Reduced pressure pain thresholds in response to exercise in chronic fatigue syndrome but not in chronic low back pain: an experimental study

Pain thresholds following maximal endurance exercise

PURPOSE

Physical exercise causes alterations in pain sensitivity. Many studies verified so-called exercise-induced analgesia caused by submaximal aerobic intensity. This study aimed to determine the effect of an endurance exercise to exhaustion on pain sensitivity of healthy young men.

METHOD

Pressure pain thresholds (PPTs) [in Newton, (N)] of 50 healthy males (mean age 26 ± 4 years) were applied to knee, ankle and elbow joints as well as to the sternum and forehead. This was followed by a bout of cycling ergometer exercise to exhaustion. The whole process was repeated after 20 and 60 min respectively.

RESULTS

Endurance exercise to exhaustion decreased PPTs at sternum and forehead significantly, while thresholds at the joints were not affected. Pain thresholds at forehead and sternum declined 20 min after exercise with the forehead's threshold being more reduced. PPTs remain decreased until 60 min after exercise (forehead: from 43.6 ± 15.2 N to 36.6 ± 19.8 N to 37.2 ± 13.4 N; sternum: from 46.8 ± 21.0 N to 42.5 ± 17.1 N to 44.8 ± 18.2 N). Modulation of pain sensitivity showed large effect sizes over time for both landmarks (forehead w = 0.65; sternum w = 0.50).

CONCLUSION

Exhaustive endurance exercise is followed by a hyperalgetic condition at forehead and sternum. This may be due to either a reduction in pain inhibiting or an activation in pain stimulating pathways.

At Completion of a Multidisciplinary Treatment Program, Are Psychophysical Variables Associated with a VAS Improvement of 30% or More, a Minimal Clinically Important Difference, or an Absolute VAS Score Improvement of 1.5 cm or More?

OBJECTIVES

Objectives were to determine at completion of a multidisciplinary pain program: 1) what percentage of chronic low back pain (CLBP) patients had improved at 30% or more (minimal clinically important difference [MCID]) and by 1.5 cm or more (minimal important change [MIC]) on the visual analog scale (VAS) and 2) whether that improvement is associated with pain matching (PM), pain threshold (PTRE), and pain tolerance (PTOL) improvements.

METHODS

One hundred and six CLBP patients had admission and discharge scores for VAS, PM, PTRE, and PTOL. Improvement was determined by absolute, MCID, and MIC VAS improvement. Logistic regression analysis controlling for age, gender, race, education, psychoactive substance dependence, and depression was utilized to develop models for the dependent variables of improvement of overall VAS; of MCID of 50% or more; and of MIC with PM, PTOL, and PTRE as independent variables.

RESULTS

Thirty-two percent and 35% of the CLBP patients were at MCID and MIC, respectively, at discharge (68% and 65% not at MCID and MIC, respectively), and 54.7% were improved overall. Of the improved patients, 59% were at MCID and 63.7% at MIC. PM was associated with overall VAS improvement, while PTRE and PM were associated with MCID improvement. MIC and 50% or above models could not be estimated.

LIMITATIONS

The VAS was treated as a ratio scale.

CONCLUSIONS

A significant percentage of CLBP patients were at MCID and at MIC at completion of multidisciplinary treatment. PM was associated with overall VAS improvement, while PTRE and PM were associated with MCID.

Polymorphism in COMT is associated with IgG3 subclass level and susceptibility to infection in patients with chronic fatigue syndrome

BACKGROUND

Chronic fatigue syndrome (CFS) is considered as a neuroimmunological disease but the etiology and pathophysiology is poorly understood. Patients suffer from sustained exhaustion, cognitive impairment and an increased sensitivity to pain and sensory stimuli. A subset of patients has frequent respiratory tract infections (RRTI). Dysregulation of the sympathetic nervous system and an association with genetic variations in the catechol-O-methyltransferase (COMT) and glucocorticoid receptor genes influencing sympathetic and glucocorticoid metabolism were reported in CFS. Here, we analyzed the prevalence of SNPs of COMT and glucocorticoid receptor-associated genes in CFS patients and correlated them to immunoglobulin levels and susceptibility to RRTI.

METHODS

We analyzed blood cells of 74 CFS patients and 76 healthy controls for polymorphisms in COMT, FKBP5 and CRHR1 by allelic discrimination PCR. Serum immunoglobulins were determined by immunoturbidimetric technique, cortisol levels by ECLIA.

RESULTS

Contrary to previous reports, we found no difference between CFS patients and healthy controls in the prevalence of SNPs for COMT, FKBP5 and CRHR1. In patients with the Met/Met variant of COMT rs4680 we observed enhanced cortisol levels providing evidence for its functional relevance. Both enhanced IgE and diminished IgG3 levels and an increased susceptibility to RRTI were observed in CFS patients with the Met/Met variant. Such an association was not observed in 68 non-CFS patients with RRTI.

CONCLUSION

Our results indicate a relationship of COMT polymorphism rs4680 with immune dysregulation in CFS providing a potential link for the association between stress and infection susceptibility in CFS.

