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

Joint inflexibility is acknowledged as a significant contributor to functional limitations in the older adult, with lengthening-type exercises identified as a potential remedial approach. Nevertheless, the responses to eccentric exercise in female older adults have not been extensively studied especially in home-based environment. Here, we aimed to assess the effectiveness of home-based static stretching (ST), dynamic closed-chain stretching (DCS), or eccentric exercise (ECC) interventions on flexibility, musculotendinous architecture, and functional ability in healthy older women. We randomly assigned 51 healthy older women (age 65.9 ± 3.4 years) to one of three interventional exercise groups: DCS (N = 17), ECC (N = 17), or ST (N = 17). The training was performed 3 times a week for 6 weeks. The participants' musculotendinous stiffness, fascicle length, eccentric strength, and functional capacities were measured before the intervention, after 6 weeks of exercise, and at a 1-month follow-up. The results showed that all three interventions improved hamstring flexibility and passive ankle dorsiflexion (p < 0.001), with increased biceps femoris and medial gastrocnemius fascicle length (p < 0.01). However, there was no significant change in musculotendinous stiffness. The ECC intervention produced a greater improvement in knee flexor and calf eccentric peak torque (p < 0.05), and gait speed (p = 0.024) than the other two interventions. The changes in flexibility and knee flexor strength remained for up to 4 weeks after detraining. In conclusion, the present study suggests that home-based ECC may be more beneficial in enhancing physical capacities in older women compared with either DCS or SS interventions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The function of a muscle is highly dependent on its architecture, which is characterized by the length, pennation, and curvature of the fascicles, and the geometry of the aponeuroses. During in vivo function, muscles regularly undergo changes in length, thereby altering their architecture. During passive muscle lengthening, fascicle length (FL) generally increases and the angle of fascicle pennation (FP) and the fascicle curvature (FC) decrease, while the aponeuroses increase in length but decrease in width. Muscles are differently structured, making their change during muscle lengthening complex and multifaceted. To obtain comprehensive data on architectural changes in muscles during passive length, the present study determined the three-dimensional fascicle geometry of rabbit M. gastrocnemius medialis (GM), M. gastrocnemius lateralis (GL), and M. plantaris (PLA). For this purpose, the left and right legs of three rabbits were histologically fixed at targeted ankle joint angles of 95° (short muscle length [SML]) and 60° (long muscle length [LML]), respectively, and the fascicles were tracked by manual three-dimensional digitization. In a second set of experiments, the GM aponeurosis dimensions of ten legs from five rabbits were determined at varying muscle lengths via optical marker tracking. The GM consisted of a uni-pennated compartment, whereas the GL and PLA contained multiple compartments of differently pennated fascicles. In the LML compared to the SML, the GM, GL, and PLA had on average a 41%, 29%, and 41% increased fascicle length, and a 30%, 25%, and 33% decrease in fascicle pennation and a 32%, 11%, and 35% decrease in fascicle curvature, respectively. Architectural properties were also differentiated among the different compartments of the PLA and GL, allowing for a more detailed description of their fascicle structure and changes. It was shown that the compartments change differently with muscle length. It was also shown that for each degree of ankle joint angle reduction, the proximal GM aponeurosis length increased by 0.11%, the aponeurosis width decreased by 0.22%, and the area was decreased by 0.20%. The data provided improve our understanding of muscles and can be used to develop and validate muscle models. [ABSTRACT FROM AUTHOR]

Objectives: The current study investigated the correlation between quadriceps muscle architecture and the knee extension rate of force development (RFD).Design: cross-sectional study.Methods: Muscle thickness, pennation angle and fascicle length normalized per the thigh-length were measured via ultrasound in vastus lateralis, rectus femoris, vastus intermedius and vastus medialis. The knee extension rate of force was assessed isometrically at 90° knee angle and calculated in different 50-ms epochs (0-50, 50-100, 100-150, 150-200 and 200-250ms). The maximum voluntary contraction was also recorded.Results: Large correlations were observed between vastus intermedius muscle thickness and the 100-150ms (r=0.694, p=0.004), 150-200ms (r=0.597, p=0.019) and 200-250ms (r=0.546, p=0.045) epochs. Large correlation was observed between vastus intermedius normalized fascicle length and 100-150ms (r=0.570, p=0.043) and large correlations with 150-200ms (r=0.643, p=0.010) and 200-250ms (r=0.629, p=0.012) epochs. Additionally, large correlations were observed between vastus lateralis normalized fascicle length and the 100-150ms (r=0.535, p=0.049), 150-200ms (r=0.629, p=0.016) and 200-250ms (r=0.563, p=0.046) epochs. Vastus intermedius muscle thickness predicted 59% (R2=0.581, p=0.002) of the RFD of the 100-150ms epoch; vastus intermedius muscle thickness and fascicle length predicted 51% (R2=0.506, p=0.029) of the 150-200ms epoch; vastus intermedius and vastus lateralis fascicle length predicted 48% (R2=0.483, p=0.037) of the 200-250ms epoch. No further correlation was observed.Conclusions: Fascicle length and muscle thickness were observed as predictive of the late phase of the rate of force development. Vastus intermedius muscle architecture has a primary role in the knee extension RFD. [ABSTRACT FROM AUTHOR]

Objectives: To investigate the architectural and strength adaptations of the hamstrings following 6-weeks of inertial flywheel resistance training.Design: Randomised, stratified training intervention METHODS: Twenty healthy males undertook 6-weeks of a conventional (n=10) or eccentrically biased (n=10) flywheel leg-curl training intervention as well as a subsequent 4-week detraining period. Biceps femoris long head (BFlh) architecture was assessed weekly, whilst assessments of eccentric and isometric knee flexor strength and rate of force development (RFD) were conducted prior to and following the intervention and detraining periods.Results: The participants who undertook the eccentrically biased flywheel intervention showed a significant 14±5% (p<0.001, d=1.98) increase in BFlh fascicle length after 6-weeks of training. These improvements in fascicle length subsequently declined by 13±4% (p<0.001. d=-2.04) following the 4-week detraining period. The conventional flywheel leg-curl training group saw no changes in BFlh fascicle length after the intervention (-0.5%±0.8%, p=0.939, d=-0.04) or detraining (-1.1%±1%, p=0.984, d=-0.03) periods. Both groups saw no changes in any of the strength or RFD variables after the intervention or the detraining period.Conclusions: Flywheel leg-curl training performed with an eccentric bias led to significant lengthening of BFlh fascicles without a change in RFD, eccentric or isometric strength. These increases in fascicle length were lost following a 4-week detraining period. Conventional flywheel leg-curl training resulted in no changes in fascicle length, strength and RFD. These findings suggest that additional eccentric bias is required during inertial flywheel resistance training to promote fascicle lengthening in the BFlh, however this may still be insufficient to cause alterations to strength and RFD. [ABSTRACT FROM AUTHOR]

