Vastus Lateralis Research Articles

A Pilot Trial of Tongue Reconstruction Using the Chimeric Innervated Vastus Lateralis Muscle and Antero-Lateral Thigh Free Flap.

Subtotal and total glossectomies for advanced tongue cancer result in significant speech- and swallow-related morbidity, impairing quality of life. This prospective pilot study compares the safety and functional outcomes associated with using a chimeric innervated muscle and fasciocutaneous flap for soft tissue reconstruction. A prospective, non-randomized controlled pilot study evaluated a standardized technique for tongue reconstruction using a chimeric innervated vastus lateralis muscle and anterolateral thigh fasciocutaneous flap. Inclusion criteria were ≥ 50% resection of the oral tongue. Participants were followed longitudinally, with measures recorded at baseline, 6-8 weeks, 6 months, and 12 months after surgery. The primary endpoints were post-operative complications, time to radiotherapy, operative time, and locoregional failure, videofluoroscopy swallow studies (dynamic imaging grade of swallowing toxicity (DIGEST), penetration and aspiration score, performance status scale for head and neck). Secondary endpoints were patient-rated outcomes. Eighteen participants were recruited (10 intervention: 8 controls). Fourteen (78%) experienced complications, only one of which was related to the innervated flap. DIGEST scores deteriorated post-operatively across all participants but did not differ significantly between the intervention and control groups (p = 0.4) at any point post-surgery, despite more extensive resections in the intervention group. Those in the intervention group had better patient-rated intelligibility (p = 0.04). Multimodality treatment was associated with worse speech (p = 0.03) and normalcy of diet (p = 0.02). Less extensive resections were associated with better scores in eating in public (p = 0.005), tongue range of movement (p = 0.0008), intelligibility (p = 0.006), and diet (p = 0.001). The innervated vastus lateralis and antero-lateral thigh free-flap technique is safe and improves speech intelligibility for patients with subtotal and total glossectomy defects. However, the technique requires refinement to optimize functional and quality-of-life outcomes.

Does increasing the resistance-training volume lead to greater gains? The effects of weekly set progressions on muscular adaptations in females

ABSTRACT We investigated the effect of increasing the number of sets per week every fortnight versus performing a constant set volume on muscular adaptations over 12 weeks. Thirty females (RT experience 2.1 ± 1.0 years) were randomly assigned to a constant group (CG, n = 9) that performed 22 sets per week, a two-set progression group (2SG, n = 11), or a four-set progression group (4SG, n = 10). Forty-five degree leg press one-repetition maximum (1RM), vastus lateralis cross-sectional area (VL-CSA), and the sum of proximal, middle and distal lateral thigh muscle thickness (∑MT) were assessed at baseline and after the intervention. We observed that the 4SG and 2SG conditions showed greater improvements in 1RM than the CG (p < 0.001, p = 0.032, respectively), with no differences between 4SG and 2SG (p = 0.118). Regarding VL-CSA, the 4SG group showed greater increases than the CG (p = 0.029) but not than the 2SG (p = 0.263), whereas no differences between the 2SG and CG (p = 0.443) were observed. There were no differences between groups for ∑MT (p = 0.783). While all groups demonstrated improvements in the measured outcomes, our findings suggest that increasing weekly sets may offer additional benefits for 1RM and vastus lateralis cross-sectional area. However, no additional benefits were observed for ∑MT.

A Study on the Effects of Gluteal Muscle Activation on the Electromyography of Lower Limb Muscles in Young Male Patients With Patellofemoral Pain Syndrome.

