Elevated Muscle Research Articles

Effects of using exposure footwear for firemen and fitness training shoes on lower limb biomechanics during walking

Exposure footwear for firemen (EFF) is a crucial component of firefighters’ personal protective equipment, designed to protect against hazards, such as heat, punctures, impact, and electrocution. However, its effect on gait biomechanics remains unclear. This study was aimed to investigate the influence of EFF on firefighters’ lower limb biomechanical performance and the underlying mechanisms. Twenty healthy male firefighters (mean height: 175.41 ± 4.39 cm, mean weight: 65.74 ± 5.81 kg, mean BMI: 21.37 ± 2.17 kg/m2) were randomly assigned to wear EFF and fitness training shoes for comparison during walking tasks. Lower limb biomechanics were analyzed, focusing on joint range of motion (ROM), moments, work and muscle activity. The results indicated that wearing EFF led to increased hip and knee joint ROM in the sagittal plane, reduced ankle and metatarsophalangeal (MTP) joint ROM in the sagittal plane, increased peak hip flexion/extension and ankle dorsiflexion moments, and decreased MTP joint dorsiflexion peak moments. EFF use also resulted in increased positive work done by the hips, increased negative work done by the ankles, reduced positive work done by the ankle joints, and increased negative work by the MTP joint, The activation levels of the rectus femoris and tibialis anterior muscles were higher when wearing EFF compared to fitness training shoes. In conclusion, EFF significantly alters the biomechanical characteristics of firefighters’ lower limbs during walking, leading to elevated muscle activation in the rectus femoris and tibialis anterior. This increased demand on the lower limb muscle groups for mechanical energy generation heightens the risk of fatigue, musculoskeletal injuries, and osteoarthritis. Therefore, it is recommended that EFF boots be designed using lightweight and flexible materials. Additionally, training programs should prioritize strengthening the hip flexor/extensor, ankle dorsiflexor muscle groups, and especially the rectus femoris and tibialis anterior muscles.

MANEJO DO SORRISO GENGIVAL ATRAVÉS DO USO DA TOXINA BOTULÍNICA TIPO A

An aesthetically pleasing smile results from the combination of several factors, such as the position, size, shape, and color of the teeth, as well as the exposure and characteristics of the gingival tissue. When evaluating the gingival tissue in a smile, several important factors must be considered: excessive vertical growth of the maxilla, reduced length of the upper lip, excessive contraction of the upper lip, and disproportion between the length and width of the clinical crown of the anterior teeth. A minimally invasive approach that can be used as a complement to dental treatment is the application of botulinum toxin, a neurotoxin produced by the anaerobic bacterium Clostridium botulinum. This toxin blocks the release of acetylcholine in the presynaptic vesicles of neuromuscular junctions, inhibiting muscle contraction. The aim of this literature review was to analyze the use of botulinum toxin type A (BTX-A) in the management of gummy smile. The search was conducted in the databases Google Scholar, PubMed, Latin American and Caribbean Health Sciences Literature (LILACS), and Scientific Electronic Library Online (SciELO). The descriptors used for the search were "botulinum toxin," "gingiva," "periodontology," and "dental aesthetics," combined using the boolean operators AND and OR. Although the evidence demonstrates favorable results, the use of botulinum toxin to correct gummy smile has limitations. It is a temporary solution, and patients should be informed about the need for periodic reapplications and the potential side effects, such as facial asymmetries. The reviewed studies indicate that this technique is particularly effective in cases of gummy smile resulting from hyperactivity of the upper lip elevator muscle, providing a significant reduction in gingival exposure, with results lasting up to 12 weeks. The combination of different therapeutic approaches, along with a careful evaluation of the causes of gummy smile, allows dental professionals to offer more integrated and personalized solutions for each patient.

Speech Outcomes After Primary Palatoplasty and Presurgical Cleft Characteristics: Is There a Predictive Association?

