Fascicle Length Research Articles

Reliability of Ultrasonographically Acquired Muscle Morphology Based on a Cohort of Men and Women

Objective: The objective was to evaluate intrarater and inter-rater reliability of ultrasonography muscle morphology measurements in men and women, considering morphological differences between the genders. Materials and Methods: Thirty-two healthy subjects (16 male; 16 female; 26.6 ± 4.9 years) participated in two evaluation days. On day 1, subjects were evaluated by a single experienced rater, who repeated the evaluation on the next testing day along with two other raters. Muscle morphology of quadriceps femoris (QMT), rectus femoris (RFMT), vastus intermedius (VIMT), vastus medialis (VMMT), and vastus lateralis (VLMT) muscle thickness, rectus femoris muscle cross-sectional area (RFCSA), vastus lateralis muscle fascicle length (VLFL), and pennation angle (VLPA) were obtained. Reliability was evaluated by intraclass correlation coefficients (ICCs). Results: All intrarater comparisons demonstrated good reliability (ICC >0.90), even after participants’ gender stratification (ICC >0.81). Inter-rater comparisons for RFCSA, and muscle thickness showed good reliability (ICC >0.76). Male’s VLFL and VLPA reliability was considered insufficient (ICC = 0.58 and 0.60, respectively), while female’s was slightly higher (ICC = 0.79 and 0.75, respectively). Conclusion: Ultrasonography has potential to be used to observe changes in muscle size, but pennation angle and fascicle length should be evaluated by the same rater.

Flywheel resistance training promotes unique muscle architectural and performance-related adaptations in young adults.

The purpose of this study was to examine the skeletal muscle hypertrophic, architectural, and performance-related adaptations in response to volume-matched, total-body flywheel versus traditional resistance training in a randomized, non-exercise controlled study in physically active young adults. Thirty-one healthy young adults (24±3y) were randomized to 10weeks of traditional resistance training (TRT; n=7F/5M), flywheel training (FWRT; n=7F/4M), or a habitual activity control (CON; n=5F/3M). Maximal voluntary isometric torque (MVIT), one repetition-maximum (1RM) for the free weight squat and bench press, three repetition work maximum (3Wmax) for the flywheel squat and bench press, countermovement jump height, and broad jump distance, as well as site-specific muscle hypertrophy, fascicle length (FL), and pennation angle, were measured. Both TRT and FWRT increased MVIT (p≤0.021) and FFM (p≤0.032) compared to CON. However, TRT promoted superior improvements in free weight squat and bench 1RM (p<0.001), and FWRT improved flywheel 3Wmax squat and bench (p<0.001). FWRT increased the FL and cross-sectional area of the distal VL, countermovement jump height, and broad jump distance (p≤0.048), whereas TRT increased the pennation angle and cross-sectional area of the proximal VL. Therefore, 10weeks of volume-matched, total-body traditional, and flywheel resistance training similarly increased maximal isometric strength and fat-free mass. However, FWRT promoted unique skeletal muscle architectural adaptations that likely contributed to region-specific VL hypertrophy and jump performance improvements. Thus, FWRT provides a novel training stimulus that promotes architectural adaptations that support improved athletic performance in a manner that is not provided by traditional resistance exercise training.

Discipline-specific adaptation patterns in respiratory and lower limb musculotendinous structures: cyclists vs. basketball players.