Patellofemoral pain syndrome (PFPS) is a common knee issue, and hip joint function significantly affects knee health. Gluteus activation exercises are a promising treatment for PFPS. This study aims to investigate the impact of gluteal muscle activation exercises on the muscle involvement and movement patterns of young male patients with PFPS. Our study was a randomized controlled clinical trial study from June 2020 to December 2021, included 18 young male patients with PFPS, randomly divided into two groups: the gluteus activation group (GAG) and control group (CON), with nine cases in each group. The GAG underwent gluteal muscle activation exercises for 40 min per session, three times per week, for 6 weeks; the CON received no intervention. At baseline and after 6 weeks, the integrated electromyography (IEMG), contribution rates (CRs), and activation times (ATs) of the gluteus maximus (GM), vastus medialis (VM), rectus femoris (RF), vastus lateralis (VL), biceps femoris (BF), and semitendinosus (ST) muscles of the affected lower limb during stair-climbing exercise were assessed. Additionally, the explosive power (EP) of the lower limbs and the visual analog scale (VAS) pain value of the knee joint were evaluated. Paired sample t-tests and independent sample t-tests were used to compare the differences within and between groups. After 6 weeks, the GAG showed a significant increase in the IEMG of GM by 118 ± 67.09 μVs compared to CON (p < 0.05), and an increase in the CR of the GM by 6.75% (p < 0.05). Additionally, the AT of the GM and BF was significantly reduced (p < 0.05), and the lower limb EP increased by 14.66% compared to the CON (p < 0.05). Concurrently, there was a very significant reduction in the knee VAS pain score (p < 0.01). The CON exhibited no significant changes in the EMG indices of the lower limbs, EP, and VAS before and after the 6 weeks (p > 0.05). A 6-week gluteal muscle activation training program for patients with PFPS can adjust and optimize the IEMG, CR, and firing order of the lower limb muscle groups, enhance EP, and alleviate pain.

Relationship Between Muscle Tone and Elasticity: Simultaneous Quantitative Assessment Using Train-of-Four Monitoring and Continuous Shear Wave Elastography During Anesthesia Induction—A Prospective Observational Study

Background/Objectives: Non-invasive evaluations of muscle elasticity and tone are crucial in musculoskeletal medicine. Shear wave elastography (SWE) provides quantitative assessments of muscle elasticity, whereas train-of-four (TOF) monitoring measures muscle tone during neuromuscular blockades. This study investigated the relationship between muscle elasticity and tone during anesthesia induction using continuous SWE (C-SWE) and TOF monitoring. Methods: Fifteen patients who underwent general anesthesia with rocuronium were recruited. The muscle elasticity of the vastus lateralis was assessed using C-SWE, and muscle tone was evaluated using TOF monitoring. Measurements were taken at two time points: before rocuronium administration and during complete muscle relaxation, confirmed by the TOF ratio (TOF = 0). Statistical analyses were performed using paired t-tests and correlation analyses. Results: Data from 11 patients were analyzed. The mean shear wave velocity (SWV) decreased significantly from 5.0 ± 0.4 m/s before rocuronium administration to 3.1 ± 0.3 m/s during complete relaxation (p &lt; 0.0001). A significant negative correlation was observed between the baseline SWV and the degree of reduction in the SWV (r = −0.728, p = 0.011). No significant correlations were found between SWV and demographic factors such as age, sex, height, or body mass index. Conclusions: C-SWE and TOF monitoring are reliable and sensitive methods for evaluating muscle elasticity and tone during general anesthesia. This study highlights the interplay between muscle tone and elasticity, suggesting that muscles with a higher baseline tone exhibit a greater reduction in elasticity after relaxation. These findings have implications for improving intraoperative muscle function assessments and advancing the application of C-SWE in clinical practice.

Relationship between muscle activation and sagittal knee joint biomechanics in patients with patellofemoral pain syndrome: a cross-sectional study

BackgroundPatellofemoral pain syndrome (PFPS) is one of the most common conditions affecting the knee joint, yet its pathomechanics remain unclear. The aim of this study was to investigate changes in muscle activation and gait patterns and to analyze the relationship between muscle activation and kinetic gait patterns in patients with PFPS.MethodsThis study included 31 patients with PFPS and 28 healthy volunteers without any symptoms. The sagittal plane motion of the knee joint, representing primary movement of the knee joint, was evaluated to identify changes in gait patterns. Electromyography (EMG) was used to measure muscle activation of vastus medialis (VM), vastus lateralis (VL), semitendinosus (ST), and gastrocnemius (GCM) muscles during gait analysis. Biomechanical features were analyzed during the three phases of the gait cycle; weight acceptance (WA), single limb support (SLS), and swing limb advancement (SLA) (0 ~ 12%, 13 ~ 50%, and 51 ~ 100% of the gait cycle, respectively).ResultsThe average knee extension moment (KEM) during WA was lower in the patient group and no significant differences were observed in the knee flexion angle (KFA). With respect to muscle activation, the patient group showed significantly higher muscle activation of the ST muscle in all phases. As the absolute value of the moment increased, the activation of the VM, VL, and ST muscles increased more rapidly in the patient group, especially when KEM was under −1% body weight × height (Bw × Ht) or over 5% Bw × Ht.ConclusionsPatients with PFPS exhibit elevated muscle activation, particularly in response to changes in the knee extension moment, which is likely a compensatory mechanism to manage knee joint loading during gait. These results highlight altered neuromuscular adaptations in PFPS, suggesting targeted therapies may help improve functional outcomes.Level of evidence III, cross-sectional study