Speech disorders related to cleft lip and palate exhibit different degrees of involvement and can occur even after primary palate repair. Hypernasality can be present as a result of velopharyngeal insufficiency, as well as nasal emission, weak pressure, articulatory errors and facial grimace, affecting speech intelligibility. Palatoplasty outcomes can be variable, and among the influencing factors are the surgical technique, the surgeon's experience, the postoperative care, and the patient/cleft characteristics. The aim of this study was to correlate speech results after primary palate repair with surgical technique and cleft characteristics, using anthropometric measurements and speech assessment in patients diagnosed with cleft lip and palate. A longitudinal, retrospective study with patients who underwent primary palatoplasty between 2015 and 2019 and still attend Craniomaxillofacial Surgery Outpatient Clinic was conducted. Patients were operated on by a single surgeon using the intravelar technique veloplasty with maximal retropositioning of the soft palate elevator muscle. Patients who underwent primary palatoplasty after 2018 had the measurements before and immediately after palatoplasty recorded: length of palate, and the distances from cleft and uvula to posterior pharyngeal wall, and uvula to adenoid. Considering the total of 39 patients, 30 (76.9%) were male, with a mean age of 20.9 months (9-53mo). All patients had their speech recorded between ages of 60 and 120 months. Speech samples were assessed by 3 different speech pathologists experienced in cleft speech, with an intrarater and inter-rater reliability >80%. The most frequent cleft type was unilateral complete cleft lip and palate (59%). One patient had mild hyponasality, 1 isolated obligatory disorder (nasal turbulence), and 3 patients presented compensatory articulation (2 isolated and 1 also presented obligatory disorder). Only 1 patient had marginal velopharyngeal insufficiency. Postoperatively, there was a mean increase in palate length from 5.4 to 5.6cm, and a statistically significant decrease in the distance from the uvula to the pharynx wall, with a mean of 1.7 to 1.1cm (P<0.001). In general, patients analyzed did not have significant alterations in speech assessment, which did not allow further comparisons and correlation. Therefore, regardless of the anatomic characteristics of the palate, it is possible to achieve good results depending on the handling experience and the technique used.

The Prediction of Radiation-Induced Trismus by the Apparent Diffusion Coefficient Values of Masseter Muscles before Chemoradiotherapy in Locally Advanced Nasopharyngeal Carcinomas.

Although the apparent diffusion coefficient (ADC) value from diffusion-weighted imaging can provide insights into various pathological processes, no studies have examined the relationship between the pre-concurrent chemoradiotherapy (CCRT) mean ADC (ADCmean) values of the masseter muscles and radiation-induced trismus (RIT) in locally advanced nasopharyngeal carcinoma (LA-NPC) patients. Therefore, the current research aimed to investigate the significance of pre-CCRT masseter muscle ADCmean values for predicting the RIT rates in LA-NPC patients treated with definitive CCRT. The pre-CCRT ADCmean values of the masseter muscles and the post-CCRT RIT rates were evaluated. A receiver operating characteristic curve analysis was employed to determine the optimal ADCmean cutoff. The primary objective was to examine the relationship between the pre-CCRT masseter muscle ADCmean values and the post-CCRT RIT rates. Seventy-seven patients were included. The optimal ADCmean cutoff value was 1381.30 × 10-6 mm2/s, which divided the patients into two groups: an ADCmean < 1381.30 × 10-6 mm2/s (n = 49) versus an ADCmean > 1381.30 × 10-6 mm2/s (n = 28). A masseter muscle ADCmean > 1381.30 × 10-6 mm2/s was found to be associated with significantly higher RIT rates than an ADCmean < 1381.30 × 10-6 mm2/s (71.42% vs. 6.12%; p < 0.001). The multivariate analysis results confirmed a pre-CCRT masseter muscle ADCmean > 1381.30 × 10-6 mm2/s as an independent predictor of RIT. Our study presents the first evidence establishing a connection between elevated masseter muscle ADCmean values and higher RIT rates in LA-NPC patients following CCRT. If confirmed with further research, these findings may help to categorize the risk of RIT in these patients.

Reliability of a new stabilization device for measurement of muscle strength using a hand-held dynamometer.

