the resources.

Touch and Pain Sensations in Diadynamic Current (DD) and Transcutaneous Electrical Nerve Stimulation (TENS): A Randomized Study.

The study investigated touch and pain sensations and the correlation between them in diadynamic current (DD) and transcutaneous electrical nerve stimulation (TENS), electrotherapies commonly applied in musculoskeletal disorders and occupational rehabilitation medicine. Forty healthy subjects were treated with either DD (n=20) or TENS (n=20). Each treatment consisted of three sessions with one-week interval. Touch sensation was determined with the JVP Domes esthesiometer, pain sensation with pressure pain threshold (PPT), and pressure pain tolerance threshold (PPTO) by an algometer. During each session the measurements were performed before the application of the procedure (T0), immediately after it (T1), and 30 minutes after the end of the procedure (T2). Both DD and TENS increased touch sensation (p<0.01) and did not significantly alter PPT and PPTO (p>0.05). No statistically significant differences in short-term effects, i.e., 3 weeks of the trial, were noted between DD and TENS in their influence on touch and pain sensations (p>0.05). There was a high significant correlation between touch and pain sensations in DD (r=0.86). TENS and DD caused similar analgesic effects. DD, which is shorter in the duration of the treatment, may comprise a realistic alternative to TENS in clinical practice of pain management.

Geotherapy combined with kinesiotherapy is efficient in reducing pain in patients with osteoarthritis

IntroductionPatients with osteoarthritis (OA) suffer from a degenerative disease that causes several physical disabilities and pain. Despite the few studies involving exercise combined with geotherapy (a therapy using poultices made from earth materials such as clay or mud) for patients with OA, this subject is still under debate, as effect of the earth material remains unclear. The aim of this study was to compare pain, joint stiffness and disability in patients who underwent kinesiotherapy (K) or geotherapy combined with kinesiotherapy (GK). MethodThis was a clinical randomized single-blinded prospective study, in which 48 individuals participated. Volunteers were evaluated for pain perception, pressure pain tolerance thresholds, and responded to questionnaires about pain, joint stiffness and physical disability (WOMAC) and about symptoms and disability (Lequesne Algofunctional Index). Patients in K group underwent 15 twice-weekly sessions of kinesiotherapy consisting of stretching and strengthening exercises for lower limbs. GK patients received a poultice of powder dolomite mixed with hot water on the knees for 25 min before each of the 15 sessions of the same kinesiotherapy program. ResultsBoth interventions were effective in reducing pain, joint stiffness and physical disability (p < 0.001), and in increasing pressure pain thresholds (p < 0.05); however, patients who underwent GK presented a more pronounced reduction in pain perception (p = 0.006) than those in K group. They also exhibited more tolerance to pain in all sites evaluated. ConclusionBoth interventions were effective in reducing pain, joint stiffness and physical disability, but GK produced significantly better results in pain perception.

Conditioning pain modulation reduces pain only during the first stimulation of thetemporal summation of pain paradigm in healthy participants.

Pro-nociceptive and anti-nociceptive mechanisms are commonly assessed in clinical and experimental pain studies, buttheir potential interaction is not well understood. Investigate the effect of conditioning pain modulation (CPM) on temporal summation of pain (TSP). Twenty healthy participants underwent cuff algometry assessment on the lower legs to establish the pressure pain tolerance threshold (PTT). For the TSP assessment, ten stimuli at the level of the PTT were delivered by computerised cuff inflations (1-s stimulation, 1-s break) while participants rated pain intensity on a 10-cm electronic visual analogue scale (VAS). This TSP paradigm was thenrepeated with a simultaneous conditioning stimulus induced by a cuff on the contralateral leg, inflated to a constant pressure corresponding to 30% (mild), 70% (moderate) or 100% (severe) of the PTT. These were assessed in a randomised order, with a fifteen-minute break between tests. A final TSP test without conditioning was reassessed at the end (post-recording). An interaction between stimuli (1-10) and repetition (p<0.05) was found for VAS scores. VAS scores for the first stimulus were decreased during 30%, 70%, and 100% conditioning intensities, compared to baselineand post-recordings (p<0.05). There was a significant increase in TSP during conditioning (p<0.05). There were no significant differences between baseline and post-recordings for any stimuli (p>0.05). The current study indicates that mild to severe stimuli administered by cuff algometry does not modulate summation effect of temporal summation of pain, which could indicate that pain facilitatory mechanisms are more potent compared with pain inhibitory mechanisms. Current knowledge on the interaction effect of pro and anti-nociceptive paradigms are the lacking. The current study indicates that conditioning pain modulation does not modulate thesummation effect of temporal summation of pain, when evaluated by computerized pressure algometry. This finding was independent of the mild, moderate and severe painful conditioning intensities.

