Pain inhibition and postexertional malaise in myalgic encephalomyelitis/chronic fatigue syndrome: an experimental study

Exercise does not cause post-exertional malaise in Veterans with Gulf War Illness: A randomized, controlled, dose-response, crossover study

Chronic multisymptom illnesses (CMI) such as Myalgic Encephalomyelitis/Chronic Fatigue Syndrome, Long-COVID, and Gulf War Illness (GWI) are associated with an elevated risk of post-exertional malaise (PEM), an acute exacerbation of symptoms and other related outcomes following exercise. These individuals may benefit from personalized exercise prescriptions which prioritize risk minimization, necessitating a better understanding of dose-response effects of exercise intensity on PEM.

METHODS

Veterans with GWI (n = 40) completed a randomized controlled crossover experiment comparing 20 min of seated rest to light-, moderate-, and vigorous-intensity cycling conditions over four separate study visits. Symptoms, pain sensitivity, cognitive performance, inflammatory markers (C-reactive protein and plasma cytokines) were measured before and within 1 h after exercise and seated rest. Physical activity behavior was measured ≥ 7 days following each study visit via actigraphy. Linear mixed effects regression models tested the central hypothesis that higher intensity exercise would elicit greater exacerbation of negative outcomes, as indicated by a significant condition-by-time interaction for symptom, pain sensitivity, cognitive performance, and inflammatory marker models and a significant main effect of condition for physical activity models.

RESULTS

Significant condition-by-time interactions were not observed for primary or secondary measures of symptoms, pain sensitivity, cognitive performance, and a majority of inflammatory markers. Similarly, a significant effect of condition was not observed for primary or secondary measures of physical activity.

CONCLUSIONS

Undesirable effects such as symptom exacerbation were observed for some participants, but the group-level risk of PEM following light-, moderate-, or vigorous-intensity exercise was no greater than seated rest. These findings challenge several prior views about PEM and lend support to a broader body of literature showing that the benefits of exercise outweigh the risks.

Physical Activity and Fatigue Symptoms: Neurotypical Adults and People with Chronic Multisymptom Illnesses

For neurotypical adults, a single bout of low-to-moderate intensity physical activity usually transiently improves feelings of energy. Similar bouts of exercise have the opposite effect of increased feelings of fatigue when performed by samples with chronic multisymptom illnesses (CMIs) such as Long-COVID, Gulf War Illness (GWI), or Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). The short-term adoption of regular moderate intensity physical activity (typical experiments are 1 to 6 months) among neurotypical adults results in small-to-moderate improvements in self-reported feelings of fatigue, energy, and vitality. Small improvements in these feelings, or no change at all, occur for CMIs, but limited data precludes strong conclusions. The mechanisms of exercise effects on fatigue, whether acute or chronic, are poorly understood but likely involve multiple neural circuits and associated transmitters. For CMIs, the mechanisms of acute worsening of fatigue with exercise may be driven by the yet unknown pathophysiological mechanisms of the disease (perhaps involving brain, immune and autonomic system dysfunction, and their interactions). Likewise, fatigue improvements may depend on whether chronic physical activity is a disease-modifying treatment.

Developing effective strategies to optimize physical activity and cardiorespiratory fitness in the long Covid population- The need for caution and objective assessment

The Post Covid-19 Condition (commonly known as Long Covid) has been defined by the World Health Organisation as occurring in individuals with a history of probable or confirmed SARS CoV 2 infection, usually within 3 months from the onset of acute Covid-19 infection with symptoms that last for at least two months which cannot be explained by an alternative diagnosis. Long Covid is associated with over two hundred recognised symptoms and affects tens of millions of people worldwide. Widely reported reductions in quality of life(QoL) and functional status are caused by extremely sensitive and cyclical symptom profiles that are augmented following exposure to physical, emotional, orthostatic, and cognitive stimuli. This manifestation prevents millions of people from engaging in routine activities of daily living (ADLs) and has important health and well-being, social and economic impacts. Post-exertional symptom exacerbation (PESE) (also known as post-exertional malaise) is an exacerbation in the severity of fatigue and other symptoms following physical, emotional, orthostatic and cognitive tasks. Typically, this will occur 24-72 h after "over-exertion" and can persist for several days and even weeks. It is a hallmark symptom of Long Covid with a reported prevalence of 86%. The debilitating nature of PESE prevents patients from engaging in physical activity which impacts functional status and QoL. In this review, the authors present an update to the literature relating to PESE in Long Covid and make the case for evidence-based guidelines that support the design and implementation of safe rehabilitation approaches for people with Long Covid. This review also considers the role of objective monitoring to quantify a patient's response to external stimuli which can be used to support the safe management of Long Covid and inform decisions relating to engagement with any stimuli that could prompt an exacerbation of symptoms.

Exercise-induced hypoalgesia in chronic neck pain: A narrative review

Chronic neck pain (CNP) is a worldwide health problem with several risk factors. One of the most widely used treatments for managing this condition is therapeutic exercise, which could generate a response called exercise-induced hypoalgesia (EIH). There is no consensus on the best exercise modality to induce hypoalgesia. Therefore, this review aims to analyze and synthesize the state-of-the-art about the hypoalgesic effect of exercise in subjects with CNP. We included articles on EIH and CNP in patients older than 18 years, with pain for more than three months, where the EIH response was measured. Articles that studied CNP associated with comorbidities or measured the response to treatments other than exercise were excluded. The studies reviewed reported variable results. Exercise in healthy subjects has been shown to reduce indicators of pain sensitivity; however, in people with chronic pain, the response is variable. Some investigations reported adverse effects with increased pain intensity and decreased pain sensitivity, others found no clinical response, and some even reported EIH with decreased pain and increased sensitivity. EIH is an identifiable, stimulable, and helpful therapeutic response in people with pain. More research is still needed on subjects with CNP to clarify the protocols and therapeutic variables that facilitate the EIH phenomenon. In addition, it is necessary to deepen the knowledge of the intrinsic and extrinsic factors that influence EIH in people with CNP.

Mixed methods system for the assessment of post-exertional malaise in myalgic encephalomyelitis/chronic fatigue syndrome: an exploratory study

Background

A central feature of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is post-exertional malaise (PEM), which is an acute worsening of symptoms after a physical, emotional and/or mental exertion. Dynamic measures of PEM have historically included scaled questionnaires, which have not been validated in ME/CFS. To enhance our understanding of PEM and how best to measure it, we conducted semistructured qualitative interviews (QIs) at the same intervals as visual analogue scale (VAS) measures after a cardiopulmonary exercise test (CPET).

Methods

Ten ME/CFS and nine healthy volunteers participated in a CPET. For each volunteer, PEM symptom VAS (12 symptoms) and semistructured QIs were administered at six timepoints over 72 hours before and after a single CPET. QI data were used to plot the severity of PEM at each time point and identify the self-described most bothersome symptom for each ME/CFS volunteer. Performance of QI and VAS data was compared with each other using Spearman correlations.

Results

Each ME/CFS volunteer had a unique PEM experience, with differences noted in the onset, severity, trajectory over time and most bothersome symptom. No healthy volunteers experienced PEM. QI and VAS fatigue data corresponded well an hour prior to exercise (pre-CPET, r=0.7) but poorly at peak PEM (r=0.28) and with the change from pre-CPET to peak (r=0.20). When the most bothersome symptom identified from QIs was used, these correlations improved (r=0.0.77, 0.42. and 0.54, respectively) and reduced the observed VAS scale ceiling effects.

Conclusion

In this exploratory study, QIs were able to capture changes in PEM severity and symptom quality over time, even when VAS scales failed to do so. Measurement of PEM can be improved by using a quantitative-qualitative mixed model approach.

Advancing Research and Treatment: An Overview of Clinical Trials in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Future Perspectives

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a chronic, debilitating, and multi-faceted illness. Heterogenous onset and clinical presentation with additional comorbidities make it difficult to diagnose, characterize, and successfully treat. Current treatment guidelines focus on symptom management, but with no clear target or causative mechanism, remission rates are low, and fewer than 5% of patients return to their pre-morbid activity levels. Therefore, there is an urgent need to undertake robust clinical trials to identify effective treatments. This review synthesizes insights from clinical trials exploring pharmacological interventions and dietary supplements targeting immunological, metabolic, gastrointestinal, neurological, and neuroendocrine dysfunction in ME/CFS patients which require further exploration. Additionally, the trialling of alternative interventions in ME/CFS based on reported efficacy in the treatment of illnesses with overlapping symptomology is also discussed. Finally, we provide important considerations and make recommendations, focusing on outcome measures, to ensure the execution of future high-quality clinical trials to establish clinical efficacy of evidence-based interventions that are needed for adoption in clinical practice.