The interplay between the medial gastrocnemius muscle and the Achilles tendon is crucial for efficient walking. In cerebral palsy, muscle and tendon remodelling alters the role of contractile and elastic components. The aim was to investigate the length changes of medial gastrocnemius belly and fascicles, and Achilles tendon to understand their interplay to gait propulsion in individuals with cerebral palsy. Twelve young individuals with cerebral palsy and 12 typically developed peers were assessed during multiple gait cycles using 3D gait analysis combined with a portable ultrasound device. By mapping ultrasound image locations into the shank reference frame, the medial gastrocnemius belly, fascicle, and Achilles tendon lengths were estimated throughout the gait cycle. Participants with cerebral palsy were classified into equinus and non-equinus groups based on their sagittal ankle kinematics. In typically developed participants, the Achilles tendon undertook most of the muscle-tendon unit lengthening during stance, whereas in individuals with cerebral palsy, this lengthening was shared between the medial gastrocnemius belly and Achilles tendon, which was more evident in the equinus group. The lengthening behaviour of the medial gastrocnemius fascicles resembled that of the Achilles tendon in cerebral palsy. The findings revealed similar length changes of the medial gastrocnemius fascicles and Achilles tendon, highlighting the enhanced role of the muscle in absorbing energy during stance in cerebral palsy. These results, together with the current knowledge of increased intramuscular stiffness, suggest the exploitation of intramuscular passive forces for such energy absorption. • Gastrocnemius muscle-Achilles tendon function is altered in cerebral palsy gait. • Both muscle and tendon contribute to muscle-tendon unit lengthening in stance phase. • Muscle fascicles and Achilles tendon resembled a similar behaviour in stance phase. • Intramuscular passive force transmission may be enhanced in cerebral palsy. [ABSTRACT FROM AUTHOR]

Abstract For detailed analyses of muscle adaptation mechanisms during growth, ageing or disease, reliable measurements of muscle architecture are required. Diffusion tensor imaging (DTI) and DTI tractography have been used to reconstruct the architecture of human muscles in vivo. However, muscle architecture measurements reconstructed with conventional DTI techniques are often anatomically implausible because the reconstructed fascicles do not terminate on aponeuroses, as real muscle fascicles are known to do. In this study, we tested the reliability of an anatomically constrained DTI-based method for measuring three-dimensional muscle architecture. Anatomical magnetic resonance images and diffusion tensor images were obtained from the left legs of eight healthy participants on two occasions one week apart. Muscle volumes, fascicle lengths, pennation angles and fascicle curvatures were measured in the medial and lateral gastrocnemius, soleus and the tibialis anterior muscles. Averaged across muscles, the intraclass correlation coefficient was 0.99 for muscle volume, 0.81 for fascicle length, 0.73 for pennation angle and 0.76 for fascicle curvature. Measurements of muscle architecture obtained using conventional DTI tractography were highly sensitive to variations in the stopping criteria for DTI tractography. The application of anatomical constraints reduced this sensitivity significantly. This study demonstrates that anatomically constrained DTI tractography can provide reliable and robust three-dimensional measurements of whole-muscle architecture. The algorithms used to constrain tractography have been made publicly available. [ABSTRACT FROM AUTHOR]

Abstract Skeletal muscle structural assembly (and its remodeling in response to loading–unloading states) can be investigated macroscopically by assessing muscle architecture, described as fascicle geometric disposition within the muscle. Over recent decades, various medical imaging techniques have been developed to facilitate the in vivo assessment of muscle architecture. However, the main advantages and limitations of these methodologies have been fragmentally discussed. In the present article, the main techniques used for the evaluation of muscle architecture are presented: conventional B-mode ultrasonography, extended-field-of-view ultrasound, 3-D ultrasound and magnetic resonance imaging-based diffusion tensor imaging. By critically discussing potentials and shortcomings of each methodology, we aim to provide readers with an overview of both established and new techniques for the in vivo assessment of muscle architecture. This review may serve as decision guidance facilitating selection of the appropriate technique to be applied in biomedical research or clinical routine. [ABSTRACT FROM AUTHOR]

Abstract Sprinters have been found to possess longer muscle fascicles than non-sprinters, which is thought to be beneficial for high-acceleration movements based on muscle force-length-velocity properties. However, it is unknown if their morphology is a result of genetics or training during growth. To explore the influence of training during growth, thirty guinea fowl (Numida meleagris) were split into exercise and sedentary groups. Exercise birds were housed in a large pen and underwent high-acceleration training during their growth period (age 4–14 weeks), while sedentary birds were housed in small pens to restrict movement. Morphological analyses (muscle mass, PCSA, optimal fascicle length, pennation angle) of a hip extensor muscle (ILPO) and plantarflexor muscle (LG), which differ in architecture and function during running, were performed post-mortem. Muscle mass for both ILPO and LG was not different between the two groups. Exercise birds were found to have ∼12% and ∼14% longer optimal fascicle lengths in ILPO and LG, respectively, than the sedentary group despite having ∼3% shorter limbs. From this study we can conclude that optimal fascicle lengths can increase as a result of high-acceleration training during growth. This increase in optimal fascicle length appears to occur irrespective of muscle architecture and in the absence of a change in muscle mass. Our findings suggest high-acceleration training during growth results in muscles that prioritize adaptations for lower strain and shortening velocity over isometric strength. Thus, the adaptations observed suggest these muscles produce higher force during dynamic contractions, which is beneficial for movements requiring large power outputs. [ABSTRACT FROM AUTHOR]