This study aimed at assessing how chronic exposure to specific exercise training (high-intensity intervals vs. endurance), comparing experienced basketball-players (BP, N.=16), cyclists (CY, N.=16), and non-specifically trained individuals (CN, N.=16), influences the structural and functional characteristics of both lower limb and respiratory musculotendinous structures. Vastus lateralis, gastrocnemius lateralis, and medialis, diaphragm muscles, as well as patellar tendon and Achilles tendon, were assessed using B-mode ultrasonography. Maximal voluntary isometric and passive torque measurements were conducted in the knee-extensors and plantar-flexors. Additionally, a subset of participants (N.=10 for each group) underwent a fatigue-inducing exercise-till-exhaustion protocol, and the strength of lower limb and respiratory muscles was evaluated immediately before and after the trial. Athletes had bigger and stronger musculotendinous structures and greater endurance to fatigue than CN (P<0.05). BP had bigger plantar-flexors and diaphragm, greater fascicles length, more explosive plantar-flexors and respiratory muscles and bigger tendons than CY (P<0.05). On the other hand, CY showed greater muscle pennation angle and greater endurance to fatigue for both, lower limb, and respiratory muscles (P<0.05). The present study emphasizes that chronic and specific exercise training leads to distinctive adaptations, not only in lower limb musculotendinous structures but also in other components such as respiratory muscles.

Acute effects of resistance exercise on the muscle architecture and tissue organization of the maximal isometrically contracted and uncontracted gastrocnemius medialis muscle

ABSTRACT This study aimed to investigate the acute effects of resistance exercise on muscle architecture and tissue organization at rest and during isometric maximum voluntary contraction (iMVC) of the gastrocnemius medialis muscle. In 16 healthy adults (25 ± 3 y), ultrasound scans were captured before (pre), immediately after (post), and 15 min after (post_15) single-leg calf raises during rest and iMVCs. Measurements included muscle thickness (MT), pennation angle (PA), and fascicle length (FL). Spatial frequency analysis (SFA) assessed tissue organization (e.g. peak spatial frequency radius (PSFR), quality factor (Q6)). MT increased significantly from pre to post (+5.7%) and post_15 (+5.6%) at rest. During iMVC, MT and FL increased significantly from pre to post (MT: +8.1%, FL: +14.9%) and post_15 (MT: +5.2%, FL: +10.5%), while PA decreased significantly from pre to post_15 (−10.2%). PSFR and Q6 decreased significantly from pre to post (−7.0-8.2%) and increased from post to post_15 (+10.3-10.6%) at rest, with no significant changes during iMVC. Resistance exercise led to altered muscle architecture for more than 15 min, while SFA parameters reverted to baseline within 15 min. Thus, SFA potentially enables early differentiation of potential physiological alterations in muscle micro-morphology.

Impact of contraction intensity and ankle joint angle on calf muscle fascicle length and pennation angle during isometric and dynamic contractions

During muscle contraction, not only are the fascicles shortening but also the pennation angle changes, which leads to a faster contraction of the muscle than of its fascicles. This phenomenon is called muscle gearing, and it has a direct influence on the force output of the muscle. There are few studies showing pennation angle changes during isometric and concentric contractions for different contraction intensities and muscle lengths. Therefore, the aim was to determine these influences over a wide range of contraction intensities and ankle joint angles for human triceps surae. Additionally, the influence of contraction intensity and ankle joint angle on muscle gearing was evaluated. Ten sport students performed concentric and isometric contractions with intensities between 0 and 90% of the maximum voluntary contraction and ankle joint angles from 50° to 120°. During these contractions, the m. gastrocnemius medialis and lateralis and the m. soleus were recorded via ultrasound imaging. A nonlinear relationship between fascicle length and pennation angle was discovered, which can be described with a quadratic fit for each of the muscles during isometric contraction. A nearly identical relationship was detected during dynamic contraction. The muscle gearing increased almost linearly with contraction intensity and ankle joint angle.

Muscle ultrasound in Spondyloarthritis patients receiving biologic disease-modifying anti-rheumatic drugs early in treatment

