Vastus Lateralis Thickness Research Articles

Validation of Ultrasound Measurement of Vastus Lateralis for Appendicular Skeletal Muscle Mass in Chronic Kidney Disease Patients with Hemodialysis.

Chronic kidney disease patients undergoing hemodialysis (HD) are at a high risk of developing sarcopenia. This study aimed to validate the performance of ultrasound (US) measurements of the vastus lateralis (VL) for estimating muscle mass and diagnosing sarcopenia in CKD patients with HD. Forty-six patients were enrolled in this study. Muscle thickness (MT) and echo intensity (EI) of VL, physical performance, and biochemical markers were collected to establish a linear regression model for predicting appendicular skeletal muscle mass (ASM), using dual-energy X-ray absorptiometry (DXA) as the reference standard. The model's performance was validated, and its diagnostic accuracy for sarcopenia was also evaluated. An ASM prediction model was derived: -20.17 + 1.90 × MT_VL (cm) + 1.58 × male + 0.16 × Height (cm) + 0.09 × Weight (kg) + 0.05 × Age (year), with a standard estimated error of 1.44 kg and adjusted R-squared of 0.84. The model exhibited high correlation and an acceptable limit of agreement, compared to DXA measurement. EI displayed a negative correlation with ASM and MT. The ASM adjusted with BMI demonstrated superior performance in diagnosing sarcopenia compared to the ASM adjusted with height. Ultrasound provides a cost-effective bedside tool for evaluating muscle conditions in HD patients.

Effects of horizontally versus vertically loaded resistance exercises on performance and muscle architecture.

The aim of this study was to compare a training program based on horizontally (HT) versus vertically (VT) loaded exercises on performance and muscle architecture of the lower body muscles. Nineteen resistance trained individuals were randomly assigned to HT (N.=10; age: 25.9±4.2 y; body mass: 72.7±11.4 kg; height: 174.0±6.0 cm) or VT group (N.=9; age: 26.9±4.4 y; body mass: 76.2±10.8 kg; height: 174.2.0±5.8 cm). Both 6-week training programs included 4 training sessions per week and were equated for the total number of repetitions. One repetition maximum (1RM) was assessed for squat and hip thrust, together with vertical and horizontal jumps and sprint. Muscle thickness (MT) and echo intensity (EI) of vastus lateralis, vastus medialis and gluteus were also evaluated pre- and post-training period. A significantly greater increase in 1RM hip thrust was detected in HT (+17.9%; P=0.004) while greater increases in 1RM squat were found in VT (+10.5%; P=0.007). A greater increase (P=0.009) in vastus medialis MT was detected in VT (4.1%) compared to HT (-7.9%). Similar increases in MT of gluteus were registered in both groups (P<0.05). A greater improvement in standing long jump (P=0.004) was detected in HT (+7.6%) compared to VT (+1.6%), while both groups significantly improved vertical jump performance. Combining both groups, strong correlations were detected between gluteus EI and 20-m sprint (r=0.79; P<0.001). Results indicate that HT was more effective than VT for horizontal jumps while both HT and VT were equally effective on vertical jumps. Both HT and VT promoted similar changes in muscle architecture of the gluteus, but not of the vastus medialis.

Quadriceps Architectural Adaptations in Team Sports Players: A Meta-analysis.

Resistance training is the most effective strategy to modify muscle architecture, enhancing sport performance and reducing injury risk. The aim of this study was to compare the effects of high loads (HL) versus lower loads (LL), maximal versus submaximal efforts, and high frequency (HF) versus low frequency (LF) on quadriceps architectural adaptations in team sports players. Five databases were searched. Vastus lateralis thickness, fascicle length and pennation angle, and rectus femoris thickness were analyzed as main outcomes. Overall, resistance training significantly improved muscle thickness and pennation angle, but not fascicle length. LL led to greater fascicle length adaptations in the vastus lateralis compared to HL (p=0.01), while no substantial differences were found for other load comparisons. Degree of effort and training frequency did not show meaningful differences (p>0.05). In conclusion, LL lengthen the fascicle to a greater extent than HL, and training with LL twice a week could maximize architectural adaptations, whereas the degree of effort does not appear to be a determinant variable on quadriceps architectural adaptations.

Relative rDNA copy number is not associated with resistance training-induced skeletal muscle hypertrophy and does not affect myotube anabolism in vitro.