Central sensitization and changes in conditioned pain modulation in people with chronic nonspecific low back pain: a case-control study

Quantitative sensory testing is widely used in human research to investigate the state of the peripheral and central nervous system contributions in pain processing. It is a valuable tool to help identify central sensitization and may be important in the treatment of low back pain. The aim of this study was to evaluate changes in local and segmental hypersensitivity and endogenous pain inhibition in people with chronic nonspecific low back pain. Thirty patients with chronic low back pain and thirty healthy subjects were studied. Pressure pain thresholds (PPTs) were measured from the lumbar region and over the tibialis anterior muscle (TA). A cold pressor test was used to assess the activation of conditioned pain modulation (CPM), and PPTs in the lumbar region were recorded 30 s after immersion of participant's foot in a bucket with cold water. People with chronic low back pain have significantly lower PPT than controls at both the lumbar region [89.5 kPa (mean difference) 95 % CI 40.9-131.1 kPa] and TA [59.45 kPa (mean difference) 95 % CI 13.49-105.42 kPa]. During CPM, people with chronic low back pain have significantly lower PPT than controls in lumbar region [118.6 kPa (mean difference) 95 % CI 77.9-159.2 kPa]. Women had significantly lower PPTs than men in both lumbar region [101.7 kPa (mean difference) 95 % CI 37.9-165.7 kPa] and over the TA [189.7 kPa (mean difference) 95 % CI 14.2-145.2 kPa]. There was no significant difference in PPTs in men between healthy controls and those with low back pain, suggesting the significant differences are mediated primarily by difference between women.

Intensity thresholds for aerobic exercise-induced hypoalgesia

INTRODUCTION

Despite many studies investigating exercise-induced hypoalgesia, there is limited understanding of the optimal intensity of aerobic exercise in producing hypoalgesic effects across different types of pain stimuli. Given that not all individuals are willing or capable of engaging in high-intensity aerobic exercise, whether moderate-intensity aerobic exercise (MAE) is associated with a hypoalgesic response and whether this response generalizes to multiple pain induction techniques needs to be substantiated.

PURPOSE

This study's purpose is to test for differences in the magnitude of pressure and heat pain modulation induced by MAE and vigorous-intensity aerobic exercise (VAE).

METHODS

Twelve healthy young males and 15 females completed one training session and three testing sessions consisting of 25 min of 1) stationary cycling at 70% HR reserve, 2) stationary cycling at 50% HR reserve, or 3) quiet rest (control). Pain testing was conducted on both forearms before and immediately after each condition and included the following tests: pressure pain thresholds, suprathreshold pressure pain test, static continuous heat test, and repetitive pulse heat pain test. Repeated-measures ANOVA was conducted on each pain measure.

RESULTS

VAE and MAE reduced pain ratings during static continuous heat stimuli and repetitive heat pulse stimuli, with VAE producing larger effects. VAE also increased pressure pain thresholds, whereas neither exercise influenced suprathreshold pressure pain ratings.

CONCLUSION

These results suggest that MAE is capable of producing a hypoalgesic effect using continuous and repetitive pulse heat stimuli. However, a dose-response effect was evident as VAE produced larger effects than MAE.

Myalgic Encephalomyelitis: Symptoms and Biomarkers

Myalgic Encephalomyelitis (ME) continues to cause significant morbidity worldwide with an estimated one million cases in the United States. Hurdles to establishing consensus to achieve accurate evaluation of patients with ME continue, fueled by poor agreement about case definitions, slow progress in development of standardized diagnostic approaches, and issues surrounding research priorities. Because there are other medical problems, such as early MS and Parkinson's Disease, which have some similar clinical presentations, it is critical to accurately diagnose ME to make a differential diagnosis. In this article, we explore and summarize advances in the physiological and neurological approaches to understanding, diagnosing, and treating ME. We identify key areas and approaches to elucidate the core and secondary symptom clusters in ME so as to provide some practical suggestions in evaluation of ME for clinicians and researchers. This review, therefore, represents a synthesis of key discussions in the literature, and has important implications for a better understanding of ME, its biological markers, and diagnostic criteria. There is a clear need for more longitudinal studies in this area with larger data sets, which correct for multiple testing.

Brain-derived neurotrophic factor as a driving force behind neuroplasticity in neuropathic and central sensitization pain: a new therapeutic target?

INTRODUCTION

Central sensitization is a form of maladaptive neuroplasticity underlying many chronic pain disorders, including neuropathic pain, fibromyalgia, whiplash, headache, chronic pelvic pain syndrome and some forms of osteoarthritis, low back pain, epicondylitis, shoulder pain and cancer pain. Brain-derived neurotrophic factor (BDNF) is a driving force behind neuroplasticity, and it is therefore crucial for neural maintenance and repair. However, BDNF also contributes to sensitization of pain pathways, making it an interesting novel therapeutic target.

AREAS COVERED

An overview of BDNF's sensitizing capacity at every level of the pain pathways is presented, including the peripheral nociceptors, dorsal root ganglia, spinal dorsal horn neurons, and brain descending inhibitory and facilitatory pathways. This is followed by the presentation of several potential therapeutic options, ranging from indirect influencing of BDNF levels (using exercise therapy, anti-inflammatory drugs, melatonin, repetitive transcranial magnetic stimulation) to more specific targeting of BDNF's receptors and signaling pathways (blocking the proteinase-activated receptors 2-NK-κβ signaling pathway, administration of phencyclidine for antagonizing NMDA receptors, or blockade of the adenosine A2A receptor).

EXPERT OPINION

This section focuses on combining pharmacotherapy with multimodal rehabilitation for balancing the deleterious and therapeutic effects of BNDF treatment in chronic pain patients, as well as accounting for the complex and biopsychosocial nature of chronic pain.

Efficacy of the addition of interferential current to Pilates method in patients with low back pain: a protocol of a randomized controlled trial

Background

Chronic low back pain is one of the four most common diseases in the world with great socioeconomic impact. Supervised exercise therapy is one of the treatments suggested for this condition; however, the recommendation on the best type of exercise is still unclear. The Pilates method of exercise is effective in reducing pain and disability in these patients, as well as the analgesia promoted by interferential current. Currently, the literature lacks information on the efficacy of the association of these two techniques in the short- and medium-term than performing one of the techniques isolated. The objective of this study will be to evaluate the efficacy of adding interferential current to the Pilates method exercises for the treatment of patients with chronic nonspecific low back pain in the short- and medium-term.

