The present study aimed to investigate the association of physical activity and with or without regular exercise habits with lower limb muscle thickness, intramuscular adipose tissue (IntraMAT) and muscle strength in healthy young collegiate women, focusing on muscle thickness and IntraMAT using ultrasound tomography. The study participants included 20 healthy young collegiate women (age, 20.7±1.0 years). Physical activity was measured using a uniaxial accelerometer, and lower limb muscle thickness and IntraMAT were measured using ultrasound tomography. Muscle strength was measured as the maximum voluntary contraction force during isometric knee extension. The present study examined the association of physical activity with lower limb muscle thickness, IntraMAT and muscle strength, depending on whether the participants followed an exercise habit or not. Single correlation analysis revealed no significant correlation between the physical activity level and muscle thickness or muscle strength in all the participants. However, in the participants without regular exercise habits, the number of step counts and physical activity levels, particularly the time spent performing moderate- to vigorous-intensity activity, were positively associated with vastus lateralis muscle thickness (P=0.018 and P=0.048), and tended to have higher echo intensity of rectus femoris (P=0.056). These results suggest that a reduction in the time spent performing moderate- to vigorous-intensity physical activity may affect lower limb muscle thickness in healthy young collegiate women without regular exercise habits. In addition, the results suggest that a lack of exercise habits may influence the increase in IntraMAT in healthy young collegiate women.

The objective of the study was to evaluate the isolated and combined effects of Type 2 Diabetes Mellitus (T2DM) and Peripheral Artery Disease (PAD) on muscle architecture, muscle quality, functional capacity.

Participated 24 older females, divided into 3 groups: T2DM + PAD Group (n = 8), T2DM Group (n = 8), and Healthy Participants Group - HPG (n = 8), all matched by age. The participants underwent body composition assessment by plethysmography, muscle architecture assessment of the vastus lateralis (VL) and tibialis anterior (TA), and muscle quality assessment of the rectus femoris (RF) and medial gastrocnemius (MG) by means of ultrasound images, and three functional tests to assess functional capacity. ANOVA was used to compare means between groups, adopting α = 0.05, and linear regression analysis was carried out between performance in the functional tests and independent variables that had significant correlations.

The results indicated that the fascicle length of the VLR in T2DM + PAD (p = 0.04) and T2DM (p = 0.01) were lower than those observed in HPG. Significant differences (p < 0.01) were also found between HPG and T2DM for the echo intensity of the GM. No significant differences were observed between groups for functional tests.

The isolated presence of T2DM or associated with PAD compromises muscle architecture and quality parameters without affecting the functional capacity of older women.

Knee osteoarthritis (OA) is a prevalent joint condition resulting in years lived with disability. A first-line treatment recommended by clinical guidelines is the therapeutic exercise to control pain and improve physical function. One possible approach for exercise supervision is telehealth using video calls, as it can be an effective alternative to in-person physical therapy for treating musculoskeletal conditions, expanding community access to physical rehabilitation. In this scenario, this study aims to investigate whether a muscle-strengthening exercise program for the lower limbs supervised remotely via video calls is as effective as the same exercise applied in person for improving pain, physical function, condition-specific patient-reported outcomes (PROMs), psychological well-being, sleep quality, functional performance, and quadriceps muscle architecture.

A Remote and In-person Supervised Exercise in Patients with Knee Osteoarthritis (RISE-KOA) study is a parallel, two-armed, single-blinded protocol for a non-inferiority randomized controlled trial. Forty-eight participants aged 45 years or more, with a symptomatic and radiographic diagnosis of unilateral or bilateral knee OA (grade II or III according to Kellgren and Lawerence) will be randomly assigned to a remote exercise group supervised by video calls or in-person exercise group supervised at a physiotherapy clinic. Both groups will receive the same muscle-strengthening exercises for the lower extremities for 12 weeks. Follow-ups will be conducted during treatment (6 weeks), after treatment (12 weeks), and 18 weeks after randomization. The primary outcomes will be pain intensity and physical function during (6 weeks) and after treatment (12 weeks). Secondary outcomes will be condition-specific PROMs, psychological well-being, sleep quality, functional performance, and quadriceps muscle architecture.

We hypothesize that muscle strengthening exercise supervised remotely via video calls will not be inferior to in-person exercise at a physiotherapy clinic in terms of primary and secondary outcomes in patients with knee OA.

The study was prospectively registered at ClinicalTrials.gov (NCT06101797). Registered on Oct 26, 2023.

Background/Objectives: Structured medium- and long-chain triglycerides (sMLCT) may be a superior vehicle for medium-chain fatty acid delivery to peripheral tissues, such as skeletal muscle. Limited information is available concerning the effect of sMLCT on muscular performance or recovery after a muscle-damaging exercise protocol. The purpose of this study was to establish the effect of a novel formulation of sMLCT on muscular performance and recovery. Methods: Forty female adults (mean ± SD age = 22 ± 3 years; body mass index = 23.5 ± 3.4 kg/m2) were randomized into one of two study groups, placebo control [CON; n = 20] or sMLCT [n = 20], and completed five total visits to the laboratory. The baseline (i.e., pre-exercise) assessments of muscle performance, size, and soreness were compared to assessments immediately following exercise and 24, 48, and 72 h post-exercise. Results: No statistically significant condition × time interactions were noted for strength outcomes, although trends for condition × time interactions were present for torque over 25 ms (p = 0.06) and peak torque (p = 0.05). Similarly, no condition x time interactions were present for ultrasound echo intensity, the subjective ratings of soreness and pain, thigh circumference, leg volume, and vertical jump performance. Conclusions: Within the context of the current study, the ingestion of sMLCT did not significantly influence the rate of muscle strength recovery following muscle damaging resistance exercise.

To evaluate the response of skeletal muscle architecture (fascicle length and pennation angle) and composition (echo intensity) markers assessed by ultrasonography to intervention in older adults.

This is a subsection of a more comprehensive systematic review of clinical trials focusing on changes in muscle quality, registered in PROSPERO (registration number: CRD42022357116).

Randomized controlled trials evaluating the effectiveness of interventions lasting ≥8 weeks in adults aged ≥60 years on fascicle length, pennation angle, and echo intensity.

After the literature search, 6 peer reviewers and 1 decider conducted a 2-stage screening process, including studies that met the eligibility criteria. Random-effects modeling for Hedges' g was applied to a meta-analysis of studies with sufficient data. The risk of bias in the included studies was assessed using version 2 of the Cochrane Risk-of-Bias tool for randomized trials.

In total, 4832 studies were initially searched, and 28 trials involving 1101 participants were included. Six trials were analyzed for fascicle length, 8 for pennation angle, and 8 for echo intensity. The standardized mean differences with 95% CIs, where a positive direction indicates improvement due to treatment, were fascicle length, -0.04 (-0.27 to 0.19); pennation angle, 0.08 (-0.02 to 0.18); and echo intensity, 0.00 (-0.02 to 0.02). No heterogeneity was observed for the outcomes (I2 = 0%). The Cochrane Risk-of-Bias tool showed that 78.6% of the trials had a high risk of bias.

Muscle architecture and composition markers assessed via ultrasound did not respond to the intervention. Further well-designed clinical trials are necessary to confirm the clinical validity of these markers.

The menopause transition is a critical period marked by significant physiological adaptations. Data on the dynamic changes in body composition and metabolism during this transition are limited. The purpose was to determine body composition and metabolic changes over a 2-year follow-up in a cross-sectional sample of premenopausal (PRE), perimenopausal (PERI), and postmenopausal (POST) females.