Ribosomal DNA (rDNA) copies exist across multiple chromosomes and inter-individual variation in copy number is speculated to influence the hypertrophic response to resistance training. Thus, we examined if rDNA copy number was associated with resistance training-induced skeletal muscle hypertrophy. Participants (n=53 males, 21±1 years old; n=29 females, 21±2 years old) performed 10-12 weeks of full-body resistance training. Hypertrophy outcomes were determined, as was relative rDNA copy number from pre-intervention vastus lateralis (VL) biopsies. Pre- and post-intervention VL biopsy total RNA was assayed in all participants, and mRNA/rRNA markers of ribosome content and biogenesis were also assayed in the 29 females prior to training, 24 hours following training bout 1, and in the basal state after 10 weeks of training. Across all participants, no significant associations were evident between relative rDNA copy number and training-induced changes in whole body lean mass (r = -0.034, p=0.764), vastus lateralis thickness (r = 0.093, p=0.408), mean myofiber cross-sectional area (r = -0.128, p=0.259), or changes in muscle RNA concentrations (r = 0.026, p=0.818), and these trends were similar when examining each gender. However, all Pol-I regulon mRNAs as well as 45S pre-rRNA, 28S rRNA and 18S rRNA increased 24 hours following the first training bout in females. Follow-up studies using LHCN-M2 myotubes demonstrated a reduction in relative rDNA copy number induced by bisphenol A (BPA) did not significantly affect insulin-like-growth factor-induced myotube hypertrophy. These findings suggest relative rDNA copy number is not associated with myofiber hypertrophy.

Different roles of circulating and intramuscular GDF15 as markers of skeletal muscle health.

Growth Differentiation Factor 15 (GDF15) is a mitokine expressed in response to various stresses whose circulating levels increase with age and are associated with numerous pathological conditions, including muscle wasting and sarcopenia. However, the use of circulating GDF15 (c-GDF15) as a biomarker of sarcopenia is still debated. Moreover, the role of GDF15 intracellular precursor, pro-GDF15, in human skeletal muscle (SM-GDF15) is not totally understood. In order to clarify these points, the association of both forms of GDF15 with parameters of muscle strength, body composition, metabolism and inflammation was investigated. the levels of c-GDF15 and SM-GDF15 were evaluated in plasma and muscle biopsies, respectively, of healthy subjects (HS) and patients with lower limb mobility impairment (LLMI), either young (<40 years-old) or old (>70 years-old). Other parameters included in the analysis were Isometric Quadriceps Strength (IQS), BMI, lean and fat mass percentage, Vastus lateralis thickness, as well as circulating levels of Adiponectin, Leptin, Resistin, IGF-1, Insulin, IL6, IL15 and c-PLIN2. Principal Component Analysis (PCA), Canonical Discriminant Analysis (CDA) and Receiving Operating Characteristics (ROC) analysis were performed. c-GDF15 but not SM-GDF15 levels resulted associated with decreased IQS and IGF-1 levels in both HS and LLMI, while only in LLMI associated with increased levels of Resistin. Moreover, in LLMI both c-GDF15 and SM-GDF15 levels were associated with IL-6 levels, but interestingly SM-GDF15 is lower in LLMI with respect to HS. Furthermore, a discrimination of the four groups of subjects based on these parameters was possible with PCA and CDA. In particular HS, LLMI over 70 years or under 40 years of age were discriminated based on SM-GDF15, c-GDF15 and Insulin levels, respectively. our data support the idea that c-GDF15 level could be used as a biomarker of decreased muscle mass and strength. Moreover, it is suggested that c-GDF15 has a different diagnostic significance with respect to SM-GDF15, which is likely linked to a healthy and active state.

Pumping up the Fight against Multiple Sclerosis: The Effects of High-Intensity Resistance Training on Functional Capacity, Muscle Mass, and Axonal Damage.

Resistance training (RT) has been recognized as a beneficial non-pharmacological intervention for multiple sclerosis (MS) patients, but its impact on neurodegeneration is not fully understood. This study aimed to investigate the effects of high-intensity RT on muscle mass, strength, functional capacity, and axonal damage in MS patients. Eleven relapsing-remitting MS patients volunteered in this within-subject counterbalanced intervention study. Serum neurofilament light-chain (NfL) concentration, vastus lateralis thickness (VL), timed up-and-go test (TUG), sit-to-stand test (60STS), and maximal voluntary isometric contraction (MVIC) were measured before and after intervention. Participants performed 18 sessions of high-intensity RT (70-80% 1-RM) over 6 weeks. Significant (p < 0.05) differences were observed post-intervention for VL (ES = 2.15), TUG (ES = 1.98), 60STS (ES = 1.70), MVIC (ES = 1.78), and NfL (ES = 1.43). Although moderate correlations between changes in VL (R = 0.434), TUG (R = -0.536), and MVIC (R = 0.477) and changes in NfL were observed, only the correlation between VL and MVIC changes was significant (R = 0.684, p = 0.029). A 6-week RT program significantly increased muscle mass, functional capacity, and neuromuscular function while also decreasing serum NfL in MS patients. These results suggest the effectiveness of RT as a non-pharmacological approach to mitigate neurodegeneration while improving functional capacity in MS patients.