Methods/Design

This study will be a randomized controlled trial with two arms and blinded evaluator, conducted at an outpatient Physical Therapy Department in Brazil. Patients with nonspecific chronic low back pain and pain equal to or greater than 3 in the Pain Numerical Rating Scale (0/10) will be randomly assigned to one of two groups: Group with active interferential current + Pilates (n = 74) will be submitted to the active interferential current associated to the modified Pilates exercises, and Group with sham interferential current + Pilates (n = 74) will be submitted to the sham interferential current associated with the modified Pilates exercises during 18 sessions. The outcomes pain intensity, pressure pain threshold, general and specific disability, global perceived effect and kinesiophobia will be evaluated by a blinded assessor at baseline, six weeks and six months after randomization.

Discussion

Because of the study design, blinding of the participants and the therapists involved in the study will not be possible. The results of this study could contribute to the process of clinical decision- making for the improvement of pain and disability in participants with nonspecific chronic low back pain.

Trial registration

ClinicalTrials.gov NCT01919268

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2474-15-420) contains supplementary material, which is available to authorized users.

Impact of dry needling and ischemic pressure in the myofascial syndrome: controlled clinical trial

Introduction Musculoskeletal pain is a common clinical condition and about 10% of the population have musculoskeletal disorder. Objective The aim of this study was to evaluate whether ischemic pressure and dry needling techniques are able to reduce the pain of patients with myofascial pain syndrome. Method 22 patients aged 20-75 years were randomized into 3 groups: ischemic pressure (IPG = 8), dry needling (DNG = 7) and control (CG = 7). Patients in the IPG and DNG were assessed before and after 10 intervention sessions, which occurred 3 times per week. The CG was assessed initially and reassessed three weeks later. The assessment of pain was done through Visual Analogic Scale (VAS) and quality of life through WHOQOL-BREF (5 domains: global, physical, psychological, social and environmental). Results There was no significant difference for clinical and demographic data of all groups at baseline, except for age (p = 0.042). The results of the VAS expressed that IPG had pain relief in most sessions, the same was not observed for DNG. Comparing the 2 groups was obtained difference in the 4th and 8th sessions. The results of the WHOQOL-BREF showed that the three groups had a significant increase in the psychological domain. The same was not true for global domains, physical, environmental and social. Conclusion Ischemic pressure and dry needling were able to reduce the pain of patients and also change their quality of life, specifically the psychological aspect.

Pain and pressure pain thresholds in adolescents with chronic fatigue syndrome and healthy controls: a cross-sectional study

OBJECTIVES

Although pain is a significant symptom in chronic fatigue syndrome (CFS), pain is poorly understood in adolescents with CFS. The aim of this study was to explore pain distribution and prevalence, pain intensity and its functional interference in everyday life, as well as pressure pain thresholds (PPT) in adolescents with CFS and compare this with a control group of healthy adolescents (HC).

METHODS

This is a case-control, cross-sectional study on pain including 120 adolescents with CFS and 39 HCs, aged 12-18 years. We measured pain frequency, pain severity and pain interference using self-reporting questionnaires. PPT was measured using pressure algometry. Data were collected from March 2010 until October 2012 as part of the Norwegian Study of Chronic Fatigue Syndrome in Adolescents: Pathophysiology and Intervention Trial.

RESULTS

Adolescents with CFS had significantly lower PPTs compared with HCs (p<0.001). The Pain Severity Score and the Pain Interference Score were significantly higher in adolescents with CFS compared with HCs (p<0.001). Almost all adolescents with CFS experienced headache, abdominal pain and/or pain in muscles and joints. Moreover, in all sites, the pain intensity levels were significantly higher than in HCs (p<0.001).

CONCLUSIONS

We found a higher prevalence of severe pain among adolescents with CFS and lowered pain thresholds compared with HCs. The mechanisms, however, are still obscure. Large longitudinal population surveys are warranted measuring pain thresholds prior to the onset of CFS.

TRIAL REGISTRATION NUMBER

Clinical Trials, NCT01040429; The Norwegian Study of Chronic Fatigue Syndrome in Adolescents: Pathophysiology and Intervention Trial (NorCAPITAL) http://www.clinicaltrials.gov.

Laser heat hyperalgesia is not a feature of non-specific chronic low back pain

BACKGROUND

Based upon studies using mechanical pin-prick, pressure, electrical or heat stimuli applied to painful and/or pain-free parts of the body, chronic low back pain (CLBP) has been shown to be associated with generalized and enhanced pain sensitivity and altered brain responses to noxious stimuli. To date, no study examined the processing of noxious laser heat pulses, which are known to selectively excite thermal nociceptors located in the superficial skin layers, in CLBP.

METHODS

We studied laser heat pain thresholds (LHPTs) and nociceptive laser-evoked brain electrical potentials (LEPs) following skin stimulation of the pain-affected back and the pain-free abdomen using noxious laser heat stimulation in 16 CLBP patients and 16 age- and gender-matched healthy controls (HCs).

RESULTS

We observed no statistically significant differences in LHPTs between CLBP patients and HCs, neither on the back nor on the abdomen. Furthermore, we found no evidence for altered brain responses between CLBP patients and HCs in response to stimulation of the back and abdomen in single-trial latencies and amplitudes of LEP components (N2, P2).

CONCLUSION

The results are in contrast to previous studies showing hypersensitivity to different experimental noxious stimuli (e.g., contact heat). We argue that these discrepancies may be due to low spatial and temporal summation within the central nervous system following laser heat stimulation. Our results indicate important methodological differences between laser heat and thermode stimulation that should be taken into account when interpreting results, such as from thermal quantitative sensory testing.