Twenty-three females who previously participated in a cross-sectional study returned for a 2-year follow-up visit were classified as PRE, PERI, or POST based on menstrual history and a Menopause Health Questionnaire. Muscle size [muscle cross-sectional area (mCSA)] and muscle quality [echo intensity, (EI)] were evaluated in the vastus lateralis with ultrasound. Bone mass and body composition were assessed using dual-energy X-ray absorptiometry, and metabolic flexibility through submax exercise with indirect calorimetry.

At the 2-year follow-up, POST females had an increase in EI (change: 26.93 ± 12.82 a.u., group×time p-adjusted = 0.001) with no change in mCSA (change: -2.03 ± 2.40 cm², group×time p = 0.980). PERI compared to PRE females had lower total bone mass (group×time p-adjusted = 0.029) with an even lower bone mass in POST compared to PERI females (group×time p-adjusted = 0.023). No differences in metabolic flexibility at any exercise intensity were observed between groups over time (group×time p = ≥ 0.05).

This study highlights a decline in muscle quality and total bone mass despite stable muscle size, emphasizing the need for targeted exercise and nutrition interventions to support muscle and bone health in females around the menopause transition.

This study investigated neuromuscular variations across low to moderate target force levels, three knee joint angles and tibial rotation positions, examining their correlations with muscle morphology and their collective impact on force steadiness (FS). Twelve young adult males performed knee extension tasks under three different tibial rotation conditions: internal rotation (IR), neutral rotation (NR), and external rotation (ER). All tasks involved submaximal isometric contractions at the knee joint. Participants performed submaximal isometric contractions at three knee joint angles (30°, 60°, and 90°) and three target force levels (10%, 40%, 70% of maximum voluntary isometric contraction (MVIC)). The electromyographic (EMG) signals from vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF) were recorded. FS was quantified using standard deviation (SD) and coefficient of variation (CV) of force output, while EMG steadiness was assessed using SD and CV of the EMG signals. Muscle morphology features, including muscle thickness (MT) and echo intensity (EI), were assessed via ultrasound imaging. Submaximal isometric contractions revealed significant FS differences across target force levels and knee angles (angle × target force interaction: F(4,44) = 3.073, P = 0.026). With increasing target force from 10 to 70% MVIC, quadriceps EMG signals showed progressive amplitude increases in all three muscles (RF, VM and VL, p < 0.05).While tibial rotation showed no significant effect on FS measures (P > 0.05), it significantly influenced EMG characteristics at 60° knee angle (tibial rotation × target force × muscle interaction: F(8,88) = 3.357, P = 0.026). Strong correlations were found between force steadiness and EMG steadiness (r = 0.557-0.657, P < 0.001). Additionally, RF echo intensity positively correlated with EMG_SD in both ER and NR positions (r = 0.644 and 0.619 respectively, P < 0.05), while quadriceps muscle thickness negatively correlated with EMG_CV in ER position (r = -0.600, P < 0.05). FS revealed that absolute fluctuations (SD) increased with target force levels, while relative fluctuations (CV) decreased. Target force levels and knee joint angles significantly influence FS, whereas tibial rotation does not directly affect FS during isometric contractions. However, tibial rotation interestingly affects EMG steadiness, and the variability in EMG-derived muscle activation correlates with both FS and muscle morphology parameters. These findings provide valuable insights into neuromuscular control mechanisms during force production.

Near-infrared spectroscopy (NIRS) can be applied to assess skeletal muscle oxidative capacity ( m V ˙ O 2 ). Specific force (SF) and echo intensity (EI) represent muscle quality. However, it is unknown how exercise participation and biological sex impact m V ˙ O 2 , and if measures of muscle quality are related to m V ˙ O 2 . The aim was to assess training history- and biological sex-related differences in m V ˙ O 2 , SF, and EI in males and females.

To determine training history, 50 adults (23 females, 66% resistance trained, age:22 ± 3 years) completed strength and cardiorespiratory fitness assessments. Ultrasonography assessed muscle cross-sectional area (mCSA) and EI of the dominant vastus lateralis. The ratio of maximal strength to mCSA was defined as SF. To assess m V ˙ O 2 , participants cycled for 5 min at 50% of their peak power observed at maximal oxygen consumption. Following this, a mono-exponential decay curve, deriving the rate constant (k), was created from post-exercise NIRS recovery slopes. Separate 2(Sex) × 2(Training History) ANOVAs examined differences in k, SF, and EI. Pearson's correlation coefficients evaluated relations among k, SF, and EI.

There was a significant interaction for k (p = 0.025,η p 2 = 0.105 ), such that k was greater in aerobically trained adults. Additionally, SF was significantly greater for resistance trained individuals (p < 0.001), whereas EI was not different between training history groups (p = 0.363). For the resistance trained group, SF and m V ˙ O 2 were related (r = - 0.455, p = 0.002). EI was associated with m V ˙ O 2 (r = 0.465, p = 0.006).

Chronic aerobic exercise promotes faster recovery following exercise bouts, whereas resistance training yields superior muscle quality, possibly demonstrating the consequences of a physiological trade-off and/or training-specificity.

This pilot study consists of a two-phase intervention to examine the effectiveness of unilateral resistance training to mitigate the negative consequences of immobilization and expedite the restoration of muscle strength and size following a period of retraining. Ten females were randomized to a unilateral training (TRAIN, n = 6) or control (CON, n = 4) group. During Phase 1, all participants wore an arm sling for a total of 4 weeks on their non-dominant arm. This phase required the TRAIN group to perform unilateral resistance training with the non-immobilized arm while the CON group did not. Phase 2 commenced thereafter and consisted of 4 weeks of bilateral resistance training for both groups. Outcome measures of neuromuscular function and muscle size were assessed at baseline and after each phase, with neuromuscular function quantified by maximal dynamic and isometric strength alongside electromyographic responses and muscle size measured using ultrasonography and regional lean mass via DEXA. Unilateral training of the non-immobilized arm during Phase 1 attenuated dynamic (p < 0.05; g > 1.2), but not isometric (p > 0.40; g < 0.095), strength loss following immobilization and showed large effects for improving the recovery of strength after retraining. Similarly, the imaging data show the relative changes in muscle size and regional lean mass of the non-dominant arm favor TRAIN. Although the small sample prevents definitive conclusions, our study suggests resistance training of the non-immobilized arm attenuates muscle weakness and atrophy for the contralateral, immobilized arm during immobilization and facilitates their recovery following retraining.