Isolated and packed muscles (e.g. in the calf) exhibit different three-dimensional muscle shapes. In packed muscles, cross-sections are more angular compared to the more elliptical ones in isolated muscles. As far as we know, it has not been examined yet, whether the shape of the muscle in its packed condition influences its internal arrangement of muscle fascicles and accordingly the contraction behavior in comparison to the isolated condition. To evaluate the impact of muscle packing, we examined the three-dimensional muscle architecture of isolated and packed rabbit M. soleus for different ankle angles (65°, 75°, 85°, 90°, and 95°) using manual digitization (MicroScribe ® MLX). In general, significantly increased values of pennation angle and fascicle curvature were found in packed compared to isolated M. soleus (except for fascicle curvature at 90° ankle angle). On average, fascicle length of isolated muscles exceeded fascicle lengths of packed muscles by 2.6%. Reduction of pennation angle in the packed condition had only marginal influence on force generation (about 1% of maximum isometric force) in longitudinal direction (along the line of action) although an increase of transversal force component (perpendicular to the line of action) of about 26% is expected. Results of this study provide initial evidence that muscle packing limits maximum muscle performance observed in isolated M. soleus . Besides an enhanced understanding of the impact of muscle packing on architectural parameters, the outcomes of this study are essential for realistic three-dimensional muscle modeling and model validation. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare quadriceps concentric and eccentric strength and muscle architecture in chronic obstructive pulmonary disease (COPD) patients vs healthy men. Thirty-five COPD patients (age = 65 ± 4 yrs, forced expiratory volume (FEV1) = 63 ± 10%; FEV1/forced vital capacity (FVC)=57 ± 13% of predicted) and 25 age-matched healthy men (age = 65 ± 4 yrs, FEV1=114 ± 17%; FEV1/FVC = 101 ± 6% of predicted) (CON) participated in the present cross-sectional study. Concentric and eccentric isokinetic peak-torque was measured at low and high angular-velocity. Vastus lateralis pennation angle, fascicle length and muscle thickness were recorded using ultrasound device. Similar eccentric peak-torque was found in COPD and CON at low (2.57 ± 0.55 and 2.80 ± 0.60 N⋅m⋅kg-1, p = 0.128 respectively) and high (2.44 ± 0.51 and 2.58 ± 0.46 N⋅m⋅kg-1, p = 0.259) angular-velocity. Lower concentric peak-torque was found in COPD than in CON (p < 0.05). Smaller pennation angle (13.8 ± 3.4 vs 16.2 ± 3.9°) and muscle thickness (17.1 ± 2.8 vs 20.3 ± 3.0 mm) were found in COPD patients vs healthy men, with no difference in fascicle length. In COPD patients only, FEV1 and FEV1/FVC were negatively correlated with the eccentric-to-concentric peak-torque ratio (r = -0.465 and r = -0.414, respectively); irrespective of the testing-modality, FEV1 and FEV1/FVC were moderately correlated with peak-torque (p < 0.05). The preserved eccentric strength in COPD patients could be accounted for both mechanical and neural adaptations caused by the disease severity. [ABSTRACT FROM AUTHOR]

• Resistance training (RT) promotes changes in muscle architecture in older adults. • The thickness of the medial gastrocnemius increased after intervention with RT. • RT showed no effect on the fasciculus and pennation angle and vastus lateralis. • Training variables interfere with morphological adaptations in the elderly. Resistance training (RT) consists of planned exercise programs to increase muscle strength capacity through neural and structural adaptations, such as changes in the geometric arrangement of muscle fibers. This study aimed to analyze the influence of RT on muscle architecture in older people. This PROSPERO-registered systematic review and meta-analysis (identification number CRD42022340477) followed the PRISMA guidelines. Four electronic databases were searched for eligible randomized controlled trials (RCTs) that observed older individuals submitted to RT programs that reported muscle architecture outcomes. Seventeen RCTs met the eligibility criteria with a total of 488 participants. The main results of the meta-analysis showed that RT interventions had a significant effect on the thickness of the medial gastrocnemius (SMD = 0.12; 95% CI: − 0.07 to 0.17; p < 0.00001; I2 = 0%). Based on available evidence, studies included in this review showed improvement in maximum isometric force, pennation angle, fascicle length, thickness, and muscle activation after RT interventions. In turn, the meta-analysis suggested a potential for improving the thickness of the medial gastrocnemius after the intervention. However, any clinical implications drawn from the analyses should be interpreted with caution, as these findings are substantially limited due to a low number of included studies and a potential heterogeneity between studies. [ABSTRACT FROM AUTHOR]

Static, B-mode ultrasound is the most common method of measuring fascicle length in vivo . However, most forearm muscles have fascicles that are longer than the field-of-view of traditional ultrasound (T-US). As such, little work has been done to quantify in vivo forearm muscle architecture. The extended field-of-view ultrasound (EFOV-US) method, which fits together a sequence of B-mode images taken from a continuous ultrasound scan, facilitates direct measurements of longer, curved fascicles. Here, we test the validity and reliability of the EFOV-US method for obtaining fascicle lengths in the extensor carpi ulnaris (ECU). Fascicle lengths from images of the ECU captured in vivo with EFOV-US were compared to lengths from a well-established method, T-US. Images were collected in a joint posture that shortens the ECU such that entire fascicle lengths were captured within a single T-US image. Resulting measurements were not significantly different (p = 0.18); a Bland-Altman test demonstrated their agreement. A novice sonographer implemented EFOV-US in a phantom and in vivo on the ECU. The novice sonographer’s measurements from the ultrasound phantom indicate that the combined imaging and analysis method is valid (average error = 2.2 ± 1.3 mm) and the in vivo fascicle length measurements demonstrate excellent reliability (ICC = 0.97). To our knowledge, this is the first study to quantify in vivo fascicle lengths of the ECU using any method. The ability to define a muscle’s architecture in vivo using EFOV-US could lead to improvements in diagnosis, model development, surgery guidance, and rehabilitation techniques. [ABSTRACT FROM AUTHOR]

