Muscles

Neuromuscular diseases (NMDs) include a heterogeneous group of progressive chronic conditions that frequently lead to substantial physical disability and loss of autonomy. Although motor and functional impairments of NMDs are well documented, the psychological burden remains underexplored. This narrative review synthesizes current literature regarding four psychological domains in individuals with NMDs: (i) anxiety, (ii) depression, (iii) coping strategies, and (iv) quality of life. Evidence indicates that anxiety and depressive symptoms are highly prevalent in the spectrum of NMDs, influenced by factors such as disease severity, onset age, and perceived social support. Maladaptive coping strategies, including avoidance and denial, are associated with poorer mental health outcomes and reduced involvement in rehabilitation. In contrast, adaptive strategies, such as acceptance and problem-focused coping, may help buffer psychological distress. Quality of life is consistently reported to be lower in people with NMDs compared to the general population, with psychosocial factors such as social support playing a role. Despite these findings, psychological care remains inconsistently integrated in NMD management. Full article

Dermatomyositis (DM) is a prototypic idiopathic inflammatory myopathy in which characteristic skin disease frequently precedes or parallels muscle involvement and signals risks such as interstitial lung disease (ILD) and malignancy. This literature review integrates recent advances across dermatology, neuromuscular medicine, and immunology to refine diagnosis and management. We surveyed the literature from 2000 to 2025, prioritizing randomized trials, large cohorts, and translational studies that spanned classic and juvenile DM, amyopathic/hypomyopathic variants, and overlap phenotypes. Key insights include the diagnostic weight of pathognomonic cutaneous lesions with nailfold microangiopathy; the utility of myositis-specific autoantibodies for endotyping and risk (e.g., anti-TIF1-γ/anti-NXP2 and cancer, anti-MDA5 and rapidly progressive ILD); and the value of myxovirus-resistance protein A (MxA) immunohistochemistry and muscle MRI patterning (including distinctions from immune-mediated necrotizing myopathy) when enzymes are normal, or biopsies are treatment-modified. Management is anchored in early steroid-sparing immunosuppression tailored to phenotype, with evidence for IVIG in active DM and growing support for JAK inhibition, particularly in interferon-high or anti-MDA5 ILD, alongside selective use of calcineurin inhibitors and rituximab, with plasma exchange considered for refractory, rapidly progressive ILD. We highlight risk-stratified malignancy screening (IMACS 2023) and complications, including calcinosis, lipodystrophy, and chronic cutaneous damage. Skin-led recognition coupled with antibody-guided, phenotype-directed therapy and interdisciplinary care offers a pragmatic precision framework to improve outcomes and reduce long-term disability. Full article

Background/Objectives: Despite the increasing use of ultrasound (US) as a tool for assessing muscle mass and diagnosing sarcopenia, its application remains limited because few studies have validated cut-off points for specific populations. This study aimed to propose US cut-off points for diagnosing sarcopenia in Brazilian individuals aged 60 years and older. Methods: Patients schedule for elective abdominal computed tomography (CT) were also evaluated with musculoskeletal US of the thigh. CT images were obtained at the level of the third lumbar vertebra. US measurements included the thickness of the rectus femoris (RF) muscle and the rectus femoris combined with the vastus intermedius (RF + VI). Receiver Operating Characteristic (ROC) curves determine the sensitivity and specificity of the US cut-off points. The area under the curve (AUC) and 95% confidence intervals (CI) were calculated. Results: The study sample (n = 88) had a mean age of 71.8 ± 8.7 years, and 64% were women. The proposed cut-off points for diagnosing sarcopenia using US, based on the mean ± SD, were ≤19.1 mm and ≤15.9 mm for RF thickness and ≤31.9 mm and ≤29.2 mm for RF + VI thickness in men and women, respectively. These cut-off points demonstrated good accuracy and significant AUC values. Conclusions: This study proposes US-based cut-off points with good accuracy for suggesting sarcopenia diagnosis, particularly when assessing RF thickness. Full article