Cost-effective and portable ultrasonography offers a promising approach for monitoring skeletal muscle damage and quality in many contexts. However, echogenicity analysis relies on precise transducer orientations and machine parameters, posing challenges for data pooling across different raters and settings. Muscle texture analysis offers a potential means of reducing inter-rater and machine-setting variability. Scans were assessed at nine angles, controlled using a custom transducer shell and software. Scans were performed three times, and different gains were applied. All scans were performed on a muscle tissue-mimicking phantom to eliminate biological variability. Intra-angle and intra-gain variability and internal consistency were assessed via coefficient of variation (CV%) and Cronbach's alpha (αc). Spearman's (ρ) correlations were employed to determine the relationship between echogenicity and each texture feature. Entropy (angle: CV=2.7-7.6%; gain: CV=10.5%; αc=0.86), and inverse difference moment (angle: CV=3.7-9.8%; gain: CV=16.5%; αc=0.87) were less variable than echogenicity (angle: CV=6.4-19.4%; gain: CV=39.0%; αc=0.82). Angular second moment (angle: CV=17.9-116.6%; gain: CV=71.6%; αc=0.68), contrast (angle: CV=7.8-14.7%; gain: CV=41.8%;αc=0.75), and correlation (angle: CV=9.0-13.5%; gain: CV=28.6%; αc=0.49) features were generally more variable. Entropy (ρ=0.82-0.98, p≤0.011) and inverse difference moment (ρ=-0.98--0.83, p≤0.008), were more strongly correlated with echogenicity than angular second moment (ρ=-0.98--0.77, p≤0.016), contrast (ρ=0.53-0.98, p≤0.15), and correlation (ρ=-0.25--0.19, p=0.520-0.631). Entropy and inverse difference moment features may allow data sharing between laboratory and clinical settings with ultrasound machine parameters and raters of varying skill levels. Clinical and mechanistic studies are required to determine if texture features can replace echogenicity assessments.

Skeletal muscle echo intensity (EI) is associated with functional outcomes in older adults, but resistance training interventions have shown mixed results. Texture analysis has been proposed as a novel approach for assessing muscle quality, as it captures spatial relationships between pixels. It is unclear whether texture analysis is able to track changes following resistance training.

To examine changes in first-order (EI) and second-order (texture) features of muscle quality following lower-body resistance training in older adults.

Twelve older adults (2 males, 10 females; mean ± SD age = 70 ± 5 years) completed 6 weeks of resistance training, consisting of twice-weekly sessions at 85% of estimated 1RM. Testing included ultrasound imaging of the rectus femoris (RF) and vastus lateralis (VL), 5-repetition maximum (5RM) leg extension strength, and maximal voluntary isometric contraction (MVIC) force. Ultrasound images were analyzed for EI and texture features using gray-level co-occurrence matrix (GLCM) analysis.

Large improvements were observed in 5RM leg extension strength (p < 0.001, effect size [ES] = 2.09), MVIC force (p = 0.006, ES = 0.969), and RF EI (uncorrected: p = 0.003, ES = 0.727; corrected: p = 0.012, ES = 0.864). No significant changes were observed in muscle size, VL EI, or texture features for either muscle.

Short-term resistance training improved strength and RF EI. However, texture analysis features were not sensitive to changes following training. These findings suggest that traditional EI measures may be more appropriate than texture analysis for tracking changes in muscle quality following resistance training in older adults.

This narrative review provides an overview of body composition methods available for use in critically ill patients. It focuses on the relevance and discussion of the most commonly used techniques. Further, we discuss the validity of these methods with a focus on muscle mass assessment, measuring changes over time and the identification of patients with lower-than-normal muscularity. Current available evidence, as well as future directions is highlighted.

Peripheral magnetic stimulation (PMS) is commonly used for neurological conditions, but its effectiveness in enhancing functional mobility and morphology in children with spastic diplegia remains underexplored. This study assessed the impact of PMS with physical therapy (PT) versus PT alone on mobility and morphology in spastic diplegia. Forty-five children with spastic diplegia (mean age 12.7 ± 3.8 years) were randomly assigned to one of three intervention groups: PMS + PT, PT, or control, with fifteen children in each group. The training was conducted thrice weekly for eight weeks, included muscle morphology assessments, the 30 s sit-to-stand test (30sSTS), functional reach test (FRT), 10 m walk test (10MWT), and 6 min walk test (6MWT). The study revealed increased left quadricep and calf muscle thickness following PMS + PT (d = 0.19, 0.39, respectively; all p < 0.05). Improvement in 30sSTS was observed after both PMS + PT (d = 0.56) and PT (d = 1.43). FRT demonstrated increases following both PMS + PT and PT interventions (d = 1.52, 0.93, respectively). Furthermore, improvements were observed in 10MWT following PMS + PT and PT interventions (d = 1.20, 0.78), while PT increased the 6MWT (d = 0.82). The control group showed declines in 10MWT and 6MWT. The treatment significantly impacted FRT, 10MWT, and 6MWT in spastic diplegia. While PMS may not enhance physical capacities beyond PT alone, it may improve FRT and 10MWT outcomes.

Measurement of thenar muscle elasticity by ultrasound shear wave elastography (SWE) may be useful for the diagnosis and evaluation of carpal tunnel syndrome (CTS), but there is a paucity of information on SWE of the thenar muscles in patients with CTS. The purpose of this study was to investigate the elasticity of the thenar muscles in patients with CTS.

Twenty-two adult patients with a referral diagnosis of CTS (27 hands) and 20 healthy volunteers as a control (20 dominant hands) participated in this study. The elastic modulus of the thenar muscles was measured with SWE in two conditions, rest and pinch. The elastic modulus and percent change between the two conditions for each muscle were compared between groups.

The elastic modulus of the abductor pollicis brevis (APB) in the patient group was lower than that in the control group at rest (20.6 ± 5.6 kPa vs. 25.0 ± 8.5 kPa; p = 0.034). However, the elastic modulus (87.9 ± 49.0 kPa vs. 62.5 ± 28.5 kPa; p = 0.044) and percent change (373.3 ± 336.4% vs. 169.2 ± 116.0%; p = 0.006) of the APB in the patient group were higher than those in the control group with pinch. For the opponens pollicis and adductor pollicis, there was no significant difference in the elastic modulus between groups.

Patients with CTS showed differences in SWE of the APB. Future studies need to investigate the accuracy of SWE in diagnosing CTS and assessing prognosis.

Muscle function deterioration in female patients with severe knee osteoarthritis (KOA) is linked to alterations in muscle morphology, composition, and mechanical properties. This study evaluates thigh muscle features in female patients with severe KOA and explores correlations with knee joint function.

Ultrasound and shear wave elastography measured physiological cross-sectional area (PCSA), echo intensity (EI), and shear modulus (G) in the rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), biceps femoris long head (BFL), and semitendinosus (ST) of 24 KOA patients and 24 controls. EI indicates intramuscular fat, while G reflects stiffness. Muscle characteristics were compared between groups, and correlations with knee function scores (WOMAC, KSS, HSS) were analyzed.

In patients, the symptomatic side displayed reduced PCSA for RF, VL, VM, BFL, and ST (15.85[Formula: see text], 28.18[Formula: see text], 21.53[Formula: see text], 11.67[Formula: see text], 6.59[Formula: see text] respectively) vs. controls (19[Formula: see text], 36.32[Formula: see text], 23.37[Formula: see text], 14.15[Formula: see text], 7.12[Formula: see text] respectively). EI was elevated (128.95, 121.12, 105.72, 90.52, 93.15) vs. controls (100.39, 93.97, 88.14, 77.69, 78.73), and G values (9.48 kPa, 7.88 kPa, 6.9 kPa, 7.2 kPa, 9.03 kPa) was higher than controls (8.85 kPa, 5.28 kPa, 5.98 kPa, 6.58 kPa, 6.73 kPa). BFL`s G, ST`s G, and VM`s EI, negatively correlated with knee function, whereas BFL`s PCSA positively correlated. The variable importance of BFL's PCSA and G ranked at the top in all scores.

Compared to controls, PCSAs in muscles on both sides of KOA patients were lowered by up to 22%, indicative of muscle loss and diminished strength. The G value is 20.65% higher, suggesting poor flexibility and elevated passive tension. EI in muscles on both sides of KOA patients was greater, reaching up to 23.88%, possibly reducing contractile components and muscle force. G, PCSA, and EI are closely correlated with function scores, and PCSA and G of BFL are the most significant predictors of knee function. These results may help explain muscle dysfunction in KOA patients.