The hand-held dynamometer (HHD) is a reliable and portable tool for quantitatively assessing muscle strength. However, a number of variables, including the strength of the tester, the adequacy of stabilization, and the selected testing position, can affect the reliability of the device. The objective of the present study was to examine the reproducibility and inter-rater reliability of strength assessments using HHD with and without a stabilization device. Strength assessments were conducted with and without the stabilization device by two independent raters. Healthy volunteers with no history of musculoskeletal disorders were included in the study. The strength of the shoulder flexion, scapula elevation, knee extension, and hip abduction muscle groups was evaluated using HHD. The reliability of the measurements was evaluated using intra-class correlation (ICC), standard error of measurement, and minimal detectable change. Fifty-two healthy volunteers (age 21.51 ± 2.02 years) participated in the study. The reproducibility was found to be excellent (ICC = 0.89-0.99). While reliability between the assessors was good to excellent (ICC = 0.85-0.93), reliability between assessors and device was found moderate to good (ICC = 0.48-0.78). The strength values obtained for all directions of movement with the stabilization device were found to be significantly higher than those obtained without fixation of the HHD. It can be concluded that the data obtained from the assessors and HHD with stabilization device are not comparable. Moreover, the utilization of a stabilization device may serve to enhance the reliability of the measurements by eliminating the rater effect.

Electrocardiogram Features of Left Ventricular Excessive Trabeculation with Preserved Cardiac Function in Light of Cardiac Magnetic Resonance and Genetics.

Background and Objectives: Although left ventricular excessive trabeculation (LVET) can cause heart failure, arrhythmia and thromboembolism, limited literature is available on the ECG characteristics of primary LVET with preserved left ventricular function (EF). We aimed to compare the ECG characteristics and cardiac MR (CMR) parameters of LVET individuals with preserved left ventricular EF to a control (C) group, to identify sex-specific differences, and to compare the genetic subgroups of LVET with each other and with a C population. Methods: In our study, we selected 69 LVET individuals (EF > 50%) without any comorbidities and compared them to 69 sex- and age-matched control subjects (42% females in both groups, p = 1.000; mean age LVET-vs-C: 38 ± 14 vs. 38 ± 14 years p = 0.814). We analyzed the pattern and notable parameters of the 12-lead ECG recordings. We determined the volumetric and functional parameters, as well as the muscle mass values of the left and right ventricles (LV, RV) based on the CMR recordings. Based on the genotype, three subgroups were established: pathogenic, variant of uncertain significance and benign. Results: In the LVET group, we found normal but elevated volumetric and muscle mass values and a decreased LV_EF, wider QRS, prolonged QTc, higher RV Sokolow index values and lower T wave amplitude compared to the C. When comparing MR and ECG parameters between genetic subgroups, only the QTc showed a significant difference. Over one-third of the LVET population had arrhythmic episodes and a positive family history. Conclusions: The subclinical morphological and ECG changes and the clinical background of the LVET group indicate the need for follow-up of this population, even with preserved EF.

Isolated humeral distalization in reverse total shoulder arthroplasty: a biorobotic shoulder simulator study

BackgroundHumeral distalization is inherent to reverse total shoulder arthroplasty (rTSA) and is often produced with concomitant humeral lateralization via the level of the humeral head cut, implant positioning, implant neck shaft angle, and polymer insert thickness. Biomechanical data on the isolated effects of humeral distalization remain limited but could be important to consider when optimizing postoperative rTSA shoulder function. This study investigated the effects of isolated humeral distalization on shoulder biomechanics using a biorobotic shoulder simulator. MethodsEight fresh-frozen cadaveric shoulders were tested using custom polymer inserts that translated the bearing surface 0, +5, +10, and +15 mm along the humeral stem axis, producing isolated distalization without lateralization. Specimens underwent passive elevation in the scapular plane with a static scapula to assess glenohumeral range of motion. Scapular plane abduction motion trajectories were then performed, driven by previously collected scapulothoracic and glenohumeral kinematics from rTSA patients. The effect of isolated distalization on passive elevation was tested using mixed-effects linear regression and the effect on muscle force, joint reaction force, and muscle excursion during active scapular-plane abduction was tested using statistical parametric mapping random effects analysis. ResultsMaximum passive scapular plane elevation increased with humeral distalization (4° per 5 mm distalization). During active elevation, deltoid and rotator cuff muscle forces, and joint reaction forces, increased up to 37% per 5 mm of distalization. Simulated deltoid muscle excursion was altered with increasing distalization but amounted to no more than 0.8 mm change from baseline per 5 mm of distalization. Rotator cuff muscles were consistently lengthened throughout abduction, up to 1.6 mm per 5 mm of distalization. These trends were observed across various patient motions. ConclusionsIsolated humeral distalization caused dramatic increases in the muscle forces required to perform scapular-plane abduction. Joint reaction forces increased correspondingly. These results suggest that implant and surgical strategies to generate deltoid muscle tension without humeral distalization may promote better active range of motion and more durable long-term outcomes over approaches that rely on distalization.