While muscle contraction in voluntary efforts has been widely investigated, little is known about contraction during neuromuscular electrical stimulation (NMES). The aim of this study was to quantify in vivo muscle architecture of agonist and antagonist muscles at the ankle joint during NMES. Muscle fascicle lengths and pennation angles of the tibialis anterior (TA) and lateral gastrocnemius muscles were assessed via ultrasonography in 8 healthy young males. Measures were obtained during maximal NMES and torque-matched voluntary dorsiflexion contractions. In the TA, NMES induced a shorter fascicle length (67.2±8.1mmvs 74.6±11.4mm; p=0.04) and a greater pennation angle (11.0±2.4° vs 9.3±2.5°; p=0.03) compared with voluntary torque-matched dorsiflexion contractions. Architectural responses in the antagonist lateral gastrocnemius muscle did not significantly differ from rest or between voluntary and electrically induced contractions (p>0.05). Contraction of the antagonist muscle was not a contributing factor to a greater fascicle shortening and increased pennation angle in the TA during NMES. TA architectural response during NMES likely arose from the contribution of muscle synergists during voluntary contractions coupled with a potentially localized contractile activity under the stimulation electrodes during NMES induced contractions. [ABSTRACT FROM AUTHOR]

Muscular contraction dynamics depends on active and passive muscle properties (e.g., the force-velocity relation) as well as on the three-dimensional (3D) muscle structure (e.g., the muscle fascicle architecture and aponeurosis dimensions). Much is known about active muscle force generation and the muscle architecture at a particular age (mostly for adult specimens), but less is known about changes in muscle structure during growth. The present study analyzed growth-related changes in the muscle structure of rabbit gastrocnemius lateralis (GL), gastrocnemius medialis (GM), flexor digitorum longus (FDL), and tibialis anterior (TA). Changes in tendon length, muscle belly dimensions (length, width, thickness), as well as aponeurosis length, width, and area were determined using 55 rabbits between 18 and 108 days old. Additionally, the 3D muscle fascicle architecture of five rabbits of different ages (21, 37, 50, 70, 100 days) was determined using a manual digitizer. We found an almost linear increase over time in most of the geometrical parameters observed. GL and GM showed very similar growth characteristics. In contrast to the pronounced increase in muscle belly length of GL and GM, FDL and TA exhibited more uniform muscle belly growth in length, width, and thickness. In general, the aponeuroses of the muscles exhibited lower growth rates in width than in length, and aponeurosis areas were larger than physiological cross-sectional areas. There were almost no changes in fascicle lengths with increasing age for GL, GM, and FDL. In contrast, there was a clear increase in TA fascicle length from about 20 to over 40 mm. Pennation angles of TA (11.0 ± 2.1°) and FDL (16.7 ± 3.2°) remained almost unchanged but increased for GL from 13.4 ± 3.3° to 24.3 ± 6.5° from the youngest to the oldest animal. For all muscles observed, the tendon-muscle fascicle length ratio ( r TFL ) changed during growth. GL and GM exhibited similar increases in r TFL from about 4–8. FDL showed the highest ratio, which increased from about 8–13, whereas TA had the lowest ratio, which decreased slightly from 2 to 1.5. The outcomes demonstrate new findings regarding changes in 3D muscle architecture and aponeurosis shape during growth, and they provide information for muscle force generation, functional relevance, and adaptation with respect to animal age. Therefore, the results help to improve understanding of muscle growth processes and can be used as input data for muscle growth modeling. [ABSTRACT FROM AUTHOR]

Introduction A precise quantitative measurement of skeletal muscle mass is fundamental for diagnosing sarcopenia in older individuals. The current techniques of assessment, including dual-energy x-ray absorptiometry (DXA), bioimpedance analysis (BIA), and magnetic resonance imaging (MRI) are either difficult to perform in everyday clinical practice or biased by concurrent clinical confounders. B-mode muscle ultrasound can be helpful in assessing muscle mass and architecture, and thus possibly useful for diagnosing or screening sarcopenia. Methods A literature search of published articles on muscle ultrasound and sarcopenia in older individuals as of July 31, 2016, was made on PubMed and Scopus. Manual search and cross-referencing from reviews and original articles was also performed. Results Most of the existing studies were carried out on healthy well-fit subjects, with a low prevalence of sarcopenia. The main parameters that can be assessed through muscle ultrasound are muscle thickness, cross-sectional area, echo intensity, and, for pennate muscles, fascicle length and pennation angle. In older subjects, all these parameters show some degree of alteration compared to young adults, particularly in lower limb muscles with antigravitary function, such as the quadriceps femoris and gastrocnemius medialis. Each of these parameters may be theoretically useful for detecting the loss of muscle mass and functionality in geriatric patients. They are also poorly influenced by the presence of acute and chronic diseases and fluid balance, unlike DXA and BIA, but a high degree of standardization in ultrasound protocols is necessary. Frontier applications of ultrasound in the assessment of sarcopenia may include contrast-enhanced and diaphragm ultrasound. Conclusions The current literature does not allow to make conclusive recommendations about the use of muscle ultrasound in geriatric practice. However, this technique is very promising, and further studies should validate its applications in the context of sarcopenia assessment. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Muscle fascicle lengths are commonly measured in vivo using static 2D ultrasound. However, static ultrasound is best suited for muscles with shorter, pennate fascicles, in which entire fascicles can be viewed in one static image. An informal review of data from cadaver dissections suggests that over 60% of muscles in the upper and lower limbs have optimal lengths longer than the field-of-view of standard ultrasound transducers. Extended field-of-view ultrasound (EFOV) has been validated for measurement of fascicle lengths, but has yet to be implemented in the upper extremity in humans. In this study, EFOV ultrasound was used to measure the lengths of fascicles sampled from the anterior portion of the biceps brachii (long head) and the distal half of the triceps brachii (lateral head). Data were collected from both limbs of eleven healthy subjects in three elbow postures under passive conditions. Image analysis was completed via Image J. Fascicle length measurements were highly reliable, with intra-class correlations ranging from .92 to .95 for biceps and .81–.92 for triceps ( p <.001). Systematic, significant differences in measured lengths, consistent with muscle function, were observed between elbow positions. In vivo measurements for both muscles in this study were within the range of cadaver data. This work establishes the feasibility and reliability of EFOV ultrasound for measurement of the long fascicles of muscles in the upper limb. [ABSTRACT FROM AUTHOR]