Not applicable.

Poor muscle quality (MQ) is a hidden health condition in obesity, commonly disregarded and underdiagnosed, associated with poor health-related outcomes. This narrative review provides an in-depth exploration of MQ in obesity, including definitions, available assessment methods and challenges, pathophysiology, association with health outcomes, and potential interventions. MQ is a broad term that can include imaging, histological, functional, or metabolic assessments, evaluating beyond muscle quantity. MQ assessment is highly heterogeneous and requires further standardization. Common definitions of MQ include 1) muscle-specific strength (or functional MQ), the ratio between muscle strength and muscle quantity, and 2) muscle composition (or morphological MQ), mainly evaluating muscle fat infiltration. An individual with obesity might still have normal or higher muscle quantity despite having poor MQ, and techniques for direct measurements are needed. However, the use of body composition and physical function assessments is still limited in clinical practice. Thus, more accessible techniques for assessing strength, muscle mass, and composition should be further explored. Obesity leads to adipocyte dysfunction, generating a low-grade chronic inflammatory state, which leads to mitochondrial dysfunction. Adipocyte and mitochondrial dysfunction result in metabolic dysfunction manifesting clinically as insulin resistance, dyslipidemia, and fat infiltration into organs such as muscle, which in excess is termed myosteatosis. Myosteatosis decreases muscle cell function and insulin sensitivity, creating a vicious cycle of inflammation and metabolic derangements. Myosteatosis increases the risk of poor muscle function, systemic metabolic complications, and mortality, presenting prognostic potential. Interventions shown to improve MQ include nutrition, physical activity/exercise, pharmacology, and metabolic and bariatric surgery.

Calaway, C, Walls, K, Levitt, H, Caplan, J, Mann, B, Martinez, K, Gastaldo, R, Haq, I, and Signorile, JF. Velocity-based-training frequency impacts changes in muscle morphology, neuromuscular performance, and functional capability in persons with Parkinson's disease. J Strength Cond Res 39(1): 99-106, 2025-Velocity-based training (VBT) positively impacts muscle morphology and performance in persons with Parkinson's disease (PD); however, optimal training frequencies for VBT in patients with PD remain undetermined. Changes in ultrasound-determined muscle thickness (MT) and echo intensity (EI)-derived muscle quality of the rectus femoris (RF) and vastus lateralis (VL), neuromuscular performance, and functional capacity were examined following 2 VBT frequencies (2-3 d·wk -1 ) using 30% velocity loss thresholds for 12 weeks. Neuromuscular performance was assessed using computerized pneumatic resistance machines. For each variable, 2 (time) × 2 (group) repeated-measures analyses of variance (ANOVA) were used to determine significant main effects and interactions. Significant time effects were seen for MT and EI of all muscles ( p < 0.05). Muscle thickness improvements included right VL (RVL) (0.171 ± 0.065 cm; p = 0.019), left VL (LVL) (0.214 ± 0.101 cm; p = 0.049), right RF (RRF) (0.194 ± 0.077 cm; p = 0.023), and left RF (LRF) (0.318 ± 0.109 cm; p = 0.010). For EI, improvements occurred in RVL (-18.688 ± 3.600; p = <0.001), LVL (-10.959 ± 4.894; p = 0.040), RRF (-9.516 ± 3.537; p = 0.016), and LRF (-9.018 ± 3.444; p = 0.019). Time effects were seen for leg-press 1-repetition maximum and peak power ( p < 0.01) and habitual walking speed ( p = 0.022), with a group by time interaction for maximal gait speed favoring the 3 d·wk -1 condition (∆0.15 m·s -1 , p = 0.002). The results indicate that VBT at 2 or 3 d·wk -1 can significantly improve muscle morphology, neuromuscular performance, and functional capability in patients with PD; however, improvements in maximal gait speed require 3 d·wk -1 . These findings provide flexibility when developing exercise prescriptions for patients with PD.

The distribution and amount of intramuscular fat and fibrous tissue can be influenced by biological sex and impact muscle quality in both the functional (force-generating capacity) and morphological (muscle composition) domains. While ultrasonography (US) has proven effective in assessing age- or sex-related differences in muscle quality, limited information is available on sex differences in children. Quantitative ultrasonographic measurements, such as echo intensity (EI), EI bands (number of pixels across 50-unit intervals) and texture, may offer a comprehensive framework for identifying sex differences in muscle composition. The aim of our study was to examine the effect of sex on the rectus femoris (RF) muscle quality in children. We used EI (mean and bands) and texture as muscle quality estimates derived from B-mode US. We hypothesised that RF muscle quality differs significantly between girls and boys. Additionally, we also hypothesised that there is a significant correlation between EI bands and texture. Forty-four non-active healthy children were recruited (n = 22 girls, 12.8 ± 1.5 years; and n = 22 boys, 13.5 ± 1.2 years). RF was assessed using EI mean, EI bands, and texture analysis (homogeneity and correlation) using the Gray-Level Co-Occurrence Matrix. The results revealed significant (p < 0.05) sex differences in RF EI bands and texture. Boys displayed higher values in the 0-50 EI band and had more homogeneous muscle texture than girls. Conversely, girls displayed greater values in the 51-100 EI band and had less homogenous texture compared to boys (p < 0.05). A positive correlation was observed between the 0-50 EI band and muscle homogeneity. However, the 51-100 EI band correlated negatively with homogeneity (p < 0.05), particularly for girls. In conclusion, our study revealed sex-specific differences in mean EI, EI bands, and texture of the RF muscle in children. The variations in the correlations between the first and second EI bands and texture reveal different levels of homogeneity in each band. This indicates that distinct muscle tissue constituents, such as intramuscular fat and/or connective tissue, may be reflected in EI bands. Overall, the methods used in this study may be useful for examining muscle quality in healthy children and those with medical conditions.

Background/Objectives: Strokes remain a major global health concern, contributing significantly to disability and healthcare costs. Currently, there are no established indicators to accurately assess the degree of muscle tissue impairment in stroke-affected individuals. However, ultrasound imaging with an echotexture analysis shows potential as a quantitative tool to assess muscle tissue quality. This study aimed to identify specific echotexture features in the gastrocnemius medialis that effectively characterize muscle impairment in post-stroke individuals. Methods: An observational study was conducted with 22 post-stroke individuals. A total of 21 echotexture features were extracted and analyzed, including first-order metrics, a grey-level co-occurrence matrix, and a grey-level run length matrix. The modified Heckmatt scale was also applied to correlate with the most informative echotexture features. Results: Among the features analyzed, echovariation (EV), echointensity, and kurtosis emerged as the most informative indicators of muscle tissue quality. The EV was highlighted as the primary feature due to its strong and significant correlation with the modified Heckmatt scale (r = -0.81, p < 0.001) and its clinical and technical robustness. Lower EV values were associated with poorer muscle tissue quality, while higher values indicated better quality. Conclusions: The EV may be used as a quantitative indicator for characterizing the gastrocnemius medialis muscle tissue quality in post-stroke individuals, offering a more nuanced assessment than traditional qualitative scales. Future studies should investigate the correlation between the EV and other clinical outcomes and explore its potential to monitor the treatment efficacy, enhancing its applicability in clinical practice.