Modified gluteus maximus transfer for hip abductor deficiency

Transfer of the gluteus maximus with refixation at the greater trochanter for treatment of abductor deficiency. Symptomatic abductor deficiency with atrophy and fatty degeneration of the gluteal muscles > 50% (grade3 by quartile) with good strength of the gluteus maximus. Low atrophy or fatty degeneration of less than 50% of the gluteal muscles, limited strength of the gluteus maximus, infection. First, the fascia lata is incised dorsally to the tensor fascia latae muscle, with the incision extending approximately 1.5 cm proximal to the iliac crest. Asecond incision divides the gluteus maximus muscle longitudinally along the muscle fibers and continues towards the fascia lata distal to the greater trochanter. These incisions result in atriangular muscle flap, which is elevated and divided into anterior and posterior portions. The posterior flap is positioned ventrally over the femoral neck and fixed to the anterior capsule and the anterior edge of the greater trochanter. The anterior flap is placed directly on the proximal femur. For this purpose, agroove is prepared in the area of the proximal femur using aspherical burr to freshen up the future footprint. The anterior flap is positioned from the tip of the greater trochanter towards the insertion of the vastus lateralis muscle. Subsequently, the anterior flap is fixed to the created groove with transosseous sutures and positioned under the elevated vastus lateralis muscle in 15° abduction of the leg. To provide additional stabilization to the tendinous part of the anterior flap, ascrew is inserted distally to the greater trochanter. The vastus lateralis muscle is attached to the distal tip of the anterior flap, and the remaining gluteus maximus muscle is sutured to the fascia lata to cover the anterior flap. Additionally, aflap of the tensor fascia latae muscle can be mobilized and adapted to the reconstruction. Layered wound closure is performed. The technique of agluteus maximus transfer represents amethod for the treatment of chronic abductor deficiencies and improves abduction function as well as the gait pattern in short-term follow-ups. Fifteen patients (mean age at time of surgery 62years) had after amean follow-up of 2.5years. The modified Harris Hip Score (mHHS) improved from 48points preoperatively to 60points at follow-up. Preoperatively, 100% had apositive Trendelenburg sign; at follow-up, this was about 50%.

Prompt response to rituximab in a patient with resistant polymyositis with complications of dysphagia and dysphonia: a case report

Introduction and importance: Polymyositis is an inflammatory process, primarily affecting proximal muscles, characterized by elevated muscle enzymes and distinctive electromyography patterns. Case presentation: The authors present a case of a 33-year-old male patient experiencing complications of polymyositis, including pharyngeal and laryngeal involvement leading to dysphagia and dysphonia. Steroids and intravenous immunoglobulin (IVIG) therapy proved ineffective. Subsequently, rituximab was administered, resulting in significant improvement in dysphagia, dysphonia, and proximal muscles within 3 days of the initial rituximab dose. Additionally, there was a remarkable decrease in creatine phosphokinase (CPK) levels. Clinical discussion: Immune-mediated myopathies (IMM) are rare diseases characterized by muscle inflammation and weakness. This case of probable polymyositis, diagnosed through clinical features and elevated CPK, was complicated by the patient’s lack of response to glucocorticoids and IVIG therapy. Remarkably, rituximab treatment led to rapid improvement in muscle strength and symptoms, highlighting its potential effectiveness in refractory cases of polymyositis. Conclusions: Primary treatment for cases of polymyositis typically involves the use of glucocorticoids. However, approximately half of the patients do not respond adequately to corticosteroids alone. Alternatives, in such cases, encompass IVIG therapy and rituximab.

