Muscle Architecture Parameters Research Articles

Optimized uniform sampling and validation of fiber tracts from magnetic resonance tractography for in vivo architectural measurement of human forearm muscles.

In vivo muscle architectural parameters can be calculated from the fiber tracts using magnetic resonance (MR) tractography. However, the reconstructed tracts may be unevenly distributed within the muscle volume and there lacks commonly used metric to quantitatively evaluate the validity of the tracts. Our objective is to measure forearm muscle architecture by uniformly sampling fiber tracts from the candidate streamlines in MR tractography and validate the reconstructed fiber tracts qualitatively and quantitatively. We proposed farthest streamline sampling (FSS) to uniformly sample fiber tracts from the candidate streamlines. The method was evaluated on the MR data acquired from 12 healthy subjects for 17 forearm muscles and was compared with two conventional methods through uniform coverage performance. Anatomical correctness was verified by: 1. visually assessing fiber orientation, 2. checking whether architectural parameters were within physiological ranges and 3. classifying architectural types. The proposed FSS yielded optimal uniform coverage performance among the three methods (P<0.05). FSS reduced the sampling of long tracts (10% fiber length reduction, P<0.05), and the estimated architectural parameters were within the physiological ranges (P<0.05). The tractography visually matched cadaveric specimens. The architectural types of 16 muscles were correctly classified except for the palmaris longus, which exhibited a linear arrangement of fiber endpoints (R2 = 0.95±0.02, P<0.001). The proposed FSS method reconstructed uniformly distributed fiber tracts and the anatomical correctness of the reconstructed tracts was verified. The novel methods allow for accurate in vivo muscle architectural measurement, which was demonstrated through the characterization of architectural properties in human forearm muscles.

Reproducibility of freehand vs. foam cast as well as the intrarater reliability of foam cast ultrasound scans assessing the muscle architecture and tissue organization of the gastrocnemius medialis and vastus lateralis muscles.

This study compares the reproducibility of freehand (FH) vs. foam cast (FC) scans and investigates the intrarater reliability of the ultrasound FC muscle architecture and tissue organization measurements of the gastrocnemius medialis (GM) and vastus lateralis (VL) muscles with fixed and repositioning FC scans. Thirteen young adults (22 ± 3 years) underwent repeated sagittal B-mode ultrasound measurements of GM and VL. FH, FC, and repositioned FC scans were conducted. Muscle architecture measurements included muscle thickness (MT), pennation angle (PA), and fascicle length (FL). Spatial frequency analysis assessed muscle tissue organization. MT decreased from 2.1 to 1.8 cm in GM and from 2.4 to 2.2 cm in VL with the FC compared with the FH. Reproducibility between the FH and the FC showed poor to good intraclass correlation coefficients (ICCs) for MT (0.46-0.77) and PA (0.09-0.86) as well as poor to moderate ICCs for FL (0.41), with very low to moderate test-retest variability (TRV) (4%-18%). Tissue organization indicated low to good ICCs (0.21-0.80) with low to moderate TRV (4%-19.5%). The re-scanning results of fixed FC indicated excellent ICCs for MT (0.95-0.996), good for PA (0.77-0.90), and moderate for FL (0.73-0.76), with low TRV (5%-10%) for both muscles. Tissue organization displayed moderate to good ICCs (0.61-0.87) with very low to low TRV (4%-9%). For repositioned FC scans in GM and VL, MT showed good to excellent ICCs (0.86-0.98) with very low to low TRV (2%-8%). PA and FL demonstrated moderate to good ICCs (0.57-0.75), with very low to moderate TRV (2%-13%). Tissue organization revealed ICCs ranging from poor to good (0.13-0.87) for both muscles, with low to moderate TRV (5%-18%). The FC systematically reduced MT by 2-3 mm. Furthermore, reproducibility revealed low ICCs and high data variability for several muscle architecture and tissue organization parameters. Thus, switching methods within a single study is not recommended. Nevertheless, FC ultrasound scans demonstrated excellent intrarater reliability for assessing MT. In the case of fixed FC scans particularly, moderate to excellent ICCs were observed for all muscle architecture and tissue organization parameters, accompanied by very low to low variability. Therefore, FC scans are recommended for investigating acute effects on muscle architecture and tissue organization when the FC remains on the leg throughout the period of measurements.