Objective: This study evaluated muscle ultrasound in spondyloarthritis (SpA) patients receiving biologic disease-modifying anti-rheumatic drugs (b-DMARDs) early in treatment. Methods: A prospective study was conducted with 110 b-DMARD-naive SpA patients. The baseline and control muscle strength, physical performance tests, ultrasonographic muscle parameters, and disease activity scores of 67 controlled patients were examined. Results: During the follow-up period, there were significant improvements in the thickness of the gastrocnemius medialis (GM) muscle (p&lt;0.001), the length of the GM fascicle (p=0.031), the thickness of the rectus femoris (RF) muscle (p&lt;0.001), the cross-sectional area of the RF (RFCSA) muscle (p&lt;0.001), the thickness of the rectus abdominis (RA) muscle (p&lt;0.001), the thickness of the transverse abdominis (TA) muscle (p=0.004), and the thickness of the external oblique (EO) muscle (p=0.042). Besides, ASDAS-CRP scores were related to GM muscle thickness, RFCSA, and TA muscle thickness percent changes in patients whose disease activity regressed from high to moderate (respectively; p=0.030, p=0.040, p=0.002). Conclusion: Muscle ultrasound examination can show muscle mass improvement in SpA patients during treatment.

Exploration of the triceps surae muscle in ambulatory children with cerebral palsy using instrumented measurements of stiffness and diffusion tensor magnetic resonance imaging for muscle architecture

BackgroundMusculoskeletal alterations causing reduced range of motion of the ankle joint are common in children with cerebral palsy (CP). Objective measurements of passive joint resistance and three-dimensional skeletal muscle volume and muscle architecture can lead to a comprehensive understanding of which factors influence joint range of motion.Research questionTo investigate the relation between the passive dorsiflexion of the ankle joint, biomechanical contributing factors to the passive joint resistance, and muscular architectural properties of the triceps surae muscle in children with CP.MethodsIn this cross-sectional observational study, 14 children with spastic CP (bilateral: 5, unilateral: 9, Gross Motor Function Classification System (GMFCS) level I:11, II:3) naïve to intramuscular tone reducing treatment, and 14 TD children were included. The passive dorsiflexion of the ankle was measured with a goniometer. Passive joint resistance and related parameters were estimated based on a biomechanical model and measurements using a motorized device, the Neuroflexor. Three-dimensional muscle architecture was quantified with diffusion tensor magnetic resonance imaging (DT-MRI).ResultsIn the CP group, the median [min, max] passive dorsiflexion was decreased in the most affected leg (MAL) compared to the less affected leg (LAL) (2.5° [-25°, 20°] vs. 12.5° [5°, 30°], p = 0.001). The stiffness coefficient (Nm/rad) in the MAL was significantly higher in children with CP compared to TD children (7.10 [3.39, 62.00] vs. 2.82 [1.24, 10.46], p = 0.015). Muscle architecture properties did not differ between CP and TD, except for pennation angle in the medial gastrocnemius (MG) of the MAL (CP 17.64° (2.29) vs. TD 21.46° (3.20), p = 0.017). The stiffness coefficient, in the MAL, correlated negatively to passive dorsiflexion (rs=-0.638) and pennation angle in medial gastrocnemius (rs=-0.964), and the non-linear coefficient (Non-linear 1) correlated negatively to the fascicle length of the medial gastrocnemius (rs=-0.857).ConclusionThis study shows that stiffness of the plantarflexors is related to decreased passive dorsiflexion of the ankle and muscle structure of the MG in high-functioning children with spastic CP. Assessments of how dynamic components as well as microscopic muscle alterations contribute to joint stiffness in the plantarflexors in individuals with CP are warranted.Trial registrationRetrospectively registered in ClinicalTrials.gov, NCT05447299. Observational study. Study start: 2019-01-15, register date: 2022-07-01.

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.

Residual force enhancement decreases when scaling from the single muscle fiber to joint level in humans

