Pain quality patterns in delayed onset muscle soreness of the lower back suggest sensitization of fascia rather than muscle afferents: a secondary analysis study

Delayed onset muscle soreness (DOMS) of the lower back is considered a surrogate for acute low back pain (aLBP) in experimental studies. Of note, it is often unquestioningly assumed to be muscle pain. To date, there has not been a study analyzing lumbar DOMS in terms of its pain origin, which was the aim of this study. Sixteen healthy individuals (L-DOMS) were enrolled for the present study and matched to participants from a previous study (n = 16, L-PAIN) who had undergone selective electrical stimulation of the thoracolumbar fascia and the multifidus muscle. DOMS was induced in the lower back of the L-DOMS group using eccentric trunk extensions performed until exhaustion. On subsequent days, pain on palpation (100-mm analogue scale), pressure pain threshold (PPT), and the Pain Sensation Scale (SES) were used to examine the sensory characteristics of DOMS. Pain on palpation showed a significant increase 24 and 48 h after eccentric training, whereas PPT was not affected (p > 0.05). Factor analysis of L-DOMS and L-PAIN sensory descriptors (SES) yielded a stable three-factor solution distinguishing superficial thermal ("heat pain ") from superficial mechanical pain ("sharp pain") and "deep pain." "Heat pain " and "deep pain" in L-DOMS were almost identical to sensory descriptors from electrical stimulation of fascial tissue (L-PAIN, all p > 0.679) but significantly different from muscle pain (all p < 0.029). The differences in sensory description patterns as well as in PPT and self-reported DOMS for palpation pain scores suggest that DOMS has a fascial rather than a muscular origin.

Neurochemical mechanism of muscular pain: Insight from the study on delayed onset muscle soreness

We reviewed fundamental studies on muscular pain, encompassing the characteristics of primary afferent fibers and neurons, spinal and thalamic projections, several muscular pain models, and possible neurochemical mechanisms of muscle pain. Most parts of this review were based on data obtained from animal experiments, and some researches on humans were also introduced. We focused on delayed-onset muscle soreness (DOMS) induced by lengthening contractions (LC), suitable for studying myofascial pain syndromes. The muscular mechanical withdrawal threshold (MMWT) decreased 1-3 days after LC in rats. Changing the speed and range of stretching showed that muscle injury seldom occurred, except in extreme conditions, and that DOMS occurred in parameters without muscle damage. The B2 bradykinin receptor-nerve growth factor (NGF) route and COX-2-glial cell line-derived neurotrophic factor (GDNF) route were involved in the development of DOMS. The interactions between these routes occurred at two levels. A repeated-bout effect was observed in MMWT and NGF upregulation, and this study showed that adaptation possibly occurred before B2 bradykinin receptor activation. We have also briefly discussed the prevention and treatment of DOMS.

Topical application of a TRPA1 antagonist reduced nociception and inflammation in a model of traumatic muscle injury in rats

Musculoskeletal pain is a widely experienced public healthcare issue, especially after traumatic muscle injury. Besides, it is a common cause of disability, but this pain remains poorly managed. However, the pathophysiology of traumatic muscle injury-associated pain and inflammation has not been fully elucidated. In this regard, the transient receptor potential ankyrin 1 (TRPA1) has been studied in inflammatory and painful conditions. Thus, this study aimed to evaluate the antinociceptive and anti-inflammatory effect of the topical application of a TRPA1 antagonist in a model of traumatic muscle injury in rats. The mechanical trauma model was developed by a single blunt trauma impact on the right gastrocnemius muscle of Wistar male rats (250-350 g). The animals were divided into four groups (Sham/Vehicle; Sham/HC-030031 0.05%; Injury/Vehicle, and Injury/HC-030031 0.05%) and topically treated with a Lanette® N cream base containing a TRPA1 antagonist (HC-030031, 0.05%; 200 mg/muscle) or vehicle (Lanette® N cream base; 200 mg/muscle), which was applied at 2, 6, 12, 24, and 46 h after muscle injury. Furthermore, we evaluated the contribution of the TRPA1 channel on nociceptive, inflammatory, and oxidative parameters. The topical application of TRPA1 antagonist reduced biomarkers of muscle injury (lactate/glucose ratio), spontaneous nociception (rat grimace scale), inflammatory (inflammatory cell infiltration, cytokine levels, myeloperoxidase, and N-acetyl-β-D-glucosaminidase activities) and oxidative (nitrite levels and dichlorofluorescein fluorescence) parameters, and mRNA Trpa1 levels in the muscle tissue. Thus, these results demonstrate that TRPA1 may be a promising anti-inflammatory and antinociceptive target in treating muscle pain after traumatic muscle injury.

Intra- and inter-session reliability of electrical detection and pain thresholds of cutaneous and muscle primary afferents in the lower back of healthy individuals

To advance evidence-based practice and targeted treatments of low back pain (LBP), a better pathophysiological understanding and reliable outcome measures are required. The processing of nociceptive information from deeper somatic structures (e.g., muscle, fascia) might play an essential role in the pathophysiology of LBP. In this study, we measured the intra- and inter-session reliability of electrical detection and pain thresholds of cutaneous and muscle primary afferents of the lower back. Twenty healthy participants attended two study visits separated by 27.7 ± 1.7 days. To determine the location-specific electrical detection threshold (EDT) and pain threshold (EPT), needle electrodes were inserted in the epidermal layer over, and in the lumbar erector spinae muscle. Additionally, established quantitative sensory testing (QST) parameters were assessed. Reliability was determined by differences between measurements, intraclass correlation coefficients (ICC2,1), Bland-Altman plots, and standard error of measurement (SEM). Correspondence between QST parameters and electrical thresholds was assessed using Pearson's correlation. Except for cutaneous EPT, no significant (p ≤ 0.05) intra- and inter-session differences were observed. Excellent intra-session reliability was shown for cutaneous and intramuscular electrical stimulations and all QST parameters (ICC: 0.76-0.93). Inter-session reliabilities were good (ICC: 0.74-0.75) except for electrical stimulations (ICC: 0.08-0.36). Limits of agreement and SEM were higher for inter-session than intra-session. A medium to strong relationship was found between electrical and mechanical/pressure pain thresholds. In conclusion, cutaneous and intramuscular electrical stimulation will potentially close an important diagnostic gap regarding the selective examination of deep tissue afferents and provide location-specific information for the excitability of non-nociceptive and nociceptive afferents.

The impact of sex and physical activity on the local immune response to muscle pain

Induction of muscle pain triggers a local immune response to produce pain and this mechanism may be sex and activity level dependent. The purpose of this study was to measure the immune system response in the muscle following induction of pain in sedentary and physically active mice. Muscle pain was produced via an activity-induced pain model using acidic saline combined with fatiguing muscle contractions. Prior to induction of muscle pain, mice (C57/BL6) were sedentary or physically active (24hr access to running wheel) for 8 weeks. The ipsilateral gastrocnemius was harvested 24hr after induction of muscle pain for RNA sequencing or flow cytometry. RNA sequencing revealed activation of several immune pathways in both sexes after induction of muscle pain, and these pathways were attenuated in physically active females. Uniquely in females, the antigen processing and presentation pathway with MHC II signaling was activated after induction of muscle pain; activation of this pathway was blocked by physical activity. Blockade of MHC II attenuated development of muscle hyperalgesia exclusively in females. Induction of muscle pain increased the number of macrophages and T-cells in the muscle in both sexes, measured by flow cytometry. In both sexes, the phenotype of macrophages shifted toward a pro-inflammatory state after induction of muscle pain in sedentary mice (M1 + M1/2) but toward an anti-inflammatory state in physically active mice (M2 + M0). Thus, induction of muscle pain activates the immune system with sex-specific differences in the transcriptome while physical activity attenuates immune response in females and alters macrophage phenotype in both sexes.

Efficiency of occlusal splint therapy on orofacial muscle pain reduction: a systematic review

BACKGROUND

This systematic review aims to examine the existing original studies to determine the effectiveness of occlusal splints (OSs) in the management of orofacial myalgia and myofascial pain (MP) in comparison with no treatment or other interventions.

MATERIALS AND METHODS

Based on the inclusion and exclusion criteria of this systematic review, randomized controlled trials were qualified, in which the effectiveness of occlusal splint therapy in the management of muscle pain was examined in comparison with no treatment or other interventions. This systematic review was conducted according to the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analysis 2020. The authors searched three databases (PubMed, CINAHL (The Cumulative Index to Nursing and Allied Health Literature) and Scopus) for English publications published between January 1, 2010, and June 1, 2022. The last database search was carried out on June 4, 2022. Data were extracted from the included studies and assessed for risk of bias using the revised Cochrane risk-of-bias tool for randomized trials.

RESULTS

Thirteen studies were identified for inclusion in this review. In total, 589 patients were diagnosed with orofacial muscle pain who underwent education and various forms of therapy including different types of OSs, light emitting diode therapy, acupuncture, low-level laser therapy, device-supported sensorimotor training, Kinesio Taping, myofunctional therapy, and physical therapy. All studies included demonstrated a high risk of bias.