Endogenous Opioids and Exercise-Related Hypoalgesia: Modern Models, Measurement, and Mechanisms of Action

This chapter will focus on the role exercise appears to have on activation and modulating factors within the central nervous system related to endogenous like opioids and its possible contribution to exercise-induced hypoalgesia. The implications for the exercise-mediated alterations of CNS activation factors related to opioids, specifically endorphins and enkephalins, will be presented. In this update, we discuss utilization of new technology and methods to monitor mechanisms of opioid involvement to suggest their contribution with exercise mediated hypoalgesia as well as their relationships to alterations of perceptions of pain and mood. Several special populations were included to suggest that not all individuals will respond to the exercise by mediating hypoalgesia. Factors that may confound the current understanding and suggestions from the recent literature will be presented as well as suggestions for future investigations.

Modulation of pain perceptions following treadmill running with different intensities in females

We aimed to compare the effects of three intensities of treadmill running on exercise-induced hypoalgesia (EIH) in healthy individuals. We anticipated that the primary and secondary changes in pain perception and modulation may differ between running intensities. Sixty-six women were randomly assigned to one of three treadmill running intensities for 35 min: 40% reserved heart rate (HRR), 55% HRR, or 70% HRR. The effects of EIH were assessed using pressure pain thresholds (PPT) and tolerance thresholds (PPTol). We measured conditional pain modulation (CPM). Compared with baseline, PPT and PPTol significantly increased in all groups during running and at the 5-10-min follow-up. The PPT and PPTol changes in the moderate- and low-intensity groups were significantly higher than those in the high-intensity group during running and 24 h after running, while the CPM responses of the high-intensity group were significantly reduced at the 24-h follow-up. Moderate- and low-intensity running may elicit significant primary and secondary (persisting over 24 h) EIH effects and increase CPM responses in females. However, high-intensity running induced only limited analgesic effects and reduced CPM responses, which may be attributed to the activation of endogenous pain modulation.

Exercise Pathophysiology in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Postacute Sequelae of SARS-CoV-2: More in Common Than Not?

TOPIC IMPORTANCE

Postacute sequelae of SARS-CoV-2 (PASC) is a long-term consequence of acute infection from COVID-19. Clinical overlap between PASC and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) has been observed, with shared symptoms including intractable fatigue, postexertional malaise, and orthostatic intolerance. The mechanistic underpinnings of such symptoms are poorly understood.

REVIEW FINDINGS

Early studies suggest deconditioning as the primary explanation for exertional intolerance in PASC. Cardiopulmonary exercise testing reveals perturbations related to systemic blood flow and ventilatory control associated with acute exercise intolerance in PASC, which are not typical of simple detraining. Hemodynamic and gas exchange derangements in PASC have substantial overlap with those observed with ME/CFS, suggestive of shared mechanisms.

SUMMARY

This review illustrates exercise pathophysiologic commonalities between PASC and ME/CFS that will help guide future diagnostics and treatment.

Evidence- and data-driven classification of low back pain via artificial intelligence: Protocol of the PREDICT-LBP study

In patients presenting with low back pain (LBP), once specific causes are excluded (fracture, infection, inflammatory arthritis, cancer, cauda equina and radiculopathy) many clinicians pose a diagnosis of non-specific LBP. Accordingly, current management of non-specific LBP is generic. There is a need for a classification of non-specific LBP that is both data- and evidence-based assessing multi-dimensional pain-related factors in a large sample size. The "PRedictive Evidence Driven Intelligent Classification Tool for Low Back Pain" (PREDICT-LBP) project is a prospective cross-sectional study which will compare 300 women and men with non-specific LBP (aged 18-55 years) with 100 matched referents without a history of LBP. Participants will be recruited from the general public and local medical facilities. Data will be collected on spinal tissue (intervertebral disc composition and morphology, vertebral fat fraction and paraspinal muscle size and composition via magnetic resonance imaging [MRI]), central nervous system adaptation (pain thresholds, temporal summation of pain, brain resting state functional connectivity, structural connectivity and regional volumes via MRI), psychosocial factors (e.g. depression, anxiety) and other musculoskeletal pain symptoms. Dimensionality reduction, cluster validation and fuzzy c-means clustering methods, classification models, and relevant sensitivity analyses, will classify non-specific LBP patients into sub-groups. This project represents a first personalised diagnostic approach to non-specific LBP, with potential for widespread uptake in clinical practice. This project will provide evidence to support clinical trials assessing specific treatments approaches for potential subgroups of patients with non-specific LBP. The classification tool may lead to better patient outcomes and reduction in economic costs.

Towards data-driven biopsychosocial classification of non-specific chronic low back pain: a pilot study

The classification of non-specific chronic low back pain (CLBP) according to multidimensional data could guide clinical management; yet recent systematic reviews show this has not been attempted. This was a prospective cross-sectional study of participants with CLBP (n = 21) and age-, sex- and height-matched pain-free controls (n = 21). Nervous system, lumbar spinal tissue and psychosocial factors were collected. Dimensionality reduction was followed by fuzzy c-means clustering to determine sub-groups. Machine learning models (Support Vector Machine, k-Nearest Neighbour, Naïve Bayes and Random Forest) were used to determine the accuracy of classification to sub-groups. The primary analysis showed that four factors (cognitive function, depressive symptoms, general self-efficacy and anxiety symptoms) and two clusters (normal versus impaired psychosocial profiles) optimally classified participants. The error rates in classification models ranged from 4.2 to 14.2% when only CLBP patients were considered and increased to 24.2 to 37.5% when pain-free controls were added. This data-driven pilot study classified participants with CLBP into sub-groups, primarily based on psychosocial factors. This contributes to the literature as it was the first study to evaluate data-driven machine learning CLBP classification based on nervous system, lumbar spinal tissue and psychosocial factors. Future studies with larger sample sizes should validate these findings.

ME/CFS and Long COVID share similar symptoms and biological abnormalities: road map to the literature

Some patients remain unwell for months after "recovering" from acute COVID-19. They develop persistent fatigue, cognitive problems, headaches, disrupted sleep, myalgias and arthralgias, post-exertional malaise, orthostatic intolerance and other symptoms that greatly interfere with their ability to function and that can leave some people housebound and disabled. The illness (Long COVID) is similar to myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) as well as to persisting illnesses that can follow a wide variety of other infectious agents and following major traumatic injury. Together, these illnesses are projected to cost the U.S. trillions of dollars. In this review, we first compare the symptoms of ME/CFS and Long COVID, noting the considerable similarities and the few differences. We then compare in extensive detail the underlying pathophysiology of these two conditions, focusing on abnormalities of the central and autonomic nervous system, lungs, heart, vasculature, immune system, gut microbiome, energy metabolism and redox balance. This comparison highlights how strong the evidence is for each abnormality, in each illness, and helps to set priorities for future investigation. The review provides a current road map to the extensive literature on the underlying biology of both illnesses.

Effectiveness of motor control exercise, aerobic walking, and muscle strengthening programs in improving outcomes in a subgroup of population with chronic low back pain positive for central sensitization: a study protocol for a randomized controlled trial

BACKGROUND

The role of pain sensitivity in the development and maintenance of chronic pain states, impaired executive functioning, and patient recovery is being investigated. Conditioned pain modulation (CPM) is widely used to measure musculoskeletal pain associated with central sensitization (CS). Despite the recommendations of many reviews and clinical practice guidelines that exercise programs reduce pain and disability, the overall confidence in these results is considered "critically low." The "active ingredient" of exercise programs and the dominant factor influencing CPM remain largely unknown. The objectives of this trial are to determine: • If different exercises cause different results on the CPM in a subgroup of people with chronic low back pain (CLBP) who are labeled as having CS pain, • If a program of exercise interventions for 12 weeks would alter executive functioning, quality of life (QoL), disability, and pain in persons with CLBP. • The relationship between patient characteristics, executive functions, CPM, and QoL METHODS: The trial is a randomized, controlled, multi-center study with four experimental groups and one healthy control group. Both the researchers and the people in the study will be blinded to the results. This paper describes the protocol for a trial examining the effects of 12-week individualized, twice-weekly exercise sessions lasting 30 to 60 min in persons with CLBP, who are positive for CS. Participants will be randomized to receive either patient education with motor control exercises (MCE), superficial strengthening (SS), aerobic exercises (AE), or patient education alone. Another group comprised of healthy volunteers will serve as controls. The primary outcomes are changes in CPM outcomes as measured by the cold pressor test (CPT). The secondary objectives are to evaluate executive functioning, pain, disability, quality of life, and spine muscle strength. The outcomes will be measured at 3 months and at a 6-month follow-up.