BackgroundResidual force enhancement (rFE), defined as increased isometric force following active lengthening compared to a fixed-end isometric contraction at the same muscle length and level of activation, is present across all scales of muscle. While rFE is always present at the cellular level, often rFE “non-responders” are observed during joint-level voluntary contractions. MethodsWe compared rFE between the joint level and single fiber level (vastus lateralis biopsies) in 16 young males. In vivo voluntary knee-extensor rFE was measured by comparing steady-state isometric torque between a stretch-hold (maximal activation at 150°, stretch to 70°, hold) and a fixed-end isometric contraction, with ultrasonographic recording of vastus lateralis fascicle length (FL). Fixed-end contractions were performed at 67.5°, 70.0°, 72.5°, and 75.0°; the joint angle that most closely matched FL of the stretch-hold contraction's isometric steady-state was used to calculate rFE. The starting and ending FLs of the stretch-hold contraction were expressed as % optimal FL, determined via torque-angle relationship. ResultsIn single fiber experiments, the starting and ending fiber lengths were matched relative to optimal length determined from in vivo testing, yielding an average sarcomere excursion of ∼2.2–3.4µm. There was a greater magnitude of rFE at the single fiber (∼20%) than joint level (∼5%) (p = 0.004), with “non-responders” only observed at the joint level. ConclusionBy comparing rFE across scales within the same participants, we show the development of the rFE non-responder phenomenon is upstream of rFE's cellular mechanisms, with rFE only lost rather than gained when scaling from single fibers to the joint level.

Multiscale hamstring muscle adaptations following 9 weeks of eccentric training.

Eccentric training, such as Nordic hamstring exercise (NHE) training, is commonly used as a preventive measure for hamstring strains. Eccentric training is believed to induce lengthening of muscle fascicles and to be associated with the addition of sarcomeres in series within muscle fibers. However, the difficulty in measuring sarcomere adaptation in human muscles has severely limited information about the precise mechanisms of adaptation. This study addressed this limitation by measuring the multiscale hamstring muscle adaptations in response to 9 weeks of NHE training and 3 weeks of detraining. Twelve participants completed 9 weeks of supervised NHE training, followed by a 3-week detraining period. We assessed biceps femoris long-head (BFlh) muscle fascicle length, sarcomere length, and serial sarcomere number in the central and distal regions of the muscle. Additionally, we measured muscle volume and eccentric strength at baseline, post-training, and post-detraining. NHE training over 9 weeks induced significant architectural and strength adaptations in the BFlh muscle. Fascicle length increased by 19% in the central muscle region and 33% in the distal muscle region. NHE also induced increases in serial sarcomere number (25% in the central region and 49% in the distal region). BFlh muscle volume increased by 8%, and knee flexion strength increased by 40% with training. Following 3 weeks of detraining, fascicle length decreased by 12% in the central region and 16% in the distal region along with reductions in serial sarcomere number. Nine weeks of NHE training produced substantial, region-specific increases in BFlh muscle fascicle length, muscle volume, and force generation. The direct measurement of sarcomere lengths revealed that the increased fascicle length was accompanied by the addition of sarcomeres in series within the muscle fascicles.

Long-term effects of different number of botulinum toxin injections into the gastrocnemius muscle on function and muscle morphology in children with cerebral palsy

BackgroundBotulinum toxin (BoNT) injections are used to reduce spasticity, and sometimes repeated injections of the toxin are required. The aim of this study is to investigate the effects of the number of injections of BoNT into the gastrocnemius muscle on function, muscle morphology, muscle stiffness and muscle vascularization in children with cerebral palsy (CP). MethodsThe study included 22 children with unilateral or bilateral spastic type CP aged 5-13 years who had previously received one, two, or three BoNT injections into the gastrocnemius muscle. A total of 29 gastrocnemius muscles were evaluated. Gastrocnemius muscle morphology (muscle cross-sectional area, thickness, fascicle length and pennation angle) was examined by ultrasonography, muscle stiffness by shear wave ultrasound elastography and muscle vascularization by Superb Microvascular Imaging. The functional status of the children was evaluated by the Gross Motor Function Measurement, the Timed-Up-and-Go Test, the Squat Test, the Vertical Jumping Test and the Sit-and-Reach Test. ResultsIn the motor functions and muscle morphology values were similar in all three groups (p>0.05). Muscle stiffness values were higher (p=0.035) and vascularization values were lower (p=0.03) in the group that received three injections compared to the groups that received one injection. There was a moderate positive correlation of the number of BoNTs with muscle stiffness (p<0.05, r=0.454) and a moderate negative correlation with muscle vascularization (p<0.05, r=-0.497). ConclusionsRepeated BoNT applications have no effect on motor functions and muscle morphology in children with CP, whereas BoNT injections administered three times increase muscle stiffness and decrease vascularization.