Interplay of Statins, Clopidogrel, and Repaglinide: Unraveling the Nexus of Hypoglycemia and Myopathy in a Geriatric Type 2 Diabetes Patient: A Case Report

Abstract Background: The management of cardiovascular diseases often includes the use of statins, which, while reducing cardiovascular risk, can interact with other medications leading to significant adverse effects. This case report explores the complex interactions between atorvastatin, clopidogrel, and repaglinide, which precipitated severe hypoglycemia and myopathy in a patient with multiple comorbidities. Case Presentation: We describe a 68-year-old female with a history of type 2 diabetes mellitus, hypertension, and ischemic heart disease, who developed severe hypoglycemia and myopathy following the adjustment of her statin therapy post-cardiac diagnosis. Her treatment regimen was modified to include an increased dose of atorvastatin and the introduction of clopidogrel, shortly after which she presented with hypoglycemia and symptoms of myopathy. Investigations revealed significantly elevated muscle injury markers and magnetic resonance imaging findings consistent with myositis. Discussion: The pharmacokinetic interactions between clopidogrel with repaglinide and repaglinide with atorvastatin exacerbated by the increased dose of atorvastatin, likely led to the observed clinical manifestations. This case highlights the critical need for careful monitoring of drug interactions, especially in patients with polypharmacy. Adjustments in drug dosages and consideration of alternative medications with fewer interaction risks are essential components of managing similar cases. Conclusion: This case underscores the importance of vigilant therapeutic management and individualized patient care in the context of complex drug regimens. Understanding and anticipating drug interactions can prevent significant adverse effects and improve patient outcomes in a population at high risk of polypharmacy complications.

A case report on congenital hypothyroidism and alpha thalassemia in children with anemia and muscle damage as the main manifestation.

This study reports the first case of congenital hypothyroidism (CH) and alpha thalassemia in a child in China, with anemia and muscle damage as the main manifestations. Analyzing and studying this case is of great significance in reducing missed and misdiagnosed CH and will provide a clinical strategy for treating these patients. Child, female, 2 years and 7 months old, the child appeared dispirited, had poor appetite, shallow complexion, reduced activities with anemia, elevated muscle enzymes, height, and growth retardation. The child was diagnosed with CH with alpha thalassemia. The patient was treated with levothyroxine sodium and anemia correction. The children's current spirit, appetite, red face, normal limb activity, physical development, and intelligence were significantly better than those of normal children of the same age. CH with alpha thalassemia, especially anemia and muscle damage as the main manifestations, has not been reported. Administration of levothyroxine sodium is effective in correcting anemia in patients with CH and alpha thalassemia. Due to CH and alpha thalassemia, there are no specific symptoms and they are prone to missed diagnosis and misdiagnosis. Therefore, patients with anemia and elevated muscle enzyme levels should be routinely tested for thyroid function to diagnose them early and provide proper treatment to avoid negative consequences.

Bee morphology: A skeletomuscular anatomy of Thyreus (Hymenoptera: Apidae).

Although the knowledge of the skeletal morphology of bees has progressed enormously, a corresponding advance has not happened for the muscular system. Most of the knowledge about bee musculature was generated over 50 years ago, well before the digital revolution for anatomical imaging, including the application of microcomputed tomography. This technique, in particular, has made it possible to dissect small insects digitally, document anatomy efficiently and in detail, and visualize these data three dimensionally. In this study, we document the skeletomuscular system of a cuckoo bee, Thyreus albomaculatus and, with that, we provide a 3D atlas of bee skeletomuscular anatomy. The results obtained for Thyreus are compared with representatives of two other bee families (Andrenidae and Halictidae), to evaluate the generality of our morphological conclusions. Besides documenting 199 specific muscles in terms of origin, insertion, and structure, we update the interpretation of complex homologies in the maxillolabial complex of bee mouthparts. We also clarify the complicated 3D structure of the cephalic endoskeleton, identifying the tentorial, hypostomal, and postgenal structures and their connecting regions. We describe the anatomy of the medial elevator muscles of the head, precisely identifying their origins and insertions as well as their homologs in other groups of Hymenoptera. We reject the hypothesis that the synapomorphic propodeal triangle of Apoidea is homologous with the metapostnotum, and instead recognize that this is a modification of the third phragma. We recognize two previously undocumented metasomal muscle groups in bees, clarifying the serial skeletomusculature of the metasoma and revealing shortcomings of Snodgrass' "internal-external" terminological system for the abdomen. Finally, we elucidate the muscular structure of the sting apparatus, resolving previously unclear interpretations. The work conducted herein not only provides new insights into bee morphology but also represents a source for future phenomic research on Hymenoptera.