Lower limb muscles’ thicknesses are weakly associated with dynamic knee valgus during single-leg squat in women with patellofemoral pain

IntroductionPatellofemoral pain (PFP) patients often show an altered lower limb alignment during the single-leg squat (SLS). There is evidence that proximal and distal-to-the-knee muscle alterations can modify the lower limb alignment in PFP patients. However, we observed a lack of studies investigating the possible association between the thickness and strength of proximal and distal-to-the-knee muscles and lower limb alignment during SLS in women with PFP. Therefore, this study aimed to investigate the association between the thickness and strength of lower limb muscles and dynamic knee valgus (DKV) during SLS in women with PFP. MethodsCross-sectional study, where fifty-five women with PFP were submitted to the following evaluations: (1) muscle thickness (MT) of Gluteus Medius (GMed), Gluteus Maximus (GMax), Vastus Lateralis (VL), and Tibialis Anterior (TA); (2) isometric peak torque of hip abductors, hip external rotators, knee extensors, and foot inversors; and (3) DKV during SLS. ResultsThere was a significant negative association between GMax's MT and DKV (r = −0.32; p = 0.01), and between TA's MT and DKV (r = −0.28; p = 0.03). No significant correlations were observed between isometric torques and DKV. Regression analysis found that GMax's MT explained 10% of the DKV's variance during SLS. DiscussionPoor lower limb alignment during SLS is weakly associated with proximal and distal-to-the-knee muscle thicknesses, with no association with isometric torque in PFP women. ConclusionOur results suggest that other factors besides strength and muscle thicknesses may explain and improve lower limb alignment in women with PFP.

Similar muscle hypertrophy following eight weeks of resistance training to momentary muscular failure or with repetitions-in-reserve in resistance-trained individuals

ABSTRACT This study examined the influence of resistance training (RT) proximity-to-failure, determined by repetitions-in-reserve (RIR), on quadriceps hypertrophy and neuromuscular fatigue. Resistance-trained males (n = 12) and females (n = 6) completed an 8-week intervention involving two RT sessions per week. Lower limbs were randomised to perform the leg press and leg extension exercises either to i) momentary muscular failure (FAIL), or ii) a perceived 2-RIR and 1-RIR, respectively (RIR). Muscle thickness of the quadriceps [rectus femoris (RF) and vastus lateralis (VL)] and acute neuromuscular fatigue (i.e., repetition and lifting velocity loss) were assessed. Data was analysed with Bayesian linear mixed-effect models. Increases in quadriceps thickness (average of RF and VL) from pre- to post-intervention were similar for FAIL [0.181 cm (HDI: 0.119 to 0.243)] and RIR [0.182 cm (HDI: 0.115 to 0.247)]. Between-protocol differences in RF thickness slightly favoured RIR [−0.036 cm (HDI: −0.113 to 0.047)], but VL thickness slightly favoured FAIL [0.033 cm (HDI: −0.046 to 0.116)]. Mean volume was similar across the RT intervention between FAIL and RIR. Lifting velocity and repetition loss were consistently greater for FAIL versus RIR, with the magnitude of difference influenced by the exercise and the stage of the RT intervention.

Changes in Lower Extremity Muscle Quantity and Quality in Patients with Subacute Stroke.