CONCLUSIONS

There is insufficient evidence regarding whether OS therapy in the treatment of orofacial myalgia and MP offers an advantage over other forms of interventions or no treatment. Further reliable clinical studies in this area are needed to improve the quality of research, which should be performed with larger groups of blinded respondents and controls.

CLINICAL RELEVANCE

Due to the large-scale nature of orofacial muscle pain, it is assumed that each dental clinician will meet patients with orofacial muscle pain repeatedly in daily practice; hence, the review of the effectiveness of OSs in the management of orofacial myalgia and MP is necessary.

[Rare diseases in the differential diagnosis of myalgia]

Myalgia describes pain in the skeletal muscles. According to the current German clinical guidelines from 2020 (AWMF register number: 030/051), the initial diagnostic assessment consists of the anamnesis, clinical examination, electrophysiological examination and standard laboratory tests. Additional special examinations, such as molecular genetic investigations, special laboratory tests, medical imaging and muscle biopsy are only needed in certain cases. This article focuses on rare neurological diseases that are classically associated with myalgia. In this context etiologically different diseases are considered, whereby some genetically linked diseases (fascioscapulohumeral dystrophy, FSHD, dystrophia myotonica, McArdle's disease, Pompe's disease, limb girdle muscular dystrophy) are contrasted with diseases with an (auto)immune-related pathogenesis (stiff-person syndrome, Isaacs syndrome). The aspects relevant for the diagnosis are particularly highlighted. The therapeutic aspects of the diseases are not part of this article.

The therapeutic effect of Värska mud and Värska mineral water baths on the overuse pain and muscle tension syndromes in the working age population

The effects of bath therapy are complex and result from a unique interaction between the aquatic environment and the human body functions. The effect of bath therapy depends on both water temperature and chemical additives (mineral substances and humic substances). Värska Resort Centre, in south-eastern Estonia, uses for the balneotherapy the local curative mud and mineral water. The aim of the study was to evaluate and compare the effects of Värska's local mud bath and mineral water bath on moderate musculoskeletal pains in working-age people. The study involved 64 working-age subjects: within two weeks, 32 of them received five general mineral water baths, and another 32 received five general curative mud baths. Pain was assessed with the Nordic Musculosceletal Questionnaire, and muscle tension was measured with a myotonometer in m. erector spinae and m. trapezius. Measurements were performed three times: before the start of the study, immediately after the last procedure, and 2-3 weeks after the last procedure. Both the Värska curative mud bath and the Värska mineral water bath showed a positive effect on musculoskeletal pain and muscle tension. Both procedures can be recommended as drug-free interventions for mild to moderate musculoskeletal pain syndrome and muscle tensions, in both prevention and treatment.

[Rare diseases in the differential diagnosis of myalgia]

Myalgia describes pain in the skeletal muscles. According to the current German clinical guidelines from 2020 (AWMF register number: 030/051), the initial diagnostic assessment consists of the anamnesis, clinical examination, electrophysiological examination and standard laboratory tests. Additional special examinations, such as molecular genetic investigations, special laboratory tests, medical imaging and muscle biopsy are only needed in certain cases. This article focuses on rare neurological diseases that are classically associated with myalgia. In this context etiologically different diseases are considered, whereby some genetically linked diseases (fascioscapulohumeral dystrophy, FSHD, dystrophia myotonica, McArdle's disease, Pompe's disease, limb girdle muscular dystrophy) are contrasted with diseases with an (auto)immune-related pathogenesis (stiff-person syndrome, Isaacs syndrome). The aspects relevant for the diagnosis are particularly highlighted. The therapeutic aspects of the diseases are not part of this article.

Muscle pain and muscle weakness in COVID19 patients: Cross-talk with statins - Preliminary results

Background

Muscle pain and muscle weakness, common symptoms among statin-treated patients, may worsen with COVID-19 infection.

Aims

The aim of the paper was to find out if concomitant COVID-19 infections increase the frequency of specific side effects of statins such as muscle pain and muscle weakness.

Method

A total of 66 patients diagnosed with COVID-19 without comorbidities participated in the study. The patients were divided into two groups: statin-users who had not experienced adverse effects of statins in the past (statin group (SG)) and patients who had not used any drugs in the past six months (control group (CG)). The severity of muscle pain and creatinine kinase (CK) activity was evaluated in each patient, and muscle weakness was confirmed by a dynamometer test (grip strength on both hands).

Results

In SG, muscle pain was more common and it was characterized by a high level of intensity. Muscle weakness occurred more frequently in the SG and it was more frequent compared to CG. The CK parameter was observed to be higher in the SG compared to the CG and was often associated with the severity of muscle pain in the range of moderate to severe.

Conclusions

Our study indicates that COVID-19 is associated with the higher risk of occurrence of typical statin-related side effects, especially with more advanced age, which should be considered in future trials and treatments.

The effect of hypertonic saline evoked muscle pain on neurophysiological changes and exercise performance in the contralateral limb

Non-local muscle pain may impair endurance performance through neurophysiological mechanisms, but these are relatively unknown. This study examined the effects of muscle pain on neuromuscular and neurophysiological responses in the contralateral limb. On separate visits, nine participants completed an isometric time to task failure (TTF) using the right knee extensors after intramuscular injection of isotonic saline (CTRL) or hypertonic saline (HYP) into the left vastus lateralis. Measures of neuromuscular fatigue were taken before, during and after the TTF using transcranial magnetic stimulation (TMS) and peripheral nerve stimulation. Mean pain intensity was greater in the left leg in HYP (3.3 ± 1.9) compared to CTRL (0.4 ± 0.7; P < 0.001) which was combined with a reduced TTF by 9.8% in HYP (4.54 ± 0.56 min) compared to CTRL (5.07 ± 0.77 min; P = 0.005). Maximum voluntary force was not different between conditions (all P > 0.05). Voluntary activation was lower in HYP compared to CTRL (P = 0.022). No difference was identified between conditions for doublet amplitude (P > 0.05). Furthermore, no difference in MEP·M_max⁻¹ or the TMS silent period between conditions was observed (all P > 0.05). Non-local pain impairs endurance performance of the contralateral limb. This impairment in performance is likely due to the faster attainment of the sensory tolerance limit from a greater amount of sensory feedback originating from the non-exercising, but painful, left leg.

The effect of elevated muscle pain on neuromuscular fatigue during exercise

PURPOSE

Muscle pain can impair exercise performance but the mechanisms for this are unknown. This study examined the effects of muscle pain on neuromuscular fatigue during an endurance task.

METHODS

On separate visits, twelve participants completed an isometric time-to-task failure (TTF) exercise of the right knee extensors at ~ 20% of maximum force following an intramuscular injection of isotonic saline (CTRL) or hypertonic saline (HYP) into the vastus lateralis. Measures of neuromuscular fatigue were taken before, during and after the TTF using transcranial magnetic stimulation (TMS) and peripheral nerve stimulation.

RESULTS

The mean pain intensity was 57 ± 10 in HYP compared to 38 ± 18 in CTRL (P < 0.001). TTF was reduced in HYP (4.36 ± 0.88 min) compared to CTRL (5.20 ± 0.39 min) (P = 0.003). Maximum voluntary force was 12% lower at minute 1 (P = 0.003) and 11% lower at minute 2 in HYP (P = 0.013) compared to CTRL. Voluntary activation was 4% lower at minute 1 in HYP compared to CTRL (P = 0.006) but not at any other time point (all P > 0.05). The TMS silent period was 9% longer at 100 s during the TTF in HYP compared to CTRL (P = 0.026).

CONCLUSION

Muscle pain reduces exercise performance through the excacerbation of neuromuscular fatigue that is central in origin. This appears to be from inhibitory feedback from group III/IV nociceptors which acts to reduce central motor output.

Long COVID: rheumatologic/musculoskeletal symptoms in hospitalized COVID-19 survivors at 3 and 6 months

Objective

To document the detailed characteristics including severity, type, and locations of rheumatic and musculoskeletal symptoms along with other COVID-19 persistent symptoms in hospitalized COVID-19 survivors at 3 and 6 months.

Methods

In this extension cohort study, two telephone surveys at 3 and 6 months following the hospitalization were carried out. In these telephone surveys, participants were asked regarding their symptoms through a previously designed standard questionnaire.

Results

At 3 months, 89.0% of survivors had at least one symptom, 74.6% had at least one rheumatic and musculoskeletal symptom, and 82.1% had at least one other COVID-19 symptom. At 6 months, 59.6% of survivors had at least one symptom, 43.2% had at least one rheumatic and musculoskeletal symptom, and 51.2% had at least one other COVID-19 symptom. Regarding the rheumatic and musculoskeletal symptoms, 31.6% had fatigue, 18.6% had joint pain, and 15.1% had myalgia; and regarding the other-COVID-19-symptoms, 25.3% had dyspnea, 20.0% had hair loss, and 17.2% sweat at 6 months. In an adjusted model, female patients were more likely to have fatigue (OR: 1.99, 95% CI: 1.18–3.34), myalgia (3.00, 1.51–5.98), and joint pain (3.39, 1.78–6.50) at 6 months.

