The Role of Autonomic Function in Exercise-induced Endogenous Analgesia: A Case-control Study in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Healthy People.

BACKGROUND: Patients with myalgic encephalomyelitis / chronic fatigue syndrome (ME/CFS) are unable to activate brain-orchestrated endogenous analgesia (or descending inhibition) in response to exercise. This physiological impairment is currently regarded as one factor explaining post-exertional malaise in these patients. Autonomic dysfunction is also a feature of ME/CFS. OBJECTIVES: This study aims to examine the role of the autonomic nervous system in exercise-induced analgesia in healthy people and those with ME/CFS, by studying the recovery of autonomic parameters following aerobic exercise and the relation to changes in self-reported pain intensity. STUDY DESIGN: A controlled experimental study. SETTING: The study was conducted at the Human Physiology lab of a University. METHODS: Twenty women with ME/CFS- and 20 healthy, sedentary controls performed a submaximal bicycle exercise test known as the Aerobic Power Index with continuous cardiorespiratory monitoring. Before and after the exercise, measures of autonomic function (i.e., heart rate variability, blood pressure, and respiration rate) were performed continuously for 10 minutes and self-reported pain levels were registered. The relation between autonomous parameters and self-reported pain parameters was examined using correlation analysis. RESULTS: Some relationships of moderate strength between autonomic and pain measures were found. The change (post-exercise minus pre-exercise score) in pain severity was correlated (r = .580, P = .007) with the change in diastolic blood pressure in the healthy group. In the ME/CFS group, positive correlations between the changes in pain severity and low frequency (r = .552, P = .014), and between the changes in bodily pain and diastolic blood pressure (r = .472, P = .036), were seen. In addition, in ME/CHFS the change in headache severity was inversely correlated (r = -.480, P = .038) with the change in high frequency heart rate variability. LIMITATIONS: Based on the cross-sectional design of the study, no firm conclusions can be drawn on the causality of the relations. CONCLUSIONS: Reduced parasympathetic reactivation during recovery from exercise is associated with the dysfunctional exercise-induced analgesia in ME/CFS. Poor recovery of diastolic blood pressure in response to exercise, with blood pressure remaining elevated, is associated with reductions of pain following exercise in ME/CFS, suggesting a role for the arterial baroreceptors in explaining dysfunctional exercise-induced analgesia in ME/CFS patients.Key words: Aerobic exercise, aerobic power index, autonomic nervous system, exercise-induced analgesia, exercise-induced hypoalgesia, fibromyalgia, heart rate variability, stress-induced analgesia, pain.

Structural Changes of Lumbar Muscles in Non-specific Low Back Pain: A Systematic Review.

BACKGROUND: Lumbar muscle dysfunction due to pain might be related to altered lumbar muscle structure. Macroscopically, muscle degeneration in low back pain (LBP) is characterized by a decrease in cross-sectional area and an increase in fat infiltration in the lumbar paraspinal muscles. In addition microscopic changes, such as changes in fiber distribution, might occur. Inconsistencies in results from different studies make it difficult to draw firm conclusions on which structural changes are present in the different types of non-specific LBP. Insights regarding structural muscle alterations in LBP are, however, important for prevention and treatment of non-specific LBP. OBJECTIVE: The goal of this article is to review which macro- and/or microscopic structural alterations of the lumbar muscles occur in case of non-specific chronic low back pain (CLBP), recurrent low back pain (RLBP), and acute low back pain (ALBP). STUDY DESIGN: Systematic review. SETTING: All selected studies were case-control studies. METHODS: A systematic literature search was conducted in the databases PubMed and Web of Science. Only full texts of original studies regarding structural alterations (atrophy, fat infiltration, and fiber type distribution) in lumbar muscles of patients with non-specific LBP compared to healthy controls were included. All included articles were scored on methodological quality. RESULTS: Fifteen studies were found eligible after screening title, abstract, and full text for inclusion and exclusion criteria. In CLBP, moderate evidence of atrophy was found in the multifidus; whereas, results in the paraspinal and the erector spinae muscle remain inconclusive. Also moderate evidence occurred in RLBP and ALBP, where no atrophy was shown in any lumbar muscle. Conflicting results were seen in undefined LBP groups. Results concerning fat infiltration were inconsistent in CLBP. On the other hand, there is moderate evidence in RLBP that fat infiltration does not occur, although a larger muscle fat index was found in the erector spinae, multifidus, and paraspinal muscles, reflecting an increased relative amount of intramuscular lipids in RLBP. However, no studies were found investigating fat infiltration in ALBP. Restricted evidence indicates no abnormalities in fiber type in the paraspinal muscles in CLBP. No studies have examined fiber type in ALBP and RLBP. LIMITATIONS: Lack of clarity concerning patient definitions, exact LBP symptoms, and applied methods. CONCLUSIONS: The results indicate atrophy in CLBP in the multifidus and paraspinal muscles but not in the erector spinae. No atrophy was shown in RLBP and ALBP. Fat infiltration did not occur in RLBP, but results in CLBP were inconsistent. No abnormalities in fiber type in the paraspinal muscles were found in CLBP. KEY WORDS: Low back pain, non-specific, chronic, recurrent, acute, muscle structure, fat infiltration, cross-sectional area, fiber type, review.

The efficacy of patient education in whiplash associated disorders: a systematic review.

BACKGROUND: Until now, there is no firm evidence for conservative therapy in patients with chronic Whiplash Associated Disorders (WAD). While chronic WAD is a biopsychosocial problem, education may be an essential part in the treatment and the prevention of chronic WAD. However, it is still unclear which type of educative intervention has already been used in WAD patients and how effective such interventions are. OBJECTIVE: This systematic literature study aimed at providing an overview of the literature regarding the currently existing educative treatments for patients with whiplash or WAD and their evidence. STUDY DESIGN: Systematic review of the literature. METHODS: A systematic literature search was conducted in the following databases: Pubmed, Springerlink, and Web of Science using different keyword combinations. We included randomized controlled clinical trials (RCT) that encompass the effectiveness of education for patients with WAD. The included articles were evaluated on their methodological quality. RESULTS: Ten RCT's of moderate to good quality remained after screening. Both oral and written advice, education integrated in exercise programs and behavioral programs appear effective interventions for reducing pain and disability and enhancing recovery and mobility in patients with WAD. In acute WAD, a simple oral education session will suffice. In subacute or chronic patients broader (multidisciplinary) programs including education which tend to modulate pain behavior and activate patients seems necessary. LIMITATIONS: Because of limited studies and the broad range of different formats and contents of education and different outcome measures, further research is needed before solid conclusions can be drawn regarding the use and the modalities of these educational interventions in clinical practice. CONCLUSION: Based on this systematic literature study is seems appropriate for the pain physician to provide education as part of a biopsychosocial approach of patients with whiplash. Such education should target removing therapy barriers, enhancing therapy compliance and preventing and treating chronicity. Still, more studies are required to provide firm evidence for the type, duration, format, and efficacy of education in the different types of whiplash patients.