Endogenous pain modulation in response to exercise in patients with rheumatoid arthritis, patients with chronic fatigue syndrome and comorbid fibromyalgia, and healthy controls: a double-blind randomized controlled trial

OBJECTIVE

Temporal summation (TS) of pain, conditioned pain modulation (CPM), and exercise-induced analgesia (EIA) are often investigated in chronic pain populations as an indicator for enhanced pain facilitation and impaired endogenous pain inhibition, respectively, but interactions are not yet clear both in healthy controls and in chronic pain patients. Therefore, the present double-blind randomized placebo-controlled study evaluates pains cores, TS, and CPM in response to exercise in healthy controls, patients with chronic fatigue syndrome and comorbid fibromyalgia (CFS/FM), and patients with rheumatoid arthritis (RA), both under placebo and paracetamol condition.

METHODS

Fifty-three female volunteers - of which 19 patients with CFS/FM, 16 patients with RA, and 18 healthy controls - underwent a submaximal exercise test on a bicycle ergometer on 2 different occasions (paracetamol vs. placebo), with an interval of 7 days. Before and after exercise, participants rated pain intensity during TS and CPM.

RESULTS

Patients with rheumatoid arthritis showed decreased TS after exercise, both after paracetamol and placebo (P < 0.05). In patients with CFS/FM, results were less univocal. A nonsignificant decrease in TS was only observed after taking paracetamol. CPM responses to exercise are inconclusive, but seem to worsen after exercise. No adverse effects were seen.

CONCLUSION

This study evaluates pain scores, TS, and CPM in response to submaximal exercise in 2 different chronic pain populations and healthy controls. In patients with RA, exercise had positive effects on TS, suggesting normal EIA. In patients with CFS/FM, these positive effects were only observed after paracetamol and results were inconsistent.

Exercise-induced hypoalgesia - interval versus continuous mode

Aerobic exercise at approximately 70% of maximal aerobic capacity moderately reduces pain sensitivity and attenuates pain, even after a single session. If the analgesic effects depend on exercise intensity, then high-intensity interval exercise at 85% of maximal aerobic capacity should further reduce pain. The aim of this study was to explore the exercise-induced analgesic effects of high-intensity interval aerobic exercise and to compare them with the analgesic effects of moderate continuous aerobic exercise. Twenty-nine young untrained healthy males were randomly assigned to aerobic-continuous (70% heart rate reserve (HRR)) and interval (4 × 4 min at 85% HRR and 2 min at 60% HRR between cycles) exercise modes, each lasting 30 min. Psychophysical pain tests, pressure and heat pain thresholds (HPT), and tonic heat pain (THP) were conducted before and after exercise sessions. Repeated measures ANOVA was used for data analysis. HPT increased (p = 0.056) and THP decreased (p = 0.013) following exercise unrelated to exercise type. However, the main time effect (pre-/postexercise) was a trend of increased HPT (45.6 ± 1.9 °C to 46.2 ± 1.8 °C; p = 0.082) and a significant reduction in THP (from 50.7 ± 25 to 45.9 ± 25.4 numeric pain scale; p = 0.043) following interval exercise. No significant change was found for the pressure pain threshold following either exercise type. In conclusion, interval exercise (85% HRR) has analgesic effects on experimental pain perception. This, in addition to its cardiovascular, muscular, and metabolic advantages may promote its inclusion in pain management programs.

Chronic pain in patients with the hypermobility type of Ehlers-Danlos syndrome: evidence for generalized hyperalgesia

Chronic widespread pain is highly present in patients with the Ehlers-Danlos syndrome hypermobility type (EDS-HT), but up to now, evidence for generalized hyperalgesia is lacking. The aim of this study is to investigate whether pressure pain thresholds (PPTs) at both symptomatic and asymptomatic body areas differ in EDS-HT patients compared to healthy subjects. Twenty-three women with EDS-HT and 23 gender- and age-matched healthy controls participated. All subjects marked on Margolis Pain Diagram where they felt pain lasting longer than 24 h in the past 4 weeks. Then, they completed several questionnaires assessing pain cognitions, fatigue, disability, and general health status, in order to take the possible influence of these factors on PPTs into account. Patients also completed a form concerning the type of pain they experienced. Thereupon, a blinded researcher assessed PPTs at 14 body locations on the trunk and extremities. PPTs were compared for the two complete groups. In addition, PPTs of patients and controls who did not report pain in a respective zone were compared. PPTs of the patients were significantly lower compared to those of the control group, also when pain-free samples per zone were compared. The mean (SD) PPT was 2.9 (1.62) kg/cm(2) in the EDS-HT patients and 5.2 (1.88) kg/cm(2) in the controls (P < 0.001). No confounding factors responsible for the observed differences could be revealed. In half of the patient group, a predominantly neuropathic pain component was likely present. This study provides evidence for the existence of hyperalgesia even in asymptomatic areas (generalized secondary hyperalgesia). The generalized hyperalgesia may represent the involvement of a sensitized central nervous system, which inquires an adapted pain management for this patient group.

Effects of the carrier frequency of interferential current on pain modulation in patients with chronic nonspecific low back pain: a protocol of a randomised controlled trial

BACKGROUND

Low back pain is an important public health problem that is associated with poor quality of life and disability. Among the electrophysical treatments, interferential current (IFC) has not been studied in patients with low back pain in a high-quality randomised controlled trial examining not only pain, but pain mechanisms and function.

METHODS/DESIGN

A three-arm randomised controlled trial with patient and assessor blinded to the group allocation. One hundred fifty patients with chronic, nonspecific low back pain from outpatient physical therapy clinics in Brazil. The patients will be randomly allocated into 3 groups (IFC 1 kHz, IFC 4 kHz or Placebo IFC). The interferential current will be applied three days per week (30 minutes per session) over four weeks.

PRIMARY OUTCOME

Pain intensity.