Conclusion

Approximately 3 in 5 patients had at least one symptom with ≈2 in 5 patients had at least one rheumatic and musculoskeletal symptom. Fatigue, joint pain, and myalgia were the most frequent rheumatic and musculoskeletal symptoms. Joint pain and myalgia were mostly widespread. This information guide rheumatologists to understand the nature and features of persistent rheumatic and musculoskeletal symptoms in hospitalized COVID-19 survivors and may contribute to better management of these individuals.

Key Points • Approximately 3 in 5 patients had at least one symptom with ≈2 in 5 patients had at least one rheumatic and musculoskeletal symptom at 6 months • Fatigue, joint pain, and myalgia were the most frequent rheumatic and musculoskeletal symptoms followed by back pain, low back pain, and neck pain • Dyspnea, hair loss, and sweat were the most frequent other-COVID-19-symptoms

Associations between strength, flexibility, and painful symptomology in university staff

BACKGROUND

In the adult population, the work environment and physical fitness levels are directly related to the onset of musculoskeletal pain, repetitive strain injuries, and decreased blood circulation. Although low levels of muscle strength and flexibility may lead to a higher prevalence of pain, specific anatomic regions are poorly addressed.

OBJECTIVE

To investigate the prevalence of musculoskeletal pain and the association between strength or flexibility and pain in university staff.

METHODS

The sample was composed of 110 members of staff from a university in Guarapuava-PR. Body mass and height values were obtained, from which the BMI was calculated. The pain evaluation was performed by means of a questionnaire, analyzing the intensity, frequency, and anatomical region. The subjects were then submitted to strength (right and left hand grip, lumbar traction, lower limb traction) and flexibility tests (sit and reach test).

RESULTS

The anatomical region with the highest prevalence of pain was the lumbar region (43.4%). When the association between the presence of pain and flexibility was performed, only the lumbar traction presented significant results, with the weakest group demonstrating pain (OR: 3.47 [1.27 - 9.49]).

CONCLUSION

The results demonstrate that low levels of strength in the lumbar region are associated with the presence of painful symptomatology.

Endogenous opioid and cannabinoid systems modulate the muscle pain: A pharmacological study into the peripheral site

The participation of the peripheral opioid and cannabinoid endogenous systems in modulating muscle pain and inflammation has not been fully explored. Thus, the aim of this study was to investigate the involvement of these endogenous systems during muscular-tissue hyperalgesia induced by inflammation. Hyperalgesia was induced by carrageenan injection into the tibialis anterior muscles of male Wistar rats. We padronized an available Randal-Sellito test adaptation to evaluate nociceptive behavior elicited by mechanical insult in muscles. Western blot analysis was performed to evaluate the expression levels of opioid and cannabinoid receptors in the dorsal root ganglia. The non-selective opioid peptide receptor antagonist (naloxone) and the selective mu opioid receptor MOP (clocinnamox) and kappa opioid receptor KOP (nor-binaltorphimine) antagonists were able to intensify carrageenan-induced muscular hyperalgesia. On the other hand, the selective delta opioid receptor (DOP) antagonist (naltrindole) did not present any effect on nociceptive behavior. Moreover, the selective inhibitor of aminopeptidases (Bestatin) provoked considerable dose-dependent analgesia when intramuscularly injected into the hyperalgesic muscle. The CB₁ receptor antagonist (AM251), but not the CB₂ receptor antagonist (AM630), intensified muscle hyperalgesia. All irreversible inhibitors of anandamide hydrolase (MAFP), the inhibitor for monoacylglycerol lipase (JZL184) and the anandamide reuptake inhibitor (VDM11) decreased carrageenan-induced hyperalgesia in muscular tissue. Lastly, MOP, KOP and CB₁ expression levels in DRG were baseline even after muscular injection with carrageenan. The endogenous opioid and cannabinoid systems participate in peripheral muscle pain control through the activation of MOP, KOP and CB₁ receptors.

Comparison of emotional disturbance, sleep, and life quality in adult patients with painful temporomandibular disorders of different origins

OBJECTIVES

This study compared the differences in emotional disturbance, sleep, and life quality among adult patients with temporomandibular (TMD) muscle and/or joint pain.

MATERIALS AND METHODS

The study involved an analytical cross-sectional design. A total of 420 consecutive patients diagnosed with pain-related TMDs based on the Diagnostic Criteria for TMDs (DC/TMD) were recruited from a TMD referral centre and stratified into three groups, namely muscle pain (MP; n = 50), joint pain (JP; n = 329), and combined muscle-joint pain (CP; n = 41). Emotional disturbance, sleep quality, and oral health-related quality of life (OHRQoL) were assessed with the Depression, Anxiety, and Stress Scale-21 (DASS-21), Pittsburgh Sleep Quality Index (PSQI), and Oral Health Impact Profile-TMDs (OHIP-TMDs) respectively. Statistical analyses were performed using the chi-square test, one-way ANOVA, and Pearson's correlation (p < 0.05).

RESULTS

Mean age for the three pain groups (females = 349; males = 71) ranged from 37.15 ± 14.91 to 38.60 ± 14.37 years (p = 0.973). Ranking of depression, anxiety, and stress scores was as follows: CP > MP > JP. Significant differences in emotional disturbances were observed (p < 0.001). CP patients had significantly poorer sleep quality than those with JP (p = 0.004). Moreover, OHRQoL was also significantly more impaired as compared to both MP (p = 0.006) and JP (p < 0.001) patients. Correlations between global PSQI and OHIP-TMDs scores were weak to moderate (r_s = 0.30-0.47).

CONCLUSIONS

Patients with combined muscle-joint pain presented higher levels of emotional disturbance than those with only MP or JP. They also had significantly poorer sleep quality and lower OHRQoL.

CLINICAL RELEVANCE

Emotional and sleep health must be considered in the management of painful TMDs.

Myositis - A common but underreported adverse effect of osimertinib: Case series and review of the literature

BACKGROUND

Lung cancer is the second most common cancer in both men and women and the leading cause of cancer death worldwide. The development of novel tyrosine kinase inhibitors (TKIs) represented a paradigm shift in the management of lung cancer and has resulted in markedly prolonged survival. Osimertinib is a TKI that was fast-tracked by the United States Food and Drug Administration in 2015 and subsequently approved for the treatment of metastatic epidermal growth factor receptor T790M mutation-positive non-small cell lung cancer. However, despite the generally favorable outcomes associated with osimertinib, rapid development and deployment of any new drug increases the risk of unforeseen adverse effects. Post-marketing surveillance studies therefore play an important role in further elucidating the risks and benefits of novel anti-neoplastic agents.

MATERIAL AND METHODS

We describe four patients with non-small cell lung cancer who developed myositis after beginning treatment with osimertinib. In addition, we review the literature on osimertinib-associated myositis. Using PubMed, the following terms were searched and relevant citations assessed: creatine phosphokinase, myositis, osimertinib, rhabdomyolysis, osimertinib, and Tagrisso.

CASE PRESENTATION

Thirty-eight patients were treated with osimertinib in our community clinic. Four with non-small cell lung cancer developed myositis after beginning treatment. The onset of symptoms and/or elevation of creatine phosphokinase occurred between two weeks and eleven months after osimertinib was initiated. Alternative causes for myositis were not identified. In two patients, myositis resolved within one month of withdrawing treatment. Two other patients continued osimertinib treatment with close monitoring.

CONCLUSION

Myositis is a serious and potentially underreported adverse effect of osimertinib. Previous studies suggest that osimertinib-associated myositis is rare, occurring in less than 1% of patients. However, myositis occurred in over 10% of patients treated with osimertinib in our clinic population. We suggest regular monitoring for myositis among patients being treated with osimertinib and dose-reduction or cessation of treatment if clinically indicated.

Dyspnea, effort and muscle pain during exercise in lung transplant recipients: an analysis of their association with cardiopulmonary function parameters using machine learning

Background

Despite improvement in lung function, most lung transplant (LTx) recipients show an unexpectedly reduced exercise capacity that could be explained by persisting peripheral muscle dysfunction of multifactorial origin. We analyzed the course of symptoms, including dyspnea, muscle effort and muscle pain and its relation with cardiac and pulmonary function parameters during an incremental exercise testing.

Methods

Twenty-four bilateral LTx recipients were evaluated in an observational cross-sectional study. Recruited patients underwent incremental cardio-pulmonary exercise testing (CPET). Arterial blood gases at rest and peak exercise were measured. Dyspnea, muscle effort and muscle pain were scored according to the Borg modified scale. Potential associations between the severity of symptoms and exercise testing parameters were analyzed using a Forest-Tree Machine Learning approach, which accomplishes for a ratio between number of observations and number of screened variables less than unit.