Degeneration of the cartilage quality is correlated with a higher intramuscular fat infiltration of the vastus medialis in older adults with pre-to-mild knee osteoarthritis.

To quantitatively verify whether degeneration in the quality of the medial femoral cartilage is correlated with muscle volume loss and intramuscular adipose tissue (IntraMAT) infiltration in quadriceps using magnetic resonance imaging (MRI). Of the 66 older adult participants ≥60years old (74.5±6.9 years), 29 were female. All participants were patients with pre-to-mild knee osteoarthritis. Muscle volume and IntraMAT infiltration of the four individual muscles, the rectus femoris (RF), vastus medialis (VM), vastus intermedius, and vastus lateralis were assessed, using proton density-weighted and 2-point Dixon MR images. Based on the MRI T2 mapping, the T2 relaxation times of the weight-bearing surface of the medial femoral cartilage were calculated. Simple linear regression analyses were performed, evaluating the correlations between the T2 relaxation time of the medial femoral cartilage and quadriceps muscle volume and IntraMAT. Multiple linear regression analysis using a stepwise method was performed, determining which indicators of the four individual muscles correlated with cartilage quality degeneration. Simple linear regression analyses revealed that a longer T2 relaxation time of the medial femoral cartilage was positively correlated with IntraMAT infiltration of the entire quadriceps muscle, RF, and VM, however not with the quadriceps muscle volume. Multiple linear regression analysis revealed that VM IntraMAT was particularly correlated with the extension of T2 relaxation time of the medial femoral cartilage. In older adults with pre-to-mild knee osteoarthritis, IntraMAT infiltration of the quadriceps muscles, particularly of the VM was correlated with degeneration in the quality of the medial femoral cartilage.

Alterations in whole muscle quality and physiological cross-sectional area measured with quantitative MRI following ACL injury

BackgroundEmerging evidence suggests that there are morphological and physiological changes to the vastus lateralis after an anterior cruciate ligament (ACL) tear. However, it is unclear whether these alterations are limited to just the vastus lateralis or are more representative of widespread changes across the thigh musculature and/or if these changes precede reconstruction. The purpose of this study was to determine T1ρ relaxation time, a measure of extracellular matrix organization in muscle, and physiological cross-sectional area (PCSA) for muscles of the quadriceps and hamstrings of the ACL-deficient and contralateral limbs soon after ACL injury.MethodsT1ρ and diffusion tensor magnetic resonance imaging were performed on both limbs of 10 participants after primary ACL tear (< 10 weeks). T1ρ relaxation time and PCSA were calculated for all muscles of the quadriceps and hamstrings. Shapiro-Wilks tests were performed to assess normality. Outcomes were compared between limbs for each muscle of interest with paired t-tests or Wilcoxon signed-rank tests with the alpha level set to 0.05.ResultsT1ρ relaxation times were significantly longer for the vastus lateralis (7.0%), rectus femoris (15.4%), and vastus intermedius (9.4%) of ACL-deficient limb; whereas, relaxation times were similar between limbs for all hamstring muscles. PCSA was smaller for the vastus lateralis (-19.6%), vastus intermedius (-20.9%), vastus medialis (-26.0%), and semitendinosus (-15.0%) of the ACL-deficient limb compared to the contralateral limb.ConclusionsThese results provide evidence that morphological and physiological alterations occur within multiple muscles of quadriceps but not the hamstrings prior to ACL reconstruction. Establishing these differences between the quadriceps and hamstrings suggests there is a differential response within the thigh musculature to an ACL injury, providing a framework for more targeted interventions.