Correlations among flexibility, stiffness, strength and muscle ultrasound parameters in older males afflicted with hamstrings tightness

IntroductionAge-induced inflexibility may lead to significant mobility impairments and declines in well-being. However, the relationship between the structural and mechanical properties of soft tissue and joint extensibility remains unclear. This study aimed to investigate the correlation between flexibility, muscle tendon unit (MTU) stiffness, muscle ultrasound characteristics, muscle strength, and hamstring flexibility prediction in older males with hamstring inflexibility. MethodsA hundred retired old males (mean age: 67.2 ± 4.9 years) participated in this investigation. Muscle ultrasound, flexibility, MTU stiffness, and knee flexors strength were measured in a single visit. ResultsThe results revealed a modest correlation between straight leg raise (SLR) and biceps femoris fascicle length (FL) elongation (r = 0.222), MTU stiffness (r = -0.401), and eccentric strength (r = 0.219) (all p < 0.05). MTU stiffness, eccentric strength, and FL elongation collectively explained 24.8% of the variance in SLR prediction, while deep fascia thickness predicted MTU stiffness with a variance of 6.4%. ConclusionIn summary, increased SLR was associated with lower MTU stiffness, lengthened FL, and higher eccentric strength. SLR was primarily predicted by MTU stiffness, with lesser contributions from FL elongation and knee flexor eccentric strength in older males experiencing hamstring tightness.

Influence of muscle packing on the three-dimensional architecture of rabbit M. plantaris

In their physiological condition, muscles are surrounded by connective tissue, other muscles and bone. These tissues exert transverse forces that change the three-dimensional shape of the muscle compared to its isolated condition, in which all surrounding tissues are removed. A change in shape affects the architecture of a muscle and therefore its mechanical properties. The rabbit M. plantaris is a multi-pennate calf muscle consisting of two compartments. A smaller, bi-pennate inner muscle compartment is embedded in a larger, uni-pennate outer compartment (Böl et al., 2015). As part of the calf, the plantaris is tightly packed between other muscles. It is unclear how packing affects the shape and architecture of the plantaris. Therefore, we examined the isolated and packed plantaris of the contralateral legs of three rabbits to determine the influence of the surrounding muscles on its shape and architectural properties using photogrammetric reconstruction and manual digitization, respectively. In the packed condition, the plantaris showed a 27% increase in fascicle pennation and a 54% increase in fascicle curvature compared to the isolated condition. Fascicle length was not affected by muscle packing. The change in muscle architecture occurred mainly in the outer compartment of the plantaris. Furthermore, the isolated plantaris showed a more circular shape and a reduced width of its muscle belly. It can be concluded that the packed plantaris is flattened by the forces exerted by the surrounding muscles, causing a complex architectural change. The data provided improve our understanding of muscle packages in general and can be used to develop and validate realistic three-dimensional muscle models.

Kinematic, Neuromuscular and Bicep Femoris In Vivo Mechanics during the Nordic Hamstring Exercise and Variations of the Nordic Hamstring Exercise