SECONDARY OUTCOMES

The pressure pain threshold, global impression of recovery, disability, function, conditioned pain modulation and temporal summation of pain, discomfort caused by the current. All outcomes will be measured at 4 weeks and 4 months after randomisation. The between-group differences will be calculated by using linear mixed models and Tukey's post-hoc tests.

DISCUSSION

The use of a placebo group and double-blinding assessor and patients strengthen this study. The present study is the first to compare different IFC carrier frequencies in patients with chronic low back pain.

TRIAL REGISTRATION

Brazilian Registry of Clinical Trials: http://RBR-8n4hg2.

Immediate effects of region-specific and non-region-specific spinal manipulative therapy in patients with chronic low back pain: a randomized controlled trial

BACKGROUND

Manual therapists typically advocate the need for a detailed clinical examination to decide which vertebral level should be manipulated in patients with low back pain. However, it is unclear whether spinal manipulation needs to be specific to a vertebral level.

OBJECTIVE

The purpose of this study was to analyze the immediate effects of a single, region-specific spinal manipulation defined during the clinical examination versus a single non-region-specific spinal manipulation (applied on an upper thoracic vertebra) in patients with chronic nonspecific low back pain for the outcome measures of pain intensity and pressure pain threshold at the time of the assessment.

DESIGN

This was a 2-arm, prospectively registered, randomized controlled trial with a blinded assessor.

SETTING

The study was conducted in an outpatient physical therapy clinic in Brazil.

PATIENTS

The study participants were 148 patients with chronic nonspecific low back pain (with pain duration of at least 12 weeks).

RANDOMIZATION

The randomization schedule was generated by an independent statistician and was concealed by using consecutively numbered, sealed, opaque envelopes.

INTERVENTIONS

A single high-velocity manipulation was administered to the upper thoracic region of the participants allocated to the non-region-specific manipulation group and to the painful lumbar levels of the participants allocated to the region-specific manipulation group.

MEASUREMENTS

Pain intensity was measured by a 0 to 10 numeric pain rating scale. Pressure pain threshold was measured using a pressure algometer.

LIMITATIONS

It was not possible to blind the therapist and participants.

RESULTS

A total of 148 patients participated in the study (74 in each group). There was no loss to follow-up. Both groups improved in terms of immediate decrease of pain intensity; however, no between-group differences were observed. The between-group difference for pain intensity and pressure pain threshold were 0.50 points (95% confidence interval=-0.10 to 1.10) and -1.78 points (95% confidence interval=-6.40 to 2.82), respectively. No adverse reactions were observed.

CONCLUSION

The immediate changes in pain intensity and pressure pain threshold after a single high-velocity manipulation do not differ by region-specific versus non-region-specific manipulation techniques in patients with chronic low back pain.

Relationship between quantitative sensory testing and pain or disability in people with spinal pain-a systematic review and meta-analysis

Sensitization of the nervous system can present as pain hypersensitivity that may contribute to clinical pain. In spinal pain, however, the relationship between sensory hypersensitivity and clinical pain remains unclear. This systematic review examined the relationship between pain sensitivity measured via quantitative sensory testing (QST) and self-reported pain or pain-related disability in people with spinal pain. Electronic databases and reference lists were searched. Correlation coefficients for the relationship between QST and pain intensity or disability were pooled using random effects models. Subgroup analyses and mixed effects meta-regression were used to assess whether the strength of the relationship was moderated by variables related to the QST method or pain condition. One hundred and forty-five effect sizes from 40 studies were included in the meta-analysis. Pooled estimates for the correlation between pain threshold and pain intensity were -0.15 (95% confidence interval [CI]: -0.18 to -0.11) and for disability -0.16 (95% CI: -0.22 to -0.10). Subgroup analyses and meta-regression did not provide evidence that these relationships were moderated by the QST testing site (primary pain/remote), pain condition (back/neck pain), pain type (acute/chronic), or type of pain induction stimulus (eg, mechanical/thermal). Fair correlations were found for the relationship between pain intensity and thermal temporal summation (0.26, 95% CI: 0.09 to 0.42) or pain tolerance (-0.30, 95% CI: -0.45 to -0.13), but only a few studies were available. Our study indicates either that pain threshold is a poor marker of central sensitization or that sensitization does not play a major role in patients' reporting of pain and disability. Future research prospects are discussed.

Peripheral and central mechanisms of fatigue in inflammatory and noninflammatory rheumatic diseases

Fatigue is a common symptom in a large number of medical and psychological disorders, including many rheumatologic illnesses. A frequent question for health care providers is related to whether reported fatigue is "in the mind" or "in the body"-that is, central or peripheral. If fatigue occurs at rest without any exertion, this suggests psychological or central origins. If patients relate their fatigue mostly to physical activities, including exercise, their symptoms can be considered peripheral. However, most syndromes of fatigue seem to depend on both peripheral and central mechanisms. Sometimes, muscle biopsy with histochemistry may be necessary for the appropriate tissue diagnosis, whereas serological tests generally provide little reliable information about the origin of muscle fatigue. Muscle function and peripheral fatigue can be quantified by contractile force and action potential measurements, whereas validated questionnaires are frequently used for assessment of mental fatigue. Fatigue is a hallmark of many rheumatologic conditions, including fibromyalgia, myalgic encephalitis/chronic fatigue syndrome, rheumatoid arthritis, systemic lupus, Sjogren's syndrome, and ankylosing spondylitis. Whereas many studies have focused on disease activity as a correlate to these patients' fatigue, it has become apparent that other factors, including negative affect and pain, are some of the most powerful predictors for fatigue. Conversely, sleep problems, including insomnia, seem to be less important for fatigue. There are several effective treatment strategies available for fatigued patients with rheumatologic disorders, including pharmacological and nonpharmacological therapies.