Attenuation of Delayed Onset Muscle Soreness with Acute Consumption of Essential Amino Acids

Introduction: Prior studies of the acute benefits of protein supplementation have determined a benefit in improving post-exercise muscle anabolism and aiding the recovery of muscle function and performance. Previous acute protein supplement studies in post-exercise protein synthesis and anabolic intracellular signaling reported no attenuation in muscle damage or elevated muscle function. The aim of this study is to implement a specific content of essential amino acids with resistance and aerobic exercises to quantify the difference in strength, endurance, and flexibility during the delayed onset muscle soreness common with a new exercise protocol. Methods: We enrolled 42 participants (22 EAA and 20 Controls) completed an hour-long aerobic and resistance exercise protocol including flexibility, resistance, and aerobic exercises for three consecutive days. The study participants were randomly assigned to the EAA (6.6g) per day (EAA + Gatorade) group or the control (Gatorade) group. The data was analyzed in a double-blinded format. Results: Both groups improved the initial flexibility respectively throughout the three exercise days but were not significantly different (p=0.32) in the sit and reach. For the resistance/power activities, the EAA group improved in the repetitions for push-ups (p=0.014 vs 0.21) and dips (0.0002 vs 0.59) compared to the controls. The EAA group was faster although not statistically significant in the 20-meter sprint and improved in the 1.5-mile run during the third day (P=0.002 vs 0.48) compared to the control group. Conclusions: The data in the results supports that acute ingestion of the essential amino acid supplements provides increased physical performance and decreases the DOMS symptoms in sedentary participants over the three-day trial period of exercise.

Chemogenetic Excitation of Ventromedial Hypothalamic Steroidogenic Factor 1 (SF1) Neurons Increases Muscle Thermogenesis in Mice.

Allostatic adaptations to a perceived threat are crucial for survival and may tap into mechanisms serving the homeostatic control of energy balance. We previously established that exposure to predator odor (PO) in rats significantly increases skeletal muscle thermogenesis and energy expenditure (EE). Evidence highlights steroidogenic factor 1 (SF1) cells within the central and dorsomedial ventromedial hypothalamus (c/dmVMH) as a modulator of both energy homeostasis and defensive behavior. However, the brain mechanism driving elevated EE and muscle thermogenesis during PO exposure has yet to be elucidated. To assess the ability of SF1 neurons of the c/dmVMH to induce muscle thermogenesis, we used the combined technology of chemogenetics, transgenic mice, temperature transponders, and indirect calorimetry. Here, we evaluate EE and muscle thermogenesis in SF1-Cre mice exposed to PO (ferret odor) compared to transgenic and viral controls. We detected significant increases in muscle temperature, EE, and oxygen consumption following the chemogenetic stimulation of SF1 cells. However, there were no detectable changes in muscle temperature in response to PO in either the presence or absence of chemogenetic stimulation. While the specific role of the VMH SF1 cells in PO-induced thermogenesis remains uncertain, these data establish a supporting role for SF1 neurons in the induction of muscle thermogenesis and EE similar to what is seen after predator threats.

Sulforaphane enhanced muscle growth by promoting lipid oxidation through modulating key signaling pathways.

Sulforaphane (SFN) has shown diverse effects on human health and diseases. SFN was administered daily to C57BL/6J mice at doses of 1 mg/kg (SFN1) and 3 mg/kg (SFN3) for 8 weeks. Both doses of SFN accelerated body weight increment. The cross-sectional area and diameter of Longissimus dorsi (LD) muscle fibers were enlarged in SFN3 group. Triglyceride (TG) and total cholesterol (TC) levels in LD muscle were decreased in SFN groups. RNA sequencing results revealed that 2455 and 2318 differentially expressed genes (DEGs) were found in SFN1 and SFN3 groups, respectively. Based on GO enrichment analysis, 754 and 911 enriched GO terms in the SFN1 and SFN3 groups, respectively. KEGG enrichment analysis shown that one KEGG pathway was enriched in the SFN1 group, while six KEGG pathways were enriched in the SFN3 group. The expressions of nine selected DEGs validated with qRT-PCR were in line with the RNA sequencing data. Furthermore, SFN treatment influenced lipid and protein metabolism related pathways including AMPK signaling, fatty acid metabolism signaling, cholesterol metabolism signalling, PPAR signaling, peroxisome signaling, TGFβ signaling, and mTOR signaling. In summary, SFN elevated muscle fibers size and reduced TG and TC content of in LD muscle by modulating protein and lipid metabolism-related signaling pathways.