The Nordic hamstring exercise (NHE) is effective at decreasing hamstring strain injury risk. Limited information is available on the in vivo mechanics of the bicep femoris long head (BFLH) during the NHE. Therefore, the purpose of this study was to observe kinematic, neuromuscular and in-vivo mechanics of the BFLH during the NHE. Thirteen participants (24.7 ± 3.7 years, 79.56 ± 7.89 kg, 177.40 ± 12.54 cm) performed three repetitions of the NHE at three horizontal planes (0°, 20° and −20°). Dynamic ultrasound of the dominant limb BFLH, surface electromyography (sEMG) of the contralateral hamstrings and sagittal plane motion data were simultaneously collected. Repeated measures analysis of variance with Bonferroni post hoc corrections were used on the in vivo mechanics and the kinematic and sEMG changes in performance of the NHE. Likely differences in ultrasound waveforms for the BFLH were determined. Significant and meaningful differences in kinematics and in vivo mechanics between NHE variations were observed. Non-significant differences were observed in sEMG measures between variations. Changes to the NHE performance angle manipulates the lever arm, increasing or decreasing the amount of force required by the hamstrings at any given muscle length, potentially changing the adaptive response when training at different planes and providing logical progressions ore regressions of the NHE. All NHE variations result in a similar magnitude of fascicle lengthening, which may indicate similar positive adaptations from the utilization of any variation.

Acute Effects of Soft Tissue Modalities on Muscular Ultrasound Characteristics and Isometric Performance

Prior to training, many athletes perform different soft-tissue preparation protocols. Many of these protocols involve stretching, foam rolling, and/or percussion massage. Many of these modalities have been studied, but not as a group to observe muscle alterations and differences in males and females. In total, 40 (20 males, 20 females) participants performed five minutes of static stretching, foam rolling, and percussion massage. Pre- and post-isometric leg strength, muscle activation and ultrasound assessments (cross-sectional area, echo intensity, pennation angle, fascicle length, and muscle thickness) were taken. The results indicate that there is no significant difference among modalities, and that they do not significantly alter any muscle characteristic or improve performance. There is a significant difference in size between males and female, with males having larger muscle and greater pennation angles than females. This allows males to generate significantly more muscle force. However, they both respond similarly to each modality. In conclusion, the muscle response to static stretching, foam rolling, and percussion massage do not differ among modalities and do not contribute to an increase or decrease in maximal isometric knee extension with similar effects between males and females.

2226 Assessing quantitative sonographic changes in the muscle mass of geriatric patients hospitalised using point of care ultrasound

Abstract Introduction One of the most important consequences of hospitalisation in older patients is sarcopenia. This study aims to determine the impact of hospitalisation on the muscle mass, functional status, nutritional status, and short-term clinical outcomes. Methods A prospective study of patients admitted to an Acute Geriatric Ward between 1st November and 30th December 2022. Muscle ultrasound, utilising Point of Care Ultrasound (POCUS) at bedside, was employed to estimate rectus femoris muscle thickness (MT), area (Ar), pennation angle (PA), and fascicle length (FL) at the time of hospital admission, 3 days post-admission, and at hospital discharge. Results 30 patients included, with a median age of 84 years (SD 72–93), 63.3% male, and 70% Clinical Frailty Scale score ≥ 4. Barthel Index and Functional Ambulation Category revealed median values of 72.33 and 3.87 respectively. Global Deterioration Scale median was 2.47. Mini Nutritional Assessment Short-Form (MNA) and total serum protein showed median values of 7.40 and 6.35 respectively. The median length of hospital stay was 5.79 days, with inpatient mortality rate of 10% and 53.3% incidence of delirium. Ultrasound showed a decrease in PA by 36.31%, Ar by 34.30%, and MT by 24.50%, and increase in FL by 10.47%. Sarcopenia classification at admission and discharge revealed an increase in mean index from 5.04 to 7.74. Conclusions In our cohort of patients admitted to an acute geriatric unit, POCUS identified real-time decreases in MT, Ar, and PA at the muscular level before these manifested as functional changes. It demonstrated an inverse relationship between frailty and muscle morphology as living with frailty associated further decreases in muscle mass at discharge. The study also established a direct relationship between MNA, muscle thickness, PA, and fascicles length at discharge. POCUS assessment of muscle mass could indirectly predict outcomes and guide decisions to address muscle mass abnormalities.

Reliability of Ultrasound Assessment of Hamstring Morphology, Quality, and Stiffness Among Healthy Adults and Athletes: A Systematic Review.