Defining Architectural Changes in Mouse Pelvic Floor Muscles During Pregnancy to Withstand Physiological Distension Associated with Parturition

Pelvic floor disorders (PFDs), which are present in ~25% of women, profoundly impact quality of life. During childbirth, pelvic floor muscles (PFMs) endure substantial mechanical strain, which can lead to PFM dysfunction. As such, vaginal childbirth is a major risk factor for PFDs. Previous studies in rats demonstrate important structural adaptations in the PFMs that help to withstand the mechanical strain of childbirth, including muscle fiber lengthening by sarcomerogenesis. However, it is diffcult to establish a comprehensive understanding of the molecular mechanisms underlying PFM dysfunction during childbirth in rat models. Here, our objective was to determine if mouse PFMs undergo similar adaptations to rats during pregnancy and vaginal distension. We hypothesized that, akin to rats, PFMs in mice would undergo muscle fiber elongation through sarcomerogenesis during pregnancy. The PFMs (coccygeus [C], iliocaudalis [ICa], pubocaudalis [PCa]) and a non-pelvic floor muscle (tibialis anterior [TA]) were collected from late-pregnant (E16.5) and non-pregnant C57BL/6NJ (3 months old) mice. These animals were subjected or not subjected to physiological vaginal distension to mimic vaginal parturition (N = 4/group); in anesthetized mice, a 6F transurethral catheter was inserted into the vagina, and it was inflated with 0.3 mL (which best approximated fetal head circumference), and a 13 g weight was attached to the catheter creating circumferential and downward strains similar to parturition. Following this, the animals were euthanized, and the pelvis was fixed in situ for assessment of muscle architectural parameters; muscle fibers length was determined using digital calipers and sarcomere length was measured by light microscopy. Pregnancy induced a significant increase in normalized muscle fiber length in all PFMs compared to non-pregnant animals (Pregnant vs. not pregnant — C: 4.71±0.06 mm vs. 3.37±0.15 mm, p&lt;0.0001; ICa 8.74±0.14 mm vs. 7.50±0.27 mm, p=0.004; PCa 7.13±0.09 mm vs. 6.28±0.34 mm, p=0.04); TA muscle fiber length was unchanged (6.92±0.17 mm vs. 6.73 ± 0.19 mm, p=0.28). Sarcomere length was not affected by pregnancy in any muscle (C: 2.44±0.002 μm vs. 2.45 ± 0.003 μm, p=0.55; ICa: 2.26±0.003 μm vs. 2.26±0.004 μm, p=0.64; PCa: 2.16±0.01 μm vs. 2.16±0.003 μm, p=0.74; TA: 2.55±0.004 μm vs. 2.54±0.003 μm, p=0.28). Balloon-mediated vaginal distention resulted in significantly longer sarcomere lengths in non-pregnant compared to pregnant animals in all PFMs (C: 2.98±0.01 μm vs. 2.43±0.01 μm, p&lt;0.0001; ICa: 2.54±0.004 μm vs. 2.24±0.005 μm, p&lt;0.0001; PCa: 2.85±0.001 μm vs. 2.17±0.001 μm, p&lt;0.0001), indicating protection against sarcomere elongation in pelvic floor muscles of pregnant animals. This study shows that, similar to rats, pregnancy causes architectural changes in mouse pelvic floor muscles, which prevent excessive sarcomere stretching during physiologic vaginal distension that is comparable to fetal delivery. This work was funded by NIH grant #K12 HD000849 (Reproductive Scientist Development Program) to LAB and UC San Diego Senate Grant to LAB. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Muscle geometry and its relevance for sports performance? A perspective of current findings and future opportunities

Muscle geometry and its relevance for sports performance? A perspective of current findings and future opportunities

Fully Automated Analysis of Muscle Architecture from B-Mode Ultrasound Images with DL_Track_US