DISCUSSION

The outcomes of the study will help in gaining more information and evidence about exercise-induced analgesia from the perspective of CPM. Measuring exercise outcomes will aid in scientifically prescribing exercise prescriptions in people with CLBP. The study outcomes will also assist in identifying the characteristics of individuals who will respond or respond indifferently to exercises. Investigating the relationship between the study's various outcomes could provide information for future trials.

TRIAL REGISTRATION

Clinical Trials Registry of India (CTRI) identifier: CTRI/2022/03/041143. Registered on 16 March 2022.

Altered motivation states for physical activity and 'appetite' for movement as compensatory mechanisms limiting the efficacy of exercise training for weight loss

Weight loss is a major motive for engaging in exercise, despite substantial evidence that exercise training results in compensatory responses that inhibit significant weight loss. According to the Laws of Thermodynamics and the CICO (Calories in, Calories out) model, increased exercise-induced energy expenditure (EE), in the absence of any compensatory increase in energy intake, should result in an energy deficit leading to reductions of body mass. However, the expected negative energy balance is met with both volitional and non-volitional (metabolic and behavioral) compensatory responses. A commonly reported compensatory response to exercise is increased food intake (i.e., Calories in) due to increased hunger, increased desire for certain foods, and/or changes in health beliefs. On the other side of the CICO model, exercise training can instigate compensatory reductions in EE that resist the maintenance of an energy deficit. This may be due to decreases in non-exercise activity thermogenesis (NEAT), increases in sedentary behavior, or alterations in sleep. Related to this EE compensation, the motivational states associated with the desire to be active tend to be overlooked when considering compensatory changes in non-exercise activity. For example, exercise-induced alterations in the wanting of physical activity could be a mechanism promoting compensatory reductions in EE. Thus, one's desires, urges or cravings for movement-also known as "motivation states" or "appetence for activity"-are thought to be proximal instigators of movement. Motivation states for activity may be influenced by genetic, metabolic, and psychological drives for activity (and inactivity), and such states are susceptible to fatigue-or reward-induced responses, which may account for reductions in NEAT in response to exercise training. Further, although the current data are limited, recent investigations have demonstrated that motivation states for physical activity are dampened by exercise and increase after periods of sedentarism. Collectively, this evidence points to additional compensatory mechanisms, associated with motivational states, by which impositions in exercise-induced changes in energy balance may be met with resistance, thus resulting in attenuated weight loss.

A Mixed Methods System for the Assessment of Post Exertional Malaise in Encephalomyelitis/Chronic Fatigue Syndrome

Background

A central feature of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is post exertional malaise (PEM), which is an acute worsening of symptoms after a physical, emotional and/or mental exertion. PEM is also a feature of Long COVID. Dynamic measures of PEM have historically included scaled questionnaires which have not been validated in ME/CFS. To enhance our understanding of PEM and how best to measure it, we conducted semi-structured qualitative interviews (QIs) at the same intervals as Visual Analog Scale (VAS) measures after a Cardiopulmonary Exercise Test (CPET).

Methods

Ten ME/CFS and nine healthy volunteers participated in a CPET. For each participant, PEM symptom VAS (7 symptoms) and semi-structured QIs were administered at six timepoints over 72 hours before and after a single CPET. QI data were used to plot the severity of PEM at each time point and identify the self-described most bothersome symptom for each patient. QI data were used to determine the symptom trajectory and peak of PEM. Performance of QI and VAS data were compared to each other using Spearman correlations.

Results

QIs documented that each ME/CFS volunteer had a unique PEM experience, with differences noted in the onset, severity, trajectory over time, and most bothersome symptom. No healthy volunteers experienced PEM. Scaled QI data were able to identify PEM peaks and trajectories, even when VAS scales were unable to do so due to known ceiling and floor effects. QI and VAS fatigue data corresponded well prior to exercise (baseline, r=0.7) but poorly at peak PEM (r=0.28) and with the change from baseline to peak (r=0.20). When the most bothersome symptom identified from QIs was used, these correlations improved (r=.0.77, 0.42. and 0.54 respectively) and reduced the observed VAS scale ceiling and floor effects.

Conclusion

QIs were able to capture changes in PEM severity and symptom quality over time in all the ME/CFS volunteers, even when VAS scales failed to do so. Information collected from QIs also improved the performance of VAS. Measurement of PEM can be improved by using a quantitative-qualitative mixed model approach.

The Interaction Between Psychosocial Factors and Exercise-Induced Hypoalgesia in Pain-Free Nurses

Purpose

This cross-sectional study aimed to investigate whether psychosocial factors were predictive for exercise-induced hypoalgesia (EIH) in pain-free adults.

Methods

A sample of 38 pain-free nurses with a mean (SD) age of 26 (6) years were included in this study. Participants completed psychosocial questionnaires prior to physical tests. Pressure pain threshold (PPT) was assessed bilaterally at the calves (local), lower back (semi-local) and forearm (remote) before and immediately after a maximal graded cycling exercise test. Separate linear mixed effects models were used to determine change in PPT before and after cycling exercise (EIH). Multiple linear regression for all psychosocial variables and best subset regression was used to identify predictors of EIH at all locations.

Results

The relative mean increase in PPT at the forearm, lumbar, calf, and globally (all sites pooled) was 6.0% (p<0.001), 10.1% (p<0.001), 13.9% (p<0.001), and 10.2% (p=0.013), respectively. Separate best subset multiple linear regression models at the forearm (predictors; Multidimensional Scale of Perceived Social Support (MSPSS) total), lumbar (predictors; MSPSS total, Pain Catastrophizing Scale (PCS) total, Depression Anxiety Stress Scale (DASS) depression), calf (predictors; MSPSS friends, PCS total), and global (predictors; MSPSS friends, PCS total) accounted for 7.5% (p=0.053), 13% (p=0.052), 24% (p=0.003), and 17% (p=0.015) of the variance, respectively.

Conclusion

These findings confirm that cycling exercise produced EIH in young nurses and provided preliminary evidence to support the interaction between perceived social support, pain catastrophizing and EIH. Further investigation is required to better understand psychological and social factors that mediate EIH on a larger sample of adults at high risk of developing chronic musculoskeletal pain.

Assessing safety and treatment efficacy of running on intervertebral discs (ASTEROID) in adults with chronic low back pain: protocol for a randomised controlled trial

Poor intervertebral disc (IVD) health is associated with low back pain (LBP). This 12-week parallel randomised controlled trial will evaluate the efficacy of a progressive interval running programme on IVD health and other clinical outcomes in adults with chronic LBP. Participants will be randomised to either a digitally delivered progressive interval running programme or waitlist control. Participants randomised to the running programme will receive three individually tailored 30 min community-based sessions per week over 12 weeks. The waitlist control will undergo no formal intervention. All participants will be assessed at baseline, 6 and 12 weeks. Primary outcomes are IVD health (lumbar IVD T2 via MRI), average LBP intensity over the prior week (100-point visual analogue scale) and disability (Oswestry Disability Index). Secondary outcomes include a range of clinical measures. All outcomes will be analysed using linear mixed models. This study has received ethical approval from the Deakin University Human Research Ethics Committee (ID: 2022-162). All participants will provide informed written consent before participation. Regardless of the results, the findings of this study will be disseminated, and anonymised data will be shared via an online repository. This will be the first study to evaluate whether a progressive interval running programme can improve IVD health in adults with chronic LBP. Identifying conservative options to improve IVD health in this susceptible population group has the potential to markedly reduce the burden of disease. This study was registered via the Australian New Zealand Clinical Trials Registry on 29 September 2022 (ACTRN12622001276741).

Assessment of Fatigue and Recovery in Sport: Narrative Review

Fatigue is a phenomenon associated with decreases in both physical and cognitive performances and increases in injury occurrence. Competitive athletes are required to complete demanding training programs with high workloads to elicit the physiological and musculoskeletal adaptations plus skill acquisition necessary for performance. High workloads, especially sudden rapid increases in training loads, are associated with the occurrence of fatigue. At present, there is limited evidence elucidating the underlying mechanisms associating the fatigue generated by higher workloads and with an increase in injury risk. The multidimensional nature and manifestation of fatigue have led to differing definitions and dichotomies of the term. Consequently, a plethora of physiological, biochemical, psychological and performance markers have been proposed to measure fatigue and recovery. Those include self-reported scales, countermovement jump performance, heart rate variability, and saliva and serum biomarker analyses. The purpose of this review is to provide an overview of fatigue and recovery plus methods of assessments.