Results

Dyspnea score was significantly associated with maximum power output (WR, watts), and minute ventilation (VE, L/min) at peak exercise. In a controlled subgroup analysis, dyspnea score was a limiting symptom only in LTx recipients who reached the higher levels of WR (≥ 101 watts) and V_E (≥ 53 L/min). Muscle effort score was significantly associated with breathing reserve as percent of maximal voluntary ventilation (BR%MVV). The lower the BR%MVV at peak exercise (< 32) the higher the muscle effort perception. Muscle pain score was significantly associated with VO₂ peak, arterial [HCO₃⁻] at rest, and V_E/VCO₂ slope. In a subgroup analysis, muscle pain was the limiting symptom in LTx recipients with a lower VO₂ peak (< 15 mL/Kg/min) and a higher V_E/VCO₂ slope (≥ 32).

Conclusions

The majority of our LTx recipients reported peripheral limitation as the prevalent reason for exercise termination. Muscle pain at peak exercise was strictly associated with basal and exercise-induced metabolic altered pathways. The onset of dyspnea (breathing effort) was associated with the intensity of ventilatory response to meet metabolic demands for increasing WR. Our study suggests that only an accurate assessment of symptoms combined with cardio-pulmonary parameters allows a correct interpretation of exercise limitation and a tailored exercise prescription. The role and mechanisms of muscle pain during exercise in LTx recipients requires further investigations.

Early neurological manifestations of hospitalized COVID-19 patients

Introduction

Neurological manifestations can occur during coronavirus disease 19 (COVID-19). Several pathogenic mechanisms have been hypothesized, without conclusive results. In this study, we evaluated the most frequent neurological symptoms in a cohort of hospitalized COVID-19 patients, and also investigated the possible relationship between plasmatic inflammatory indices and olfactory disorders (ODs) and between muscle pain and creatine kinase (CK).

Methods

We consecutively enrolled hospitalized COVID-19 patients. A structured questionnaire concerning typical and neurological symptoms, focusing on headache, dizziness, ODs, taste disorders (TDs), and muscle pain, was administrated by telephone interviews.

Results

Common neurological symptoms were reported in the early phase of the disease, with a median onset ranging from 1 to 3 days. Headache showed tension-type features and was more frequently associated with a history of headache. Patients with ODs less frequently needed oxygen therapy. Inflammatory indices did not significantly differ between patients with and without ODs. Muscle pain did not show any association with CK level but was more frequently associated with arthralgia and headache.

Conclusion

In our cohort, ODs were an early symptom of COVID-19, more frequently reported by patients with milder forms of disease. Headache in association with arthralgia and muscle pain seems to reflect the common symptoms of the flu-like syndrome, and not COVID-19 infection-specific.

An unusual case of recurrent episodes of muscle weakness: Co-occurrence of Andersen-Tawil syndrome and glycogen storage disease type IXd

A 25-year-old male patient presented with periodic paralysis that increased in severity and frequency with age, accompanied with muscle pain and significantly elevated creatine kinase (CK) levels. Initial clinical and genetic examination confirmed Andersen-Tawil syndrome. Although his father carried the same genetic mutation (p.G300A), he experienced minor and infrequent attacks of paralysis. A change in the patient's symptoms, such as accompanying pain, contracture, and significant CK elevation, lead to a reconsideration of the diagnosis. A muscle biopsy of the biceps brachii in the patient revealed glycogen storage, but no tubular aggregates. Analysis of the phosphorylase kinase regulatory subunit alpha 1 (PHKA1) gene revealed a pathogenic mutation (p.C1082X), indicating glycogen storage disease type Ⅸd. The case demonstrates that co-occurrence of glycogen storage disease type Ⅸd may prolong attacks of muscle weakness, and cause serious muscle pain in patients with Andersen-Tawil syndrome.

Involvement of inflammasome activation via elevation of uric acid level in nociception in a mouse model of muscle pain

Muscle pain is a common condition in many diseases and is induced by muscle overuse. Muscle overuse induces an increase in uric acid, which stimulates the nucleotide-binding oligomerization domain-like receptor (NLR). This receptor contains the pyrin domain NLRP-3 inflammasome which when activated, results in the secretion of potent pro-inflammatory cytokines such as interleukin-1β (IL-1β). The aim of this study was to investigate the involvement of inflammasome activation via the elevation of uric acid level in nociception in a mouse model of muscle pain. The right hind leg muscles of BALB/c mice were stimulated electrically to induce excessive muscle contraction. The left hind leg muscles were not stimulated as a control. Mechanical withdrawal thresholds, levels of uric acid, IL-1β, and NLRP3, caspase-1 activity, and the number of macrophages were investigated. Furthermore, the effects of xanthine oxidase inhibitors, such as Brilliant Blue G, caspase-1 inhibitor, and clodronate liposome, on pain were investigated. In the stimulated muscles, mechanical withdrawal thresholds decreased, and the levels of uric acid, NLRP3, and IL-1β, caspase-1 activity, and the number of macrophages increased compared to that in the non-stimulated muscles. Administration of the inhibitors attenuated hyperalgesia caused by excessive muscle contraction. These results suggested that IL-1β secretion and NLRP3 inflammasome activation in macrophages produced mechanical hyperalgesia by elevating uric acid level, and xanthine oxidase inhibitors may potentially reduce over-exercised muscle pain.

Treatment of hypophosphatasia

Hypophosphatasia (HPP) is a rare disorder with perinatal, infantile, childhood, and adult presentations. Severe forms are autosomal recessive with an early onset, whereas milder forms have a later onset. The underlying cause of the disease is a mutation based on a genetic disorder of the tissue non-specific alkaline phosphatase (TNSALP) gene, leading on the one hand to decreased activity of the TNSALP enzyme, and on the other hand to accumulation of TNSALP substrates. Symptoms like non-traumatic and non-healing fractures, musculoskeletal pain, chondrocalcinosis, seizures, premature loss of fully rooted teeth or delayed development of milk teeth, respiratory insufficiency, and calcinosis in muscles, kidneys, and joints occur. Supportive treatment is important for HPP patients, including mechanical ventilation, accurate fracture treatment, physical therapy, dental monitoring, and follow-up care to avoid subsequent problems. A causal enzyme therapy replacement with asfotase-alfa was approved by the Food and Drug Administration (FDA) in 2015. Asfotase-alfa improves respiratory insufficiency, bone mineralization, and long-term survival, and has a very good safety profile.

Treatment of Temporomandibular Disorders of Muscular Origin with a Silicon Oral Device (Alifix®): Electromyographic Analysis

AIM

The aim of this work was to evaluate if the use of a silicone device for muscular rebalancing (Alifix®) can be useful in treating of temporomandibular disorders (TMD) of muscular origin and improving the electromyographic indexes of the chewing muscles.

MATERIALS AND METHODS

Thirteen patients (11 F and 2 M aged between 24 years and 65 years) with TMD of muscular origin according to diagnostic criteria (DC)/TMD were involved. At the first visit (T0), each patient reported the pain intensity of masseters and temporal muscles. A surface electromyography (EMG) was performed using Teethan® (Teethan S.p.A.) and then Alifix® was delivered instructing the patient on its use. Each subject was visited again after 1 month (T1) and 2 months (T2). New EMG had been made at T1 and T2, and patients were asked again to report the pain intensity. Statistical analysis was calculated between T0 and T1, T1 and T2, and T0 and T2 for all EMG, and muscle pain measurements by Wilcoxon test with statistical significance p < 0.05.

RESULTS

Regarding the pain values between T0 and T1, T1 and T2, and T0 and T2, the difference is statistically significant, since the intensity of pain between T0 and T2 is decreased, if not disappeared, in 90% of cases. The use of Alifix® also determined a gradual improvement in the values of the EMG indexes, which, however, is not statistically significant.

CONCLUSION

The effectiveness of Alifix® is demonstrated clinically but not at an instrumental level. Further studies involving a larger sample and taking longer therapy duration are needed.

CLINICAL SIGNIFICANCE

Alifix® works by improving the blood circulation of the muscle, which allows the removal of catabolites with a consequent reduction of the algic symptomatology and promotes a greater supply of oxygen. It also encourages a conversion of IIA type muscle fibers into slow-twitch type I fibers that are more resistant to neuromuscular fatigue.

How to investigate: Suspected systemic rheumatic diseases in patients presenting with muscle complaints

Muscular symptoms, which may be due to multiple causes, are one of the most common early complaints in a rheumatology practice. Musculoskeletal symptoms in rheumatic conditions are very varied, ranging from mechanical problems to muscular symptoms derived from inflammatory and systemic autoimmune diseases. Several drugs commonly used by different specialists and certain drugs used in rheumatology can also cause a wide variety of muscle symptoms. A description of different systemic autoimmune diseases follows to describe the different forms of involvement of the musculoskeletal system that they cause, as well as the main causes with which a differential diagnosis should be made. In this chapter, we will try to give some clues to reach an early diagnosis using clinical criteria, particularly based on a directed anamnesis and physical examination, discussing possible guidelines for the complimentary tests that may be required in patients with muscle complaints.