Effects of various modes of forward and backward cycling on neuro-biomechanical outcomes in individuals after stroke and healthy controls.

Stationary cycling is recommended for post-stroke rehabilitation. This study assessed neuro-biomechanical outcomes of forward and backward cycling in three different modes: free-pedalling, constant speed (30 RPM) and constant resistance (5 or 10Nm) in healthy controls and individuals after stroke. Ten individuals after stroke and 10 healthy controls performed 60s cycling trials in different directions and modes on a semi-recumbent bike prototype. Cycling performance (speed, torque, coefficient of variation) and the activity of the non-dominant limb muscles (rectus femoris, vastus lateralis, tensor fascia latae, and biceps femoris) were collected. Cycling performance was lower in backward than forward direction in both groups, but to a greater extent in individuals after stroke. Variability was reduced in backward compared to forward pedalling except for free-pedalling. At constant speed, both groups showed similar increase in rectus femoris activation during the propulsive phase of backward cycling while an increase was only observed in the stroke group for the tensor fascia latae. The constant resistance mode revealed more difference between groups: individuals after stroke showed changes of rectus femoris and vastus lateralis activation with pedalling direction in both phases while healthy controls had changes only in the vastus lateralis. Tensor fascia latae activation differed between groups but was not affected by direction. The biceps femoris activation was more variable. Various cycling directions and modes influenced neuro-biomechanical outcomes, even more in individuals after stroke. Future research should determine how they could enhance functional abilities after stroke when used during rehabilitation.

Effects of leg immobilization and recovery resistance training on skeletal muscle-molecular markers in previously resistance trained versus untrained adults.

We sought to examine how resistance training (RT) status in young healthy individuals, either well resistance trained (T, n=10) or untrained (UT, n=11), affected molecular markers with leg immobilization followed by recovery RT. All participants underwent two weeks of left leg immobilization via a locking leg brace. Afterwards, all participants underwent eight weeks (3 d/week) of knee extensor focused progressive RT. Vastus lateralis (VL) ultrasound-derived thickness and muscle cross-sectional area were measured at baseline (PRE), immediately after disuse (MID), and after RT (POST) with VL muscle biopsies also being collected at these time points. Both groups presented lower ultrasound derived VL size metrics at MID versus PRE (p<0.001), and values increased in both groups from MID to POST (p<0.05); however, VL size increased from PRE to POST in UT only (p<0.001). Mean and type II myofiber cross-sectional area values were greater at PRE and POST versus MID (p<0.05), with T being greater than UT throughout (P<0.012). In both groups, satellite cell number was not affected by leg immobilization but increased in response to RT (p<0.014), with T being greater than UT throughout (p=0.004). Total RNA (ribosome content) decreased (p=0.010) from PRE to MID, while total RNA and certain endoplasmic reticulum stress proteins increased from MID to POST regardless of training status. Immobilization-induced muscle atrophy and recovery RT hypertrophy outcomes are similar between UT and T participants, and the lack of molecular signature differences between groups supports these findings. However, results are limited to younger adults undergoing non-complicated disuse.

Effects of functional strength training on pain, function, and lower extremity biomechanics in patients with patellofemoral pain syndrome: a randomized clinical trial

BackgroundPatellofemoral pain syndrome (PFPS) is a common disorder affecting the lower extremity. This study aimed to compare the effects of functional strength training (FST) and standard strength training (SST) in PFPS patients.MethodsForty college students (aged 18–30 years) with PFPS and no exercise habits were randomized into FST group (n = 20) and SST group (n = 20). FST group underwent six weeks of lower extremity training focused on functional adaptations, whereas SST group focus on lower extremity strength training. Function (Kujala Patellofemoral Scale, KPS), pain (visual analog scale, VAS), peak joint angles of hip, knee, and ankle, along with muscle activation (step-down test) of Vastus medialis, Vastus lateralis, Biceps femoris, Semitendinosus, Gluteus maximus, and Gluteus medius were assessed at baseline and after intervention.ResultsFST outperformed SST in pain reduction (p = 0.026) and function (p = 0.006) post-intervention. The FST group also showed increased hip flexion (p < 0.001), gluteus maximus activation (p < 0.001), and reduced knee valgus (p = 0.032), while SST group exhibited greater knee flexion (p = 0.008), and higher activation of the lateral femoral (p < 0.001) and semitendinosus (p < 0.001).ConclusionInterventions focused on functional adaptations result in differential kinematic and muscle activation changes that may result in greater improvements in pain and knee function than lower limb muscle strengthening alone.Trial registrationchictr.org.cn. NO: ChiCTR2400087664. Date 01/08/2024.