B-mode ultrasound can be used to image musculoskeletal tissues, but one major bottleneck is analyses of muscle architectural parameters (i.e., muscle thickness, pennation angle and fascicle length), which are most often performed manually. In this study we trained two different neural networks (classic U-Net and U-Net with VGG16 pre-trained encoder) to detect muscle fascicles and aponeuroses using a set of labeled musculoskeletal ultrasound images. We determined the best-performing model based on intersection over union and loss metrics. We then compared neural network predictions on an unseen test set with those obtained via manual analysis and two existing semi/automated analysis approaches (simple muscle architecture analysis [SMA] and UltraTrack). DL_Track_US detects the locations of the superficial and deep aponeuroses, as well as multiple fascicle fragments per image. For single images, DL_Track_US yielded results similar to those produced by a non-trainable automated method (SMA; mean difference in fascicle length: 5.1 mm) and human manual analysis (mean difference: -2.4 mm). Between-method differences in pennation angle were within 1.5°, and mean differences in muscle thickness were less than 1 mm. Similarly, for videos, there was overlap between the results produced with UltraTrack and DL_Track_US, with intraclass correlations ranging between 0.19 and 0.88. DL_Track_US is fully automated and open source and can estimate fascicle length, pennation angle and muscle thickness from single images or videos, as well as from multiple superficial muscles. We also provide a user interface and all necessary code and training data for custom model development.

Acute and Chronic Effects of Static Stretching on Neuromuscular Properties: A Meta-Analytical Review

The aim of this review was to provide an overview of the recent findings on the acute and chronic effects of static stretching on joint behaviors and neuromuscular responses and to discuss the overall effects of acute and chronic static stretching on selected outcomes via meta-analyses, using a total of 50 recent studies. The results of our meta-analyses demonstrated that acute static stretching results in increased range of motion (ROM), decreased passive resistive torque (PRT), increased maximum tolerable PRT (PRTmax), decreased maximum voluntary isometric torque, decreased muscle–tendon unit stiffness, decreased muscle stiffness, decreased tendon stiffness, and decreased shear elastic modulus. Moreover, the chronic effects of static stretching included increased ROM, increased PRTmax, decreased muscle stiffness, and decreased shear elastic modulus (or shear wave speed). These results suggest that static stretching interventions have the potential to increase ROM and reduce the mechanical properties of muscle–tendon tissue, but they may not change corticospinal excitability and spinal reflex excitability or muscle architecture parameters.

Three-dimensional architecture of the human subscapularis muscle in vivo

Detailed analysis of skeletal muscle architecture provides insights into skeletal muscle function. To date, measurements of the human subscapularis architecture have been limited to cadaveric measurements. In this study we demonstrate the feasibility of using anatomically constrained fibre tractography to reconstruct and quantify the 3D architecture of the human subscapularis muscle, and provide the first quantitative measurements of the architecture of the human subscapularis muscle in vivo. mDixon and diffusion tensor magnetic resonance images were obtained from the right shoulders of 20 healthy young adults. Anatomically constrained fibre tractography, in which fascicle reconstructions were forced to terminate on the internal aponeurosis of the subscapularis, was used to reconstruct muscle fibre architecture of the subscapularis muscles. Qualitatively, architectural reconstructions resembled the known subscapularis anatomy well, demonstrating face validity of the reconstructions. Muscle architectural parameters (means ± SDs) were: muscle volume 138 ± 42 cm3, fascicle length 63.6 ± 5.9 mm, physiological cross-sectional area (PCSA) 22 ± 6 cm2, and pennation angle 16 ± 2°. Architectural measurements of the subscapularis fell within the range reported in cadaver studies and were relatively insensitive to variations in fibre tractography parameters. The anatomically detailed whole-muscle reconstructions can be used to quantify the effects of joint surgery on muscle architecture and to advance computational models of the human shoulder.

Ultrasound changes in lower limb muscle architectural parameters and ambulatory outcomes in early stroke survivors.

Ultrasound changes in lower limb muscle architectural parameters and ambulatory outcomes in early stroke survivors.

Adaptations in athletic performance and muscle architecture are not meaningfully conditioned by training free-weight versus machine-based exercises: Challenging a traditional assumption using the velocity-based method.