Clinical characteristics of a novel subgroup of chronic fatigue syndrome patients with postural orthostatic tachycardia syndrome

OBJECTIVES

A significant proportion of patients with chronic fatigue syndrome (CFS) also have postural orthostatic tachycardia syndrome (POTS). We aimed to characterize these patients and differentiate them from CFS patients without POTS in terms of clinical and autonomic features.

METHODS

A total of 179 patients with CFS (1994 Centers for Disease Control and Prevention criteria) attending one of the largest Department of Health-funded CFS clinical services were included in this study. Outcome measures were as follows: (i) symptom assessment tools including the fatigue impact scale, Chalder fatigue scale, Epworth sleepiness scale (ESS), orthostatic grading scale (OGS) and hospital anxiety and depression scale (HADS-A and -D, respectively), (ii) autonomic function analysis including heart rate variability and (iii) haemodynamic responses including left ventricular ejection time and systolic blood pressure drop upon standing.

RESULTS

CFS patients with POTS (13%, n = 24) were younger (29 ± 12 vs. 42 ± 13 years, P < 0.0001), less fatigued (Chalder fatigue scale, 8 ± 4 vs. 10 ± 2, P = 0.002), less depressed (HADS-D, 6 ± 4 vs. 9 ± 4, P = 0.01) and had reduced daytime hypersomnolence (ESS, 7 ± 6 vs. 10 ± 5, P = 0.02), compared with patients without POTS. In addition, they exhibited greater orthostatic intolerance (OGS, 11 ± 5; P < 0.0001) and autonomic dysfunction. A combined clinical assessment tool of ESS ≤9 and OGS ≥9 identifies accurately CFS patients with POTS with 100% positive and negative predictive values.

CONCLUSIONS

The presence of POTS marks a distinct clinical group of CFS patents, with phenotypic features differentiating them from those without POTS. A combination of validated clinical assessment tools can determine which CFS patients have POTS with a high degree of accuracy, and thus potentially identify those who require further investigation and consideration for therapy to control heart rate.

A meta-analytic review of the hypoalgesic effects of exercise

The purpose of this article was to examine the effects of acute exercise on pain perception in healthy adults and adults with chronic pain using meta-analytic techniques. Specifically, studies using a repeated measures design to examine the effect of acute isometric, aerobic, or dynamic resistance exercise on pain threshold and pain intensity measures were included in this meta-analysis. The results suggest that all 3 types of exercise reduce perception of experimentally induced pain in healthy participants, with effects ranging from small to large depending on pain induction method and exercise protocol. In healthy participants, the mean effect size for aerobic exercise was moderate (d(thr) = .41, d(int) = .59), while the mean effect sizes for isometric exercise (d(thr) = 1.02, d(int) = .72) and dynamic resistance exercise (d(thr) = .83, d(int) = .75) were large. In chronic pain populations, the magnitude and direction of the effect sizes were highly variable for aerobic and isometric exercise and appeared to depend on the chronic pain condition being studied as well as the intensity of the exercise. While trends could be identified, the optimal dose of exercise that is needed to produce hypoalgesia could not be systematically determined with the amount of data available.

PERSPECTIVE

This article presents a quantitative review of the exercise-induced hypoalgesia literature. This review raises several important questions that need to be addressed while also demonstrating that acute exercise has a hypoalgesic effect on experimentally induced pain in healthy adults, and both a hypoalgesic and hyperalgesic effect in adults with chronic pain.

In the mind or in the brain? Scientific evidence for central sensitisation in chronic fatigue syndrome

BACKGROUND

Central sensitisation entails several top-down and bottom-up mechanisms, all contributing to the hyperresponsiveness of the central nervous system to a variety of inputs. In the late nineties, it was first hypothesised that chronic fatigue syndrome (CFS) is characterised by hypersensitivity of the central nervous system (i.e. central sensitisation). Since then, several studies have examined central sensitisation in patients with CFS. This study provides an overview of such studies.

MATERIALS AND METHODS

Narrative review.

RESULTS

Various studies showed generalised hyperalgesia in CFS for a variety of sensory stimuli, including electrical stimulation, mechanical pressure, heat and histamine. Various tissues are affected by generalised hyperalgesia: the skin, muscle tissue and the lungs. Generalised hyperalgesia in CFS is augmented, rather than decreased, following various types of stressors like exercise and noxious heat pain. Endogenous inhibition is not activated in response to exercise and activation of diffuse noxious inhibitory controls following noxious heat application to the skin is delayed.

CONCLUSIONS

The observation of central sensitisation in CFS is in line with our current understanding of CFS. The presence of central sensitisation in CFS corroborates with the presence of several psychological influences on the illness, the presence of infectious agents and immune dysfunctions and the dysfunctional hypothalamus-pituitary-adrenal axis as seen in these severely debilitated patients.

Loss of capacity to recover from acidosis on repeat exercise in chronic fatigue syndrome: a case-control study

BACKGROUND

Chronic fatigue syndrome (CFS) patients frequently describe difficulties with repeat exercise. Here, we explore muscle bioenergetic function in response to three bouts of exercise.

METHODS

A total of 18 CFS (CDC 1994) patients and 12 sedentary controls underwent assessment of maximal voluntary contraction (MVC), repeat exercise with magnetic resonance spectroscopy and cardio-respiratory fitness test to determine anaerobic threshold.

RESULT

Chronic fatigue syndrome patients undertaking MVC fell into two distinct groups: 8 (45%) showed normal PCr depletion in response to exercise at 35% of MVC (PCr depletion >33%; lower 95% CI for controls); 10 CFS patients had low PCr depletion (generating abnormally low MVC values). The CFS whole group exhibited significantly reduced anaerobic threshold, heart rate, VO(2) , VO(2) peak and peak work compared to controls. Resting muscle pH was similar in controls and both CFS patient groups. However, the CFS group achieving normal PCr depletion values showed increased intramuscular acidosis compared to controls after similar work after each of the three exercise periods with no apparent reduction in acidosis with repeat exercise of the type reported in normal subjects. This CFS group also exhibited significant prolongation (almost 4-fold) of the time taken for pH to recover to baseline.