Is the time to task failure during severe intensity exercise associated with muscle, blood, and respiratory changes?

Purpose: The study aimed to verify the physiological and metabolic parameters associated with the time to task failure (TTF) during cycling exercise performed within the severe-intensity domain. Methods: Forty-five healthy and physically active males participated in two independent experiments. In experiment 1, after a graded exercise test, participants underwent constant work rate cycling efforts (CWR) at 115% of peak power output to assess neuromuscular function (Potentiated twitch) pre- and post-exercise. Experiment 2 was similarl to experiment 1, but with physiological (respiratory parameters, energetic pathway contribution) and metabolic parameters in the blood (gasometry and blood lactate responses) and vastus lateralis muscle tissue (target metabolomic analysis, glycogen content, muscle pH and buffering capacity in vitro) measured instead of neuromuscular function. Results: Experiment 1 evidenced a significant decrease in muscle force with instauration of peripheral fatigability indices and no change in central fatigue indices. Severe-intensity domain exercise in Experiment 2 was accompanied by changes in physiological and metabolic parameters and in blood and muscle parameters. However, the TTF was associated with oxidative contribution (r=0.811, p<0.001), as well as anaerobic capacity (r=0.554, p=0.027), muscle buffering capacity (r=0.792, p=0.035), phosphagen energy contribution (r=0.583, p=0.017), and carnitine changes (r=0.855, p=0.016), but no correlated with electromyographic response, blood acid-base balance, and muscular glycogen content and pH. Conclusion: TTF during CWR exercise within the severe-intensity domain is likely explained by a combination of interacting mechanisms, with oxidative and phosphagen contributions, and muscle buffering capacity suggested as the main peripherals limiting factors to exercise within this exercise intensity domain.

Different whole body HIIT protocols do not promote different muscle thickness and functional adaptations among healthy physically active subjects

IntroductionDespite robust evidence on the benefits of high intensity interval training using body weight (WB-HIIT), the effects of different training configurations on morpho-functional adaptations are still unclear. Therefore, the aim of the present study was to assess the effects of two distinct WB-HIIT protocols on morphological and general fitness adaptations in healthy active young individuals.MethodsThirty-four participants (22 males and 12 females) were randomly assigned to one of the following groups: 30 s of all-out effort interspersed with 10 s of passive recovery (G30 × 10, n = 17) or 40 s of an all-out effort interspersed with 20 s of passive recovery (G40 × 20, n = 17). Nine exercises were performed for both protocols, in two weekly sessions, during a 6-week intervention period. Morphological (ultrasound-derived muscle thickness of the vastus lateralis [MTVL]) and general fitness (muscle endurance and maximal oxygen consumption) assessments were performed at pre- and post-intervention moments.ResultsBoth training protocols elicited significant improvements in all dependent variables (p &amp;lt; 0.05), with no significant between-group differences.ConclusionRegardless of the training configuration, both WB-HIIT programs serve as time-efficient strategies to induce changes in muscle thickness of the vastus lateralis and functional adaptations in healthy, physically active young individuals.

Statistical Parametric Mapping Differences in Muscle Recruitment Patterns Between Comfort- and Performance-Oriented Saddle Positions

This study investigates whether electromyography (EMG) analysis can reflect ergonomic improvements for commuter bike users by assessing muscle activity differences between comfort- and performance-oriented saddle positions. A cohort of 30 city bike riders underwent a comprehensive fitting procedure, where one position was individually established based on a comfort perception questionnaire and adjusted by a bike fitter. The aim was to compare the EMG activity of muscles involved in propulsion and lumbar spine stabilisation across different positions. The Statistical Parametric Mapping (SPM) method was also used to analyse muscle activity throughout the pedalling cycle. The results revealed that the customised position significantly reduced EMG activity in muscles, particularly during key pedalling phases, significantly improving rider comfort and muscle efficiency. SPM analysis highlighted decreased strain in the vastus lateralis and tibialis anterior, indicating improved muscular efficiency and enhanced comfort for urban cyclists. This underscores the importance of personalised bike fitting in promoting comfort and reducing the risk of injury, suggesting that EMG analysis is a valuable tool in both clinical and recreational bike-fitting practices. Future research should explore the long-term effects and potential applications of the proposed fitting method for other bicycle geometries whenever comfort and lower back stability are priorities.