Intake of anthocyanin-rich blackcurrant extract showed muscle fibre-type specific force responses during fatigue development from combined use of voluntary maximal isometric contractions and electrically evoked twitch contractions of the m. quadriceps femoris. In the present exploratory study, we examined the fibre-type specific effects by blackcurrant extract on high-intensity intermittent treadmill running performance to exhaustion. Active males (n = 16, age: 23 ± 3 years, height: 179 ± 5 cm, body mass: 79 ± 3 kg, $\dot{V}$O_2max: 55.3 ± 5.0 mL·kg⁻¹·min⁻¹) completed a fatiguing protocol with 16 voluntary maximal isometric contractions to predict muscle fibre typology. The high-intensity intermittent running protocol was completed twice following a 7-day intake of blackcurrant extract (210 mg anthocyanins per day) and twice following a placebo (PL) in a randomized, double blind, crossover design. Heart rate and lactate were recorded at exhaustion. Data were averaged for each condition. There were no significant correlations between the percentage force decline by the repeated isometric contractions (mean ± SD: 29.3 ± 12.4%) and total and high-intensity running distance. Participants were categorized into a predominant muscle fibre type I (slow-twitch, n = 3 with the lowest isometric force decline: 12 ± 9%) and type II typology (fast-twitch, n = 3 with the highest isometric force decline: 46 ± 10%). Only the individuals with a predominant type I fibre typology improved the total running and high-intensity running distance by 17 ± 12% and 15 ± 11%. At exhaustion, there were no differences between individuals with a type I or II fibre typology for heart rate and lactate. These exploratory results suggest that the ergogenic potential of anthocyanin-rich blackcurrant extract on high-intensity intermittent exercise may depend on muscle fibre type, though larger and more robust studies are needed to confirm this observation. Future work will establish whether our exploratory results contributed to our understanding of the underpinning of inter-individual responses to the intake of anthocyanin-rich nutritional ergogenic aids. Full article

Sarcopenia, the loss of skeletal muscle mass and function, is a common and critical comorbidity in patients with conditions frequently managed by interventional radiologists, such as liver cirrhosis and hepatocellular carcinoma (HCC). Interventional radiologists are well positioned to incorporate opportunistic screening for this condition during routine preprocedural cross-sectional imaging. This review summarizes the current evidence on how sarcopenia influences patient outcomes and informs procedural planning across a spectrum of interventional radiology (IR) procedures. In transarterial embolizations for HCC, sarcopenia is a robust independent predictor of increased mortality, with meta-analyses suggesting it may also predict a lower tumor response rate. Even earlier stages of muscle loss (pre-sarcopenia) are associated with worse survival, and dynamic changes in muscle mass post-treatment can serve as a biomarker for tumor progression. For patients undergoing transjugular intrahepatic portosystemic shunt, pre-procedural sarcopenia and myosteatosis are strong, independent predictors of both mortality and the development of post-procedural hepatic encephalopathy, with the presence of both conferring the highest risk. In the context of pre-surgical portal vein embolization, sarcopenia is consistently associated with impaired volumetric liver growth, although this does not always translate to worse short-term surgical outcomes, as functional liver regeneration may be preserved. Following percutaneous liver tumor ablation, sarcopenia is a powerful predictor of overall mortality, while its role in predicting tumor recurrence remains an area of active investigation. Finally, in non-oncologic interventions for peripheral arterial disease, sarcopenia is highly prevalent and is associated with worse functional status, higher mortality, and a significantly increased risk of major amputation after endovascular therapy. In conclusion, sarcopenia is a powerful and readily available biomarker that provides crucial prognostic information—often independent of standard clinical scores—across a wide spectrum of IR procedures. The consistent evidence supports integrating sarcopenia evaluation into routine practice to enhance risk stratification, improve patient counseling, and guide multidisciplinary treatment planning. Full article