Superficial temperature and pain tolerance in patients with chronic low back pain

IntroductionLow back pain is a common and very prevalent disease and can impose limitations that negatively impact patients. The objective of this study was to verify and compare the association between lumbar superficial temperature and pressure pain tolerance thresholds in individuals with chronic nonspecific low back pain and healthy controls. MethodsThis was a cross-sectional observational study involving 38 individuals with nonspecific chronic low back pain and 19 healthy controls. Volunteers underwent thermographic (infrared sensor), pain perception (visual analog scale), and pressure pain tolerance thresholds (algometry) evaluations in the right and left paravertebral muscles and L4-L5 ligament. ResultsA lower tolerance to pressure pain was found in patients compared to controls at all evaluated sites (p ≤ 0.003). Superficial temperature was significantly higher in the sites evaluated in the low back pain group (p < 0.001). In patients with low back pain, pain perception was weakly and inversely correlated with pressure pain tolerance (r = -0.31; p = 0.05) and moderately correlated to the temperature of the evaluated sites (r = 0.51 to 0.59, p ≤ 0.001). Also, an inverse and weak to moderate association was observed between pressure pain tolerance thresholds and temperature in patients only (r = -0.36 to −0.49; p ≤ 0.02). ConclusionIndividuals with low back pain have lower pressure pain tolerance thresholds and higher superficial temperature in the lumbar region when compared to healthy individuals. The associations observed show that the higher the pain perception, the lower the pain tolerance and the higher the superficial temperature in the lumbar region. Also, the higher the temperature, the lower the pain tolerance.

Effects of repeated conditioning pain modulation in healthy volunteers.

Conditioned pain modulation (CPM) may be impaired in chronic pain patients compared with healthy subjects. The CPM-effect is the difference between pain sensitivity assessments (test-stimuli) with and without a painful conditioning stimulus. CPM has been extensively explored but effects of repeated CPM-effects and differences between repeated CPM assessments and comparable control conditions are less studied. In 20 healthy men, four 5-min bouts with a test-stimulus in the beginning and midway were applied by cuff-algometry to the dominant leg. The 2nd test-stimulus in each bout was conditioned in parallel by a painful cuff pressure on the contralateral leg. A control-session was performed without conditioning. The conditioning intensity was 70% of the pressure-pain tolerance threshold (PTT) assessed at baseline. Pain detection threshold (PDT) was extracted from test-stimuli. CPM/Control-effects were calculated as second minus first test-stimulus, and netCPM-effects were calculated as the difference between CPM-effects and Control-effects. Pain detection threshold increased in all four bouts (p<0.02) compared to the unconditioned test-stimulus and compared to the 2nd test-stimulus in bout1, bout3 and bout4 of the control-session (p<0.04). In the control-session, the 1st test-stimulus PDT increased from bout1 to bout2, bout3 and bout4 (p<0.03). The netCPM-effect increased progressively over the four bouts (p=0.03). Conditioned pain modulation-effects were maintained over four consecutive bouts and in the control-session repeated pain thresholds assessments habituated more than in the CPM-session leading to an increase in netCPM-effect over the four bouts. Conditioning pain modulation can be assessed in 5-min intervals by cuff algometry with a fixed conditioning stimulus. Without applying conditioning stimuli the pain sensitivity of test-stimuli habituated. As a consequence, it can be speculated that the conditioning stimulus may negate the temporal habituation effects during repeated sessions, whereas this may not be the case for unconditioned stimuli. Applying both conditioned and unconditioned repeated test-stimuli may be a way to assess different parts of the pain modulatory system, and a model for measuring a netCPM-effect, which could indicate a balance between habituation and sensitization, is proposed.