The incidence and recurrence rate of hamstring strain injuries remain persistently high, with recurrent injuries leading to increased time lost during play and extended recovery periods compared with initial injury. Ultrasound imaging assesses important factors such as hamstring fascicle length (FL), pennation angle (PA), cross-sectional area (CSA), muscle thickness (MT), echo intensity (EI), and shear wave elastography (SWE), all impacting athletic performance. However, its reliability must be established before employing any measurement tool in research or clinical settings. To determine the reliability and measurement error of ultrasound for assessing hamstring FL, PA, CSA, MT, EI, and SWE among healthy adults and athletes; to synthesize the information regarding the operationalization of ultrasound. A systematic literature search was done from January 1990 to February 5, 2023, to identify reliability and validity studies of hamstring ultrasound assessment published in peer-reviewed journals with identifiable methodology of outcome measures. Intraclass correlation coefficient measurement of 14 included studies reported moderate to excellent intrarater, interrater, and test-retest reliabilities of FL, PA, and MT regardless of the site of muscle testing, probe size, and setting, state of muscle, and use of different techniques in the extrapolation of FL. Good to excellent test-retest reliability rates for all hamstring anatomic CSA along midmuscle and different percentages of thigh length using panoramic imaging. Good intrarater reliability of EI regardless of gender and orientation of the probe but with excellent intrarater reliability in transverse scan using maximum region of interest. Good intrarater, interrater, and interday repeatability on SWE with the muscle in a stretched position. Evidence from studies with a predominantly low risk of bias shows that ultrasound is a reliable tool to measure hamstring FL, PA, CSA, MT, EI, and SWE in healthy adults and athletes under various experimental conditions.

Unlocking the benefit of active stretch: the eccentric muscle action, not the preload, maximizes muscle-tendon unit stretch-shortening cycle performance.

Stretch-shortening cycles (SSCs) outperform shortening contractions preceded by isometric contractions in terms of enhanced force/torque, work, and power production during shortening. This so-called SSC effect is presumably related to the active muscle stretch before shortening in SSCs. However, it remains unclear whether the effects of stretch-induced higher preload level or stretch-induced history dependence maximize the SSC effect. Therefore, we analyzed fascicle behavior, muscle-tendon unit (MTU) shortening work, and torque/force (n = 12 participants) via ultrasound and dynamometry during electrically stimulated submaximal plantar flexion contractions from 10° plantarflexion to 15° dorsiflexion. To elucidate the effects of preload level and preload modality (i.e., contraction type) on shortening performance, muscle-tendon unit shortening was preceded by fixed-end (SHO), active stretch (SSC), and preload-matched fixed-end (MATCHED) contractions. Before shortening, MATCHED and SCC had the same preload level (1% torque difference), similar joint position, and muscle fascicle lengths. Compared with SHO, shortening work was significantly (P < 0.001, partial η2 = 0.749) increased by 85% and 55% for SSC and MATCHED, respectively, with SSC shortening work being significantly higher than MATCHED (P = 0.016). This indicates that preload contributes by 65% to the overall SSC effect so that 35% needs to be referred to stretched-induced history-dependent mechanisms. In addition, SSC showed larger fascicle forces at the end of shortening (P < 0.001) and 20% less depressed isometric torque following shortening compared with MATCHED (P < 0.001). As potential decoupling effects by the series elastic element were controlled by matching the preload levels, we conclude that the difference between SSC and MATCHED is related to stretch-induced long-lasting history-dependent effects.NEW & NOTEWORTHY Using a torque-matched preload protocol, we found that 2/3 of the performance enhancement in muscle-tendon unit stretch-shortening cycles (SSCs) is caused by the increased preload level. The remaining 1/3 is owed to the long-lasting history-dependent effects triggered during the stretch in SSCs. This increased performance output is attributed to passive elastic structures within the contractile element that do not require additional muscle activation, therefore contributing to the higher efficiency of the neuromuscular system in SSCs.