To analyze the changes in muscle mass and quality with time on the paretic and non-paretic sides in subacute stroke patients and identify correlations between the variation of muscle mass and quality and lower limb functions. Thirty hemiplegia patients diagnosed with stroke participated in this study. To evaluate poststroke muscle changes, longitudinal measurement of muscle mass and quality was conducted with bilateral lower limbs. The elastic shear modulus was measured using shear wave elastography and muscle thickness (MT) of rectus femoris, vastus intermedius, vastus lateralis (VL), vastus medialis, tibialis anterior, and gastrocnemius (GCM) muscles. Functional evaluation was performed using Berg Balance Scale (BBS), Five Times Sit to Stand Test (FTSST). Follow-up was performed at discharge. The muscle mass and quality were compared according to time. We analyzed whether muscle quantity and quality were related to function. MT demonstrated no significant change with time. The elastic shear modulus increased significantly in the paretic VL and GCM muscles and did not change significantly in the muscles on the non-paretic side. Correlation analysis detected that elastic shear modulus in the VL has a cross-sectional negative relationship between BBS and positive relationship between FTSST. There were significant correlation between variation of FTSST and the variation of the elastic shear modulus in VL. Only paretic VL and GCM muscle quality changed in subacute stroke patients and muscle's property related to lower limb functions. Therefore, the lower extremity requires an approach to muscle quality rather than quantity for subacute stroke patients.

Influences of Sex on Muscle Architecture and Performance in Elite Field Hockey Players

The aim of this study was to compare muscle architecture and performance between male and female elite Field Hockey players and to investigate the relationships between echo intensity and performance. Twenty-one male (24.3 ± 3.6 y; 75.1 ± 8.5 kg; 176.8 ± 6.4 cm) and nineteen female players (27.4 ± 3.9 y; 61.2 ± 7.4 kg; 164.4 ± 4.9 cm) were tested for muscle thickness (MT) and echo intensity (EI) of trapezius (Trap) and vastus lateralis (VL) muscles. Participants were also assessed for bench press power, and 30 m sprint. Results showed a higher VLMT and TrapMT in male players compared to female players (+22.1%; p = 0.004 and +25.8%; p = 0.001 for VLMT and TrapMT, respectively). A lower VLEI was detected in male players compared to female players (−20.7%; p = 0.001), while no significant differences were detected for TrapEI. Male players were faster than female players in a 30 m sprint and more powerful at the bench press (p &lt; 0.001). Significant correlations were detected between VLEI and 30 m sprint (r = 0.74) in female players only. Results indicate that differences exist between male and female elite Field Hockey players in the EI of lower body muscles, while these differences are not present in the upper body muscles. EI, together with other sprint and power assessments, may represent an important parameter for elite Field Hockey players.

Resistance training diminishes mitochondrial adaptations to subsequent endurance training in healthy untrained men.

We investigated the effects of performing a period of resistance training (RT) on the performance and molecular adaptations to a subsequent period of endurance training (ET). Twenty-five young adults were divided into an RT+ET group (n=13), which underwent 7weeks of RT followed by 7weeks of ET, and an ET-only group (n=12), which performed 7weeks of ET. Body composition, endurance performance and muscle biopsies were collected before RT (T1, baseline for RT+ET), before ET (T2, after RT for RT+ET and baseline for ET) and after ET (T3). Immunohistochemistry was performed to determine fibre cross-sectional area (fCSA), myonuclear content, myonuclear domain size, satellite cell number and mitochondrial content. Western blots were used to quantify markers of mitochondrial remodelling. Citrate synthase activity and markers of ribosome content were also investigated. RT improved body composition and strength, increased vastus lateralis thickness, mixed and type II fCSA, myonuclear number, markers of ribosome content, and satellite cell content (P<0.050). In response to ET, both groups similarly decreased body fat percentage (P<0.0001) and improved endurance performance (e.g. , and speed at which the onset of blood lactate accumulation occurred, P<0.0001). Levels of mitochondrial complexes I-IV in the ET-only group increased 32-66%, while those in the RT+ET group increased 1-11% (time, P<0.050). Additionally, mixed fibre relative mitochondrial content increased 15% in the ET-only group but decreased 13% in the RT+ET group (interaction, P=0.043). In conclusion, RT performed prior to ET had no additional benefits to ET adaptations. Moreover, prior RT seemed to impair mitochondrial adaptations to ET. KEY POINTS: Resistance training is largely underappreciated as a method to improve endurance performance, despite reports showing it may improve mitochondrial function. Although several concurrent training studies are available, in this study we investigated the effects of performing a period of resistance training on the performance and molecular adaptations to subsequent endurance training. Prior resistance training did not improve endurance performance and impaired most mitochondrial adaptations to subsequent endurance training, but this effect may have been a result of detraining from resistance training.