An unusual presentation of dermatomyositis: dermatomyositis sine dermatitis presenting with rapidly progressive myositis

Dermatomyositis sine dermatitis (DMSD) is a rare variant of dermatomyositis where progressive muscle weakness presents without the characteristic rash but with muscle histology of dermatomyositis. A 55-year-old woman presented with progressive severe proximal limb, neck, pharyngeal and respiratory muscle weakness, without dermatologic manifestations. Elevated muscle enzymes and myopathic electromyogram pointed towards inflammatory myositis while the muscle biopsy confirmed DMSD. Her condition improved with steroids, intravenous immunoglobulin, methotrexate, and rituximab. This case emphasises the necessity of maintaining a high index of suspicion for dermatomyositis, even when a classic skin rash is absent and the criticality of early aggressive treatment. Anti-NXP-2 antibody positivity could indicate severe disease.

Elevated muscle pain induced by a hypertonic saline injection reduces power output independent of physiological changes during fixed perceived effort cycling.

Pain is a naturally occurring phenomenon that consistently inhibits exercise performance by imposing unconscious, neurophysiological alterations (e.g., corticospinal changes) as well as conscious, psychophysiological pressures (e.g., shared effort demands). Although several studies indicate that pain would elicit lower task outputs for a set intensity of perceived effort, no study has tested this. Therefore, this study investigated the impact of elevated muscle pain through a hypertonic saline injection on the power output, psychophysiological, cerebral oxygenation, and perceptual changes during fixed perceived effort exercise. Ten participants completed three visits (1 familiarization + 2 fixed perceived effort trials). Fixed perceived effort cycling corresponded to 15% above gas exchange threshold (GET) [mean rating of perceived effort (RPE) = 15 "hard"]. Before the 30-min fixed perceived effort exercise, participants received a randomized bilateral hypertonic or isotonic saline injection in the vastus lateralis. Power output, cardiorespiratory, cerebral oxygenation, and perceptual markers (e.g., affective valence) were recorded during exercise. Linear mixed-model regression assessed the condition and time effects and condition × time interactions. Significant condition effects showed that power output was significantly lower during hypertonic conditions [t107 = 208, P = 0.040, β = 4.77 W, 95% confidence interval (95% CI) [0.27 to 9.26 W]]. Meanwhile, all physiological variables (e.g., heart rate, oxygen uptake, minute ventilation) demonstrated no significant condition effects. Condition effects were observed for deoxyhemoglobin changes from baseline (t107 = -3.29, P = 0.001, β = -1.50 ΔμM, 95% CI [-2.40 to -0.61 ΔμM]) and affective valence (t127 = 6.12, P = 0.001, β = 0.93, 95% CI [0.63 to 1.23]). Results infer that pain impacts the self-regulation of fixed perceived effort exercise, as differences in power output mainly occurred when pain ratings were higher after hypertonic versus isotonic saline administration.NEW & NOTEWORTHY This study identifies that elevated muscle pain through a hypertonic saline injection causes significantly lower power output when pain is experienced but does not seem to affect exercise behavior in a residual manner. Results provide some evidence that pain operates on a psychophysiological level to alter the self-regulation of exercise behavior due to differences between conditions in cerebral deoxyhemoglobin and other perceptual parameters.

Intramuscular diacylglycerol accumulates with acute hyperinsulinemia in insulin-resistant phenotypes.