Quantitative Sensory Changes Related to Physical Activity in Adult Populations: A Scoping Review

ABSTRACT

Exercise-induced hypoalgesia related to physical activity produces sensory adaptations, but its mechanism remains unclear. Quantitative sensory testing is an effective measurement tool to identify sensory changes, but the extent of evidence linking quantitative sensory testing and physical activity has not been explored. The purpose of this scoping review is to synthesize the evidence on using quantitative sensory testing to evaluate psychophysical changes related to physical activity in adult populations. The researchers developed a comprehensive search strategy with a Health Sciences Librarian using the Arksey and O'Malley Methodological framework. Four databases (Medline [PubMed], CINAHL, Web of Science, and Embase) were searched for peer-reviewed primary research. After 2790 articles were evaluated, 196 studies were included for final review. More than half of studies used randomized controlled trial design (50.5%), followed by quasi-experimental (24.0%) and observational (25.5%) strategies. Healthy adults (42.9%) and individuals with chronic health conditions (20.9%) were examined most frequently. Aerobic (27.6%) and strength (21.4%) physical activity types were most commonly studied. Static quantitative sensory testing measures of pressure pain threshold (84%) were used most frequently. The findings of this scoping review demonstrate available evidence for quantitative sensory testing as a measurement tool of neuromodulation related to physical activity in adult populations. A systematic review is warranted to examine outcomes and recommendations.

Symptomatic but not Asymptomatic COVID-19 Impairs Conditioned Pain Modulation in Young Adults

Pain is a common symptom reported in COVID-19 patients. Impaired endogenous pain-modulatory mechanisms such as conditioned pain modulation (CPM), and exercise-induced hypoalgesia (EIH) have been found in chronic pain conditions but is often overlooked in acute conditions that evoke painful symptoms, such as COVID-19. The purpose was to compare pressure-pain sensitivity, CPM, and EIH function among individuals who previously had COVID-19, both symptomatically and asymptomatically, and a healthy control group. Pressure pain thresholds of 59 participants were assessed in the forearm and leg using a pressure algometer before and after 1) submersion of their dominant foot in cold water (2°C) for 1min; and 2) isometric knee extension performed to task-failure at 25% of their maximal contraction. The CPM response was attenuated in individuals who were infected with symptomatic COVID-19 (N = 26) compared to asymptomatic COVID-19 (N = 13) in arm (-1.0% ± 20.3 vs 33.3% ± 26.2; P < .001) and leg (12.8% ± 22.0 vs 33.8% ± 28.2; P = .014) and compared to controls (N = 20) in arm only (-1.0% ± 26.2 vs 23.4% ± 28.2; P = .004). The EIH response was not different between groups. CPM was impaired in individuals who had symptomatic COVID-19, which may have long-term implications on pain modulation.

Perspective

This study reveals that CPM was impaired in individuals who had symptomatic COVID-19 during the first wave of COVID-19, pre vaccine. These findings present a preliminary motive to study the long-term implications of COVID-19 and its effects on pain modulation.

The Updated NICE Guidance Exposed the Serious Flaws in CBT and Graded Exercise Therapy Trials for ME/CFS

The British National Institute for Health and Care Excellence (NICE) recently published its updated guidelines for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). NICE concluded, after an extensive review of the literature, that graded exercise therapy (GET) is harmful and should not be used, and that cognitive behavioural therapy (CBT) is only an adjunctive and not a curative treatment. Leading proponents of the cognitive behavioural model (CBmodel) find it difficult to accept this paradigm shift. In, for example, an article in The Lancet, they try to argue that the new NICE guideline is based on ideology instead of science. In this article we reviewed the evidence they used to support their claims. Our analysis shows that the trials they used in support suffered from serious flaws which included badly designed control groups, relying on subjective primary outcomes in non-blinded studies, including patients in their trials who didn't have the disease under investigation or had a self-limiting disease, selective reporting, outcome switching and making extensive endpoint changes, which created an overlap in entry and recovery criteria, using a post-hoc definition of recovery which included the severely ill, not publishing results that contradict their own conclusion, ignoring their own (objective) null effect, etc. The flaws in these trials all created a bias in favour of the interventions. Despite all these flaws, treatments that are said to lead to recovery in reality do not lead to objective improvement. Therefore, these studies do not support the claim that CBT and GET are effective treatments. Moreover, the arguments that are used to claim that NICE was wrong, in reality, highlight the absence of evidence for the safety and efficacy of CBT and GET and strengthen the decision by NICE to drop CBT and GET as curative treatments for ME/CFS.

Exploring pain mechanisms in hypermobile Ehlers-Danlos syndrome: a case-control study

BACKGROUND

The hypermobile type of Ehlers-Danlos syndrome (hEDS) is a heritable connective tissue disorder, associated with joint hypermobility and prominent chronic pain. Because experimental pain testing in hEDS is scarce, the underlying mechanisms are still poorly understood.

OBJECTIVE

The present study assesses endogenous pain facilitation and pain inhibition in hEDS, using a protocol for temporal summation of pain (TSP), conditioned pain modulation (CPM), and exercise-induced hypoalgesia (EIH).

METHODS

Twenty women with hEDS and 20 age-matched healthy controls participated. After evaluating thermal and mechanical pain thresholds (PPT), TSP was assessed using 10 repetitive painful pressure stimuli. CPM was provoked using pressure as the test stimulus and hand immersion in hot water (46°) as the conditioning stimulus. EIH was assessed after a submaximal cycling protocol.

RESULTS

The hEDS group demonstrated reduced PPTs and showed significantly more TSP after repeated painful stimuli than the control group. The increase in PPTs caused by the submaximal cycling protocol (EIH) did not reach statistical significance in the hEDS group. Furthermore, in comparison to the healthy control group, the hEDS group demonstrated significantly less EIH at the quadriceps test location. At the trapezius, EIH did not significantly differ between groups. No significant differences were found between the hEDS group and control group in the CPM response.

CONCLUSION

The results demonstrate increased TSP in hEDS, suggesting increased central pain facilitation. EIH should be studied more extensively, but may be disturbed when evaluated in working muscles. The CPM results are inconclusive and require more research.

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Essentials of Diagnosis and Management

Despite myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) affecting millions of people worldwide, many clinicians lack the knowledge to appropriately diagnose or manage ME/CFS. Unfortunately, clinical guidance has been scarce, obsolete, or potentially harmful. Consequently, up to 91% of patients in the United States remain undiagnosed, and those diagnosed often receive inappropriate treatment. These problems are of increasing importance because after acute COVID-19, a significant percentage of people remain ill for many months with an illness similar to ME/CFS. In 2015, the US National Academy of Medicine published new evidence-based clinical diagnostic criteria that have been adopted by the US Centers for Disease Control and Prevention. Furthermore, the United States and other governments as well as major health care organizations have recently withdrawn graded exercise and cognitive-behavioral therapy as the treatment of choice for patients with ME/CFS. Recently, 21 clinicians specializing in ME/CFS convened to discuss best clinical practices for adults affected by ME/CFS. This article summarizes their top recommendations for generalist and specialist health care providers based on recent scientific progress and decades of clinical experience. There are many steps that clinicians can take to improve the health, function, and quality of life of those with ME/CFS, including those in whom ME/CFS develops after COVID-19. Patients with a lingering illness that follows acute COVID-19 who do not fully meet criteria for ME/CFS may also benefit from these approaches.

Pain-related post-exertional malaise in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Fibromyalgia: A systematic review and three-level meta-analysis

OBJECTIVE

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Fibromyalgia (FM) are two debilitating, moderately comorbid illnesses in which chronic musculoskeletal pain symptoms are prevalent. These individuals can experience post-exertional malaise (PEM), a phenomenon where symptom severity is worsened 24hr or longer following physical stress, but the pain-related component of PEM is not well characterized.

DESIGN

Systematic review and meta-analysis.

METHODS

Case-control studies involving adults with ME/CFS or FM and measuring pain symptoms before and after exposure to a standardized aerobic exercise test were included. Hedges' d effect sizes were aggregated using random effects models and potential moderators were explored with meta-regression analysis. Results were adjusted for nesting effects using three-level modeling.