This investigation sought to determine the effects of fatigue on fascicle architecture across the length of the human gastrocnemius medialis (GM). With institutional ethical approval, fifteen healthy males performed repeated isometric plantar flexion maximal voluntary contractions (MVC) until peak force fell 30% below baseline. Brightness-mode ultrasound was used to determine fascicle length and pennation angle at rest and during MVC prior to and following the fatiguing contractions. The results show a significant increase in fascicle length during MVC in the distal (2.8 mm, 8.1%) middle, (4.9 mm, 14.1%), and proximal (5.2 mm, 14.7%) regions post-fatigue compared to pre-fatigue (p < 0.05). There was also a significant decrease of pennation angle during MVC in the distal (3.3°, 8.8%), middle (3.9°, 9.4%), and proximal (2.9°, 6.9%) regions post-fatigue compared to pre-fatigue (p < 0.05). These changes, however, were not region specific. These are the first results to show that fascicle shortening within the GM remains homogeneous following fatigue, suggesting that the fascicles were fatigued in a similar pattern throughout the muscle. The significant reduction of fascicle shortening may reflect an additional strategy to maintain an optimal force output in fatigued conditions, although future work is needed to confirm this notion. [ABSTRACT FROM AUTHOR]

The study aimed to evaluate the stretch-induced changes in muscle architecture in different portions of the gastrocnemius medialis (GM) and lateralis (GL) muscles. The reliability and sensitivity of the measurements were also assessed. Fascicle length (FL) and pennation angle (PA) were calculated in the middle and distal portions of GM and GL at 0°, 10° and 20° of ankle dorsiflexion. At the same angles, passive torque ( T pass ), peak torque (pT) and myotendinous junction displacement of GM were determined. Stiffness was calculated at muscle–tendon unit (MTU), muscle and tendon level. After static stretching administration, T pass , pT and MTU stiffness decreased by 22%, 12% and 16%, respectively ( p < 0.05). Muscle and tendon stiffness decreased by 15% and 16% ( p < 0.05). Nevertheless, no changes in FL and PA occurred. The reliability of the approach was always very high (intraclass correlation coefficient > 0.90), with an adequate level of sensitivity. pT after static stretching was related to decreases in MTU, muscle and tendon stiffness, but not to alterations in muscle architecture. [ABSTRACT FROM AUTHOR]

Muscle imaging is a promising field of research to understand the biological and bioelectrical characteristics of muscles through the observation of muscle architectural change. Sonomyography (SMG) is a technique which can quantify the real-time architectural change of muscles under different contractions and motions with ultrasound imaging. The pennation angle and fascicle length are two crucial SMG parameters to understand the contraction mechanics at muscle level, but they have to be manually detected on ultrasound images frame by frame. In this study, we proposed an automatic method to quantitatively identify pennation angle and fascicle length of gastrocnemius (GM) muscle based on multi-resolution analysis and line feature extraction, which could overcome the limitations of tedious and time-consuming manual measurement. The method started with convolving Gabor wavelet specially designed for enhancing the line-like structure detection in GM ultrasound image. The resulting image was then used to detect the fascicles and aponeuroses for calculating the pennation angle and fascicle length with the consideration of their distribution in ultrasound image. The performance of this method was tested on computer simulated images and experimental images in vivo obtained from normal subjects. Tests on synthetic images showed that the method could identify the fascicle orientation with an average error less than 0.1°. The result of in vivo experiment showed a good agreement between the results obtained by the automatic and the manual measurements ( r = 0.94 ± 0.03; p < 0.001, and r = 0.95 ± 0.02, p < 0.001). Furthermore, a significant correlation between the ankle angle and pennation angle ( r = 0.89 ± 0.05; p < 0.001) and fascicle length ( r = −0.90 ± 0.04; p < 0.001) was found for the ankle plantar flexion. This study demonstrated that the proposed method was able to automatically measure the pennation angle and fascicle length of GM ultrasound images, which made it feasible to investigate muscle-level mechanics more comprehensively in vivo. [ABSTRACT FROM AUTHOR]

Abstract: Background: The purpose of this study was to compare the elastic properties and size of tendinous structures and muscle architecture for knee extensors and plantar flexors in boys and men. Methods: Twenty-two early pubescent boys (9.6–12.7yrs) and 23 young adult men (19.8–26.2yrs) participated in this study. The maximal strain and thickness of tendinous structures for knee extensors and plantar flexors were measured using ultrasonography. In addition, the fascicle lengths of vastus lateralis and medial gastrocnemius muscles were measured. Findings: The maximal strain of tendinous structures for plantar flexors was significantly greater in boys than in men, while there was no difference in the maximal strain for knee extensors between the two groups. The relative thickness (to body mass1/3) of Achilles tendon was significantly greater in boys than in men, although there was no difference in that of patellar tendon between the two groups. The relative fascicle length (to limb length) of vastus lateralis muscle was significantly lower in boys than in men, although there was no difference in that of medial gastrocnemius muscle between the two groups. Interpretation: These results suggest that the amount of changes in the elastic properties and sizes of tendinous structures and in the fascicle lengths from early pubescence to maturity is different for different muscle groups (in particular, the knee extensors and the plantar flexors). [Copyright &y& Elsevier]