Multimodal prehabilitation programs, which may incorporate nutritional supplementation and exercise, have been developed to combat sarcopenia in surgical patients to enhance post-operative outcomes. However, the optimal regime remains unknown. The use of beta-hydroxy beta-methylbutyrate (HMB) has beneficial effects on muscle mass and strength. However, its effect on muscle quality in the perioperative setting has yet to be established. This study aims to explore the impact of a multimodal prehabilitation program using a bundle of care that includes high-protein oral nutritional supplementation (HP ONS) with HMB and resistance exercise on muscle quality and functional outcomes in sarcopenic surgical patients.

Sarcopenic adult patients undergoing elective major gastrointestinal surgeries were recruited for this pilot interventional cohort study. They were enrolled in a 2-4-week multimodal prehabilitation program comprising resistance exercise, nutritional supplementation, vitamin supplementation, comorbid optimization and smoking cessation. Participants were provided three units of HP ONS with HMB per day pre-operatively. The primary outcome was changes in intramuscular adipose tissue (IMAT) as a proxy of muscle quality, assessed using Artificial Intelligence (AI)-aided ultrasonography. Secondary outcomes include changes in anthropometric measurements and functional characteristics. Outcomes were measured before prehabilitation, after prehabilitation and 1 month post-operatively.

A total of 36 sarcopenic patients, with a median age of 71.5 years, were included in this study. There was an increase in the IMAT index after two weeks of prehabilitation (p = 0.032) to 1 month after surgery (p = 0.028). Among functional parameters, improvement was observed in gait speed (p = 0.01) after two weeks of prehabilitation, which returned to baseline post-operatively. The median length of hospital stay was 7 (range: 2-75) days.

The increase in the IMAT index in a sarcopenic surgical cohort undergoing prehabilitation may be due to altered muscle metabolism in elderly sarcopenic patients. A prehabilitation regime in sarcopenic patients incorporating HP ONS with HMB and resistance exercise is feasible and is associated with increased gait speed.

Hospitalization exacerbates sarcopenia and physical dysfunction in older adults. Whether tailored inpatient exercise prevents acute sarcopenia is unknown. This study aimed to examine the effect of a multicomponent exercise programme on muscle and physical function in hospitalized older adults. We hypothesized that participation in a brief tailored exercise regimen (i.e., 3-5 days) would attenuate muscle function and structure changes compared with usual hospital care alone.

This randomized clinical trial with blinded outcome assessment was conducted from May 2018 to April 2021 at Hospital Universitario de Navarra, Spain. Participants were 130 patients aged 75 years and older admitted to an acute care geriatric unit. Patients were randomized to a tailored 3- to 5-day exercise programme (n = 64) or usual hospital care (control, n = 66) consisting of physical therapy if needed. The coprimary endpoints were between-group differences in changes in short physical performance battery (SPPB) score and usual gait velocity from hospital admission to discharge. Secondary endpoints included changes in rectus femoris echo intensity, cross-sectional area, thickness and subcutaneous and intramuscular fat by ultrasound.

Among 130 randomized patients (mean [SD] age, 87.7 [4.6] years; 57 [44%] women), the exercise group increased their mean SPPB score by 0.98 points (95% CI, 0.28-1.69 points) and gait velocity by 0.09 m/s (95% CI, 0.03-0.15 m/s) more than controls (both p < 0.01). No between-group differences were observed in any ultrasound muscle outcomes. There were no study-related adverse events.

Three to 5 days of tailored multicomponent exercise provided functional benefits but did not alter muscle or fat architecture compared with usual hospital care alone among vulnerable older patients. Brief exercise may help prevent acute sarcopenia during hospitalization.

ClinicalTrials.gov identifier: NCT04600453.

Phase angle (PhA) is a biomarker derived from raw bioelectrical impedance analysis (BIA) values: resistance (R) and reactance (Xc). PhA reflects cellular membrane integrity and, as a result, has been considered a marker of fluid distribution, making it a potential prognostic indicator. A growing body of research demonstrates independent associations between PhA and muscle strength, mass, and composition. In this context, PhA has the extra potential to serve as a marker of muscle quality. However, the evidence supporting its use for this purpose is not well established. This study aimed to investigate the relationship between PhA and markers of muscle quality.

This systematic review and meta-analysis (Internal Prospective Register of Systematic Reviews - PROSPERO on a registration code: CRD42024507853) focused on observational studies assessing the relationship between PhA and markers of both concepts of muscle quality: the muscle quality index (MQI: strength by a unit of mass) and the muscle composition (i.e., skeletal muscle radiodensity [SMD], muscle echogenicity, muscle fat fraction, inter- and intramuscular adiposity). Risk of bias was assessed using the Newcastle-Ottawa Scale (NOS) and Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2), while the certainty of evidence was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. Meta-analyses with a random-effects model were conducted.

Seventeen studies were included in this systematic review, encompassing 2710 participants. Meta-analyses demonstrated that PhA had a moderate positive correlation coefficient with SMD (4 studies, 924 participants; r = 0.54, 95 % confidence interval (CI) 0.38 to 0.69, heterogeneity (I2) = 92 %) and good accuracy (85 %) for classifying low SMD (2 studies, 390 participants; Area Under the Curve - AUCpooled 0.85, 95 % CI 0.78 to 0.92, I2 = 0 %). PhA was inversely-moderately correlated with muscle echogenicity (8 studies, 1401 participants; r = - 0.42, 95 % CI - 0.57 to - 0.24, I2 = 82 %) and positively-weakly correlated with MQI (2 studies, 191 participants; r = 0.36, 95 % CI 0.21 to 0.49, I2 = 17 %). All studies had a higher risk of bias. The certainty of evidence ranged from low to very low.

Despite technical challenges, this study demonstrates the potential of PhA as a surrogate marker for muscle quality, particularly expressing muscle composition (SMD). Future studies should utilize BIA with standardized protocols to potentially establish specific cutoff values for PhA, thereby enhancing its diagnostic accuracy and clinical applicability. These studies could additionally explore the mechanisms underlying the associations between PhA and muscle quality aspects. In cases where technical factors are not easily controlled, the use of standardized PhA (SPhA), which converts PhA into Z-scores, could be beneficial. Although this warrants investigation, this approach (SPhA) has the potential to account for variables such as age, sex, device differences, and health status.

Skeletal muscle echo intensity (EI) is affected by ageing and physical activity; however, the effects of nutrition are less understood. The aim of this study was to explore whether habitual nutrient intake may be associated with ultrasound-derived EI. Partial least squares regression (PLSR) models were trained on an initial sample (n = 100, M = 45; F = 55; 38 ± 15 years) to predict EI of two quadriceps muscles from 19 variables, using the "jack-knife" function within the "pls" package (RStudio), which was then tested in an additional dataset (n = 30, M = 13; F = 17; 38 ± 16 years). EI was determined using B-mode ultrasonography of the rectus femoris (RF) and vastus lateralis (VL) and nutritional intake determined via 3-day weighed food diaries. Mean daily intake of specific nutrients were included as predictor variables with age, sex, and self-reported physical activity. PLSR training model 1 explained ∼52% and model 2 ∼46% of the variance in RF and VL EI, respectively. Model 1 also explained ∼35% and model 2 ∼30% of the variance in RF and VL EI in the additional testing dataset. Age and biological sex were associated with EI in both models (P < 0.025). Dietary protein (RF: β = -7.617, VL: β = -7.480), and selenium (RF: β = -7.144, VL: β = -4.775) were associated with EI in both muscles (P < 0.05), whereas fibre intake (RF: β = -5.215) was associated with RF EI only and omega-3 fatty acids (n-3/ω-3 FAs, RF: β = 3.145) with VL EI only (P < 0.05). Therefore, absolute protein, selenium, fibre, and n-3 FAs may be associated with skeletal muscle EI, although further mechanistic work is required before claiming causal inference.