RESULTS

Forty-five effects were extracted from 15 studies involving 306 patients and 292 healthy controls. After adjusting for nesting effects, we observed a small-to-moderate effect indicating higher post-exercise pain in patients than controls (Hedges' d=0.42; 95% CI: 0.16, 0.67). The mean effect was significantly moderated by pain measurement timepoint (b = -0.19, z = -2.57, P = 0.01) such that studies measuring pain 8-72hr post-exercise showed larger effects (d = 0.71, 95% CI = 0.28-1.14) than those measuring pain 0-2hr post-exercise (d = 0.32, 95% CI = 0.10-0.53).

CONCLUSIONS

People with ME/CFS and FM experience small-to-moderate increases in pain severity following exercise which confirms pain as a component of PEM and emphasizes its debilitating impact in ME/CFS and FM. Future directions include determining mechanisms of pain-related PEM and developing exercise prescriptions that minimize symptom exacerbation in these illnesses.

Network Analysis of Symptoms Co-Occurrence in Chronic Fatigue Syndrome

Chronic fatigue syndrome (CFS) is a heterogenous disorder of multiple disabling symptoms with complex manifestations. Network analysis is a statistical and interrogative methodology to investigate the prevalence of symptoms (nodes) and their inter-dependent (inter-nodal) relationships. In the present study, we explored the co-occurrence of symptoms in a cohort of Polish CFS patients using network analysis. A total of 110 patients with CFS were examined (75 females). The mean age of the total sample was 37.93 (8.5) years old while the mean duration of symptoms in years was 4.4 (4). Post-exertional malaise (PEM) was present in 75.45% of patients, unrefreshing sleep was noted in 89.09% and impaired memory or concentration was observed in 87.27% of patients. The least prevalent symptom was tender cervical or axillary lymph nodes, noted in 34.55% of the total sample. Three of the most densely connected nodes were the total number of symptoms, sore throat and PEM. PEM was positively related with impairment in memory or concentration. Both PEM and impairment in memory or concentration presence are related to more severe fatigue measured by CFQ and FIS. PEM presence was positively related with the presence of multi-joint pain and negatively with tender lymph nodes and muscle pain. Sore throat was related with objective and subjective autonomic nervous system impairment. This study helps define symptom presentation of CFS with the pathophysiology of specific systems and links with multidisciplinary contemporary molecular pathology, including comparative MRI.

Reduced Parasympathetic Reactivation during Recovery from Exercise in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Although autonomic nervous system (ANS) dysfunction in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) has been proposed, conflicting evidence makes it difficult to draw firm conclusions regarding ANS activity at rest in ME/CFS patients. Although severe exercise intolerance is one of the core features of ME/CFS, little attempts have been made to study ANS responses to physical exercise. Therefore, impairments in ANS activation at rest and following exercise were examined using a case-control study in 20 ME/CFS patients and 20 healthy people. Different autonomous variables, including cardiac, respiratory, and electrodermal responses were assessed at rest and following an acute exercise bout. At rest, parameters in the time-domain represented normal autonomic function in ME/CFS, while frequency-domain parameters indicated the possible presence of diminished (para)sympathetic activation. Reduced parasympathetic reactivation during recovery from exercise was observed in ME/CFS. This is the first study showing reduced parasympathetic reactivation during recovery from physical exercise in ME/CFS. Delayed HR recovery and/or a reduced HRV as seen in ME/CFS have been associated with poor disease prognosis, high risk for adverse cardiac events, and morbidity in other pathologies, implying that future studies should examine whether this is also the case in ME/CFS and how to safely improve HR recovery in this population.

Insights from myalgic encephalomyelitis/chronic fatigue syndrome may help unravel the pathogenesis of postacute COVID-19 syndrome

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can cause chronic and acute disease. Postacute sequelae of SARS-CoV-2 infection (PASC) include injury to the lungs, heart, kidneys, and brain that may produce a variety of symptoms. PASC also includes a post-coronavirus disease 2019 (COVID-19) syndrome ('long COVID') with features that can follow other acute infectious diseases and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Here we summarize what is known about the pathogenesis of ME/CFS and of 'acute' COVID-19, and we speculate that the pathogenesis of post-COVID-19 syndrome in some people may be similar to that of ME/CFS. We propose molecular mechanisms that might explain the fatigue and related symptoms in both illnesses, and we suggest a research agenda for both ME/CFS and post-COVID-19 syndrome.

Warning Signals of Post-Exertional Malaise in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Retrospective Analysis of 197 Patients

Post-exertional malaise (PEM), the key feature of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), is characterized by baseline symptom exacerbation after exposure to a stressor, and some patients can experience new or non-typical symptoms. We hypothesized that new or non-typical symptoms occurring long enough before onset of baseline symptom exacerbation could be warning signals predicting PEM. Adult ME/CFS patients who attended the internal medicine department of Angers University Hospital (France) between October 2011 and December 2019 were included in a retrospective medical records review. Patients who experienced one or more new or non-typical symptoms before baseline symptom exacerbation were compared with the rest of the study population for PEM features, epidemiological characteristics, fatigue features, and comorbidities. New or non-typical symptoms preceded baseline symptom exacerbation in 27/197 (13.7%) patients, and the most frequent ones were mood disorders (37%). When compared to the rest of the study population, only PEM intensity was significantly lower in these patients (p = 0.004), even after adjustment for sex and age at disease onset (p = 0.007). New or non-typical symptoms preceding baseline symptom exacerbation in some ME/CFS patients could be warning signals for PEM. Their identification could help preventing PEM occurrences or reducing their intensity leading to improving disease prognosis.

Numeric Rating Scales Show Prolonged Post-exertional Symptoms After Orthostatic Testing of Adults With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Introduction: Muscle pain, fatigue, and concentration problems are common among individuals with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). These symptoms are commonly increased as part of the phenomenon of postexertional malaise (PEM). An increase in the severity of these symptoms is described following physical or mental exercise in ME/CFS patients. Another important symptom of ME/CFS is orthostatic intolerance, which can be detected by head-up tilt testing (HUT). The effect of HUT on PEM has not been studied extensively. For this purpose, we assessed numeric rating scales (NRS) for pain, fatigue, and concentration pre- and post-HUT. As pain is a core symptom in fibromyalgia (FM), we subgrouped ME/CFS patients by the presence or absence of FM. Methods and Results: In eligible ME/CFS patients who underwent HUT, NRS of pain, fatigue, and concentration were obtained pre-HUT, immediately after HUT, at 24 and 48 h, and at 7 days posttest. We studied 174 ME/CFS patients with FM, 104 without FM, and 30 healthy controls (HC). Values for all symptoms were unchanged for HC pre- and post-HUT. Compared with pre-HUT, the three NRS post-HUT were significantly elevated in both ME/CFS patient groups even after 7 days. NRS pain was significantly higher at all time points measured in the ME/CFS patients with FM compared with those without FM. In ME/CFS patients, the maximum fatigue and concentration scores occurred directly post-HUT, whereas pain perception reached the maximum 24 h post-HUT. Conclusion: NRS scores of pain, fatigue, and concentration were significantly increased even at 7 days post-HUT compared with pre-HUT in ME/CFS patients with and without FM, suggesting that orthostatic stress is an important determinant of PEM.

Prediction of Discontinuation of Structured Exercise Programme in Chronic Fatigue Syndrome Patients

Purpose: The purpose of this study was to assess differences in the physiological profiles of completers vs. non-completers following a structured exercise programme (SEP) and the ability to predict non-completers, which is currently unknown in this group. Methods: Sixty-nine patients met the Fukuda criteria. Patients completed baseline measures assessing fatigue, autonomic nervous system (ANS), cognitive, and cardiovascular function. Thirty-four patients completed a home-based SEP consisting of 10–40 min per day at between 30 and 80% actual HR max. Exercise intensity and time was increased gradually across the 16 weeks and baseline measures were repeated following the SEP. Results: Thirty-five patients discontinued, while 34 completed SEP. For every increase in sympathetic drive for blood pressure control as measured by the taskforce, completion of SEP decreased by a multiple of 0.1. For a 1 millisecond increase in reaction time for the simple reaction time (SRT), the probability for completion of SEP also decreases by a multiple of 0.01. For a one beat HRmax increase, there is a 4% increase in the odds of completing SEP. Conclusion: The more sympathetic drive in the control of blood vessels, the longer the reaction time on simple visual stimuli and the lower the HRmax during physical exercise, then the lower the chance of SEP completion in ME/CFS.

Exercise-induced hypoalgesia after acute and regular exercise: experimental and clinical manifestations and possible mechanisms in individuals with and without pain

This review describes methodology used in the assessment of the manifestations of exercise-induced hypoalgesia in humans and previous findings in individuals with and without pain. Possible mechanisms and future directions are discussed.