Although the superior effectiveness of free-weight over machine-based training has been a traditionally widespread assumption, longitudinal studies comparing these training modalities were scarce and heterogeneous. This research used the velocity-based method to compare the effects of free-weight and machine-based resistance training on athletic performance and muscle architecture. Thirty-four resistance-trained men participated in an 8-week resistance training program allocated into free-weight (n = 17) or machine-based (n = 17) groups. Training variables (intensity, intraset fatigue, and recovery) were identical for both groups, so they only differed in the use of a barbell or specific machines to execute the full squat, bench press, prone bench pull, and shoulder press exercises. The velocity-based method was implemented to accurately adjust the planned intensity. Analysis of covariance and effect size (ES) statistics were used to compare both training modalities on a comprehensive set of athletic and muscle architecture parameters. No between-group differences were found for any athletic (p ≥ 0.146) and muscle architecture (p ≥ 0.184) variable. Both training modalities significantly and similarly improved vertical jump (Free-weight: ES ≥ 0.45, p ≤ 0.001; Machine-based: ES ≥ 0.41, p ≤ 0.001) and lower limb anaerobic capacity (Free-weight: ES ≥ 0.39, p ≤ 0.007; Machine-based: ES ≥ 0.31, p ≤ 0.003). Additionally, the machine-based group meaningfully enhanced upper limb anaerobic power (ES = 0.41, p = 0.021), whereas the free-weight group significantly improved the change of direction (ES = -0.54, p = 0.003) and 2/6 balance conditions analyzed (p ≤ 0.012). Changes in sprint capacity (ES ≥ -0.13, p ≥ 0.274), fascicle length, and pennation angle (ES ≤ 0.19, p ≥ 0.129) were not significant for either training modality. Adaptations in athletic performance and muscle architecture would not be meaningfully influenced by the resistance modality trained.

In vivo 3D muscle architecture quantification based on 3D freehand ultrasound and magnetic resonance imaging

Muscle architecture parameters, such as the fascicle length, pennation angle, and volume, are important muscle morphology characteristics. Accurate in vivo quantification of these parameters allows to detect changes due to pathologies, interventions, and rehabilitation trainings, which ultimately impact on muscles’ force-producing capacity. In this study, we compared three-dimensional (3D) muscle architecture parameters of the tibialis anterior and gastrocnemius medialis, which were quantified by 3D freehand ultrasound (3DfUS) and a magnetic resonance imaging (MRI) technique, diffusion tensor imaging (DTI), respectively. Sixteen able-bodied subjects were recruited where seven of them received both 3DfUS and MRI measurement, while the rest underwent 3DfUS measurements twice. Good to excellent intra-rater reliability and inter-session repeatability were found in 3DfUS measurements (intra-class correlation coefficient > 0.81). Overall, the two imaging modalities yielded consistent measurements of the fascicle length, pennation angle, and volume with mean differences smaller than 2.9 mm, 1.8°, and 5.7 cm3, respectively. The only significant difference was found in the pennation angle of the tibialis anterior, although the discrepancy was small. Our study demonstrated, for the first time, that 3DfUS measurement had high reliability and repeatability for measurement of muscle architecture in vivo and could be regarded as an alternative to MRI for 3D evaluation of muscle morphology.

Effects of Spinal Stabilization Exercises Delivered Using Telerehabilitation on Outcomes in Patients with Chronic Neck Pain: A Randomized Controlled Trial

Background When spinal stabilization exercises (SSE) are performed regularly, they may provide benefits on outcome measures in chronic nonspecific neck pain (CNNP) patients. The pandemic has made it difficult for CNNP patients to access regular physiotherapy-exercise services. This study aims to compare telerehabilitation (TR) with face-to-face rehabilitation in CNNP patients. Methods Neck Functional Capacity Evaluation Test (NFCET) results were the primary outcomes. Pain intensity (PI), disability, awareness, the architecture of the neck muscles, and exercise satisfaction were the secondary outcomes. Patients were randomized into the TR group (TRG) (n=15) and the control group (CG) (n=16). All patients performed SSE 3 days a week, for 8 weeks. The TRG was instructed remotely while the CG was instructed in the clinic. Results After 8 weeks, NFCET values increased (p<0.05). In both groups, PI and disability decreased and neck awareness increased (p<0.05). Muscle architecture parameters improved in both groups (p<0.05), except for the Right Sternocleidomastoideus in both groups and the Right Upper-Trapezius in TRG (p>0.05). There was no difference between the groups for all variables and exercise satisfaction after 8 weeks (p>0.05). Conclusion SSE for neck pain, whether supervised by a therapist in the clinic or by telerehabilitation, was equally effective.