Ultrasonography of Knee Muscles During SLR With Different Positions of Hip and Ankle in Patellofemoral Pain Syndrome

Objective Due to the substantial prevalence of patellofemoral pain syndrome and the importance of quadriceps strengthening in knee rehabilitation, determining the best way to activate and strengthen the patella stabilizing muscles is considered as one of important keys of treatment. The aim of this study is to evaluate the effect of different hip rotations associated with ankle dorsiflexion during maximal straight leg raising (SLR) maneuver in the sitting position on thickness and fibers angle of vastus medialis oblique (VMO) and vastus lateralis (VL) muscles using ultrasonography. Materials &amp; Methods This quasi-experimental study was performed on 40 individuals (healthy group: 20, patellofemoral pain syndrome [PFPS] group: 20). VMO and VL thickness and fiber angle were measured using ultrasonography during maximal SLR in 6 positions: hip internal, hip external, and neutral rotations with and without ankle dorsiflexion. Results In between-group comparison, no significant difference was found for all variables with different SLR maneuvers (P&gt;0.05). In the within-group comparison, hip external rotation compared to other hip positions without ankle dorsiflexion resulted in a significant increase in VMO thickness and fiber angle in both groups (P&lt;0.05). Also, adding ankle dorsiflexion to different hip rotations during SLR significantly increased the thickness and fiber angle of VMO and VL. Conclusion By changing hip rotations with or without ankle dorsiflexion during SLR, the trend of changes in VMO and VL thickness and fiber angle in the two groups followed the same pattern. Moreover, performing SLR in hip external rotation with ankle dorsiflexion can be recommendable for the rehabilitation of PFPS.

Comparison of the asymmetries in muscle mass, biomechanical property and muscle activation asymmetry of quadriceps femoris between patients with unilateral and bilateral knee osteoarthritis.

Background: More and more attention has been paid to the research of muscle mass and muscle quality of quadriceps femoris (QF) in knee osteoarthritis (KOA). This study aimed to explore the asymmetric changes of muscle mass, biomechanical property and muscle activation in the inter-limbs QF of KOA patients, and tried to provide a novel insight for the evaluation, prevention and treatment of KOA. Methods: A total of 56 Participants with unilateral or bilateral KOA were included in this study: 30 patients with unilateral pain and 26 patients with bilateral pain were assigned to the bilateral group (BG) and unilateral group (UG), respectively. The symptom severity of bilateral lower limbs was evaluated by visual analogue scale, and the relatively serious leg (RSL) and relatively moderate leg (RML) were classified. The thickness of rectus femoris (RF), vastus intermedius (VI), vastus medialis (VM) and vastus lateralis (VL) were measured by ultrasound. The Shear wave elastography (SWE) techniqie was used to measure the shear modulus of RF, VM and VL. Surface electromyography (sEMG) was used to assess the root mean square (RMS) of the RF, VM, and VL during straight leg raising in a sitting position and squatting task. We calculated the asymmetry indexes of inter-limbs for the corresponding indices of the measured muscles. Result: Thickness of RF, VI and VL of RSL was lower than those on RML (p < 0.05), and thickness of VM was lower more significant (p < 0.01). Thickness of RF, VI and VL of RSL was also lower than those of RML in BG (p < 0.05), however, there was no significant difference in VM thickness (p > 0.05). There were no significant difference in Asymmetry indexes of all measured muscle thickness between the two groups (p > 0.05). The Shear modulus of RF, VM, and VL in the RML of UG and BG was higher than those in the RSL (p < 0.05). In sitting and straight leg raising task, the RMS of RF, VM and VL in RML were higher than those in RSL, UG and BG both showed this trend (p < 0.05). About squatting task, in UG, the RMS of the three muscles in RML of patients were also higher than those in the RSL (p < 0.05). However, the difference was not significant in BG (p > 0.05). In the straight leg raising task, the asymmetry indexes of RMS in RF, VM, and VL of both the two groups were positively correlated with VAS scores (p < 0.05). Conclusion: The muscle thickness, shear modulus and muscle activation electromyography of QF in RML were higher than those of RSL in unilateral KOA patients. The VM of RML in bilateral KOA patients may show muscle thickness degeneration earlier, which is closer to the VM of RSL. The shear modulus of RF, VM, and VL were higher on the RML side during the single-leg task, but there may be passive compensation for muscle activation in both lower limbs during the bipedal task. In conclusion, there is a general asymmetry of QF muscle mass, biomechanics Characteristic and performance in patients with KOA, which may provide new ideas for the assessment, treatment and rehabilitation of the disease.

Impaired lower limb muscle mass, quality and function in end stage liver disease: A cross-sectional study.