The inclusion of vibration therapy in rehabilitating a gastrocnemius tear: a case study in master athlete

[Purpose] The aim of this case study was to determine if VT could be included into a rehabilitation programme by monitoring the progress of muscle pain, range of motion and muscle strength. [Participant and Methods] An international male master hockey player sustained a medial gastrocnemius 5 cm tear prior to the World Cup. VT was applied early in the rehabilitation programme where 9 sessions of VT were performed during the first 16 days. Other conventional rehabilitative exercises were included. [Results] Twenty-eight days post-injury the athlete returned to full playing. Calf pain had subsided by day 8 with a change of 12° in ankle dorsi flexion range of motion. Grade 5 calf strength was attained by day 16, which was equivalent to the unaffected limb’s strength. There were no residual side effects of including VT into the rehabilitation programme and it did not compromise the athlete’s recovery. [Conclusion] To ensure optimal loading of VT, 9 sessions were implemented and progressively increased; consequently, there was no detrimental effect on the rehabilitative process. The athlete reported no side effects of using VT and its ease and time efficient application has a role to complementing soft tissue injury rehabilitation.

Statin-induced muscular side effects at rest and exercise - An anatomical mapping

BACKGROUND AND AIMS

Muscle-related symptoms with or without creatine kinase (CK) elevation are common adverse effects associated with statin use. Symptoms are ranging from benign myalgia to myositis and in rare cases to rhabdomyolysis. The aim was to characterize and describe muscular side effects and create an anatomical frequency mapping.

METHODS

The prospective observational study was performed at a large lipidology outpatient unit in Vienna. 1111 consecutively admitted patients with muscular side effects on statin monotherapy were included during a 4-year period. Anatomical mapping of the affected muscles, signs and symptoms, the onset of symptoms after starting statin therapy and disappearance after cessation of treatment was assessed.

RESULTS

In 96.5% of the patients with muscle symptoms, there was no elevation of CK. The anatomical mapping revealed exercised muscles as being mainly affected in 84%. In the upper extremity, symptoms were mainly described at the dominating side. Mostly affected muscles were the pectoral (61.4%), followed by the quadriceps femoris (59.8%), the biceps brachii (54.3%) and the deltoid (22.5%) muscles. The majority of symptoms (76.9%, n = 854) appeared within 29 days. Symptoms disappeared after discontinuation of statin therapy at a mean of 5.4 days.

CONCLUSIONS

Physical activity seems to be a key trigger for onset of statin-induced muscular side effects. The appearance of symptoms can be symmetrical, asymmetrical, generalized or in isolated muscle groups only. Different statins usually produce similar symptoms, but often some patients tolerate one statin better than another.

Pressure pain hypersensitivity and referred pain from muscle trigger points in elite male wheelchair basketball players

BACKGROUND

Shoulder injuries are common in individuals who use wheelchairs.

OBJECTIVES

This study investigated the presence of mechanical pain hypersensitivity and trigger points in the neck-shoulder muscles in elite wheelchair basketball players with/without shoulder pain and asymptomatic able-bodied elite basketball players.

METHODS

Eighteen male wheelchair basketball players with shoulder pain, 22 players without shoulder pain, and 20 able-bodied elite male basketball players were recruited. Pressure pain thresholds were assessed over C5-C6 zygapophyseal joint, deltoid muscle, and second metacarpal. Trigger points in the upper trapezius, supraspinatus, teres minor, infraspinatus, teres major, latissimus dorsi, subscapularis, pectoralis minor, pectoralis major and deltoid muscles were also examined.

RESULTS

Wheelchair basketball players with shoulder pain showed lower pressure pain thresholds over the C5-C6 joint and second metacarpal than elite wheelchair basketball players without pain (between-groups differences: 1.1, 95%CI 0.4, 1.8 and 1.8, 95%CI 0.8, 2.8, respectively) and able-bodied basketball players without pain (between-groups differences: 0.8, 95%CI 0.4, 1.2; 1.6, 95%CI 0.8, 2.4, respectively). The mean number of myofascial trigger points for wheelchair basketball players with unilateral shoulder pain was 4.8±2.7 (2±1 active, 2.9±2.2 latent). Wheelchair basketball players and able-bodied basketball players without shoulder pain exhibited a similar number of latent trigger points (2.4±2.0 and 2.4±1.8, respectively). Wheelchair basketball players with shoulder pain exhibited higher number of active myofascial trigger points than those without pain (either with or without wheelchair), but all groups had a similar number of latent trigger points (P<0.05).

CONCLUSIONS

The reported mechanical pain hypersensitivity suggests that active trigger points may play a role in the development of shoulder pain in elite male wheelchair basketball players.

Reversible tactile hypoesthesia associated with myofascial trigger points: a pilot study on prevalence and clinical implications

Introduction:

Tactile hypoesthesia observed in patients with myofascial pain syndrome (MPS) is sometimes reversible when pain is relieved by trigger point injections (TPIs). We aimed to investigate the prevalence of such reversible hypoesthesia during TPI therapy and topographical relations between areas of tactile hypoesthesia and myofascial trigger points (MTrP) in patients with MPS.

Methods:

Forty-six consecutive patients with MTrP were enrolled in this study. We closely observed changes in areas of tactile hypoesthesia in patients who had tactile hypoesthesia at the first visit, and throughout TPI therapy. Tactile stimulation was given using cotton swabs, and the areas of tactile hypoesthesia were delineated with an aqueous marker and recorded in photographs.

Results:

A reduction in the size of hypoesthetic area with TPI was observed in 27 (58.7%) patients. All the 27 patients experienced a reduction in pain intensity by more than 50% in a numerical rating scale score through TPI therapy. In 9 patients, the reduction in the sizes of hypoesthetic areas occurred 10 minutes after TPI. Complete disappearance of tactile hypoesthesia after TPI therapy was observed in 6 of the 27 patients. Myofascial trigger points were located in the muscles in the vicinity of ipsilateral cutaneous dermatomes to which the hypoesthetic areas belonged.

Conclusion:

Our results indicate a relatively high prevalence of reversible tactile hypoesthesia in patients with MPS. Mapping of tactile hypoesthetic areas seems clinically useful for detecting MTrP. In addition, treating MTrP with TPI may be important for distinguishing tactile hypoesthesia associated with MPS from that with neuropathic pain.

Muscle pain in mitochondrial diseases: a picture from the Italian network

Muscle pain may be part of many neuromuscular disorders including myopathies, peripheral neuropathies and lower motor neuron diseases. Although it has been reported also in mitochondrial diseases (MD), no extensive studies in this group of diseases have been performed so far. We reviewed clinical data from 1398 patients affected with mitochondrial diseases listed in the database of the "Nation-wide Italian Collaborative Network of Mitochondrial Diseases", to assess muscle pain and its features. Muscle pain was present in 164 patients (11.7%). It was commonly observed in subjects with chronic progressive external ophthalmoplegia (cPEO) and with primary myopathy without cPEO, but also-although less frequently-in multisystem phenotypes such as MELAS, MERFF, Kearns Sayre syndrome, NARP, MNGIE and Leigh syndrome. Patients mainly complain of diffuse exercise-related muscle pain, but focal/multifocal and at rest myalgia were often also reported. Muscle pain was more commonly detected in patients with mitochondrial DNA mutations (67.8%) than with nuclear DNA changes (32.2%). Only 34% of the patients showed a good response to drug therapy. Interestingly, patients with nuclear DNA mutations tend to have a better therapeutic response than patients with mtDNA mutations. Muscle pain is present in a significant number of patients with MD, being one of the most common symptoms. Although patients with a myopathic phenotype are more prone to develop muscle pain, this is also observed in patients with a multi system involvement, representing an important and disabling symptom having poor response to current therapy.

Orofacial operant behaviors and electrophysiological properties of trigeminal ganglion neurons following masseter muscle inflammation in rats

Orofacial muscle pain is a significant clinical problem because it affects eating, speaking, and other orofacial functions in patients. However, mechanisms underlying orofacial muscle pain are not fully understood. In the present study we induced orofacial muscle pain by injecting Complete Freund's Adjuvant (CFA) into masseter muscle of rats and assessed pain by the orofacial operant test. In comparison with the control group, CFA-injected animals (CFA group) showed decreases in operant behaviors, suggesting the presence of orofacial pain. Trigeminal ganglion (TG) neurons innervating masseter muscles were retrograde-labeled with DiI and their electrophysiological properties studied using patch-clamp recordings. About 20% of DiI-labeled TG neurons showed spontaneous action potentials (APs) in the CFA group but none in the control group. AP rheobase levels were significantly lower in DiI-labeled TG neurons of the CFA group than in the control group. Membrane input resistance of DiI-labeled TG neurons was significantly higher in the CFA group than in the control group. Several other membrane parameters were also different between DiI-labeled TG neurons of the CFA and control groups. Voltage-dependent currents were examined and the most significant changes following CFA were background K⁺ currents, which showed significantly smaller in DiI-labeled TG neurons of CFA group compared to the control group. Collectively, orofacial muscle pain in CFA model is accompanied with changes of electrophysiological properties and background K⁺ currents in TG neurons that innervate masseter muscles.