Abstract: The purpose of this study was to determine the validity of fascicle length estimation in the vastus lateralis (VL) and vastus intermedius (VI) using ultrasonography. The fascicle lengths of the VL and VI muscles were measured directly (dFL) using calipers, and were estimated (estmFL) using ultrasonography, in 10 legs from five Thiel’s embalmed cadavers. To determine the validity of the estmFLs, FL was estimated using five previously published models and compared with dFL. The intraclass correlation coefficients (ICCs) of two of the five models were>0.75, indicating that these estimates were valid. Both of these models combined measurement of the length of the visible part of the fascicle with linear extrapolation of the length of the part of the fascicle that was not visible on the sonographic image. The ICCs and absolute% difference were best in models that used appropriate pennation angles. These results suggest that two of the five previously published models are valid for obtaining estmFL of the VL and VI using ultrasonography. [Copyright &y& Elsevier]

Abstract: Background: Fascicle length and fascicle excursion measurements in children with cerebral palsy have yielded inconsistent results. The purpose of this study was to measure in vivo passive fascicle lengths and fascicle excursions in the Medial Gastrocnemius muscle of children with cerebral palsy and typically developing controls. Methods: We measured 11 children with spastic cerebral palsy and 14 controls between the ages of 9 and 16years. Ultrasound imaging was used to measure fascicle lengths while a dynamometer moved the ankle joint through the range of motion. A common range of motion for all subjects was used for analysis of fascicle excursion. Findings: Fascicle lengths in children with cerebral palsy were 43% smaller than those for control subjects throughout the range of motion. The relative fascicle excursion was 92% greater on average for the cerebral palsy compared to the control group children. The muscle excursion for the control group children was greater than for the cerebral palsy group children. Interpretation: Since the fascicles in children with spastic cerebral palsy are shorter, but they go through the same excursion as fascicles in typically developing children, sarcomeres within the medial gastrocnemius muscle must be working over a larger range of sarcomere lengths. Combined with findings of overstretched sarcomeres in spastic muscles reported in the literature, our results suggest that the increased passive forces and the weakness found in spastic muscles may be caused by a decrease in contractile filament overlap as sarcomeres are pulled to extreme lengths in children with cerebral palsy. [Copyright &y& Elsevier]

Highlights: [•] Soleus fascicle length patterns in old and young adults are the same only at preferred walking speeds. [•] Walking slower allows a modulation of muscle function in older adults that may permit greater force and power production. [•] Slower walking in older adults results, in part, to conserve muscle function similar to that of younger adults. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to assess the reproducibility of fascicle length (FL) and pennation angle (PA) of gastrocnemius medialis (GM) muscle during running in vivo. Twelve male recreational long distance runners (mean±SD; age: 24±3years, mass: 76±7kg) ran on a treadmill at a speed of 3.0m/s, wearing their own running shoes, for two different 10min sessions that were at least 2days apart. For each test day 10 acceptable trials were recorded. Ankle and knee joint angle data were recorded by a Vicon 624 system with three cameras operating at 120Hz. B-mode ultrasonography was used to examine fascicle length and pennation angle of gastrocnemius medialis muscle. The ultrasound probe was firmly secured on the muscle belly using a lightweight foam fixation. The results indicated that fascicle length and pennation angle demonstrated high reproducibility values during treadmill running both for within and between test days. The root mean square scores between the repeated waveforms of pennation angle and fascicle length were small (∼2° and ∼3.5mm, respectively). However, ∼14 trials for pennation angle and ∼9 trials for fascicle length may be required in order to record accurate data from muscle architecture parameters. In conclusion, ultrasound measurements may be highly reproducible during dynamic movements such as treadmill running, provided that a proper fixation is used in order to assure the constant location and orientation of the ultrasound probe throughout the movement. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to investigate whether sprint performance is related to lower leg musculoskeletal geometry within a homogeneous group of highly trained 100-m sprinters. Using a cluster analysis, eighteen male sprinters were divided into two groups based on their personal best (fast: N =11, 10.30±0.07s; slow: N =7, 10.70±0.08s). Calf muscular fascicle arrangement and Achilles tendon moment arms (calculated by the gradient of tendon excursion versus ankle joint angle) were analyzed for each athlete using ultrasonography. Achilles tendon moment arm, foot and ankle skeletal geometry, fascicle arrangement as well as the ratio of fascicle length to Achilles tendon moment arm showed no significant (p >0.05) correlation with sprint performance, nor were there any differences in the analyzed musculoskeletal parameters between the fast and slow sprinter group. Our findings provide evidence that differences in sprint ability in world-class athletes are not a result of differences in the geometrical design of the lower leg even when considering both skeletal and muscular components. [Copyright &y& Elsevier]

Abstract: Objectives: The study aimed to assess acute changes in muscle architecture and its recovery after exhaustive exercise. We hypothesised that repetitive leg press exercise would decrease vastus lateralis fascicle length, while increasing both muscle thickness and pennation angles. By investigating the time kinetics of recovery of these parameters, we wished to gain insight into the mechanisms responsible for muscle architectural changes during exercise. Design: Muscle architecture was assessed in 41 male volunteers (25.2±3.7yrs; 1.78±0.06m; 76.4±11.7kg) before and directly after, as well as 5, 10, 15, and 30min after induction of fatigue by leg press exercise. Method: Vastus lateralis muscle thickness, pennation angles and fascicle lengths were measured at rest by ultrasonography. Muscular fatigue was induced by an exhaustive series of maximum power, single leg press repetitions. Results: Following leg press exercise vastus lateralis muscle thickness and pennation angles were increased by approximately 7 and 10%, whereas fascicle lengths decreased by 2%. Different recovery times (muscle thickness: 30min; pennation angles: 15min; fascicle lengths: 5min) were observed. Conclusions: The differential time courses of recovery suggest that changes in muscle thickness, pennation angles, and fascicle lengths are driven by different exercise-related stimuli. Increased muscle perfusion and tendon creep are likely candidates accounting for short-term changes in muscle architecture. [Copyright &y& Elsevier]