What is the central question of this study? To what extent does musculoskeletal impairment occur (i.e., muscle mass, quality and function) in patients with end stage liver disease (ESLD) by comparison to a healthy age/sex-matched control group? What is the main finding and its importance? Muscle mass, quality and function are impaired in patients with ESLD (compared to age/sex matched controls). Importantly, greater impairments were seen in lower limb compared to arm and trunk muscle groups. These findings may suggest that there should be greater consideration of muscle health in functionally relevant lower limb muscle groups. Sarcopenia is associated with reduced quality of life and increased mortality in patients with end stage liver disease (ESLD). Historically, sarcopenia identification in ESLD utilised L3 skeletal muscle index (SMI). There are few data on muscle quality and function within lower limb muscle groups with high functional relevance. The aim of this prospective case-control study was to evaluate the quadriceps muscle in patients with ESLD. Muscle mass and quality were evaluated using MRI (quadriceps anatomical cross sectional area (ACSA), quadriceps volume index, L3 SMI, quadriceps intermuscular adipose tissue (IMAT)), mid-arm muscle circumference (MAMC) and ultrasonography (vastus lateralis (VL) thickness and quadriceps ACSA). Muscle strength/function was assessed by handgrip strength, peak quadriceps isokinetic torque and chair rise time. Thirty-nine patients with ESLD (55 years, 61% male, 48% alcoholic related liver disease (ArLD), 71% Child-Pugh B/C) and 18 age/sex-matched healthy control participants (HC) were studied. Quadriceps mass was significantly reduced in ESLD versus HC (-17%), but L3 SMI and MAMC were unchanged. Quadriceps IMAT percentage was increased in ESLD (+103%). Handgrip strength (-15%), peak isokinetic torque (-29%), and chair rise time (+56%) were impaired in ESLD. Ultrasound measures of VL thickness (r=0.56, r=0.57, r=0.42) and quadriceps ACSA (r=0.98, r=0.86, r=0.67) correlated to MRI quadriceps ACSA, quadriceps volume and L3 SMI, respectively. Quadriceps muscle mass, quality, and function were impaired in patients with ESLD, whereas conventional assessments of muscle (L3 SMI and MAMC) highlighted no differences between ESLD and HC. Full evaluation of lower limb muscle health is essential in ESLD in order to accurately assess sarcopenia and target future interventions.

Effects of Plyometric Training on Sonographic Characteristics of Quadriceps Muscle and Patellar Tendon, Quadriceps Strength, and Jump Height in Adolescent Female Volleyball Players

The aim of this study was to investigate the effects of plyometric training on vastus lateralis (VL) and patellar tendon size, quadriceps isokinetic strength, and vertical jump height in adolescent female volleyball players. Thirty players (age mean ± SD: 15.7 ± 1.1 years) participated in a 6-week Sportsmetrics™ plyometric training program. VL thickness, echo intensity, and patellar tendon cross-sectional area were assessed by real-time ultrasound. Isokinetic quadriceps strength and vertical jump were assessed. The VL thickness, quadriceps strength, and VJ height increased and VL–echo intensity decreased after training. We recommended that 6-week Sportmetrics plyometric training program may be implemented in adolescent female volleyball programs especially before the beginning of the volleyball season.

Extracellular matrix content and remodeling markers do not differ in college-aged men classified as higher and lower responders to resistance training.

We determined if skeletal muscle extracellular matrix (ECM) content and remodeling markers adapted with resistance training or were associated with hypertrophic outcomes. Thirty-eight untrained males (21 ± 3 yr) participated in whole body resistance training (10 wk, 2 × weekly). Participants completed testing [ultrasound, peripheral quantitative computed tomography (pQCT)] and donated a vastus lateralis (VL) biopsy 1 wk before training and 72 h following the last training bout. Higher responders (HR, n = 10) and lower responders (LR, n = 10) were stratified based on a composite score considering changes in pQCT-derived mid-thigh cross-sectional area (mCSA), ultrasound-derived VL thickness, and mean fiber cross-sectional area (fCSA). In all participants, training reduced matrix metalloprotease (MMP)-14 protein (P < 0.001) and increased satellite cell abundance (P < 0.001); however, VL fascial thickness, ECM protein content per myofiber, MMP-2/-9 protein content, tissue inhibitor of metalloproteinase (TIMP)-1/-2 protein content, collagen-1/-4 protein content, macrophage abundance, or fibroadipogenic progenitor cell abundance were not altered. Regarding responder analysis, MMP-14 exhibited an interaction (P = 0.007), and post hoc analysis revealed higher protein content in HR versus LR before training (P = 0.026) and a significant decrease from pre to posttraining in HR only (P = 0.002). In summary, basal skeletal muscle ECM markers are minimally affected with 10 wk of resistance training, and these findings could be related to not capturing more dynamic alterations in the assayed markers earlier in training. However, the downregulation in MMP-14 in college-aged men classified as HR is a novel finding and warrants continued investigation, and further research is needed to delineate muscle connective tissue strength attributes between HR and LR.NEW & NOTEWORTHY Although past studies have examined aspects of extracellular matrix remodeling in relation to mechanical overload or resistance training, this study serves to expand our knowledge on a multitude of extracellular matrix markers and whether these markers adapt to resistance training or are associated with differential hypertrophic responses.