Body Composition, Vascular Health, Cardiorespiratory Fitness, Lung Function, Muscle Architecture, and Physical Activity in People with Young Onset Dementia: A Case-Control Study

BackgroundBody composition, blood pressure, estimated maximal oxygen uptake (VO2max), lung function, physical activity, muscle architecture, and endothelial function had not previously been examined in people with young onset dementia. Therefore, the study measured these variables in a young onset dementia group, compared them to age-matched controls. MethodsEstimated VO2max (via the Astrand-Rhyming test), body composition, blood pressure, lung function (via spirometry), muscle architecture (via ultrasonography) and endothelial function (via flow mediated dilation) were assessed. Physical activity was measured using ActiGraph accelerometers for 7 days. ResultsWe recruited 33 participants (16 young onset dementia, 17 controls). The young onset dementia group had shorter fascicle lengths of the vastus lateralis, were sedentary for longer over a seven-day period, and completed less moderate-vigorous physical activity than controls (p=0.028, d=0.81; large effect, p=0.029, d=0.54; moderate effect, and p=0.014, d=0.97; large effect, respectively for pairwise comparisons). Pairwise comparisons suggest no differences at the p<0.05 level between young onset dementia and controls for estimated VO2max (despite a moderate effect size [d=0.66]), height, body mass, BMI, blood pressure, light physical activity, lung function, muscle thickness, pennation angle, or endothelial function. ConclusionThis study highlights differences between people with young onset dementia and controls, underscoring the need for multicomponent exercise interventions. Future interventions should target muscle architecture, increase moderate-vigorous physical activity, and reduce sedentariness, with the goal of improving quality of life and promoting functional independence.

Muscle structure predictors of vertical jump performance in elite male volleyball players: a cross-sectional study based on ultrasonography.

The objective of this investigation is to examine the contribution of key muscle groups in the lower limbs to vertical jumping performance in elite male volleyball players. Specifically, the study focuses on the rectus femoris (RF), vastus lateralis (VL), and lateral gastrocnemius (LG), as well as exploring differences between attack jump and other vertical jump types. To achieve this, we employed B-mode ultrasound to evaluate the anatomical cross-sectional area (ACSA), muscle thickness (MT), pennation angle (PA), and fascicle length (FL) of the RF, VL, and LG in the participants. Fifteen elite male volleyball players were recruited as participants for this study. Jump heights were measured for four types of vertical jumps: attack jump (AJ), countermovement jump (CMJ), squat jump (SJ), and drop jump (DJ). We conducted regression analyses to assess whether the previously mentioned muscle structures could predict jump performance. Our findings reveal that the muscle structure of the RF does not exhibit any significant correlation with the height of any jump. However, VL-ACSA displays a significant and the most potent predictive effect on jump height for all four jump types (AJ: R 2 = 0.32, p = 0.001; CMJ: R 2 = 0.37, p = 0.005; SJ: R 2 = 0.52, p = 0.001; DJ: R 2 = 0.25, p = 0.021). Conversely, LG-FL only demonstrates a significant and stronger predictive effect on AJ jump height (R 2 = 0.18, p = 0.009). Combining VL-ACSA, LG-FL, and training age through multiple linear regression analysis resulted in a highly significant model for predicting AJ jump height (F = 13.86, R 2 = 0.73). Moreover, the model incorporating VL-ACSA and training age is also important for predicting CMJ, SJ, and DJ jump heights (F = 8.41, R 2 = 0.51; F = 13.14, R 2 = 0.63; F = 5.95, R 2 = 0.41; respectively). The muscle structure indicators in the lower limbs significantly predict jump performance among elite male volleyball players. However, different jump types are influenced by distinct indicators, particularly in the case of AJ, which is associated with LG-FL. This suggests that enhancing LG-FL may positively impact AJ ability, thereby emphasizing the importance of specificity in training. To optimize specialized jump performance in volleyball players, practitioners are advised to assess VL-ACSA and LG-FL and incorporate step-up and eccentric strength training targeting the calf muscles to yield considerable benefits.