Individuals diagnosed with Chronic Obstructive Pulmonary Disease (COPD) are exposed to an increased risk of metabolic syndrome (MetS), which negatively affects their health outcomes and quality of life. Lifestyle interventions have shown promise in managing MetS. This study outlines the protocol for a web-based multimodal self-care program, Digital Metabolic Rehabilitation, for managing MetS in patients with COPD. The Digital Metabolic Rehabilitation is a single-arm pilot trial that integrates the Canadian Health Advanced by Nutrition and Graded Exercise (CHANGE) Program and a web-based wellness platform. The web-based wellness platform employed in this study is My Viva Plan (MVP)®, which integrates a holistic, multicomponent approach to promote wellness. The intervention will primarily focus on lifestyle changes for patients with COPD. Over 6 months, participants will use the web-based wellness platform and engage in weekly online support group sessions. Fifty patients diagnosed with stage I-II COPD and MetS will participate. Blood tests, anthropometrics, body composition, physical function, muscle strength, physical activity, energy metabolism, quality of life and mental health will be assessed at baseline, 3, and 6 months. The Digital Metabolic Rehabilitation program aims to explore whether a multimodal integrative intervention delivered through a web-based wellness platform can be implemented by patients with COPD with MetS. By combining the expertise of the CHANGE Program with the digital delivery format, the intervention seeks to enhance self-monitoring and foster better self-management practices. The protocol outlines a novel and potentially impactful intervention for managing MetS in patients with COPD.

Symptomatic heart failure (HF) negatively affects the quantity and quality of skeletal muscles. However, the association between asymptomatic HF and skeletal muscle function remains unclear. We aimed to use ultrasonography to elucidate the association between asymptomatic HF and skeletal muscle function in community-dwelling older adults.

This cross-sectional study comprised community-dwelling older adults aged ≥ 60 years who could perform activities of daily living independently and had never had symptomatic HF (n = 52, 76.3 ± 6.1 years). The participants were classified into three groups namely, non-HF (n = 26), stage A (n = 19), and stage B (n = 7) according to the HF stage criteria of the American Heart Association /American College of Cardiology /Heart Failure Society of America guideline. Skeletal muscle quantity and quality were assessed using ultrasonography (thickness and echo intensity) of the rectus femoris (RF) and vastus intermedius (VI) muscles. The group effects on muscle thickness and echo intensity in each group were assessed using a multivariate analysis.

Both muscles consistently demonstrated significant group effects on the thickness and echo intensity. Thicknesses of the RF (p = 0.020) and VI (p = 0.035) were lower in the stage B group than that in the non-HF group. The echo intensities in the RF (p = 0.006) and VI (p = 0.009) were higher in the stage B group than that in the non-HF group.

Asymptomatic HF negatively associated with the characteristics of skeletal muscle function, as assessed by ultrasonography in community-dwelling older adults. The stage B HF contributes to reduced skeletal muscle function as well as symptomatic HF.

Sarcopenia is a prevalent condition with significant clinical implications, and it is expected to escalate globally, demanding for effective diagnostic strategies, possibly at an early stage of the disease. Imaging techniques play a pivotal role in comprehensively evaluating sarcopenia, offering insights into both muscle quantity and quality. Among all the imaging techniques currently used for the diagnosis and follow up of sarcopenia, it is possible to distinguish two classes: Rx based techniques, using ionizing radiations, and non-invasive techniques, which are based on the use of safe and low risk diagnostic procedures. Dual-energy x-ray Absorptiometry and Computed Tomography, while widely utilized, entail radiation exposure concerns. Ultrasound imaging offers portability, real-time imaging, and absence of ionizing radiation, making it a promising tool Magnetic Resonance Imaging, particularly T1-weighted and Dixon sequences, provides cross- sectional and high-resolution images and fat-water separation capabilities, facilitating precise sarcopenia quantification. Bioelectrical Impedance Analysis (BIA), a non-invasive technique, estimates body composition, including muscle mass, albeit influenced by hydration status. Standardized protocols, such as those proposed by the Sarcopenia through Ultrasound (SARCUS) Working Group, are imperative for ensuring consistency across assessments. Future research should focus on refining these techniques and harnessing the potential of radiomics and artificial intelligence to enhance diagnostic accuracy and prognostic capabilities in sarcopenia.

In Streptococcus pyogenes, the type II fatty acid (FA) synthesis pathway FASII is feedback-controlled by the FabT repressor bound to an acyl-Acyl carrier protein. Although FabT defects confer reduced virulence in animal models, spontaneous fabT mutants arise in vivo. We resolved this paradox by characterizing the conditions and mechanisms requiring FabT activity, and those promoting fabT mutant emergence. The fabT defect leads to energy dissipation, limiting mutant growth on human tissue products, which explains the FabT requirement during infection. Conversely, emerging fabT mutants show superior growth in biotopes rich in saturated FAs, where continued FASII activity limits their incorporation. We propose that membrane alterations and continued FASII synthesis are the primary causes for increased fabT mutant mortality in nutrient-limited biotopes, by failing to stop metabolic consumption. Our findings elucidate the rationale for emerging fabT mutants that improve bacterial survival in lipid-rich biotopes, but lead to a genetic impasse for infection.

Age-induced inflexibility may lead to significant mobility impairments and declines in well-being. However, the relationship between the structural and mechanical properties of soft tissue and joint extensibility remains unclear. This study aimed to investigate the correlation between flexibility, muscle tendon unit (MTU) stiffness, muscle ultrasound characteristics, muscle strength, and hamstring flexibility prediction in older males with hamstring inflexibility.

A hundred retired old males (mean age: 67.2 ± 4.9 years) participated in this investigation. Muscle ultrasound, flexibility, MTU stiffness, and knee flexors strength were measured in a single visit.

The results revealed a modest correlation between straight leg raise (SLR) and biceps femoris fascicle length (FL) elongation (r = 0.222), MTU stiffness (r = -0.401), and eccentric strength (r = 0.219) (all p < 0.05). MTU stiffness, eccentric strength, and FL elongation collectively explained 24.8% of the variance in SLR prediction, while deep fascia thickness predicted MTU stiffness with a variance of 6.4%.

In summary, increased SLR was associated with lower MTU stiffness, lengthened FL, and higher eccentric strength. SLR was primarily predicted by MTU stiffness, with lesser contributions from FL elongation and knee flexor eccentric strength in older males experiencing hamstring tightness.

Malnutrition and physical function impairment are prevalent concerns in long-term care facilities. This study investigated the relationship between quadriceps muscle thickness (QMT) or echo intensity (QEI), nutritional status, and activities of daily living (ADL) in residents of an Integrated Facility for Medical and Long-term Care (IFMLC) in Japan.

Using a cross-sectional design, 126 residents (86 women, median age 89 years) at an IFMLC were assessed. Malnutrition was diagnosed using the Global Leadership Initiative on Malnutrition (GLIM) criteria including disease burden/inflammation, while ADL status was evaluated using the Barthel Index (BI). QMT and QEI, indicative of muscle mass and intramuscular adipose tissue, were measured by ultrasound. Multivariate logistic and linear regression analyses were conducted to explore the association of QMT or QEI with malnutrition and ADL.