Quantitative assessment of muscle properties in polymyositis and dermatomyositis using high-frequency ultrasound and shear wave elastography

Polymyositis (PM) and dermatomyositis (DM) are two common types of idiopathic inflammatory myopathy and can lead to a poor prognosis and quality of life. We designed this cross-sectional study to investigate the abilities of high-frequency ultrasound (HFUS) and shear wave elastography (SWE) to assess muscle properties in patients with PM and DM and to distinguish healthy muscles from diseased muscles with PM and DM. A total of 60 patients (26 PM cases and 34 DM cases) and 65 matched healthy volunteers were continuously included in the case and control groups, respectively. For the bilateral deltoid, biceps brachii, rectus femoris, and vastus lateralis, the muscle thickness, echo intensity, and longitudinal shear wave velocity (SWV) of all participants were measured using HFUS and SWE. The intra- and interobserver reliability of SWV measurements of patients with PM and DM and the receiver operating characteristic curve for HFUS and SWE for PM and DM were analyzed. Patients with PM and DM had significantly decreased muscle thickness and increased muscle echo intensity compared to healthy controls (P<0.001). The patients' and healthy participants' deltoid, biceps brachii, rectus femoris, and vastus lateralis thickness was 19.75 and 23.00 mm, 20.45 and 22.80 mm, 18.40 and 20.20 mm, and 20.00 and 22.80 mm, respectively. Except for the biceps brachii, the mean SWV in the longitudinal orientation in patients with PM and DM significantly decreased (P<0.01). The mean SWV of the patients' and healthy participants' deltoid, rectus femoris, and vastus lateralis was 2.47 and 2.57 m/s, 1.73 and 1.87 m/s, and 1.57 and 1.77 m/s, respectively. Excellent intra- and interobserver reliability of SWV measurements on the deltoid and rectus femoris of PM and DM patients were found (intraclass correlation coefficient >0.95; P<0.001). The diagnostic performance of echo intensity in lower-extremity proximal muscles for PM and DM was excellent [area under the curve (AUC) >0.9]. The thickness of most muscles displayed moderate diagnostic performance (the AUC ranged from 0.700 to 0.775). The SWV of the vastus lateralis showed a stable performance (AUC =0.741). The combined diagnostic performance of echo intensity and thickness and the combined diagnostic performance of the 3 indicators were relatively high (the AUC ranged from 0.871 to 0.936 and from 0.898 to 0.938, respectively). Muscle thickness and echo intensity showed statistical differences in different disease stages of PM and DM (P'<0.01). HFUS and SWE may serve as imaging biomarkers for the diagnosis of PM and DM by detecting abnormal muscle thinning, enhanced muscle echo intensity, and reduced muscle SWV.

Different time course recovery of muscle edema within the quadriceps femoris and functional performance after single- vs multi-joint exercises.

This study aimed to verify the time course recovery of muscle edema within the quadriceps femoris and functional performance after lower-body single- and multi-joint exercises. For this within-participant unilateral and contralateral experimental design, fourteen untrained young males performed a unilateral knee extension exercise (KE), and a unilateral leg press (LP) exercise in a counterbalanced order. At pre-, post-, 24 h, 48 h, 72 h, and 96 h after exercise, the peak torque (PT), unilateral countermovement jump (uCMJ) performance, and rectus femoris (RF) and vastus lateralis (VL) muscle thicknesses were recorded in both legs. The PT decreased immediately after (p = 0.01) both exercises (KE and LP) and was fully recovered 24 h after KE (p = 0.38) and 48 h after LP (p = 0.68). Jump height and power, in the uCMJ, followed the same PT recovery pattern after both exercises. However, vertical stiffness (Kvert) was not affected at any time point after both protocols. The RF thickness increased after both exercises (p = 0.01) and was fully restored 48 h after KE (p = 0.86) and 96 h after LP (p = 1.00). The VL thickness increased after both exercises (p = 0.01) and was fully restored 24 h after LP (p = 1.00) and 48 h after KE (p = 1.00). The LP exercise, compared to KE, induced more prolonged impairment of functional performance and delayed recovery of RF muscle edema. However, the VL edema-induced muscle swelling recovery was delayed after the KE exercise. The different recovery kinetics between functional performance and muscle damage should be taken into consideration depending on the objectives of the next training sessions.