CONCLUSION

When exercising to comparable levels to normal controls, CFS patients exhibit profound abnormality in bioenergetic function and response to it. Although exercise intervention is the logical treatment for patients showing acidosis, any trial must exclude subjects who do not initiate exercise as they will not benefit. This potentially explains previous mixed results in CFS exercise trials.

Experimental pressure-pain assessments: Test-retest reliability, convergence and dimensionality

Introduction

Experimental pain studies can provide unique insight into the dimensions of pain and into individual differences in pain responsiveness by controlling different aspects of pain-eliciting stimuli and pain measures. In experimental pain studies, pain responsiveness can be assessed as pain threshold, pain tolerance or pain ratings. The test-theoretical qualities of these different measures, however, have not yet been completely documented. In the current study, several of these qualities were investigated in a pain experiment applying different algometric techniques. The objective of the study was to investigate the reliability (test–retest) and the convergent validity (correspondence) of the different methods found in the literature of measuring pressure-pain threshold, and the interrelationship between pressure-pain threshold, pressure-pain tolerance, and pressure-pain ratings.

Methods

Sixty-six healthy female subjects were enrolled in the study. All pressure stimuli were applied by a trained investigator, using a digital algometer with a 1 cm2 rubber tip. Pressure-pain thresholds were assessed repeatedly on six different body points (i.e. left and right calf one third of total calf muscle length below the popliteal space), the lower back (5 cm left and right from the L3), and left and right forearm (thickest part of brachioradialis muscle). Next, pressure-pain tolerance was measured on the thumbnail of the non-dominant hand, followed by rating affective and sensory components (on visual analogue scales) of a stimulus at tolerance level. Last, affective and sensory ratings were obtained for two pressure intensities.

Results

With intraclass correlations above .75 for pain responses per body point, test–retest reliability was found to be good. However, values obtained from all first measurements were significantly higher as compared with the two succeeding ones. Convergent validity of pain thresholds across different body points was found to be high for all combinations assessed (Cronbach’s alpha values >.80), but the highest for bilateral similar body parts (>.89). Finally, principal components analysis including measures of threshold, tolerance and pain ratings yielded a three-factor solution that explained 81.9% of the variance: Moderate-level stimulus appraisal & pain tolerance; Pain threshold; Tolerance-level stimulus appraisal.

Conclusion and implications

Findings of the current study were used to formulate recommendations for future algometric pain studies. Concerning pressure-pain threshold, it is recommended to exclude first measurements for every body point from further analyses, as these measurements were found to be consistently higher compared with the following measurements. Further, no more than two consecutive measurements (after the first measurement) are needed for a reliable mean threshold value per body point. When combining threshold values of several body points into one mean-aggregated threshold value, we suggest to combine bilateral similar points, as convergent validity values were highest for these combinations. The three-factor solution that was found with principal components analyses indicates that pressure-pain threshold, subjective ratings of moderate intensity stimuli, and subjective ratings of the maximum (tolerance) intensity are distinct aspects of pain responsiveness. It is therefore recommended to include a measure of each of these three dimensions of pain when assessing pressure pain responsiveness. Some limitations of our study are discussed.

Differences in metabolite-detecting, adrenergic, and immune gene expression after moderate exercise in patients with chronic fatigue syndrome, patients with multiple sclerosis, and healthy controls

OBJECTIVE

Chronic fatigue syndrome (CFS) and multiple sclerosis (MS) are characterized by debilitating fatigue, yet evaluation of this symptom is subjective. We examined metabolite-detecting, adrenergic, and immune gene expression (messenger ribonucleic acid [mRNA]) in patients with CFS (n = 22) versus patients with MS (n = 20) versus healthy controls (n = 23) and determined their relationship to fatigue and pain before and after exercise.

METHODS

Blood samples and fatigue and pain ratings were obtained at baseline and 0.5, 8, 24, and 48 hours after sustained moderate exercise. Leukocyte mRNA of four metabolite-detecting receptors (acid-sensing ion channel 3, purinergic type 2X4 and 2X5 receptors, and transient receptor potential vanilloid type 1) and four adrenergic (α-2a, β-1, and β-2 receptors and catechol-O-methyltransferase) and five immune markers (CD14, toll-like receptor 4 [TLR4], interleukin [IL] 6, IL-10, and lymphotoxin α) was examined using quantitative polymerase chain reaction.

RESULTS

Patients with CFS had greater postexercise increases in fatigue and pain (10-29 points above baseline, p < .001) and greater mRNA increases in purinergic type 2X4 receptor, transient receptor potential vanilloid type 1, CD14, and all adrenergic receptors than controls (mean ± standard error = 1.3 ± 0.14- to 3.4 ± 0.90-fold increase above baseline, p = .04-.005). Patients with CFS with comorbid fibromyalgia (n = 18) also showed greater increases in acid-sensing ion channel 3 and purinergic type 2X5 receptors (p < .05). Patients with MS had greater postexercise increases than controls in β-1 and β-2 adrenergic receptor expressions (1.4 ± 0.27- and 1.3 ± 0.06-fold increases, respectively, p = .02 and p < .001) and greater decreases in TLR4 (p = .02). In MS, IL-10 and TLR4 decreases correlated with higher fatigue scores.

CONCLUSIONS

Postexercise mRNA increases in metabolite-detecting receptors were unique to patients with CFS, whereas both patients with MS and patients with CFS showed abnormal increases in adrenergic receptors. Among patients with MS, greater fatigue was correlated with blunted immune marker expression.