Muscle-specific neuromuscular responses during running with blood flow restriction.

The purpose of this investigation was to examine muscle excitation at maximal running capacity without blood flow restriction (BFR) relative to submaximal running bouts with BFR. Fourteen college-aged males randomly completed four, three-minute running bouts at 70, 80, and 90% of peak speed with BFR (70%BFR, 80%BFR, and 90%BFR) and without BFR at 100% of their peak speed (100%NOBFR). The surface electromyographic amplitudes of the vastus lateralis, rectus femoris, and vastus medialis muscles were assessed. Muscle excitation of the vastus lateralis was similar across most bouts; however, it was lower during the 70%BFR compared to 90%BFR (Meandiff =-4.67±- 0.22%; Bayesian 95% high-density interval [HDI]: - 7.07 to - 2.2) and 100%NOBFR (Meandiff =-2.94±- 0.27%; 95% HDI:-5.33 to-0.50) bouts. For the rectus femoris, muscle excitation largely increased across running speeds (70%BFR<80%BFR < 90%BFR; 90%BFR < 100%NOBFR). For the vastus medialis, muscle excitation was lower during the 70%BFR compared to 90%BFR (Meandiff =-8.15±- 0.28%; 95% HDI:-15.3 to-0.89). Submaximal running with BFR increased muscle excitation responses for the vastus lateralis and vastus medialis, such that muscle excitation was similar to 100%BFR, despite 10-20% reductions in running speed. The rectus femoris muscle, however, was not affected by BFR during the submaximal running bouts.

The Impact of Exercise Play on the Biomechanical Characteristics of Single-Leg Jumping in 5- to 6-Year-Old Preschool Children.

This study aimed to investigate the effects of a 12-week self-designed exercise game intervention on the kinematic and kinetic data of the supporting leg in preschool children during the single-leg jump. Thirty 5- to 6-year-old preschool children were randomly divided into an experimental group (EG) and a control group (CG). The BTS SMART DX motion capture analysis system was used to collect single-leg jump data before the intervention. The experimental group underwent a 12-week intervention, with self-designed exercise games conducted three times a week for 30 min each session, while the control group only participated in regular kindergarten recess activities and physical education classes. After the intervention, the same equipment was used to collect single-leg jump data again, and the kinematic and kinetic data were analyzed using Anybody 7.4 simulation software. After the intervention, the experimental group showed significant changes in joint angles and joint torques, with a notable increase in the force exerted by dominant muscles such as the vastus medialis, vastus lateralis, and gastrocnemius and a significant increase in the ground reaction force. Although the control group also showed some changes in the dominant muscles, the changes were not as significant as those in the experimental group. A 12-week exercise game intervention significantly improved the technique and force characteristics of 5- to 6-year-old preschool children during the single-leg jump, making muscle exertion more focused and efficient and effectively enhancing explosive power and performance during the single-leg jump.

Previous short-term disuse dictates muscle gene expression and physiological adaptations to subsequent resistance exercise.