Adding High-Intensity Interval Training to Classical Resistance Training Does Not Impede the Recovery from Inactivity-Induced Leg Muscle Weakness.

Inactivity is known to induce muscle weakness, and chronically increased levels of reactive oxygen species (ROS) are proposed to have a central causative role in this process. Intriguingly, high-intensity interval training (HIIT), which involves bursts of high ROS production, can have positive effects in pathological conditions with chronically increased ROS. Here, young male volunteers were exposed to 3 weeks of unloading of the dominant leg followed by 3 weeks of resistance training without (Ctrl group) or with the addition of all-out cycling HIIT. Changes in muscle thickness were assessed by ultrasonography, and contractile function was studied by measuring the torque during maximal voluntary contractions (MVC). The results show an ~6% decrease in vastus lateralis thickness after the unloading period, which was fully restored after the subsequent training period in both the Ctrl and HIIT groups. MVC torque was decreased by ~11% after the unloading period and recovered fully during the subsequent training period in both groups. All-out cycling performance was improved by the 3 weeks of HIIT. In conclusion, the decline in muscle size and function after 3 weeks of unloading was restored by 3 weeks of resistance training regardless of whether it was combined with HIIT.

762 FOR OLDER PATIENTS WITH FRAILTY, SIX WEEKS OF ENFORCED IMMOBILITY HAS NO DETRIMENTAL IMPACT ON MUSCLE STRENGTH OR THICKNESS

Abstract Introduction Immobility can lead to rapid reductions in muscle size, strength and function. Understanding these changes could inform interventions to prevent or slow decline. This longitudinal study aimed to assess the extent of muscle changes in older patients admitted with fragility fractures where clinical management was immobilisation (non-weight bearing) of the affected limb for at least 6 weeks. Method Handgrip strength (HGS); knee extensor strength(KES); Vastus Lateralis thickness and cross-sectional area at ultrasound (VLMT, VLCSA); and skeletal mass index (SMI; bioimpedance analysis) were measured in the non-injured limb of 50 patients (88% female) aged ≥70. Pre-existing physical frailty meant patients were limited to transfers only while non-weight bearing. Measurements were performed at hospital admission, 1, 3 and 6 weeks. One-way repeated measures ANOVA was used to assess changes in measurements over time. Additionally, baseline measurements in female patients (n = 36) were compared to 11 healthy, non-frail, non-hospitalised females with comparable BMI, aged ≥70, using independent t-tests. Data are mean + SD. Results Patient Clinical Frailty Score (median, IQR) was 5 (4–6). At hospital admission, female patients were older (84 ± 7 years vs. 77 ± 6 years, p &amp;lt; 0.05), weaker (HGS of 9.2 ± 4.7 kg vs. 19.9 ± 5.8 kg, p &amp;lt; 0.001; KES 4.5 ± 1.5 kg vs. 7.8 ± 1.3 kg, p &amp;lt; 0.001) and had lower VLMT (1.38 ± 0.47 cm vs. 1.75 ± 0.30 cm, p = 0.02) than non-frail female controls. Six weeks immobility had no temporal effect on any variable: HGS (F(2,51) = 1.04,p = 0.38,n = 27), KES (F(3,45) = 3.22,p = 0.81,n = 16), VLMT (F(3,54) = 2.52,p = 0.07,n = 19), VLCSA (F(3,42) = 0.74,p = 0.53,n = 15) and SMI (F(2,59) = 0.09,p = 0.94,n = 26). Conclusion Older patients admitted with fragility fractures were weaker and had lower VLMT compared to healthy, non-frail older people. This, together with the lack of decline in muscle strength and thickness with 6 weeks immobility strongly suggests muscle resilience was attenuated pre-admission, such that immobility had no further detrimental effect. These results differ from muscle changes seen in younger and non-frail cohorts, and warrants assessment of clinical interventions aimed at increasing muscle mass and function specifically in older people with frailty.