62 residents (49%) were in the lower QMT group and 63 residents (50%) were in the upper QEI group. The prevalence of severe malnutrition in the lower QMT group was significantly higher than that in the upper QMT group. Moreover, the lower QMT group had significantly lower BI points than the upper QMT group. The upper QEI group had significantly lower BI points than the lower QEI group. lower QMT was associated with severe malnutrition (odds ratio 3.170; 95% CI 1.238 to 8.725; P = 0.016). Furthermore, both lower QMT (B = -12.520; 95% CI -17.069 to -7.973; P < 0.001) and upper QEI (B = -7.598; 95% CI -12.565 to -2.631; P = 0.003) showed an independent correlation with lower BI scores.

This study found a relationship between lower QMT correlated with severe malnutrition and poor ADL, while higher QEI is associated with poor ADL.

The diagnostic criteria for respiratory sarcopenia have been recently reported. However, no studies have clarified the characteristics of skeletal muscle impairment of the limbs in subjects with respiratory sarcopenia. This study aimed to explore the factors, including skeletal muscle, associated with probable respiratory sarcopenia in elderly subjects.

Subjects were classified into the probable respiratory sarcopenia group and nonrespiratory sarcopenia group. Probable respiratory sarcopenia was defined as the concurrent presence of respiratory muscle weakness (as less than the predicted value calculated from age, sex, and height) and low skeletal muscle mass (<7.0 kg/m2 in males and 5.7 kg/m2 in females). The following factors were measured: respiratory muscle strength, skeletal muscle mass index, muscle thickness and echo intensity of the rectus femoris, extracellular-to-intracellular water ratio, hand grip strength, 5 sit-to-stand, knee extension strength, bone mineral density, age, sex, body mass index, degree of frailty, presence or absence of medical history, presence or absence of habitual exercise, period of time since the start of exercise, and number of hours of exercise at a time. The association subjects with probable respiratory sarcopenia were analyzed using hierarchical logistic regression analysis.

Twenty-six with probable respiratory sarcopenia and 54 with nonrespiratory sarcopenia were included. Hierarchical logistic regression analysis revealed that echo intensity was a significant predictor of probable respiratory sarcopenia. The odds ratio for echo intensity was 2.54 (95% confidence interval: 1.04-6.23).

Our results suggest that a decrease in muscle quality in the lower extremity is associated with probable respiratory sarcopenia.

To assess intrarater reliability of ultrasound-determined measurements of skeletal muscle characteristics across different measurement outcomes, imaging techniques, and age groups.

2D ultrasound images (B-mode) of the quadriceps were obtained from young (26 ± 4 year, n = 8 M, 8 F) and older (70 ± 7 year, n = 7 M, 5 F) adults on two occasions, separated by 6 ± 3 days. With participants in both standing and supine postures, images were collected from five anatomical sites along the anterior (two sites) and lateral (three sites) compartments of the thigh corresponding to 56%, 39%, and 22% (lateral only) of femur length. Images were analysed for muscle thickness, pennation angle, and echogenicity. Intraclass correlation coefficients (ICC) were used to assess reliability.

Muscle thickness values were higher (p < 0.05) on images collected in the stand versus supine posture only for muscles of the anterior compartment, independent of age. Echogenicity values were higher (p < 0.05) in the vastus intermedius on images collected in the supine versus stand posture only in older adults. Pennation angle values were not impacted by imaging posture (p > 0.05). ICC values for thickness, echogenicity, and pennation angle were generally higher for analyses conducted on images collected in the supine versus stand posture. Imaging posture generated a greater difference in ICC values in the lateral versus anterior muscles and in older versus younger participants.

Our findings suggest that participant posture during imaging impacts the absolute values and intrarater reliability of ultrasound-determined muscle characteristics in a muscle-specific fashion, and this effect is greater in older compared to younger individuals.

Skeletal muscle dysfunction is common in chronic kidney disease (CKD). Of interest is the concept of "muscle quality," of which measures include ultrasound-derived echo intensity (EI). Alternative parameters of muscle texture, for example, gray level of co-occurrence matrix (GCLM), are available and may circumvent limitations in EI. The validity of EI is limited in humans, particularly in chronic diseases. This study aimed to investigate the associations between ultrasound-derived parameters of muscle texture with MRI. Images of the thigh were acquired using a 3 Tesla MRI scanner. Quantification of muscle (contractile), fat (non-contractile), and miscellaneous (connective tissue, fascia) components were estimated. Anatomical rectus femoris cross-sectional area was measured using B-mode 2D ultrasonography. To assess muscle texture, first (i.e., EI)- and second (i.e., GLCM)-order statistical analyses were performed. Fourteen participants with CKD were included (age: 58.0 ± 11.9 years, 50% male, eGFR: 27.0 ± 7.4 ml/min/1.73m2, 55% Stage 4). Higher EI was associated with lower muscle % (quadriceps: β = -.568, p = .034; hamstrings: β = -.644, p = .010). Higher EI was associated with a higher fat % in the hamstrings (β = -.626, p = .017). A higher angular second moment from GLCM analysis was associated with greater muscle % (β = .570, p = .033) and lower fat % (β = -.534, p = .049). A higher inverse difference moment was associated with greater muscle % (β = .610, p = .021 and lower fat % (β = -.599, p = .024). This is the first study to investigate the associations between ultrasound-derived parameters of muscle texture with MRI. Our preliminary findings suggest ultrasound-derived texture analysis provides a novel indicator of reduced skeletal muscle % and thus increased intramuscular fat.

Our study aims to evaluate differences in muscle parameters of the quadriceps muscles in patients with knee osteoarthritis (KOA) in older adults.

The study included 40 patients diagnosed with unilateral knee osteoarthritis in the KOA group (KG) and 40 asymptomatic elderly individuals in the control group (CG). Muscle ultrasonic mean echo intensity and shear modulus, as well as tone and stiffness of the rectus femoris (RF), vastus medialis (VM), and vastus lateralis (VL) were analyzed. Additionally, clinical correlations were performed.

In the KG group, there were significant differences in echo intensity, shear modulus, and tone between the affected and unaffected sides for RF (p=0.003, 0.019, 0.014), while VM showed significant differences in shear modulus and tone (p=0.006, 0.002). Additionally, VL exhibited significant differences in echo intensity, shear modulus, and stiffness (p=0.007, 0.006, 0.010). Compared to the CG group, the KG group showed significant differences in echo intensity of the affected side RF (p=0.001). VM exhibited statistically significant differences in echo intensity and shear modulus (p < 0.001, p=0.008), while VL showed statistically significant differences in echo intensity, tone, and stiffness (p < 0.001, p=0.028, p < 0.001). The correlation results showed that patients with unilateral KOA, VM, and VL echo intensity were correlated with K-L grade (r = 0.443, p=0.004; r = 0.469, p=0.002). The tone of VL was correlated with VAS and WOMAC (r = 0.327, p=0.039; r = 0.344, p=0.030).

The parameters of the quadriceps femoris muscle exhibit asymmetry between the affected and unaffected sides in patients with unilateral KOA, as well as a difference between the dominant side of healthy older individuals and the affected side of KOA.