Pacing as a strategy to improve energy management in myalgic encephalomyelitis/chronic fatigue syndrome: a consensus document

PURPOSE

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating condition characterized by a number of symptoms which typically worsen following minimal exertion. Various strategies to manage the limited energy levels have been proposed. Of these, pacing has been consistently rated as one of the most helpful in surveys conducted by patient groups. This review is a response to the paucity of the information on pacing in the scientific literature.

METHOD

We describe the principle of pacing and how this can be adapted to meet individual abilities and preferences. A critical evaluation of the research was conducted to ascertain the benefits and limitations of this strategy.

RESULTS

Based on various studies, it is proposed that pacing can help to stabilize the condition and avoid post-exertional malaise.

CONCLUSION

Pacing offers practitioners an additional therapeutic option which is acceptable to the majority of patients and can reduce the severity of the exertion-related symptoms of ME/CFS.

Symptom fluctuations and daily physical activity in patients with chronic fatigue syndrome: a case-control study

OBJECTIVES

To compare the activity pattern of patients with chronic fatigue syndrome (CFS) with healthy sedentary subjects and examine the relationship between the different parameters of performed activity (registered by an accelerometer device) and symptom severity and fluctuation (registered by questionnaires) in patients with CFS.

DESIGN

Case-control study. Participants were asked to wear an accelerometer device on the nondominant hand for 6 consecutive days. Every morning, afternoon, and evening patients scored the intensity of their pain, fatigue, and concentration difficulties on a visual analog scale.

SETTING

Patients were recruited from a specialized chronic fatigue clinic in the university hospital, where all subjects were invited for 2 appointments (for questionnaire and accelerometer adjustments). In between, activity data were collected in the subject's normal home environment.

PARTICIPANTS

Female patients (n=67) with CFS and female age-matched healthy sedentary controls.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Accelerometry (average activity counts, peak activity counts, ratio peak/average, minutes spent per activity category) and symptom severity (intensity of pain, fatigue, and concentration difficulties).

RESULTS

Patients with CFS were less active, spent more time sedentary, and less time lightly active (P<.05). The course of the activity level during the registration period (P interaction>.05), peak activity, and the staggering of activities (ratio peak/average) on 1 day were not different between groups (P>.05). Negative correlations (-.242 varying to -.307) were observed for sedentary activity and the ratio with symptom severity and variation on the same and the next day. Light, moderate, and vigorous, as well as the average activity and the peak activity, were positively correlated (.242 varying to .421) with symptom severity and variation.

CONCLUSIONS

The more patients with CFS are sedentary and the better activity is dispersed, the fewer symptoms and variations they experience on the same and next day. Inversely, more symptoms and variability is experienced when patients were more active that day or the previous day. The direction of these relations cannot be determined in a cross-sectional study and requires further study.

Myalgic encephalomyelitis: International Consensus Criteria

The label 'chronic fatigue syndrome' (CFS) has persisted for many years because of the lack of knowledge of the aetiological agents and the disease process. In view of more recent research and clinical experience that strongly point to widespread inflammation and multisystemic neuropathology, it is more appropriate and correct to use the term 'myalgic encephalomyelitis' (ME) because it indicates an underlying pathophysiology. It is also consistent with the neurological classification of ME in the World Health Organization's International Classification of Diseases (ICD G93.3). Consequently, an International Consensus Panel consisting of clinicians, researchers, teaching faculty and an independent patient advocate was formed with the purpose of developing criteria based on current knowledge. Thirteen countries and a wide range of specialties were represented. Collectively, members have approximately 400 years of both clinical and teaching experience, authored hundreds of peer-reviewed publications, diagnosed or treated approximately 50 000 patients with ME, and several members coauthored previous criteria. The expertise and experience of the panel members as well as PubMed and other medical sources were utilized in a progression of suggestions/drafts/reviews/revisions. The authors, free of any sponsoring organization, achieved 100% consensus through a Delphi-type process. The scope of this paper is limited to criteria of ME and their application. Accordingly, the criteria reflect the complex symptomatology. Operational notes enhance clarity and specificity by providing guidance in the expression and interpretation of symptoms. Clinical and research application guidelines promote optimal recognition of ME by primary physicians and other healthcare providers, improve the consistency of diagnoses in adult and paediatric patients internationally and facilitate clearer identification of patients for research studies.

Intra- and interrater agreement of pressure pain thresholds in children with orthopedic disorders

PURPOSE

Pressure algometry is widely used to obtain measures of mechanical pain sensitivity in adults, both in experimental and clinical pain conditions. Only very few studies describe the use of pressure algometry in children. The purpose of this study was to produce reference values of pressure pain thresholds and to determine the intra- and interrater agreement, in order to introduce pressure algometry as a standardized method for the assessment of pain thresholds in children with orthopedic disorders.

METHODS

Pressure pain thresholds were determined at the leg and at the thenar in 50 children aged 4-12 years. All were scheduled for physical examination at the outpatient Orthopedic Clinic at Aarhus University Hospital, Denmark, because of various orthopedic disorders such as clubfoot and Baker's cyst. Pressure pain thresholds were determined by two different raters: 20 children were examined twice by rater 1 (intrarater agreement), and another 20 children were examined by both rater 1 and rater 2 (interrater agreement). An additional ten children were examined once by rater 1 to increase the number of children used to determine the reference values.

RESULTS

The pressure pain threshold was 183.1 kPa (mean, SD: 90.7) at the leg and 179.1 kPa (mean, SD: 97.4 kPa) at the thenar (n = 50). Pressure pain thresholds were similar in boys (n = 27) and girls (n = 23). Also, pressure pain thresholds were not affected by age. Bland-Altman plots showed excellent intrarater agreement and satisfactory interrater agreement.

CONCLUSION

Pressure algometry has excellent intrarater agreement and satisfactory interrater agreement. Pressure algometry was well-tolerated even by very young children. The method deserves more widespread use both in clinical and experimental settings.