Psychological responses, muscle damage, inflammation, and delayed onset muscle soreness to high-intensity interval and moderate-intensity continuous exercise in overweight men

We compared in-task affect to HIIE and MICE, and its relationship with time spent at different metabolic domains, perceived exertion (RPE), self-efficacy, enjoyment, and future intention of exercise in overweight inactive men. Muscle damage and soreness, and inflammation were assessed post-exercise. Fifteen participants (28.9 ± 5.0 yr; 29.2 ± 3.8 kg/m²) completed a HIIE (10 × 1 min at 100% V_max, 1 min recovery) and MICE (20 min at 55-59% VO_2reserve) session. Affect, alertness, RPE, and self-efficacy were assessed in-task, and enjoyment and future intention post-task. At baseline, 24 and 48 h, creatine kinase, lactate dehydrogenase, interleukin-6 and -10, tumor necrosis factor alpha, and muscle soreness were assessed. Affect (-3.1 ± 1.8 vs. 0.8 ± 1.8, P < .001) and self-efficacy (70 ± 15 vs. 90 ± 15%, P < .001) were lower, while RPE and alertness were higher in HIIE compared to MICE (Ps ≤ .02). Affect was negatively correlated with RPE in HIIE (r = -0.90) and MICE (r = -0.72), and time spent above respiratory compensation point in HIIE (r = -0.59). Affect was positively correlated with self-efficacy in MICE (r = 0.74). Enjoyment, future intention, muscle damage and soreness, and inflammation were similar between HIIE and MICE post-exercise. Therefore, in-task HIIE was experienced as unpleasant compared to MICE, but the psychological and physiological responses post-task were similar in overweight inactive men.

Effect of short-term cold-water immersion on muscle pain sensitivity in elite track cyclists

OBJECTIVE

To determine the effect of short-term cold-water immersion (CWI) on muscle pain sensitivity after maximal anaerobic power training in track cyclists.

DESIGN

Repeated measures.

SETTING

University Laboratory.

PARTICIPANTS

12 elite sprint track cyclists (age 24,75 ± 4,23 years).

MAIN OUTCOME MEASURES

PPT measurements were made on dominant lower extremity (right) in 20 reference points, including anterior thigh muscles, posterior thigh muscles and posterior cuff muscles. PPT levels were measured: 1) before workout, 2) immediately after workout, but before CWI 3) 1 h after CWI and 4) 12 h after CWI. Mean PPT values for each muscle group per participant were calculated for further statistical analysis.

RESULTS

The average PPT for anterior thigh muscles decreased significantly after effort (p = 0.001) and increased significantly 1 h after CWI (p = 0.048). In posterior thigh muscles PPT decreased significantly after effort (p = 0.014) and increased significantly 1 h and 12 h after CWI (p = 0.045 and p = 0.25 respectively). However, in posterior cuff muscles PPT decreased only after effort (p = 0.001).

CONCLUSIONS

Short-term repeated sprint exercise appears to affect PPT in track cyclists. This study have reported that CWI in 5 °C for 5 min have had a beneficial effect in minimizing PPT 1 h post repeated maximal sprint training.

Involvement of neutrophils and interleukin-18 in nociception in a mouse model of muscle pain

Muscle pain is a common condition that relates to various pathologies. Muscle overuse induces muscle pain, and neutrophils are key players in pain production. Neutrophils also play a central role in chronic pain by secreting interleukin (IL)-18. The aim of this study was to investigate the involvement of neutrophils and IL-18 in a mouse model of muscle pain. The right hind leg muscles of BALB/c mice were stimulated electrically to induce excessive muscle contraction. The left hind leg muscles were not stimulated. The pressure pain threshold, number of neutrophils, and IL-18 levels were investigated. Furthermore, the effects of the IL-18-binding protein and Brilliant Blue G on pain were investigated. In stimulated muscles, pressure pain thresholds decreased, and neutrophil and IL-18 levels increased compared with that in non-stimulated muscles. The administration of IL-18-binding protein and Brilliant Blue G attenuated hyperalgesia caused by excessive muscle contraction. These results suggest that increased IL-18 secretion from larger numbers of neutrophils elicits mechanical hyperalgesia.

High but not moderate-intensity endurance training increases pain tolerance: a randomised trial

PURPOSE

To examine the effect of high-intensity interval training (HIIT) compared to volume-matched moderate-intensity continuous training (CONT) on muscle pain tolerance and high-intensity exercise tolerance.

METHODS

Twenty healthy adults were randomly assigned (1:1) to either 6 weeks of HIIT [6-8 × 5 min at halfway between lactate threshold and maximal oxygen uptake (50%Δ)] or volume-matched CONT (~60-80 min at 90% lactate threshold) on a cycle ergometer. A tourniquet test to examine muscle pain tolerance and two time to exhaustion (TTE) trials at 50%Δ to examine exercise tolerance were completed pre- and post-training; the post-training TTE trials were completed at the pre-training 50%Δ (same absolute-intensity) and the post-training 50%Δ (same relative-intensity).

RESULTS

HIIT and CONT resulted in similar improvements in markers of aerobic fitness (all P ≥ 0.081). HIIT increased TTE at the same absolute- and relative-intensity as pre-training (148 and 43%, respectively) to a greater extent than CONT (38 and -4%, respectively) (both P ≤ 0.019). HIIT increased pain tolerance (41%, P < 0.001), whereas CONT had no effect (-3%, P = 0.720). Changes in pain tolerance demonstrated positive relationships with changes in TTE at the same absolute- (r = 0.44, P = 0.027) and relative-intensity (r = 0.51, P = 0.011) as pre-training.

CONCLUSION

The repeated exposure to a high-intensity training stimulus increases muscle pain tolerance, which is independent of the improvements in aerobic fitness induced by endurance training, and may contribute to the increase in high-intensity exercise tolerance following HIIT.

Spontaneous and Bite-Evoked Muscle Pain Are Mediated by a Common Nociceptive Pathway With Differential Contribution by TRPV1

Spontaneous pain and function-associated pain are prevalent symptoms of multiple acute and chronic muscle pathologies. We established mouse models for evaluating spontaneous pain and bite-evoked pain from masseter muscle, and determined the roles of transient receptor potential cation channel subfamily V member 1 (TRPV1) and the contribution of TRPV1- or neurokinin 1 (NK1)-dependent nociceptive pathways. Masseter muscle inflammation increased Mouse Grimace Scale scores and face-wiping behavior, which were attenuated by pharmacological or genetic inhibition of TRPV1. Masseter inflammation led to a significant reduction in bite force. Inhibition of TRPV1 only marginally relieved the inflammation-induced reduction of bite force. These results suggest a differential extent of contribution of TRPV1 to the 2 types of muscle pain. However, chemical ablation of TRPV1-expressing nociceptors or chemogenetic silencing of TRPV1-lineage nerve terminals in masseter muscle attenuated inflammation-induced changes in Mouse Grimace Scale scores as well as bite force. Furthermore, ablation of neurons expressing NK1 receptor in trigeminal subnucleus caudalis also prevented both types of muscle pain. Our results suggest that TRPV1 differentially contributes to spontaneous pain and bite-evoked muscle pain, but TRPV1-expressing afferents and NK1-expressing second-order neurons commonly mediate both types of muscle pain. Therefore, manipulation of the nociceptive circuit may provide a novel approach for management of acute or chronic craniofacial muscle pain.

PERSPECTIVE

We report the profound contribution of TRPV1 to spontaneous muscle pain but not to bite-evoked muscle pain. These 2 types of muscle pain are transmitted through a common nociceptive pathway. These results may help to develop new strategies to manage multiple modes of muscle pain simultaneously by manipulating pain circuits.

A Placebo-Controlled Trial of Riboflavin for Enhancement of Ultramarathon Recovery

Background

Riboflavin is known to protect tissue from oxidative damage but, to our knowledge, has not been explored as a means to control exercise-related muscle soreness. This study investigated whether acute ingestion of riboflavin reduces muscle pain and soreness during and after completion of a 161-km ultramarathon and improves functional recovery after the event.

Methods

In this double-blind, placebo-controlled trial, participants of the 2016 161-km Western States Endurance Run were assigned to receive a riboflavin or placebo capsule shortly before the race start and when reaching 90 km. Capsules contained either 100 mg of riboflavin or 95 mg of maltodextrin and 5 mg of 10% ß-carotene. Subjects provided muscle pain and soreness ratings before, during, and immediately after the race and for the 10 subsequent days. Subjects also completed 400-m runs at maximum speed on days 3, 5, and 10 after the race.

Results

For the 32 (18 in the riboflavin group, 14 in the placebo group) race finishers completing the study, muscle pain and soreness ratings during and immediately after the race were found to be significantly lower (p = .043) for the riboflavin group. Analysis of the 400-m run times also showed significantly faster (p < .05) times for the riboflavin group than the placebo group at post-race days 3 and 5. Both groups showed that muscle pain and soreness had returned to pre-race levels by 5 days after the race and that 400-m run times had returned to pre-race performance levels by 10 days after the race.

Conclusions

This preliminary work suggests that riboflavin supplementation before and during prolonged running might reduce muscle pain and soreness during and at the completion of the exercise and may enhance early functional recovery after the exercise.