Short-term unloading experienced following injury or hospitalisation induces muscle atrophy and weakness. The effects of exercise following unloading have been scarcely investigated. We investigated the functional and molecular adaptations to a resistance training (RT) programme following short-term unloading. Eleven males (22.09±2.91years) underwent 10days of unilateral lower limb suspension (ULLS) followed by 21days of knee extensor RT (three times/week). Data collection occurred at Baseline (LS0), after ULLS (LS10) and at active recovery (AR21). Knee extensor maximum voluntary contraction (MVC) was evaluated. Quadriceps volume was estimated by ultrasonography. Muscle fibre cross-sectional area, fibre type distribution, glycogen content and succinate dehydrogenase (SDH) activity were measured from vastus lateralis biopsies. Mitochondrial-related proteins were quantified by western blot and transcriptional responses were assessed by RNA sequencing. Following ULLS, quadriceps volume and MVC decreased significantly (3.7%, P<0.05; 29.3%, P<0.001). At AR21 (vs. LS10), MVC was fully restored (42%) and quadriceps volume increased markedly (18.6%, P<0.001). Glycogen content and whole-body water increased at AR21 (14%, P<0.001; 3.1%, P<0.05). We observed a marked increase in fibre type I at AR21 (38%, P<0.05). SDH immunoreactivity increased significantly after exercise (20%, P<0.001). Mitochondrial fusion (MFN1, MFN2 and OPA1) and fission (DRP1) proteins were markedly increased by RT, and the most differentially expressed genes belonged to oxidative phosphorylation pathways. In contrast with what is usually observed after RT, oxidative metabolism, slow fibre type and mitochondrial dynamics were enhanced beyond expected. We propose that prior exposure to short-term muscle unloading may drive the nature of molecular adaptations to subsequent RT. KEY POINTS: Short-term unloading is often experienced during recovery from injuries and hospitalisation, leading to loss of muscle mass and strength. Although exercise can be beneficial in mitigating/reversing such alterations during disuse, only a few studies have focused on the effects of exercise following muscle unloading. With an integrative physiological approach, we aimed to elucidate the basic mechanisms of muscle function recovery in response to 21days of resistance exercise that followed 10days of unilateral lower limb suspension (ULLS), assessing whether the mechanisms underlying recovery are defined by a specific reversal of those that occurred during disuse. Resistance training was successful in recovering functional and structural muscle properties after 10days of ULLS, but in contrast with what is usually observed in response to this training modality, oxidative metabolism and slow fibre type were mostly enhanced. We propose that prior exposure to short-term muscle unloading may drive the adaptations to subsequent exercise.

In situ spatial transcriptomic analysis of human skeletal muscle using the Xenium platform.

Traditional transcriptomic studies often overlook the complex heterogeneity of skeletal muscle, as they typically isolate RNA from mixed muscle fibre and cell populations, resulting in an averaged transcriptomic profile that obscures fibre type-specific differences. This study assessed the potential of the recently developed Xenium platform for high-resolution spatial transcriptomic analysis of human skeletal muscle histological sections. Human vastus lateralis muscle samples from two individuals were analysed using the Xenium platform and Human Multi-Tissue and Cancer Panel targeting 377 genes complemented by staining of successive sections for Myosin Heavy Chain isoforms to differentiate between type 1 and type 2 muscle fibres. Manual segmentation of muscle fibres allowed accurate comparisons of transcript densities across fibre types and subcellular regions, overcoming limitations in the platform's automated segmentation. The analysis revealed higher transcript density in type 1 fibres, particularly in nuclear and perinuclear areas, and identified 191 out of 377 genes with differential expression between muscle fibres and perimysium. Genes such as PROX1, S100A1, LGR5, ACTA2, and LPL exhibited higher expression in type 1 fibres, whereas PEBP4, CAVIN1, GATM, and PVALB in type 2 fibres. We demonstrated that the Xenium platform is capable of high-resolution spatial in situ transcriptomic analysis of skeletal muscle histological sections. This study demonstrates that, with manual segmentation, the Xenium platform effectively performs fibre type-specific transcriptomic analysis, providing new insights into skeletal muscle biology.

Muscle-specific miRNAs in plasma and skeletal muscle of patients with idiopathic inflammatory myopathy are modulated by disease and training.