Abstract: The purposes of this study were to examine (a) whether the morphological properties of the muscle gastrocnemius medialis (GM) contribute to the known enhanced muscle fatigue resistance during submaximal sustained isometric plantar flexion contraction of old compared to young adults and (b) whether a submaximal fatiguing contraction differently affects the mechanical properties of the GM tendon and aponeurosis of old and young adults. Fourteen old and 12 young male subjects performed maximal voluntary isometric plantar flexions (MVC) on a dynamometer before and after a submaximal fatiguing task (40% MVC). Moments and EMG signals from the gastrocnemius medialis and lateralis, soleus and tibialis anterior muscles were measured. The elongation of the GM tendon and aponeurosis and the morphological properties of its contractile element were examined by means of ultrasonography. The old adults showed lower maximal ankle joint moment, stiffness and fascicle length in both tested conditions. The submaximal fatiguing contraction did not affect the force–strain relationship of the GM tendon and aponeurosis of either young or old adults. The time to task failure was longer for the old adults and was strongly correlated with the fascicle length (r 2 =0.50, P <0.001). This provides evidence on that the lower ratio of the active muscle volume to muscle force for the old adults might be an additional mechanism contributing to the known age related increase in muscle fatigue resistance. [Copyright &y& Elsevier]

Abstract: The purpose of this paper was to examine how muscle architecture parameter (MAP) measurements made using brightness-mode ultrasonography (BMU) differ based on probe orientation. The human tibialis anterior muscle was imaged from nine different probe orientations during concentric contractions at four joint angles to determine the effect of probe orientation on the measurement of muscle architecture parameters. Ankle dorsi-flexion torque, tibialis anterior electromyography (EMG), and measures of MAP including fascicle length (FL), pennation angle (PA) and muscle thickness (MT) were collected. Statistically significant differences were found between joint angles for measures of FL and PA and between probe orientations for measures of FL and MT. A comparison of actual MAP values to a geometric model used by researchers to determine an ideal probe orientation show that the actual values vary to a greater extent and do not follow the trend predicted by the model. The results suggest that ultrasound probe orientation affects measures of MAP but the effect either cannot be predicted from a geometric model and/or the error in the measurement technique does not allow a comparison. [Copyright &y& Elsevier]

Abstract: Background: The aim of this study was to investigate the architectural alterations of skeletal muscle following hemiplegic cerebral palsy. If associated with functional and clinical measures of disability, information on muscle architecture could then be used as an objective tool in the assessment of motor disability in these patients. Methods: Ultrasonography was used to assess in vivo the gastrocnemius muscle architecture in the paretic and non-paretic legs of eight children with cerebral palsy. Findings: Fascicle length and muscle thickness at the resting ankle position were reduced in the paretic compared to the non-paretic legs by up to 18% and 20%, respectively (P <0.05), indicating a loss of both in-series and in-parallel sarcomeres in the affected muscles. However, pennation angle was similar (P >0.05) in the two legs. Interpretation: The present results indicate that paresis in hemiplegic cerebral palsy may affect the geometry of skeletal muscle. Further studies are required to examine the relation between muscle architecture, severity of motor disability, and treatment. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to quantify the influence of inevitable ankle joint motion during an isometric contraction on the measured change of the gastrocnemius medialis muscle (GM) architecture in vivo during the loading and the unloading phase. Sitting on a dynamometer subjects performed isometric maximal voluntary contractions as well as contractions induced by electrostimulation. Synchronous joint angular motion, plantarflexion moment, foot’s centre of pressure and real-time ultrasonography of muscle architecture changes of the GM were obtained. During the contraction the ankle joint position altered and significantly affected the change in muscle architecture. At maximal tendon force (1094±323N), the measured fascicle length overestimated the change in fascicle length due to the tendon force by 1.53cm, while the measured pennation angle overestimated the change in pennation angle due to the tendon force by 5.5°. At the same tendon force the measured fascicle length and pennation angle were significantly different between loading and unloading conditions. After correcting the values for the change in ankle joint angle no differences between the loading and the unloading phase at the same tendon force were found. Concerning the estimation of GM fascicle length–force and pennation angle–force curves during the loading and unloading phase of an isometric contraction, these findings indicate that not accounting for ankle joint motion will produce unreliable results. [Copyright &y& Elsevier]

With aging comes reductions in the quality and size of skeletal muscle. These changes influence the force-generating capacity of skeletal muscle and contribute to movement deficits that accompany aging. Although declines in strength remain a significant barrier to mobility in older adults, the association between age-related changes in muscle structure and function remain unresolved. In this study, we compared age-related differences in (i) muscle volume and architecture, (ii) the quantity and distribution of intramuscular fat, and (iii) muscle shear modulus (an index of stiffness) in the triceps surae in 21 younger (24.6 ± 4.3 years) and 15 older (70.4 ± 2.4 years) healthy adults. Additionally, we explored the relationship between muscle volume, architecture, intramuscular fat and ankle plantar flexion strength in young and older adults. Magnetic resonance imaging was used to determine muscle volume and intramuscular fat content. B-mode ultrasound was used to quantify muscle architecture, shear-wave elastography was used to measure shear modulus, and ankle strength was measured during maximal isometric plantar flexion contractions. We found that older adults displayed higher levels of intramuscular fat yet similar muscle volumes in the medial (MG) and lateral gastrocnemius (LG) and soleus, compared to younger adults. These age-related higher levels of intramuscular fat were associated with lower muscle shear modulus in the LG and MG. We also found that muscle physiological cross-sectional area (PCSA) that accounted for age-associated differences in intramuscular fat showed a modest increase in its association with ankle strength compared to PCSA that did not account for fat content. This highlights that skeletal muscle fat infiltration plays a role in age-related strength deficits, but does not fully explain the age-related loss in muscle strength, suggesting that other factors play a more significant role. • We used MR and ultrasound imaging to determine the influence of aging on triceps surae muscle structure and function. • Intramuscular fat was higher in older adults, with no differences in muscle volume between young and older individuals. • Higher amounts of intramuscular fat was associated with lower muscle shear modulus (an index of muscle stiffness). • Age-related differences in PCSA that accounted for intramuscular fat displayed a modest increase in their association with ankle strength. [ABSTRACT FROM AUTHOR]