Background: Sarcopenia has been recognized as a determining factor in surgical outcomes and is associated with an increased risk of postoperative complications and readmission. Diagnosis is currently based on clinical guidelines, which includes assessment of skeletal muscle mass but not quality. Ultrasound has been proposed as a useful point-of-care diagnostic tool to assess muscle quality, but no validated cut-offs for sarcopenia have been reported. Using novel automated artificial intelligence (AI) software to interpret ultrasound images may assist in mitigating the operator-dependent nature of the modality. Our study aims to evaluate the fidelity of AI-aided ultrasound as a reliable and reproducible modality to assess muscle quality and diagnose sarcopenia in surgical patients. Methods: Thirty-six adult participants from an outpatient clinic were recruited for this prospective cohort study. Sarcopenia was diagnosed according to Asian Working Group for Sarcopenia (AWGS) 2019 guidelines. Ultrasonography of the rectus femoris muscle was performed, and images were analyzed by an AI software (MuscleSound® (Version 5.69.0)) to derive muscle parameters including intramuscular adipose tissue (IMAT) as a proxy of muscle quality. A receiver operative characteristic (ROC) curve was used to assess the predictive capability of IMAT and its derivatives, with area under the curve (AUC) as a measure of overall diagnostic accuracy. To evaluate consistency between ultrasound users of different experience, intra- and inter-rater reliability of muscle ultrasound parameters was analyzed in a separate cohort using intraclass correlation coefficients (ICC) and Bland-Altman plots. Results: The median age was 69.5 years (range: 26-87), and the prevalence of sarcopenia in the cohort was 30.6%. The ROC curve plotted with IMAT index (IMAT% divided by muscle area) yielded an AUC of 0.727 (95% CI: 0.551-0.904). An optimal cut-off point of 4.827%/cm2 for IMAT index was determined with a Youden's Index of 0.498. We also demonstrated that IMAT index has excellent intra-rater reliability (ICC = 0.938, CI: 0.905-0.961) and good inter-rater reliability (ICC = 0.776, CI: 0.627-0.866). In Bland-Altman plots, the limits of agreement were from -1.489 to 1.566 and -2.107 to 4.562, respectively. Discussion: IMAT index obtained via ultrasound has the potential to act as a point-of-care evaluation for sarcopenia screening and diagnosis, with good intra- and inter-rater reliability. The proposed IMAT index cut-off maximizes sensitivity for case finding, supporting its use as an easily implementable point-of-care test in the community for sarcopenia screening. Further research incorporating other ultrasound parameters of muscle quality may provide the basis for a more robust diagnostic tool to help predict surgical risk and outcomes.

Skeletal muscle is the largest organ system in the human body and plays critical roles in athletic performance, mobility, and disease pathogenesis. Despite growing recognition of its importance by major health organizations, significant knowledge gaps remain regarding skeletal muscle health and its crosstalk with nearly every physiological system. Relevant public health challenges like pain, injury, obesity, and sarcopenia underscore the need to accurately assess skeletal muscle health and function. Feasible, non-invasive techniques that reliably evaluate metrics including muscle pain, dynamic structure, contractility, circulatory function, body composition, and emerging biomarkers are imperative to unraveling the complexities of skeletal muscle. Our concise review highlights innovative or overlooked approaches for comprehensively assessing skeletal muscle in vivo. We summarize recent advances in leveraging dynamic ultrasound imaging, muscle echogenicity, tensiomyography, blood flow restriction protocols, molecular techniques, body composition, and pain assessments to gain novel insight into muscle physiology from cellular to whole-body perspectives. Continued development of precise, non-invasive tools to investigate skeletal muscle are critical in informing impactful discoveries in exercise and rehabilitation science.

This study investigated reliability and validity of muscle cross-sectional area and echo intensity using an automatic image analysis program.

Twenty-two participants completed two data collection trials consisting of ultrasound imaging of the vastus lateralis (VL) at 10 and 12 MHz. Images were analyzed manually and with Deep Anatomical Cross-Sectional Area (DeepACSA). Reliability statistics (i.e., intraclass correlation coefficient [ICC] model 2,1, standard error of measure expressed as a percentage of the mean [SEM%], minimal differences [MD] values needed to be considered real) and validity statistics (i.e., constant error [CE], total error [TE], standard error of the estimate [SEE]) were calculated.

Automatic analyses of ACSA and EI demonstrated good reliability (10 MHz: ICC2,1 = 0.83 - 0.90; 12 MHz: ICC2,1 = 0.87-0.88), while manual analyses demonstrated moderate to excellent reliability (10 MHz: ICC2,1 = 0.82-0.99; 12 MHz: ICC2,1 = 0.73-0.99). Automatic analyses of ACSA presented greater error at 10 (CE = -0.76 cm2, TE = 4.94 cm2, SEE = 3.65 cm2) than 12 MHz (CE = 0.17 cm2, TE = 3.44 cm2, SEE = 3.11 cm2). Analyses of EI presented greater error at 10 (CE = 3.35 a.u., TE = 2.70 a.u., SEE = 2.58 a.u.) than at 12 MHz (CE = 3.21 a.u., TE = 2.61 a.u., SEE = 2.34 a.u.).

The results suggest the DeepACSA program may be less reliable compared to manual analysis for VL ACSA but displayed similar reliability for EI. In addition, the results demonstrated the automatic program had low error for 10 and 12 MHz.

Knee osteoarthritis (OA) is a leading cause of chronic pain in adults and shows wide interindividual variability, with peripheral and central factors contributing to the pain experience. Periarticular factors, such as muscle quality (eg, echo intensity [EI] and shear wave velocity [SWV]), may contribute to knee OA pain; however, the role of muscle quality in OA symptoms has yet to be fully established.

Twenty-six adults (age >50 years) meeting clinical criteria for knee OA were included in this cross-sectional study. Quantitative ultrasound imaging was used to quantify EI and SWV in the rectus femoris of the index leg. Pearson correlations followed by multiple linear regression was used to determine associations between muscle quality and pain, controlling for strength, age, sex, and body mass index.

EI and SWV were significantly associated with movement-evoked pain (b = 0.452-0.839, P = 0.024-0.029). Clinical pain intensity was significantly associated with SWV (b = 0.45, P = 0.034), as were pressure pain thresholds at the medial (b = -0.41, P = 0.025) and lateral (b = -0.54, P = 0.009) index knee joint line, adjusting for all covariates. Pain interference was significantly associated with knee extension strength (b = -0.51, P = 0.041).

These preliminary findings suggest that EI and SWV may impact knee OA pain and could serve as malleable treatment targets. Findings also demonstrate that muscle quality is a unique construct, distinct from muscle strength, which may impact pain and treatment outcomes. More research is needed to fully understand the role of muscle quality in knee OA.

Fatty infiltration (FI) of the rotator cuff has important clinical implications. Quantitatively estimating FI using ultrasound (US) has considerable benefits for assessing FI in a non-invasive, accessible manner. This research investigated whether FI of the supraspinatus (SS) and infraspinatus (IS), estimated using US was related to intramuscular fat fractions measured from magnetic resonance images (MRI).

Data from 12 healthy young adult participants were used for analysis. US images of the SS and IS were captured using multiple transducer placement techniques from which echogenicity of the muscle region was quantified. Shoulder MRI were captured from which SS and IS were manually segmented and intramuscular fat fractions calculated. Six upper limb strength exertions were performed, resisted by a hand dynamometer.

IS and SS echogenicity explained a significant amount of variance in MRI fat fractions for certain body positions and transducer techniques. Echogenicity agreement was higher for IS than SS. Significant relationships were identified between strength exertions and both echogenicity and MRI muscle volume, but not MRI fat fraction.

This research provides preliminary evidence showing that quantitative-based US methods can be used to estimate MRI calculated fat fractions for the rotator cuff.