DL_Track - Automated analysis of muscle architecture from B-mode ultrasonography images using deep learning

B-mode ultrasound is commonly used to image musculoskeletal tissues, but one major bottleneck is data analysis. Manual analysis is commonly deployed for assessment of muscle thickness, pennation angle and fascicle length in muscle ultrasonography images. However, manual analysis is somewhat subjective, laborious and requires thorough experience. We provide an openly available algorithm (DL_Track) to automatically analyze muscle architectural parameters in ultrasonography images or videos of human lower limb muscles.&#x0D; We trained two different neural networks (classic U-net [Ronneberger et al., 2021] and U-net with VGG16 [Simonyan &amp; Zisserman, 2015] pretrained encoder) one to detect muscle fascicles and another to detect muscle aponeuroses using a set of labelled musculoskeletal ultrasound images. We included images from four different devices of the vastus lateralis, gastrocnemius medialis, tibilias anterior and soleus. In total, we included 310 images for the fascicle model and 570 images for the aponeuroses model, which we augmented to about 1,700 images per set. Each dataset was randomly split into a training and test set for model training, using a common 80/20 train/test split. We determined the best performing model based on intersection-over-union and loss metrics calculated during model training. We compared neural network predictions on an unseen test set consisting of 35 images to those obtained via manual analysis and two existing semi/automated analysis approaches (SMA and Ultratrack).&#x0D; Across the set of 35 unseen images, the mean differences between DL_Track and manual analysis were for fascicle length -2.4 mm (95% compatibility interval (CI) = -3.7 to -1.2), for pennation angle 0.6° (-0.2 to 1.4), and for muscle thickness -0.6 mm (-1.2 to 0.002). The corresponding values comparing DL_Track with SMA were for fascicle length 5.2 mm (1.3 to 9.0), for pennation angle -1.4° (-2.6 to -0.4) and for muscle thickness -0.9 mm (-1.5 to -0.3) respectively. ICC values between DL_Track and Ultratrack were 0.19 (0.00 to 0.35) for medial gastrocnemius passive contraction, 0.79 (0.77 to 0.81) for medial gastrocnemius maximal voluntary contraction, 0.88 (0.87 to 0.89) for calf raise, 0.67 (0.07 to 0.86) for medial gastrocnemius during walking, 0.80 (0.79 to 0.82) for tibialis passive plantar and dorsiflexion, and 0.85 (0.83 to 0.86) for tibialis anterior maximum voluntary contraction.&#x0D; Our method is fully automated and can estimate fascicle length, pennation angle and muscle thickness from single images or videos in multiple superficial muscles. For single images, the method gave results that are in agreement with those produced by SMA or manual analysis. Similarly, for videos, there was overlap between the results produced with Ultratrack and our method. In contrast to Ultratrack, DL_Track analyzes each frame independently of the previous frames, which might explain the observerd variability.&#x0D; References&#x0D; Ronneberger, O., Fischer, P., &amp; Brox, T. (2021). U-Net: Convolutional networks for biomedical image segmentation. arXiv. https://doi.org/10.48550/arXiv.1505.04597&#x0D; Simonyan, K., &amp; Zisserman, A. (2015). Very deep convolutional networks for large-scale image recognition. arXiv. https://doi.org/10.48550/arXiv.1409.1556

Muscle architecture and muscle fibre type composition in the forelimb of two African mole-rat species, Bathyergus suillus and Heterocephalus glaber.