Potential use of (18)F-FDG-PET/CT to visualize hypermetabolism associated with muscle pain in patients with adult spinal deformity: a case report

Patients with adult spinal deformity (ASD) are surgically treated for pain relief; however, visualization of the exact origin of the pain with imaging modalities is still challenging. We report the first case of a 60-year-old female patient who presented with painful degenerative kyphoscoliosis and was evaluated with flourine-18-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography ((18)F-FDG-PET/CT) preoperatively. Because her low back pain was resistant to conservative treatment, she was treated with posterior spinal correction and fusion surgery from Th2 to the ilium. One year after the surgery, her low back pain had disappeared completely. In accordance with her clinical course, (18)F-FDG-PET imaging revealed the uptake of (18)F-FDG in the paravertebral muscles preoperatively and showed the complete absence of uptake at 1 year after surgery. The uptake site coincided with the convex part of each curve of the lumbar spine and was thought to be the result of the increased activity of paravertebral muscles due to their chronic stretched state in the kyphotic posture. This case report suggests the possibility of using (18)F-FDG-PET/CT to visualize increased activity in paravertebral muscles and the ensuing pain in ASD patients.

NADPH-diaphorase reactivity and Fos-immunoreactivity within the ventral horn of the lumbar spinal cord of cats submitted to acute muscle inflammation induced by injection of carrageenan

The NADPH-diaphorase activity and Fos-immunoreactivity within the ventral horn of the lumbar spinal cord were studied in cats with acute unilateral myositis following injection of carrageenan into the m.m. gastrocnemius-soleus. In carrageenan-injected cats maximum in the mean number of intensely stained NADPH-diaphorase reactive (NADPH-dr) neurons was found in lamina VII (+100%) and VIII (+33%) of the contralateral ventral horn of the L6/L7 segments as compared with control animals. The maximumal level of Fos-immunoreactivity was registered in the same laminae with ipsilateral predominance (39.3±4.6 and 7.6±0.9 cells), in comparison with the contralateral side (13.6±0.8 and 5.5±0.6 cells, respectively; P<0.05). We also visualized low-intensely stained and double labelled (Fos immunoreactive+low-intensely stained NADPH-dr) multipolar and fusiform Renshaw-like cells (RLCs) within the ventral horn on both sides of the L6/L7 segments in carrageenan-injected cats. We visualized the double labelled (Fos-ir+NADPH-dr) multipolar and fusiform Renshaw-like cells (RLCs) within the ventral horn on both sides of the L6/L7 segments in carrageenan-injected cats. A significant difference in the mean number of RLCs was recorded between the ipsi- and contralateral sides in the lamina VII (13.6±2.5 vs. 4.9±0.7 cells, respectively). We suppose that activation of inhibitory RLCs in ipsilateral lamina VII could be directed on attenuation of activation of motoneurons during muscle pain development. Our study showed that a significant contralateral increase in the number of NADPH-dr cells is accompanied by an ipsilateral increase in c-Fos expression in lamina VII. These data may suggest that NADPH-dr neurons of the contralateral ventral horn through commissural connections also involved in the maintenance of the neuronal activity associated with acute muscle inflammation. It is also hypothesized, that during acute myositis, plastic changes in the ventral horn activate the processes of disinhibition due to an increase in the number of NADPH-d-reactive neurons in the spinal gray matter.

[Chronic pain : Perception, reward and neural processing]

Many chronic pain syndromes are characterized by enhanced perception of painful stimuli as well as alterations in cortical processing in sensory and motor regions. In this review article the alterations in muscle pain and neuropathic pain are described. Alterations in patients with fibromyalgia and chronic back pain are described as examples for musculoskeletal pain and also in patients with phantom limb pain after amputation and complex regional pain syndrome as examples for neuropathic pain. In addition to altered pain perception, cumulative evidence on alterations in the processing of reward and the underlying mechanisms in chronic pain has been described. A description is given of what is known on how pain and reward interact and affect each other. The relevance of such interactions for chronic pain is discussed. The implications of these findings for therapeutic approaches are delineated with respect to sensorimotor training and behavioral therapy, focusing on the effectiveness of these approaches, mechanisms and future developments. In particular, we discuss operant behavioral therapy in patients with chronic back pain and fibromyalgia as well as prosthesis training in patients with phantom limb pain and discrimination, mirror and imaginary training in patients with phantom limb pain and complex regional pain syndrome. With respect to the processing of reward, the focus of the discussion is on the role of reward and associated learning in pain therapy.

[Osteomalacia and vitamin D deficiency]

BACKGROUND

Vitamin D and calcium deficiency has a higher incidence in the orthopedic-trauma surgery patient population than generally supposed. In the long term this can result in osteomalacia, a form of altered bone mineralization in adults, in which the cartilaginous, non-calcified osteoid does not mature to hard bone.

AIM

The current value of vitamin D and its importance for bones and other body cells are demonstrated.

RESULTS

The causes of vitamin D deficiency are insufficient sunlight exposure, a lack of vitamin D3 and calcium, malabsorption, and rare alterations of VDR signaling and phosphate metabolism. The main symptoms are bone pain, fatigue fractures, muscular cramps, muscle pain, and gait disorders, with an increased incidence of falls in the elderly. Osteopathies induced by pharmaceuticals, tumors, rheumatism or osteoporosis have to be considered as the main differential diagnoses.

CONCLUSIONS

In addition to the recording of symptoms and medical imaging, the diagnosis of osteomalacia should be ensured by laboratory parameters. Adequate treatment consists of the high-dose intake of vitamin D3 and the replacement of phosphate if deficient. Vitamin D is one of the important hormone-like vitamins and is required in all human cells. Deficiency of vitamin D has far-reaching consequences not only for bone, but also for other organ systems.

Metabolic syndrome is associated with muscle symptoms among statin users

BACKGROUND

Muscle symptoms have been associated with statin use, but the relationship of statin-associated muscle symptoms with metabolic syndrome (MS) has not been reported previously.

OBJECTIVE

To evaluate the relationships between MS and its individual components with statin-associated muscle symptoms.

METHODS

Data were analyzed from the Understanding Statin Use in America and Gaps in Education (USAGE) study. Modified criteria to define the MS were used based on self-reported survey data.

RESULTS

Among USAGE subjects, the MS was present in 1364 of 3992 men (34.2%) and in 1716 women of 6149 women (27.9%). Subjects with the MS were 19% more likely (P = .0002) to report new or worsening muscle symptoms while on a statin. Three MS criteria-increased BMI, elevated triglycerides (TG), and low high-density lipoprotein cholesterol (HDL-C)-were associated with increased odds of muscle symptoms, by 18%, 32%, and 28%, respectively (all P < .001). The presence of MS also predicted increased odds of having discontinued a statin due to muscle symptoms (13% higher, P = .043). Among criteria for the MS, elevated TG (38% higher odds, P < .0001) and low HDL-C (37% higher odds, P = .0003) were positively associated with statin discontinuation, whereas hypertension (13% lower odds, P = .019) and diabetes mellitus (12% lower odds, P = .036) were inversely associated.

CONCLUSION

USAGE participants with MS were more likely to report experiencing muscle symptoms while taking a statin and to have discontinued a statin due to muscle symptoms. This appears to be attributable mainly to associations of muscle symptoms with elevated TG and low HDL-C levels. Additional research is warranted to confirm and further investigate these associations.

Inter-individual responses to experimental muscle pain: Baseline anxiety ratings and attitudes to pain do not determine the direction of the sympathetic response to tonic muscle pain in humans

We have recently shown that intramuscular infusion of hypertonic saline, causing pain lasting ~60min, increases muscle sympathetic nerve activity (MSNA) in one group of subjects, yet decreases it in another. Across subjects these divergent sympathetic responses to long-lasting muscle pain are consistent over time and cannot be foreseen on the basis of baseline MSNA, blood pressure, heart rate or sex. We predicted that differences in anxiety or attitudes to pain may account for these differences. Psychometric measures were assessed prior to the induction of pain using the State and Trait Anxiety Inventory (STAI), Pain Vigilance and Awareness Questionnaire (PVAQ), Pain Anxiety Symptoms Scale (PASS) and Pain Catastrophising Scale (PCS); PCS was also administered after the experiment. MSNA was recorded from the common peroneal nerve, before and during a 45-minute intramuscular infusion of hypertonic saline solution into the tibialis anterior muscle of 66 awake human subjects. Forty-one subjects showed an increase in mean burst amplitude of MSNA (172.8±10.6%) while 25 showed a decrease (69.9±3.8%). None of the measured psychological parameters showed significant differences between the increasing and the decreasing groups. We conclude that inter-individual anxiety or pain attitudes do not determine whether MSNA increases or decreases during long-lasting experimental muscle pain in healthy human subjects.

Dry needling for the management of thoracic spine pain

Thoracic spine pain is as disabling as neck and low back pain without receiving the same level of attention in the scientific literature. Among the different structures that can refer pain to the thoracic spine, muscles often play a relevant role. Trigger points (TrPs) from neck, shoulder and spinal muscles can induce pain in the region of the thoracic spine. There is a lack of evidence reporting the presence of TrPs in the region of the thoracic spine, but clinical evidence suggests that TrPs can be a potential source of thoracic spine pain. The current paper discusses the role of TrPs in the thoracic spine and dry needling (DN) for the management of TrPs in the thoracic multifidi and longissimus thoracis. This paper also includes a brief discussion of the application of DN in other tissues such as tendons, ligaments and scars.