Football requires repeated sprint ability for game-changing moments; however, the demand on the skeletal muscles is unknown. The aim of the current study was to determine the muscle oxygen response during duplicate sprints in professional footballers. Eight male professional footballers (age: 29 ± 5 y; height: 181 ± 8 cm; weight: 78 ± 8 kg) were recruited. Participants wore their normal GPS unit and completed their normal match warm-up before near-infrared monitors were attached to the rectus femoris and bicep femoris muscles. Participants then completed two 30 m sprints with 10 s of recovery, while GPS data and muscle oxygenation were recorded. Max speed was unaltered across the two sprints (s1: 8.4 ± 0.3 m.s⁻¹; s2: 8.4 ± 0.4 m.s⁻¹), but max acceleration (s1: 5.0 ± 1.5 m.s⁻²; s2: 3.7 ± 1.2 m.s⁻²) and time to max acceleration (s1: 1.0 ± 0.3 s; s2: 1.8 ± 0.8 s) were significantly different in sprint 2 compared with sprint 1. Change in muscle oxygenation was greater in the bicep femoris muscle than in the rectus femoris muscle in sprint 1 (right BF: 37.0 ± 14.7%; right RF: 23.4 ± 14.8%). Time to fast delay was longer in sprint 2 than in sprint 1 in the bicep femoris muscle (right BFs1: 1.6 ± 1.2 s; right BFs2: 5.2 ± 2.3 s), reflecting different recovery kinetics in the two muscles. During duplicate sprints there is a difference in oxygen response between the two muscles, and the overall recovery of the bicep femoris is much slower. This suggests poorer conditioning of the bicep femoris muscle, which may impact injury risk in professional football players. Full article

Inclusion body myositis (IBM) is a late-onset, treatment-resistant inflammatory myopathy. Approximately half of IBM patients develop autoantibodies against cytosolic $5^{\prime }$-nucleotidase 1A (cN1A), but their role in disease pathogenesis remains unclear. This pilot study examined the effects of anti-cN1A-positive IBM serum on human primary myotubes’ transcriptome profile, using anti-cN1A-negative IBM and healthy sera as controls. Exposure to anti-cN1A-positive serum altered the expression of 1126 genes, with upregulation of adaptive immune response genes, notably CTSH and CTSZ, encoding cathepsins H and Z. These findings were validated using a publicly available independent dataset comprising transcriptomes from fresh muscle tissue samples. NT5C1A mRNA, which encodes cN1A, was not detected in cultured myotubes regardless of the presence of autoantibodies. The findings suggest distinct pathological mechanisms in anti-cN1A-positive IBM, independent of direct antibody-target interactions. The role of cathepsins in IBM pathogenesis warrants further investigation. Full article

Duchenne muscular dystrophy (DMD), which results from mutations that disrupt the expression of dystrophin proteins, is characterized by progressive muscle fiber wasting and the development of skeletal muscle fibrosis. The severe pathology leads to loss of ambulation, respiratory insufficiency, cardiomyopathy, and early death in patients. Dystrophin-focused therapies based on adeno-associated viral (AAV) vector-mediated gene addition, antisense oligonucleotide-induced repair of the transcript reading frame, and chemically driven stop codon readthrough have been conditionally approved for use in subsets of patients. From trials, it is apparent that these therapies act to stabilize the disease phenotype rather than improve it significantly, meaning that early treatment results in better outcomes. AAV-mediated delivery of a form of utrophin, a structural and functional homolog of dystrophin, GALGT2, a sarcolemmal stabilizer, and Klotho, the anti-aging hormone that is silenced in a mouse model of DMD as a result of the disease pathology, have been explored in preclinical compensatory gene addition studies. Recombinant follistatin protein has been used to target the fibrosis seen. An all-in-one type of therapy is likely to provide a synergistic effect such that efficacy of the dystrophin restoration strategy would be improved. For this, CRISPRa could hold potential through the targeting of multiple relevant genes simultaneously. The suitability of targeting these genes will be discussed, as will the stages of the development of CRISPRa for DMD. A perspective on the future prospects of CRISPRa in relation to likely issues that would need addressing and how they may be overcame will be given. Full article