Elevated skeletal muscle diacylglycerols (DAGs) and ceramides can impair insulin signaling, and acylcarnitines (acylCNs) reflect impaired mitochondrial fatty acid oxidation, thus, the intramuscular lipid profile is indicative of insulin resistance. Acute (i.e., postprandial) hyperinsulinemia has been shown to elevate lipid concentrations in healthy muscle and is an independent risk factor for type 2 diabetes (T2D). However, it is unclear how the relationship between acute hyperinsulinemia and the muscle lipidome interacts across metabolic phenotypes, thus contributing to or exacerbating insulin resistance. We therefore investigated the impact of acute hyperinsulinemia on the skeletal muscle lipid profile to help characterize the physiological basis in which hyperinsulinemia elevates T2D risk. In a cross-sectional comparison, endurance athletes (n = 12), sedentary lean adults (n = 12), and individuals with obesity (n = 13) and T2D (n = 7) underwent a hyperinsulinemic-euglycemic clamp with muscle biopsies. Although there were no significant differences in total 1,2-DAG fluctuations, there was a 2% decrease in athletes versus a 53% increase in T2D during acute hyperinsulinemia (P = 0.087). Moreover, C18 1,2-DAG species increased during the clamp with T2D only, which negatively correlated with insulin sensitivity (P < 0.050). Basal muscle C18:0 total ceramides were elevated with T2D (P = 0.029), but not altered by clamp. Acylcarnitines were universally lowered during hyperinsulinemia, with more robust reductions of 80% in athletes compared with only 46% with T2D (albeit not statistically significant, main effect of group, P = 0.624). Similar fluctuations with acute hyperinsulinemia increasing 1,2 DAGs in insulin-resistant phenotypes and universally lowering acylcarnitines were observed in male mice. In conclusion, acute hyperinsulinemia elevates muscle 1,2-DAG levels with insulin-resistant phenotypes. This suggests a possible dysregulation of intramuscular lipid metabolism in the fed state in individuals with low insulin sensitivity, which may exacerbate insulin resistance.NEW & NOTEWORTHY Postprandial hyperinsulinemia is a risk factor for type 2 diabetes and may increase muscle lipids. However, it is unclear how the relationship between acute hyperinsulinemia and the muscle lipidome interacts across metabolic phenotypes, thus contributing to insulin resistance. We observed that acute hyperinsulinemia elevates muscle 1,2-DAGs in insulin-resistant phenotypes, whereas ceramides were unaltered. Insulin-mediated acylcarnitine reductions are also hindered with high-fat feeding. The postprandial period may exacerbate insulin resistance in metabolically unhealthy phenotypes.

Idiopathic inflammatory myopathies : An interdisciplinary challenge

Idiopathic inflammatory myopathies (IIM) are rare diseases (incidence 1:100,000) with awide range of clinical symptoms and manifestations. Typical indicators of IIM are proximally emphasized muscle weakness and myalgias, which are usually accompanied by elevated creatine kinase levels and muscle atrophy. The autoantibody diagnostics separate IIM into different entities, which are each associated with atypical risk of organ manifestations and the occurrence of tumors. The IIM represents an interdisciplinary challenge and the diagnostics and treatment require the involvement of several disciplines including rheumatology, neurology, neuropathology, dermatology and pneumology. An accurate diagnosis and careful tumor screening are essential because of the association between certain subgroups of IIM and the occurrence of malignant tumors.

Exploring the link between occupationally relevant whole body vibration and headache and neck pain: is elevated muscle tension an intermediary factor?

Whole body vibration (WBV) is linked to short- and longer-term adverse health outcomes, including cognitive impairment, stress and memory loss, loss of balance, reduced proprioception, visual and vestibular disturbances, gastrointestinal problems, and musculoskeletal disorders. Epidemiological evidence supports the link between WBV and headache and head discomfort, but few experimental studies have examined this relationship, particularly with increased muscle tension, as an intermediary. This study aimed to investigate the relationship between muscle tension and vibration intensity, between perceived neck pain and headache/head discomfort and vibration intensity, and between muscle tension and reported neck pain and headache symptoms from simulated WBV based on field measurements of all-terrain vehicle operation on farm terrain. We observed significantly higher electromyography amplitude in the High condition (equivalent to EU Directive's Exposure Limit Value) compared to both Low (equivalent to EU Directive's Exposure Action Value) and Control (quiet sitting) conditions at the left upper trapezius muscle but there were no significant time effects. Neck pain and headache/head discomfort significantly increased after both Low (91% increase from baseline) and High (154% increase from baseline) vibration conditions but there were no significant differences between conditions. Based on simple regression modeling, the relationship between muscle activity and neck pain or headache was very weak (R2 = 0-0.093). Given the possibility of multiple factors contributing to headache symptoms, future research should not only consider the role of muscle tension but also sensory conflict, excessive noise, biodynamic responses, and a combination of these factors.