The effects of smartphone use on upper extremity muscle activity and pain threshold

[Purpose] The purpose of this study was to determine whether muscle activity and pressure-induced pain in the upper extremities are affected by smartphone use, and to compare the effects of phone handling with one hand and with both hands. [Subjects] The study subjects were asymptomatic women 20-22 years of age. [Methods] The subjects sat in a chair with their feet on the floor and the elbow flexed, holding a smartphone positioned on the thigh. Subsequently, the subjects typed the Korean anthem for 3 min, one-handed or with both hands. Each subject repeated the task three times, with a 5-min rest period between tasks to minimize fatigue. Electromyography (EMG) was used to record the muscle activity of the upper trapezius (UT), extensor pollicis longus (EPL), and abductor pollicis (AP) during phone operation. We also used a dolorimeter to measure the pressure-induced pain threshold in the UT. [Results] We observed higher muscle activity in the UT, AP, and EPL in one-handed smartphone use than in its two-handed use. The pressure-induced pain threshold of the UT was lower after use of the smartphone, especially after one-handed use. [Conclusion] Our results show that smartphone operation with one hand caused greater UT pain and induced increased upper extremity muscle activity.

Prevalence of gluteus medius weakness in people with chronic low back pain compared to healthy controls

PURPOSE

Clinical observation suggests that hip abductor weakness is common in patients with low back pain (LBP). The purpose of this study is to describe and compare the prevalence of hip abductor weakness in a clinical population with chronic non-specific LBP and a matched sample without LBP.

METHODS

One hundred fifty subjects with chronic non-specific LBP and a matched cohort of 75 control subjects were recruited. A standardized back and hip physical exam was performed. Specifically tensor fascia lata, gluteus medius, and gluteus maximus strength were assessed with manual muscle testing. Functional assessment of the hip abductors was performed with assessment for the presence of the Trendelenburg sign. Palpation examination of the back, gluteal and hip region was performed to try and reproduce the subject's pain complaint. Friedman's test or Cochran's Q with post hoc comparisons adjusted for multiple comparisons was used to compare differences between healthy controls and people with chronic low back pain for both the affected and unaffected sides. Mann-Whitney U was used to compare differences in prevalence between groups. Hierarchical linear regression was used to identify predictors of LBP in this sample.

RESULTS

Gluteus medius is weaker in people with LBP compared to controls or the unaffected side (Friedman's test, p < 0.001). The Trendelenburg sign is more prevalent in subjects with LBP than controls (Cochran's Q, p < 0.001). There is more palpation tenderness over the gluteals, greater trochanter, and paraspinals in people with low back pain compared to controls (Cochran's Q, p < 0.001). Hierarchical linear regression, with BMI as a covariate, demonstrated that gluteus medius weakness, low back regional tenderness, and male sex were predictive of LBP in this sample.

CONCLUSION

Gluteus medius weakness and gluteal muscle tenderness are common symptoms in people with chronic non-specific LBP. Future investigations should validate these findings with quantitative measures as well as investigate the effect of gluteus medius strengthening in people with LBP.

Dexmedetomidine ameliorates nocifensive behavior in humanized sickle cell mice

Patients with sickle cell disease (SCD) can have recurrent episodes of vaso-occlusive crises, which are associated with severe pain. While opioids are the mainstay of analgesic therapy, in some patients, increasing opioid use results in continued and increasing pain. Many believe that this phenomenon results from opioid-induced tolerance or hyperalgesia or that SCD pain involves non-opioid-responsive mechanisms. Dexmedetomidine, a specific α2-adrenoreceptor agonist, which has sedative and analgesic properties, reduces opioid requirements, and can facilitate opioid withdrawal in clinical settings. We hypothesized that dexmedetomidine would ameliorate the nociception phenotype of SCD mice. Townes and BERK SCD mice, strains known to have altered nociception phenotypes, were used in a crossover preclinical trial that measured nocifensive behavior before and after treatment with dexmedetomidine or vehicle. In a linear dose-effect relationship, over 60-min, dexmedetomidine, compared with vehicle, significantly increased hot plate latency in Townes and BERK mice (P≤0.006). In sickle, but not control mice, dexmedetomidine improved grip force, an indicator of muscle pain (P=0.002). As expected, dexmedetomidine had a sedative effect in sickle and control mice as it decreased wakefulness scores compared with vehicle (all P<0.001). Interestingly, the effects of dexmedetomidine on hot plate latency and wakefulness scores were different in sickle and control mice, i.e., dexmedetomidine-related increases in hotplate latency and decreases in wakefulness scores were significantly smaller in Townes sickle compared to control mice. In conclusion, these findings of beneficial effects of dexmedetomidine on the nociception phenotype in SCD mice might support the conduct of studies of dexmedetomidine in SCD patients.

Acute increases in intramuscular inflammatory cytokines are necessary for the development of mechanical hypersensitivity in a mouse model of musculoskeletal sensitization

Musculoskeletal pain is a widespread health problem in the United States. Back pain, neck pain, and facial pain are three of the most prevalent types of chronic pain, and each is characterized as musculoskeletal in origin. Despite its prevalence, preclinical research investigating musculoskeletal pain is limited. Musculoskeletal sensitization is a preclinical model of muscle pain that produces mechanical hypersensitivity. In a rodent model of musculoskeletal sensitization, mechanical hypersensitivity develops at the hind paws after injection of acidified saline (pH 4.0) into the gastrocnemius muscle. Inflammatory cytokines contribute to pain during a variety of pathologies, and in this study we investigate the role of local, intramuscular cytokines in the development of mechanical hypersensitivity after musculoskeletal sensitization in mice. Local intramuscular concentrations of interleukin-1β (IL-1), IL-6 and tumor necrosis factor-α (TNF) were quantified following injection of normal (pH 7.2) or acidified saline into the gastrocnemius muscle. A cell-permeable inhibitor was used to determine the impact on mechanical hypersensitivity of inhibiting nuclear translocation of the transcription factor nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) prior to musculoskeletal sensitization. The role of individual cytokines in mechanical hypersensitivity following musculoskeletal sensitization was assessed using knockout mice lacking components of the IL-1, IL-6 or TNF systems. Collectively, our data demonstrate that acidified saline injection increases intramuscular IL-1 and IL-6, but not TNF; that intramuscular pre-treatment with an NF-κB inhibitor blocks mechanical hypersensitivity; and that genetic manipulation of the IL-1 and IL-6, but not TNF systems, prevents mechanical hypersensitivity following musculoskeletal sensitization. These data establish that actions of IL-1 and IL-6 in local muscle tissue play an acute regulatory role in the development of mechanical hypersensitivity following musculoskeletal sensitization.

A randomized trial of coenzyme Q10 in patients with confirmed statin myopathy

BACKGROUND

Coenzyme Q10 (CoQ10) supplementation is the most popular therapy for statin myalgia among both physicians and patients despite limited and conflicting evidence of its efficacy.

OBJECTIVE

This study examined the effect of coenzyme Q10 (CoQ10) supplementation on simvastatin-associated muscle pain, muscle strength and aerobic performance in patients with confirmed statin myalgia.

METHODS

Statin myalgia was confirmed in 120 patients with prior symptoms of statin myalgia using an 8-week randomized, double-blind crossover trial of simvastatin 20 mg/d and placebo. Forty-one subjects developed muscle pain with simvastatin but not with placebo and were randomized to simvastatin 20 mg/d combined with CoQ10 (600 mg/d ubiquinol) or placebo for 8 weeks. Muscle pain (Brief Pain Inventory [BPI]), time to pain onset, arm and leg muscle strength, and maximal oxygen uptake (VO2max) were measured before and after each treatment.

RESULTS

Serum CoQ10 increased from 1.3 ± 0.4 to 5.2 ± 2.3 mcg/mL with simvastatin and CoQ10, but did not increase with simvastatin and placebo (1.3 ± 0.3 to 0.8 ± 0.2) (p < 0.05). BPI pain severity and interference scores increased with simvastatin therapy (both p < 0.01), irrespective of CoQ10 assignment (p = 0.53 and 0.56). There were no changes in muscle strength or VO2max with simvastatin with or without CoQ10 (all p > 0.10). Marginally more subjects reported pain with CoQ10 (14 of 20 vs 7 of 18; p = 0.05). There was no difference in time to pain onset in the CoQ10 (3.0 ± 2.0 weeks) vs. placebo (2.4 ± 2.1 wks) groups (p = 0.55). A similar lack of CoQ10 effect was observed in 24 subjects who were then crossed over to the alternative treatment.

CONCLUSIONS

Only 36% of patients complaining of statin myalgia develop symptoms during a randomized, double-blind crossover of statin vs placebo. CoQ10 supplementation does not reduce muscle pain in patients with statin myalgia. Trial RegistrationNCT01140308; www.clinicaltrials.gov.