Exercise and physical activity is recommended treatment for a wide range of chronic pain conditions. In addition to several well-documented effects on physical and mental health, 8 to 12 weeks of exercise therapy can induce clinically relevant reductions in pain. However, exercise can also induce hypoalgesia after as little as 1 session, which is commonly referred to as exercise-induced hypoalgesia (EIH). In this review, we give a brief introduction to the methodology used in the assessment of EIH in humans followed by an overview of the findings from previous experimental studies investigating the pain response after acute and regular exercise in pain-free individuals and in individuals with different chronic pain conditions. Finally, we discuss potential mechanisms underlying the change in pain after exercise in pain-free individuals and in individuals with different chronic pain conditions, and how this may have implications for clinical exercise prescription as well as for future studies on EIH.

Cognitive Function Declines Following Orthostatic Stress in Adults With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)

Introduction

Orthostatic intolerance (OI) is common among individuals with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Cognitive dysfunction has been demonstrated during head-up tilt testing (HUT) in those with ME/CFS: worse scores on cognitive tests occur with increasing tilt angles and increasing complexity of the cognitive challenge. The aim of our study was to determine whether cognitive impairment persists after completion of HUT.

Methods and Results

Eligible participants were consecutive individuals satisfying criteria for ME/CFS who underwent HUT because of OI. The 2- and 3-back tests were performed before the start of HUT and within 5 min after completion of HUT. We measured the percentage of correct responses and raw reaction times before and after HUT for both the 2- and 3-back tests. We studied 128 ME/CFS patients who underwent HUT and had a complete set of N-back data before and after HUT. Compared to pre-tilt responses, the percentage of correct responses on the 2-back test decreased post-HUT from 77(18) to 62(21) and of the 3-back test from 57(17) to 41(17) (both p < 0.0001). The raw reaction time of the 2-back test increased post-HUT from 783(190) to 941(234) m/s and of the 3-back test from 950(170) to 1102(176) (both p < 0.0001). There was no difference in the N-back test data for subgroups dichotomized based on disease severity, the presence of co-morbid fibromyalgia, or the presence of postural orthostatic tachycardia syndrome.

Conclusion

As measured by the N-back test, working memory remains impaired in adults with ME/CFS following a 30-min head-up tilt test.

The Association of Psychosocial Factors and Exercise-Induced Hypoalgesia in Healthy People and People With Musculoskeletal Pain: A Systematic Review

BACKGROUND

Exercise, a cornerstone in current treatments for people with musculoskeletal pain, elicits a phenomenon called exercise-induced hypoalgesia (EIH), which may result in reduced pain intensity and/or increased pain thresholds. However, EIH can be impaired in patients with musculoskeletal pain, and psychosocial factors may play a mediating role in EIH.

OBJECTIVE

The aim of this study was to systematically review the scientific literature regarding the association between psychosocial factors and EIH in healthy people and people with musculoskeletal pain.

METHODS

An extensive search in databases including Medline Ovid, Embase, Web of Science, PsycINFO Ovid, and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) EBSCOhost was carried out. Two reviewers independently carried out study selection, data extraction, and critical appraisal. Included studies analyzed the association or effect of psychosocial factors on EIH in adults with or without musculoskeletal pain.

RESULTS

Nine cross-sectional studies were included, 6 involving healthy people and 4 involving people with musculoskeletal pain; 1 study included both. Overall risk of bias was high. Different types of exercise bouts, psychosocial factors, and/or outcome measures were used across studies. In healthy people and people with musculoskeletal pain, most studies did not find an association between psychosocial factors and EIH. However, 1 study involving musculoskeletal pain and 2 studies with healthy people did find a significant association.

CONCLUSION

Due to poor quality and heterogeneity between studies, no conclusions can be drawn regarding whether psychosocial factors are associated with EIH or not. This review includes recommendations and directions for further research to investigate the role of psychosocial factors on EIH.

Post-exertional malaise in veterans with gulf war illness

Post-exertional malaise (PEM) is a potentially debilitating aspect of Gulf War Illness (GWI) that has received limited research attention. The purpose of the present investigation was to determine symptom severity changes following exercise in Veterans with GWI compared to control Veterans without GWI (CO). Sixty-seven Veterans (n = 39 GWI; n = 28 CO) underwent a 30-minute submaximal exercise challenge at 70% of heart rate reserve. Symptom measurements (e.g. fatigue, pain) occurred pre-, immediately post-, and 24-hour post-exercise. Self-reported physical and mental health, and physiological and perceptual responses to exercise were compared between groups using descriptive statistics, independent samples t-tests and repeated measures Analysis of Variance (RM-ANOVA). Post-exertional malaise was modeled using Group by Time (2 × 3) doubly-multivariate, RM-MANOVAs for (1) mood, (2) pain and (3) GWI-related symptoms, respectively (α = 0.05). Data were analyzed for the full sample of Veterans with GWI (n = 39) compared to CO (n = 28) and a subsample of Veterans (n = 18) who endorsed "feeling unwell after physical exercise or exertion" ("PEM endorsers") during screening. Veterans with GWI reported significantly lower physical and mental health. Groups exercised at similar relative exercise intensities, but GWI perceived exercise as more painful and fatiguing. Group-by-Time interactions were not significant for the entire sample for the three PEM models, however limiting the GWI sample to "PEM endorsers" resulted in significant interactions for Pain- and GWI-related PEM models. These results indicate that not all GVs with GWI experience PEM 24 h after exercise, and that more research is needed to determine the extent that exercise worsens symptoms in GWI.

Evidence of altered cardiac autonomic regulation in myalgic encephalomyelitis/chronic fatigue syndrome: A systematic review and meta-analysis

BACKGROUND

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a complex condition with no reliable diagnostic biomarkers. Studies have shown evidence of autonomic dysfunction in patients with ME/CFS, but results have been equivocal. Heart rate (HR) parameters can reflect changes in autonomic function in healthy individuals; however, this has not been thoroughly evaluated in ME/CFS.

METHODS

A systematic database search for case-control literature was performed. Meta-analysis was performed to determine differences in HR parameters between ME/CFS patients and controls.

RESULTS

Sixty-four articles were included in the systematic review. HR parameters assessed in ME/CFS patients and controls were grouped into ten categories: resting HR (RHR), maximal HR (HRmax), HR during submaximal exercise, HR response to head-up tilt testing (HRtilt), resting HR variability (HRVrest), HR variability during head-up tilt testing (HRVtilt), orthostatic HR response (HROR), HR during mental task(s) (HRmentaltask), daily average HR (HRdailyaverage), and HR recovery (HRR) Meta-analysis revealed RHR (MD ± 95% CI = 4.14 ± 1.38, P < .001), HRtilt (SMD ± 95% CI = 0.92 ± 0.24, P < .001), HROR (0.50 ± 0.27, P < .001), and the ratio of low frequency power to high frequency power of HRVrest (0.39 ± 0.22, P < .001) were higher in ME/CFS patients compared to controls, while HRmax (MD ± 95% CI = -13.81 ± 4.15, P < .001), HR at anaerobic threshold (SMD ± 95% CI = -0.44 ± 0.30, P = 0.005) and the high frequency portion of HRVrest (-0.34 ± 0.22, P = .002) were lower in ME/CFS patients.

CONCLUSIONS

The differences in HR parameters identified by the meta-analysis indicate that ME/CFS patients have altered autonomic cardiac regulation when compared to healthy controls. These alterations in HR parameters may be symptomatic of the condition.