The scratch-digging Cape dune mole-rat (Bathyergus suillus), and the chisel-toothed digging naked mole-rat (Heterocephalus glaber) are African mole-rats that differ in their digging strategy. The aim of this study was to determine if these behavioural differences are reflected in the muscle architecture and fibre-type composition of the forelimb muscles. Muscle architecture parameters of 39 forelimb muscles in both species were compared. Furthermore, muscle fibre type composition of 21 forelimb muscles were analysed using multiple staining protocols. In B. suillus, muscles involved with the power stroke of digging (limb retractors and scapula elevators), showed higher muscle mass percentage, force output and shortening capacity compared to those in H. glaber. Additionally, significantly higher percentages of glycolytic fibres were observed in the scapular elevators and digital flexors of B. suillus compared to H. glaber, suggesting that the forelimb muscles involved in digging in B. suillus provide fast, powerful motions for effective burrowing. In contrast, the m. sternohyoideus a head and neck flexor, had significantly more oxidative fibres in H. glaber compared to B. suillus. In addition, significantly greater physiological cross-sectional areaand fascicle length values were seen in the neck flexor, m. sternocleidomastoideus, in H. glaber compared to B. suillus, which indicates a possible adaptation for chisel-tooth digging. While functional demands may play a significant role in muscle morphology, the phylogenetic differences between the two species may play an additional role which needs further study.

Non-Invasive estimation of muscle fiber type using ultra Sonography

Introduction: The aim of this study was to estimate the muscle fiber type i.e., fast/white muscle fibers and slow/red muscle fibers) on the basis of selected muscle architectural parameters i.e., Pen-nation angle, Muscle thickness and Fascicle Length of Rectus Femoris and Vastus Lateralis using ultrasound image analysis. Materials and Methods: In this work of investigation, a total sample comprised of 30 highly trained male athletes of Lakshmibai National Institute of Physical Education Gwalior, Madhya Pradesh was considered as sample for present investigation. Purposive sampling technique was employed for selecting sample, out of which 15 were marathon runners and 15 were 100-meter sprinters. The selected subjects’ age ranged between 19 to 25 years. Muscle architectural parameters such as Pen-nation angle, Fascicle length, and Muscle thickness were measured using a B-Mode ultrasonography method (Model-WIPRO GE VOLUSON E 6). Results: The developed estimate model explains 54.6% to 72.8% of the variation in muscle fiber type. Thus, the logistic regression equation developed was: - Log p/(1-p) = 10.955 - 3.278 (VL_FL) + 1.267 (VL_PA). Conclusion: The wald statistics obtained from the logistic model revealed that decreasing the vastus lateralis pen nation angle by one unit increases the likelihood of having white muscle fiber by 2.54 times, while increasing the Vastus Lateralis Fascicle Length by one unit increases the likelihood of having white muscle fiber by 0.62 times. In order to determine muscle fiber type on the basis of muscle architectural parameters Vastus lateralis pen-nation angle and fascicle length were the most discriminating variables among selected fiber types.

A classification of the plantar intrinsic foot muscles based on the physiological cross-sectional area and muscle fiber length in healthy young adult males

BackgroundPlantar intrinsic foot muscles (PIFMs) are composed of 10 muscles and play an essential role in achieving functional diversity in the foot. Previous studies have identified that the morphological profiles of PIFMs vary between individuals. The morphological profiles of a muscle theoretically reflect its output potentials: the physiological cross-sectional area (PCSA) of a muscle is proportional to its maximum force generation, and the muscle fiber length (FL) is its shortening velocity. This implies that the PCSA and FL may be useful variables for characterizing the functional diversity of the individual PIFM. The purpose of this study was to examine how individual PIFMs can be classified based on their PCSA and FL.MethodsIn 26 healthy young adult males, the muscle volume and muscle length of seven PIFMs (abductor hallucis, ABDH; abductor digiti minimi, ABDM; adductor hallucis oblique head, ADDH-OH; ADDH transverse head, ADDH-TH; flexor digitorum brevis, FDB; flexor hallucis brevis, FHB; quadratus plantae, QP) were measured using magnetic resonance imaging. The PCSA and FL of each of the seven PIFMs were then estimated by combining the data measured from the participants and those of muscle architectural parameters documented from cadavers in previous studies. A total of 182 data samples (26 participants × 7 muscles) were classified into clusters using k-means cluster analysis. The optimal number of clusters was evaluated using the elbow method.ResultsThe data samples of PIFMs were assigned to four clusters with different morphological profiles: ADDH-OH and FHB, characterised by large PCSA and short FL (high force generation and slow shortening velocity potentials); ABDM and FDB, moderate PCSA and moderate FL (moderate force generation and moderate shortening velocity potentials); QP, moderate PCSA and long FL (moderate force generation and rapid shortening velocity potentials); ADDH-TH, small PCSA and moderate FL (low force generation and moderate shortening velocity potentials). ABDH components were assigned equivalently to the first and second clusters.ConclusionsThe approach adopted in this study may provide a novel perspective for interpreting the PIFMs’ function based on their maximal force generation and shortening velocity potentials.