Sarcopenia and reduced skeletal muscle radiodensity have been proposed as potential biomarkers influencing the outcomes of immunotherapy in cancer patients. This retrospective study aimed to evaluate the prognostic significance of skeletal muscle index (SMI) and skeletal muscle radiodensity (SMD), assessed by means of computed tomography imaging at the L3 level, in 76 male patients with metastatic non-small cell lung cancer treated with PD-1/PD-L1 inhibitors. Patients were categorized into high and low SMI/SMD groups based on body mass index-adjusted cut-off values. Clinical outcomes included treatment response, overall survival, and immune-related adverse events. While no statistically significant differences in overall survival were observed between groups stratified by SMI or SMD, patients with higher SMD demonstrated a significantly greater disease control rate (56.22 ± 8.04 vs. 48.36 ± 10.34 HU; p = 0.031). Additionally, a statistically significant interaction was observed between PD-L1 expression and SMI (p = 0.027), indicating that muscle mass may influence the prognostic value of PD-L1. Neither SMI nor SMD were associated with immune-related adverse event incidence. Multivariate analysis identified PD-L1 expression ≥ 50% as the only independent predictor of longer overall survival (Hazard Ratio = 0.29; p = 0.001). In conclusion, while neither SMI nor SMD independently predicted overall survival, SMD was associated with treatment response. Notably, SMI modified the prognostic relevance of PD-L1 expression, suggesting a potential role for muscle mass in refining immunotherapy stratification. Full article

Hamstring strain injuries (HSI) are common in soccer and remain challenging to predict, as traditional risk factors often fail to capture the multifactorial nature of injury susceptibility. This prospective cohort study aimed to develop and internally validate a machine learning-assisted logistic regression model for predicting hamstring injuries in amateur soccer players using preseason clinical and strength-related variables. A total of 120 male players were followed for one competitive season (30 weeks). Baseline predictors included age, body mass index, previous injury, and bilateral isometric hip and knee strength measured via handheld dynamometry. Twenty initial predictors were reduced to ten through symmetrical uncertainty feature ranking before training a logistic regression model with elastic-net regularization (training set: n = 83; test set: n = 37) using nested four-fold cross-validation. Model performance was evaluated using the area under the receiver operating characteristic curve (AUC), calibration metrics, and confusion matrices. During follow-up, 21 players sustained at least one HSI (32 events; 28% reinjuries), yielding an events-per-variable ratio of 2.1, below ideal thresholds and suggesting possible overfitting. On the independent test set, the model achieved an accuracy of 64.9%, AUC of 0.68 (95% CI 0.52–0.84), calibration slope of 0.85, and intercept of −0.12, with a sensitivity of 60% and specificity of 65.6%. Dominant-leg hip abduction strength was the only statistically significant predictor (OR = 0.82, 95% CI 0.70–0.96), while permutation importance analyses identified previous hamstring injury as the most stable contributor to model performance. Neither age nor hamstring isometric strength demonstrated predictive value. Although model discrimination was moderate and calibration indicated mild overfitting, findings reinforce the prognostic relevance of prior injury and suggest that reduced hip abduction strength may serve as an emerging candidate marker. This study, classified as a TRIPOD Category 2 model (development without external validation), provides preliminary, hypothesis-generating evidence supporting the use of multivariate strength and history-based predictors in future, larger-scale injury prediction research. Full article

Chronic whiplash-associated disorders describe a cluster of symptoms that result from a sudden neck acceleration/deceleration movement, including pain, musculoskeletal and neurological signs, inducing functional disability. The aim of this study was to compare the effects of physiotherapy treatment based on neck-specific exercises, with or without a behavioral approach, in individuals with whiplash-associated disorders. Computerized research was performed in PubMed, PEDro, National Institute for Health and Care Excellence, and ScienceDirect to identify randomized controlled trials that evaluated the effectiveness of neck-specific exercises, with or without a behavioral approach, for chronic whiplash. For the meta-analysis, the outcomes of pain and disability were assessed. Thirteen studies were included in the systematic review, with a total of 2427 participants of both sexes, with ages between 18 and 63 years. Although interventions with a behavioral approach decreased pain and disability more significantly in 4 and 6 studies when compared to neck-specific exercises without such an approach, respectively, the meta-analysis revealed no differences between them. Although interventions for chronic whiplash-associated disorders based on neck-specific exercises with a behavioral approach seem to be more effective in reducing pain and disability, there is no quantitative difference favoring one over the other. Full article