Exercise-induce hyperalgesia, complement system and elastase activation in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome - a secondary analysis of experimental comparative studies

Background and aims The interaction between the immune system and pain has been thoroughly explored in the recent decades. The release of inflammatory mediators from immune cells has the capability of activating neurons and glial cells, in turn sensitizing the nervous system. Both immune system alterations and pain modulation dysfunctions have been shown in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) following exercise. However, no studies tried to explore whether these two phenomena are linked and can explain exercise-induced symptoms worsening in people with ME/CFS. We hypothesized that exercise-induced changes in descending pain modulation is associated to changes in immune system functions. We used complement system product C4a and elastase activity as indicators of immune system activity. Methods The study design was a secondary analysis of controlled experimental studies. Twenty-two patients with ME/CFS and 22 healthy sedentary controls were enrolled. In experiment 1, subjects performed an aerobic submaximal exercise test; in experiment 2 they underwent a self-paced exercise test. One week of rest period were set between the two exercise tests. Before and after each experiment, subjects underwent clinical assessment, pain thresholds (PPTs) measurement, and blood sampling. Immune system function was assessed measuring complement system C4a products and elastase activity. Results Changes in elastase activity were not associated to changes in PPTs. Associations were observed in the ME/CFS group between changes in PPTs and C4a products, following both types of exercise. After submaximal exercise, the change in C4a products was associated with the change in PPT at the thumb in patients (r=0.669, p=0.001). Similarly, after self-paced exercise the change in C4a products was associated witht the change in PPT at the calf in patients (r=0.429, p=0.047). No such correlations were found in healthy controls. Regression analysis showed that C4a changes after the submaximal exercise significantly predicted the change in PPTs (R2=0.236; p=0.02). Conclusions Moderate associations between exercise-induced changes in PPTs and immune system activity were found only in ME/CFS. The change in the complement system following submaximal exercise might be able to explain part of the change in patient's pain thresholds, providing evidence for a potential link between immune system alteration and dysfunctional endogenous pain modulation. These results have to be taken with caution, as only one out of three measures of PPTs was found associated with C4a changes. We cannot reject the hypothesis that C4a might therefore be a confounding factor, and changes during exercise might be mediated by other mechanism. Implications Immune system changes following exercise might contribute to exercise-induced symptoms worsening in patients with ME/CFS. However, the role of the complement system is questionable.

Exercise-Induced Hypoalgesia in Pain-Free and Chronic Pain Populations: State of the Art and Future Directions

Exercise is considered an important component of effective chronic pain management and it is well-established that long-term exercise training provides pain relief. In healthy, pain-free populations, a single bout of aerobic or resistance exercise typically leads to exercise-induced hypoalgesia (EIH), a generalized reduction in pain and pain sensitivity that occurs during exercise and for some time afterward. In contrast, EIH is more variable in chronic pain populations and is more frequently impaired; with pain and pain sensitivity decreasing, remaining unchanged or, in some cases, even increasing in response to exercise. Pain exacerbation with exercise may be a major barrier to adherence, precipitating a cycle of physical inactivity that can lead to long-term worsening of both pain and disability. To optimize the therapeutic benefits of exercise, it is important to understand how EIH works, why it may be impaired in some people with chronic pain, and how this should be addressed in clinical practice. In this article, we provide an overview of EIH across different chronic pain conditions. We discuss possible biological mechanisms of EIH and the potential influence of sex and psychosocial factors, both in pain-free adults and, where possible, in individuals with chronic pain. The clinical implications of impaired EIH are discussed and recommendations are made for future research, including further exploration of individual differences in EIH, the relationship between exercise dose and EIH, the efficacy of combined treatments and the use of alternative measures to quantify EIH. PERSPECTIVE: This article provides a contemporary review of the acute effects of exercise on pain and pain sensitivity, including in people with chronic pain conditions. Existing findings are critically reviewed, clinical implications are discussed, and recommendations are offered for future research.

Relationship Between Exercise-induced Oxidative Stress Changes and Parasympathetic Activity in Chronic Fatigue Syndrome: An Observational Study in Patients and Healthy Subjects

PURPOSE

Oxidative stress has been proposed as a contributor to pain in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). During incremental exercise in patients with ME/CFS, oxidative stress enhances sooner and antioxidant response is delayed. We explored whether oxidative stress is associated with pain symptoms or pain changes following exercise, and the possible relationships between oxidative stress and parasympathetic vagal nerve activity in patients with ME/CFS versus healthy, inactive controls.

METHODS

The present study reports secondary outcomes from a previous work. Data from 36 participants were studied (women with ME/CFS and healthy controls). Subjects performed a submaximal exercise test with continuous cardiorespiratory monitoring. Levels of thiobarbituric acid-reactive substances (TBARSs) were used as a measure of oxidative stress, and heart rate variability was used to assess vagal activity. Before and after the exercise, subjects were asked to rate their pain using a visual analogic scale.

FINDINGS

Significant between-group differences in pain at both baseline and following exercise were found (both, P < 0.007). In healthy controls, pain was significantly improved following exercise (P = 0.002). No change in oxidative stress level after exercise was found. Significant correlation between TBARS levels and pain was found at baseline (r = 0.540; P = 0.021) and after exercise (r = 0.524; P = 0.024) in patients only. No significant correlation between TBARS and heart rate variability at baseline or following exercise was found in either group. However, a significant correlation was found between exercise-induced changes in HRV and TBARS in healthy controls (r = -0.720; P = 0.001).

IMPLICATIONS

Oxidative stress showed an association with pain symptoms in people with ME/CFS, but no exercise-induced changes in oxidative stress were found. In addition, the change in parasympathetic activity following exercise partially accounted for the change in oxidative stress in healthy controls. More research is required to further explore this link.

Myalgic encephalomyelitis/chronic fatigue syndrome and the biopsychosocial model: a review of patient harm and distress in the medical encounter

Objective: Despite the growing evidence of physiological and cellular abnormalities in myalgic encephalomyelitis (ME)/chronic fatigue syndrome (CFS), there has been a strong impetus to tackle the illness utilizing a biopsychosocial model. However, many sufferers of this disabling condition report distress and dissatisfaction following medical encounters. This review seeks to account for this discord.Methods: A narrative review methodology is employed to synthesize the evidence for potential iatrogenesis.Results: We identify seven potential modalities of iatrogenesis or harm reported by patients:difficulties in reaching an acceptable diagnosis;misdiagnosis, including of other medical and psychological conditions;difficulties in accessing the sick role, medical care and social support;high levels of patient dissatisfaction with the quality of medical care;negative responses to controversial therapies (cognitive behavioral therapy and graded exercise therapy);challenges to the patient narrative and experience;psychological harm (individual and collective distress).Conclusion: The biopsychosocial framework currently applied to ME/CFS is too narrow in focus and fails to adequately incorporate the patient narrative. Misdiagnosis, conflict, and harm are observable outcomes where doctors' and patients' perspectives remain incongruent. Biopsychosocial practices should be scrutinized for potential harms. Clinicians should consider adopting alternative patient-centred approaches.Implications for rehabilitationPatients with ME/CFS may report or experience one or more of the modalities of harms and distress identified in this review.It is important health and rehabilitation professionals seek to avoid and minimize harms when treating or assisting ME/CFS patients.There are conflicting models of ME/CFS; we highlight two divergent models, a biopsychosocial model and a biomedical model that is preferred by patients.The 'biopsychosocial framework' applied in clinical practice promotes treatments such as cognitive behavioral therapy and exercise therapy, however, the evidence for their success is contested and many patients reject the notion their illness is perpetuated by dysfunctional beliefs, personality traits, or behaviors.Health professionals may avoid conflict and harm causation in ME/CFS by adopting more concordant 'patient-centred' approaches that give greater prominence to the patient narrative and experience of illness.

Deconstructing post-exertional malaise in myalgic encephalomyelitis/ chronic fatigue syndrome: A patient-centered, cross-sectional survey

BACKGROUND

Post-exertional malaise (PEM) is considered to be the hallmark characteristic of myalgic encephalomyelitis/ chronic fatigue syndrome (ME/CFS). Yet, patients have rarely been asked in formal studies to describe their experience of PEM.

OBJECTIVES

To describe symptoms associated with and the time course of PEM.

METHODS

One hundred and fifty subjects, diagnosed via the 1994 Fukuda CFS criteria, completed a survey concerning 11 symptoms they could experience after exposure to two different types of triggers. We also inquired about onset and duration of PEM and included space for subjects to write in any additional symptoms. Results were summarized with descriptive statistics; McNemar's, paired t-, Fisher's exact and chi-square goodness-of-fit tests were used to assess for statistical significance.

RESULTS

One hundred and twenty-nine subjects (90%) experienced PEM with both physical and cognitive exertion and emotional distress. Almost all were affected by exertion but 14 (10%) reported no effect with emotion. Fatigue was the most commonly exacerbated symptom but cognitive difficulties, sleep disturbances, headaches, muscle pain, and flu-like feelings were cited by over 30% of subjects. Sixty percent of subjects experienced at least one inflammatory/ immune-related symptom. Subjects also cited gastrointestinal, orthostatic, mood-related, neurologic and other symptoms. Exertion precipitated significantly more symptoms than emotional distress (7±2.8 vs. 5±3.3 symptoms (median, standard deviation), p<0.001). Onset and duration of PEM varied for most subjects. However, 11% reported a consistent post-trigger delay of at least 24 hours before onset and 84% endure PEM for 24 hours or more.

CONCLUSIONS

This study provides exact symptom and time patterns for PEM that is generated in the course of patients' lives. PEM involves exacerbation of multiple, atypical symptoms, is occasionally delayed, and persists for extended periods. Highlighting these characteristics may improve diagnosis of ME/CFS. Incorporating them into the design of future research will accelerate our understanding of ME/CFS.