Contribution of stroke-related changes in neuromuscular factors to gear ratio during isometric contraction of medial gastrocnemius muscle: A simulation study

BackgroundIt is not clear which neuromuscular factors are most closely associated with the loss of variable fascicle gearing after chronic stroke. The purpose of this simulation study is to determine the effects of stroke-related changes in key neuromuscular factors on the gear ratio. MethodsA modified Hill-type model of the medial gastrocnemius was developed to determine the gear ratio for a given muscle activation level and musculotendon length. Model parameters were then systematically adjusted to simulate known stroke-related changes in neuromuscular factors, and the gear ratio was computed for each change in the parameters. A Monte Carlo simulation was performed to understand which neuromuscular factors and fiber behavior-related parameters are most relevant to the loss of variable gearing. Dominance analyses were also conducted to quantify the relative importance of fiber behavior-related parameters on the gear ratio. FindingsThe gear ratio decreases significantly with smaller pennation angle and with shorter optimal fiber length. In addition, muscle thickness and pennation angle at optimal fiber length appear to be the most important muscle architectural parameters. Dominance analyses further suggest that primary determinants of gear ratio include initial pennation angle, fiber rotation-shortening ratio, initial muscle thickness, and fiber rotation. InterpretationOur findings provide insight that the pennation angle may play an important role for efficient muscular contraction, implying that maintaining muscle architecture and/or improving fiber/fascicle rotation could a key goal in rehabilitation interventions. Our findings will help us to better interpret altered gearing behavior in aging and pathological muscles.

Ultrasound Assessment of Changes in Muscle Architecture of the Brachialis Muscle After Stroke—A Prospective Study

ObjectiveTo investigate changes in ultrasound-derived muscle architecture parameters of the brachialis and correlations in patients with subacute stroke. DesignProspective longitudinal observational study. SettingTertiary inpatient rehabilitation center. ParticipantsFifty adult patients (N=50) who were recruited within the first month poststroke. The patients had a mean age of 57.2±12.3 years and 68.0% were male. The majority of patients had significant upper limb weakness with a low mean Motricity Index of 18.5±24.7 and median elbow flexor strength of grade 0. InterventionNot applicable. Main Outcome MeasuresUltrasound of the intact and hemiparetic brachialis was performed at 3-time intervals: within 1 month of stroke onset and at 1 and 6 months after first assessment. Clinical variables captured included upper limb motor power and elbow flexor spasticity. ResultsCompared to the intact brachialis, there was reduced muscle thickness (1.93 cm vs 2.07 cm, 1.86 cm vs 2.08 cm, 1.85 cm vs 2.05 cm; P=.022) and increased echo intensity (63.3 arbitrary units [AU] vs 56.8 AU, 69.4 AU vs 56.6 AU, 77.4 AU vs 58.2 AU; P<.001) in the hemiparetic brachialis at all assessment intervals (baseline, 1 month, 6 months). Reduction in muscle mass was greater in older patients, with the correlation coefficient ranging from −0.30 (P=.03) at baseline to −0.50 (P<.001) at 6 months. Presence of elbow flexor spasticity at 1-month assessment interval was associated with lower muscle mass reduction (1.93 cm vs 1.74 cm; P=.017), lower echo intensity (65.1 AU vs 75.1 AU; P=.023), and longer fascicle lengths (12.92 cm vs 9.83 cm; P=.002). ConclusionsChanges including decreased muscle thickness and increased echo intensity of the hemiparetic brachialis were noted over time. Elbow flexor spasticity at 1-month assessment interval appears to mitigate against these changes.