Light therapy has been shown to produce several beneficial physiological effects in a wide range of tissues. The musculoskeletal system can be irradiated with deeply penetrating wavelengths in near infrared (NIR) regions. Photobiomodulation therapy (PBMT) reduces pain and inflammation and enhances physical performance. However, the mechanism(s) of cellular responses to PBMT in muscle is not clearly understood. Therefore, the goal of this study is to improve our understanding of the mechanism(s) of action of PBMT effects in exercised and sedentary muscle. In sedentary mice, PBMT using a wavelength of 830 nm increased the gene expression for muscle tissue development, including cFos, which is critical for activating interstitial and satellite cells that repair muscle. Immunostaining for cFOS expression confirmed an increase in the number of activated cells in PBMT-treated muscle. We observed that PBMT-treated mice showed increased performance on the treadmill, reduced muscle fiber damage, and altered mitochondrial structure. RNA sequencing from fatigued TA tissue suggested that PBMT treatment increased the gene expression of tissue regeneration and remodeling, suggesting tissue adaptation and muscle repair after exercise with PBMT. In conclusion, our study suggests that the 830 nm wavelength may have altered the muscle by activating regenerative genes that protect the tissue from exercise-induced cellular stress. Full article

Maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) are commonly used proxies to measure respiratory muscle strength. Current literature lacks recent large-scale normative reference values (NRV) for these pressures in healthy Singaporean adults. Moreover, no consensus exists on the variables that could influence MIP and MEP. This cross-sectional study aims to: (1) establish the NRV of MIP and MEP; (2) determine the correlations of variables that could influence these pressures; and (3) develop regression equations using non-spirometry variables to estimate reference values for MIP and MEP in the healthy Singaporean population aged 21 to 80 years. MIP and MEP were measured alongside demographic and anthropometric data collected from 391 participants (202 females, 189 males) recruited via convenience sampling. Median MIP and MEP values were significantly higher in males (112 and 85 cmH₂O) than in females (83 and 64 cmH₂O). Spearman correlations revealed significant associations between MIP/MEP and gender, height, weight, body mass index (BMI), waist–hip ratio, and spirometric variables. Regression models using age, gender, height, and weight explained 27.5% and 32.1% of the variance in MIP and MEP, respectively. This study updated the NRV of MIP and MEP and provided practical predictive equations for assessing respiratory muscle strength in Singapore. Full article

Although previous studies have examined various factors that influence biceps brachii activation, such as grip position, load, and exercise variation, to our knowledge, no prior studies have compared muscle activation during a traditional biceps curl and a Bayesian cable curl. Therefore, this study aimed to examine the differences in biceps brachii muscle activation between these two training modalities. Data from eleven volunteers (age: 25 ± 6 y; weight: 86 ± 13 kg; height: 177 ± 8 cm) were included in the analysis. Muscle activity was assessed using the normalized root mean square (RMS) values obtained from surface electromyography (sEMG). A within-subjects, counterbalanced design was utilized where all participants completed both testing conditions in a randomized order to control for potential order effects. Participants visited the laboratory and fitness center on two occasions. On the first day, anthropometric measurements were obtained, along with one repetition maximum (1-RM) for both the dumbbell biceps curl and the Bayesian curl. On the second day, participants performed an isometric maximal voluntary contraction (MVC), followed by electromyographic assessment of muscle activity during the dumbbell biceps curl and the Bayesian curl, each performed at 80% of their respective 1-RM. When the normal distribution was confirmed via the Shapiro–Wilk test (p > 0.05), a paired t-test was used for statistical analysis. On the other hand, when normality was not confirmed, the Wilcoxon test was utilized. Statistically significant differences (p = 0.003) were observed in the EMG amplitude (%) between the biceps curl (111.46 ± 26.80) and the Bayesian curl (93.39 ± 15.65) with a large effect size (d = 0.82). Based on the EMG analysis, the dumbbell biceps curl elicited significantly greater muscle activation compared to the Bayesian curl, suggesting that the conventional movement places a higher mechanical and neuromuscular demand on the biceps brachii. Full article

Applied muscular strain and hamstring strain capacity have a joint interaction on hamstring strain injury (HSI) with modifiable risk factors frequently assessed. However, to date there is limited observations on the interaction between these factors. The purpose of the present study was to observe if spatiotemporal characteristics, running kinematics and muscle activation were related to modifiable risk factors of HSI. Twenty-two competitive team sport athletes (24.7 ± 4.3 years, 1.82 ± 0.07 m, 84.9 ± 8.5 kg) participated whereby the Bicep femoris long head (BF_LH) fascicle length assessed via ultrasound and isokinetic eccentric hamstring strength was assessed. With running assessment performed at 18 km/h, capturing running kinematics and muscle activation. Multiple linear regressions were used to examine the relationship of running kinematics and muscle activation on the modifiable risk factors of HSI on. The overall model (F_2,19) was statistically significant for both relative eccentric hamstring strength (F = 23.58, p < 0.001) and BF_LH fascicle length (F = 18.87, p < 0.001) highlighting spatiotemporal characteristics, running kinematics and hamstring activation were found to be significantly related to the modifiable risk factors. There is a complex interrelationship between running mechanics and hamstring muscle properties, with the potential of either cause or consequence association. Full article