Objective of this work was to examine myomiR levels in plasma, skeletal muscle, and skeletal muscle cells of patients with idiopathic inflammatory myopathy (IIM), their interrelations with the disease-related clinical phenotypes and with the effects of the disease-modifying 6-month training-intervention. Samples of vastus lateralis muscle (n = 12/13) and plasma (n = 20/21) were obtained from IIM patients and healthy controls, respectively. Muscle and plasma were obtained before and after a 6-month training-intervention in 7 patients. MyomiRs miR-1,-206,-133a,-133b were quantified by qPCR. Effects of pro-inflammatory (TNF), metabolic (glucose, insulin) systemic factors and the immunosuppressive therapy (dexamethasone) on the myomiRs were examined in muscle cells in vitro. MiR-133b was lower in skeletal muscle of IIM patients compared with healthy controls (p= 0.03). Levels of miR-133a, miR-1, and miR-206 were not regulated. Moreover, plasma levels of miR-133b and miR-1 were reduced in IIM compared with healthy controls (p< 0.05). Exercise induced reciprocal regulation of specific myomiRs in muscle and plasma of IIM patients, it lowered miR-133b in muscle while increasing miR-133b and miR-206 in plasma. Treatment of myotubes with TNF, insulin, and glucose and dexamethasone induced distinct myomiRs down-regulation. Lower myomiR levels in skeletal muscle of IIM patients might indicate reduced muscle regenerative potential in IIM, which could be linked to inflammation, metabolic dysfunction, and immunosuppressive therapy. Training-induced changes of muscle and plasma myomiRs indicate an increase in myomiRs release, which could contribute to the adaptive response underlying the positive systemic effects of exercise in IIM.

Shatavari supplementation during eight weeks of resistance training increases training load, enhances skeletal muscle contractility and alters the skeletal muscle proteome in older women.

Shatavari is a herbal dietary supplement that may increase skeletal muscle strength in younger and older adults. Shatavari contains compounds with both estradiol-like and antioxidant properties, which could enhance muscle function. Postmenopausal women may derive the greatest benefit, as estrogen deficiency adversely impacts skeletal muscle function. However, mechanistic insights are limited and the effects of shatavari on muscle function require further characterization. In this randomized, double-blind trial, 17 young (23 ± 5 yr) and 22 older (63 ± 5 yr) women completed an 8-week leg resistance training programme. They consumed either a placebo or shatavari (1000 mg/d, equivalent to 26,500 mg/d fresh weight) supplement throughout. Pre and post training, measures of leg strength, neuromuscular function and vastus lateralis (VL) biopsies were obtained. Tandem-mass-tagged VL proteomic analyses were performed. Data were analyzed using a differential expression (Reactome) approach. Shatavari supplementation increased 8-week training load in older women (leg press repetitions completed, p = 0.049, η p 2 = 0.198; maximum weight lifted each week, p = 0.03, η p 2 = 0.386; ANCOVA). There was no effect of shatavari on muscle strength post-training. VL half relaxation time was shortened post-training in older women supplemented with shatavari (post-training change: shatavari -11.74 ± 11.93%, placebo 0.42 ± 14.73%, p = 0.021; ANCOVA). Shatavari supplementation diminished the expression of extracellular matrix proteins in both cohorts. Expression of proteins related to striated muscle contraction, transcription and translation were decreased by shatavari supplementation in older women. These novel observations support the notion that shatavari supplementation confers resistance to neuromuscular fatigue in older women. This could ameliorate sarcopenic declines in skeletal muscle function.

Association of Physical Function, Quantity, and Quality of the Quadriceps with Postoperative Physical Activity Before Total Knee Arthroplasty.

Background/Objectives: This single-center cohort study investigated preoperative risk factors such as physical function, quantity, and quality of the quadriceps femoris for physical activity (PA) 1 year after total knee arthroplasty (TKA). Methods: This study included 204 patients with knee osteoarthritis who underwent TKA; they were divided into increased and decreased PA groups. Items with significant differences between the two groups in non-operative-side quadriceps strength, knee injury and osteoarthritis outcome scores (KOOS), Sport/Rec scores, operative-side cross-sectional area (CSA) of the vastus medialis (VM), and operative-side computed tomography attenuation values (CTV) of the vastus lateralis (VL) were fitted in the multiple logistic regression analysis. The cutoff value of the preoperative CSA of the VM required for PA to exceed the required points at 1 year postoperatively was calculated using the receiver operating characteristic (ROC) curve. Results: Multivariate logistic regression analysis showed that the non-operative-side quadriceps strength KOOS sport/rec, operative-side CSA of VM, and operative-side CTV of the VL were significantly associated with increased PA after TKA. The ROC-calculated cutoff value was 10.2 cm2. Conclusions: These results suggested that preoperative muscle quantity and quality, particularly in the VM, could play important roles in postoperative PA outcomes after TKA.