The effect of aerobic training on motor function and muscle architecture in children with Duchenne muscular dystrophy: A randomized controlled study

Objective To explore the effects of aerobic training adding to home-based exercise program on motor function and muscle architectural properties in children with Duchenne muscular dystrophy. Design This is a prospective randomized controlled study. Setting Pediatric neuromuscular clinic in a tertiary care center. Subjects Children with Duchenne muscular dystrophy. Interventions Children were randomly divided into two groups whereby 12-weeks aerobic training was additionally given in treatment group in contrast to the control group which received only home-based exercise program. Main Measures Motor Function Measure and Six Minute Walk Test were used for clinical evaluation, and muscle architectural properties (thickness, pennation angle and fascicle length) were measured by ultrasound imaging. Both groups were assessed at baseline and after 12-weeks of training. Results Median age of children was 7.9 years in the treatment group and 8.6 years in the control group (p > 0.05). Significant improvements were obtained for Motor Function Measure and Six Minute Walk Test from baseline to 12-weeks in the treatment group; Motor Function Measure total score changed from 83.2 (6.1) to 86.9 (4.0) vs. 82.3 (10.2) to 80.4 (9.4) points in the control group (p = 0.006); 6 Minute Walk Test distance changed from 395.3 (46.6) to 413.0 (52.3) vs. 421.7 (64.4) to 393.8 (68.2) meters in the control group (p < 0.001). However, muscle architectural parameters did not change during study period (p > 0.05). Conclusion Aerobic training may be of additional value in improving motor function and performance with no remarkable effect on muscle architectural properties.

A Comparative Study of White Muscle and Red Muscle Fiber Architectural Parameters

The primary objective of this research was to compare red muscle fiber and white muscle fiber muscle architectural parameters of vastus lateralis (VL). The study sample consisted of 70 recreationally active male students from Gwalior, Madhya Pradesh. One repetition maximum Dr. Hatfield test was used to determine muscle fiber type. Thirty (N1 = 15 red muscle fiber group and N2 = 15 red muscle fiber group) out of 70 samples were retained in study for further evaluation. Muscle architectural parameters (VL, pennation angle [PA], fascicle length [FA], and muscle thickness [MT]) were measured using B-mode ultrasonography. Independent sample t-test was employed to determine a significant difference between selected white muscle fibers group and selected red muscle fibers on the basis of selected muscle architectural parameters. The vastus lateralis muscle showed differences in its PA, FA, and MT between different muscle fiber groups. The PA of red muscle fiber group was greater than white muscle fiber group, whereas the FA and MT of white muscle fiber group were greater than red muscle fiber group. In conclusion, architectural parameters studies carried on specific sports group will be helpful in future, and muscle architectural parameters may be considered as a new approach for muscle fiber type classification in the future.

Adductor longus: An anatomical study to better understand groin pain.

We investigated the shear modulus-passive force relationship in the hip adductor longus (AL) muscles of human cadavers and explored the effect of muscle architecture on the elastic properties of the AL muscle using shear wave elastography (SWE). Nine AL muscles were harvested from a soft, embalmed cadaver. The AL muscles were affixed to a custom-built device comprising two clamps, a pulley, and a cable to provide passive loads, which were increased from 0 to 600 g in 60-g increments. The shear modulus of the AL muscle was measured in the proximal (Pro), middle (Mid), and distal (Dis) regions. The masses and anatomical cross-sectional areas (ACSAs) of the AL muscles were measured. The shear modulus-passive load relationship of each tested muscle region was analyzed by fitting a least-squares regression line. Moreover, the rate of increase in the shear modulus per unit load (s) was calculated. The shear modulus and passive force were linearly correlated for all AL muscles in each region (p < 0.01). The mean coefficients of determination (R2 ) for Pro, Mid, and Dis were 0.989, 0.986, and 0.982, respectively. The rate of increase in the shear modulus per unit load significantly correlated with the reciprocal of the muscle mass (r=0.77, p=0.02) and ACSA (r=0.43, p=0.03). Shear wave elastography can be used as an indirect measure of passive force in any region of the AL muscle. Additionally, the rate of increase in the shear modulus per unit load could be associated with muscle architectural parameters.