Aim: The study developed and validated AppER, an mHealth tool for informal caregivers of children with Duchenne Muscular Dystrophy, and examined differences between app users and non-users. Methods: Four phases were followed: (1) focus groups with experts and caregivers to identify care-related domains; (2) prototype development and validity testing (CVR, I-CVI, I-FVI) using the MARS scale; (3) implementation of the final app; and (4) psychosocial profiling of 88 caregivers (42 users and 46 non-users) measuring quality of life, dependency, somatic symptoms, and coping strategies. Results: AppER showed high content and face validity, surpassing reference thresholds. In the psychosocial analysis, users reported lower perceived quality of life than non-users, despite no significant differences in dependency, somatic symptoms, or coping strategies. Conclusions: Employment patterns differed: more users were dedicated to household tasks, while more non-users were self-employed, suggesting economic factors may affect app uptake and quality of life perceptions. Findings indicate AppER is a valid, well-rated support tool, and that caregivers with lower perceived quality of life may be more inclined to adopt digital health solutions, potentially to address complex care demands. Designing targeted digital interventions may be particularly valuable for those in less favorable socioeconomic contexts. Because of the small sample and between-group imbalances, results are exploratory and warrant confirmation in larger, balanced samples. Full article

Purpose: Despite significant attention being paid to compression garments (CG) in the sports field, there remains ongoing debate regarding their actual effectiveness in enhancing athletic performance and expediting post-exercise recovery. This article examines their various aspects, with a focus on CG design and the materials they are made of, aiming to analyze the importance of personalized compression strategies based on individual anthropometric measurements and non-linear compression designs. Methods: Using anthropometric analysis of 40 healthy participants, this study examines the morphological characteristics of the lower limb and their implications for CG design. Results: Measurements of limb length and circumferences revealed complex interactions among anatomical variables, emphasizing the need for customized and adaptable device design. Finite element simulations clarified the challenges in achieving uniform pressure gradients along the lower limb, highlighting the limitations of one-piece devices and suggesting tailored segmented designs for individual limb segments. Conclusion: The results demonstrate that one-piece devices often fail to provide optimal compression due to non-linear variations in limb dimensions. Conversely, segmented devices, particularly those with bilinear progression, exhibited superior performance in applying targeted compression across different limb segments. This more detailed approach to customization could significantly contribute to optimizing outcomes and user comfort. Full article

Background: Sarcopenia is associated with adverse surgical outcomes across multiple specialties. The psoas muscle index (PMI), a radiologic marker of sarcopenia, may offer prognostic value in patients undergoing left ventricular assist device (LVAD) implantation, a population frequently characterized by frailty and high perioperative risk. Methods: We conducted a single-center retrospective study of 32 patients who underwent LVAD implantation between 2017 and 2022 and had preoperative CT imaging within 45 days. PMI was calculated from bilateral psoas muscle area at the L3 vertebral level, normalized to height. Sarcopenia was defined as the lowest sex-specific quartile of PMI. Primary outcomes were overall survival (OS), 90-day mortality, and postoperative length of stay (LOS). Results: Eight patients (25%) met criteria for sarcopenia. Sarcopenic and non-sarcopenic groups had similar demographics, comorbidities, and nutritional status. While there were no significant differences in overall, 90-day, or 1-year mortality between groups, among those who died post-implantation, the sarcopenic group had significantly shorter OS (median 38 vs. 597 days, p = 0.006). All sarcopenic deaths occurred within 90 days post-implant. LOS did not differ significantly between groups. Conclusions: PMI-defined sarcopenia was associated with early postoperative mortality among LVAD recipients, though not with overall or long-term mortality. Full article