Development and Validity of the Rating-of-Fatigue Scale

OBJECTIVE

The purpose of these experiments was to develop a rating-of-fatigue (ROF) scale capable of tracking the intensity of perceived fatigue in a variety of contexts.

METHODS

Four experiments were carried out. The first provided the evidential basis for the construction of the ROF scale. The second tested the face validity of the ROF, and the third tested the convergent and divergent validity of the ROF scale during ramped cycling to exhaustion and 30 min of resting recovery. The final experiment tested the convergent validity of the ROF scale with time of day and physical activity (accelerometer counts) across a whole week.

RESULTS

Modal selections of descriptions and diagrams at different levels of exertion and recovery were found during Experiment 1 upon which the ROF scale was constructed and finalised. In Experiment 2, a high level of face validity was indicated, in that ROF was reported to represent fatigue rather than exertion. Descriptor and diagrammatic elements of ROF reportedly added to the coherence and ease of use of the scale. In Experiment 3, high convergence between ROF and various physiological measures were found during exercise and recovery (heart rate, blood lactate concentration, oxygen uptake, carbon dioxide production, respiratory exchange ratio and ventilation rate were all P < 0.001). During ramped cycling to exhaustion ROF and RPE did correspond (P < 0.0001) but not during recovery, demonstrating discriminant validity. Experiment 4 found ROF to correspond with waking time during each day (Mon-Sun all P < 0.0001) and with physical activity (accelerometer count) (Mon-Sun all P < 0.001).

CONCLUSIONS

The ROF scale has good face validity and high levels of convergent validity during ramped cycling to exhaustion, resting recovery and daily living activities. The ROF scale has both theoretical and applied potential in understanding changes in fatigue in a variety of contexts.

Mechanisms Explaining Muscle Fatigue and Muscle Pain in Patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS): a Review of Recent Findings

PURPOSE OF REVIEW

Here, we review potential causes of muscle dysfunction seen in many patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) such as the effects of oxidative and nitrosative stress (O&NS) and mitochondrial impairments together with reduced heat shock protein production and a range of metabolic abnormalities.

RECENT FINDINGS

Several studies published in the last few years have highlighted the existence of chronic O&NS, inflammation, impaired mitochondrial function and reduced heat shock protein production in many patients with ME/CFS. These studies have also highlighted the detrimental effects of chronically elevated O&NS on muscle functions such as reducing the time to muscle fatigue during exercise and impairing muscle contractility. Mechanisms have also been revealed by which chronic O&NS and or impaired heat shock production may impair muscle repair following exercise and indeed the adaptive responses in the striated muscle to acute and chronic increases in physical activity. The presence of chronic O&NS, low-grade inflammation and impaired heat shock protein production may well explain the objective findings of increased muscle fatigue, impaired contractility and multiple dimensions of exercise intolerance in many patients with ME/CFS.

Effect of Acute Exercise on Fatigue in People with ME/CFS/SEID: A Meta-analysis

PURPOSE

A prominent symptom of myalgic encephalomyelitis, chronic fatigue syndrome, or systemic exertion intolerance disease (ME/CFS/SEID) is persistent fatigue that is worsened by physical exertion. Here the population effect of a single bout of exercise on fatigue symptoms in people with ME/CFS/SEID was estimated and effect moderators were identified.

METHODS

Google Scholar was systematically searched for peer-reviewed articles published between February 1991 and May 2015. Studies were included where people diagnosed with ME/CFS/SEID and matched control participants completed a single bout of exercise and fatigue self-reports were obtained before and after exercise. Fatigue means, standard deviations, and sample sizes were extracted to calculate effect sizes and the 95% confidence interval. Effects were pooled using a random-effects model and corrected for small sample bias to generate mean Δ. Multilevel regression modeling adjusted for nesting of effects within studies. Moderators identified a priori were diagnostic criteria, fibromyalgia comorbidity, exercise factors (intensity, duration, and type), and measurement factors.

RESULTS

Seven studies examining 159 people with ME/CFS/SEID met inclusion criteria, and 47 fatigue effects were derived. The mean fatigue effect was Δ = 0.73 (95% confidence interval = 0.24-1.23). Fatigue increases were larger for people with ME/CFS/SEID when fatigue was measured 4 h or more after exercise ended rather than during or immediately after exercise ceased.

CONCLUSIONS

This preliminary evidence indicates that acute exercise increases fatigue in people with ME/CFS/SEID more than that in control groups, but effects were heterogeneous between studies. Future studies with no-exercise control groups of people with ME/CFS/SEID are needed to obtain a more precise estimate of the effect of exercise on fatigue in this population.

Neural consequences of post-exertion malaise in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Post exertion malaise is one of the most debilitating aspects of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome, yet the neurobiological consequences are largely unexplored. The objective of the study was to determine the neural consequences of acute exercise using functional brain imaging. Fifteen female Myalgic Encephalomyelitis/Chronic Fatigue Syndrome patients and 15 healthy female controls completed 30min of submaximal exercise (70% of peak heart rate) on a cycle ergometer. Symptom assessments (e.g. fatigue, pain, mood) and brain imaging data were collected one week prior to and 24h following exercise. Functional brain images were obtained during performance of: 1) a fatiguing cognitive task - the Paced Auditory Serial Addition Task, 2) a non-fatiguing cognitive task - simple number recognition, and 3) a non-fatiguing motor task - finger tapping. Symptom and exercise data were analyzed using independent samples t-tests. Cognitive performance data were analyzed using mixed-model analysis of variance with repeated measures. Brain responses to fatiguing and non-fatiguing tasks were analyzed using linear mixed effects with cluster-wise (101-voxels) alpha of 0.05. Myalgic Encephalomyelitis/Chronic Fatigue Syndrome patients reported large symptom changes compared to controls (effect size ≥0.8, p<0.05). Patients and controls had similar physiological responses to exercise (p>0.05). However, patients exercised at significantly lower Watts and reported greater exertion and leg muscle pain (p<0.05). For cognitive performance, a significant Group by Time interaction (p<0.05), demonstrated pre- to post-exercise improvements for controls and worsening for patients. Brain responses to finger tapping did not differ between groups at either time point. During number recognition, controls exhibited greater brain activity (p<0.05) in the posterior cingulate cortex, but only for the pre-exercise scan. For the Paced Serial Auditory Addition Task, there was a significant Group by Time interaction (p<0.05) with patients exhibiting increased brain activity from pre- to post-exercise compared to controls bilaterally for inferior and superior parietal and cingulate cortices. Changes in brain activity were significantly related to symptoms for patients (p<0.05). Acute exercise exacerbated symptoms, impaired cognitive performance and affected brain function in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome patients. These converging results, linking symptom exacerbation with brain function, provide objective evidence of the detrimental neurophysiological effects of post-exertion malaise.

Differences in ME and CFS Symptomology in Patients with Normal and Abnormal Exercise Test Results

Post-exertional malaise (PEM) is a cardinal symptom of myalgic encephalomyelitis (ME) and chronic fatigue syndrome (CFS), which often distinguishes patients with this illness from healthy controls or individuals with exclusionary illnesses such as depression. However, occurrence rates for PEM fluctuate from subject to how the symptom is operationalized. One commonly utilized method is exercise testing, maximal or submaximal. Many patients with ME and CFS experience PEM after participating in these tests, and often show abnormal results. However, some patients still exhibit normal results after participating in the exercise testing. This study examined the differences between two patient groups with ME and CFS, those with normal results and those with abnormal results, on several PEM-related symptoms and illness characteristics. The results suggest those that displayed abnormal results following testing have more frequent and severe PEM, worse overall functioning, and are more likely to be bedbound than those that displayed normal results.

Do graded activity therapies cause harm in chronic fatigue syndrome?

Reporting of harms was much better in the PACE (Pacing, graded Activity, and Cognitive behavioural therapy: a randomised Evaluation) trial than earlier chronic fatigue syndrome trials of graded exercise therapy and cognitive behavioural therapy. However, some issues remain. The trial's poor results on objective measures of fitness suggest a lack of adherence to the activity component of these therapies. Therefore, the safety findings may not apply in other clinical contexts. Outside of clinical trials, many patients report deterioration with cognitive behavioural therapy and particularly graded exercise therapy. Also, exercise physiology studies reveal abnormalities in chronic fatigue syndrome patients' responses to exertion. Given these considerations, one cannot conclude that these interventions are safe and risk-free.