Muscle architecture has a significant influence on the mechanical properties of skeletal muscles. Important parameters include the fascicle length, the angle of pennation, the physiological cross-sectional area (PCSA) as well as aponeurosis and tendon dimensions. During growth, skeletal muscles have to react to an increasing body mass and size demanding adaptations in muscle dimensions. Investigations of muscle architectural changes during growth are sparse, and existing studies often confine their scope to specific parameters or regions of the muscle. For this cross-sectional study, we determined the entire three-dimensional fascicle architecture of rabbit M. soleus via manual digitization. To this end, the investigations covered nine rabbits in the age-range between 29 days and 109 days. Fascicle length, muscle belly length, and aponeurosis length increased by 40%, 107%, and 111%, respectively. As the pennation angle remained almost constant and the contribution of fascicle length growth to muscle belly growth was minor, the increase in muscle mass primarily led to an increase in PCSA (462%), which required a similar increase in aponeurosis area (434%). Results gain new insight into the build-up of rabbit M. soleus and reveal that increases in muscle belly length are primarily connected to increases in aponeurosis length (83%). Contributions from fascicle length increase (17%) only play a minor role. [ABSTRACT FROM AUTHOR]

We are proposing optimal training conditions that can lead to an increase in the number of serial sarcomeres (SSN) and muscle fascicle length (FL) in spastic muscles. Therapeutic interventions for increasing FL in clinical populations with neurological origin, in whom relative shortness of muscle fascicles contributed to the presentation of symptoms such as spasticity, contracture, and limited functional abilities, do not generally meet these conditions, and therefore, result in less than satisfactory outcomes. Based on a review of literature, we argue that protocols of exercise interventions that led to sarcomerogenesis, and increases in SSN and FL in healthy animal and human models satisfied three criteria: 1) all involved eccentric exercise at appropriately high velocity; 2) resulted in positive strain of muscle fascicles; and 3) momentary deactivation in the stretched muscle. Accordingly, to increase FL in spastic muscles, new exercise protocols in which the three presumed criteria are satisfied, must be developed, and long-term muscle architectural and functional adaptations to such trainings must be examined. [ABSTRACT FROM AUTHOR]

Muscle architecture parameters change when the muscle changes in length. This has multiple effects on the function of the muscle, e.g. on force production and on contraction velocity. Here we present a versatile geometrical model that predicts changes in muscle architecture as a consequence of length changes of the muscle on the basis of the known architecture at a given muscle length. The model accounts for small changes in aponeuroses' dimensions relative to changes in fascicle length and keeps muscle volume constant. We evaluate the model on the rabbit soleus muscle by comparing model predictions of fascicle lengths and pennation angles with experimental data. For this, we determined the internal architecture of the soleus muscle at different muscle belly lengths (67.8 mm at 35° ankle angle and 59.3 mm at 80° ankle angle). The long and the short soleus muscle exhibited mean fascicle lengths and pennation angles of 20.8 ± 1.3 mm, 4 ± 2° and 13.5 ± 1 mm, 10 ± 4°, respectively. The model predicted reasonable mean fascicle lengths and pennation angles for the long and short soleus that differed only by 1 mm and 1° from the measured data, respectively. Differences between predicted and measured distributions seem to stem from interindividual variability in muscle architecture. Even if the proposed approach has been used for the soleus muscle, which is relatively simple in architecture, it is not restricted to homogeneous unipennate architectures. [ABSTRACT FROM AUTHOR]

Objective The effects of long-term (> 6 months) stretching in spastic paresis are unknown. The objective of this study was to compare the architectural and clinical changes in plantar flexors in patients with chronic hemiparesis following a one-year daily self-stretch program vs. standard rehabilitation. Material/patients and methods Twenty-three patients with chronic hemiparesis (8 W; mean age, 56 [12]; time since lesion 9 [8]) participated in a one-year randomized controlled trial involving either conventional therapy (CONV) or a daily self-stretch program within a Guided Self-rehabilitation Contract (GSC). Assessments involved: (i) soleus and medial gastrocnemius (MG) fascicle length, pennation angle, thickness, tendon length, measured by ultrasonography; (ii) XV1, angle of arrest at slow stretch in soleus (XV1SOL), gastro-soleus complex (XV1GAS), gluteus maximus (XV1GM) and rectus femoris (XV1RF); (iii) 10-meter maximal ambulation speed. Correlations (Pearson's) between architectural parameters and XV1 were also explored. Results After one year, soleus fascicle length increased by +16.6 mm (CI95 [+10.3; +22.9]; +42%), in the GSC group vs. −0.1 mm (CI95 [−7.3; +7.1]; −3.7%), in the CONV group ( P = 0.005, Rank-Ancova), MG fascicle length increased by +5.2 mm (CI95 [+2.75; +7.65]; +13%), in the GSC group vs. +1.2 mm (CI95 [−2.0; +4.4]; +7%), in the CONV group ( P = 0.01), soleus thickness increased by +4.3 mm (CI95 [+2.7; +5.9]; +33%), vs. −0.3 mm (CI95 [−2.4; +1.8]; −0.8%), in the CONV group ( P = 0.005). Changes in XV1 involved XV1SOL, +2.4° (CI95 [+0.9; +4.0]; +2.4%), in the GSC group vs. +0.1° (CI95 [−2.7; +2.8]; +0.1%), in the CONV group ( P = 6.9 E-05); XV1GAS, +7.4° (CI95[+5.0; +9.8]; +8%) vs. +1.5° (CI95 [−3.3; +6.3]; +1.5%; P = 0.003); XV1GM, +5.3° (CI95[+2.7; + 7.9]; 4.2%) vs. +1.5° (CI95[+0.1; +5.4]; +1.2%; P = 0.025); XV1RF, +10.5° (CI95 [+5.8; + 16.4]; +3.4%) vs. +1.5° (CI95 [−3.75; +6.65]; +1.9%; P = 0.08). Walking speed increased by +0.08 m/s (CI95 [+0.04; +0.12]; +14%, P = 0.006, t -test) in the GSC group vs. +0.04 m/s (CI95[0.0; +0.08]; +5%, NS) in the CONV group. At baseline, XV1SOL correlated negatively with soleus tendon length ( R = −0.74, P = 0.0003) and positively with muscle thickness ( R = 0.68, P = 0.015). Discussion – conclusion In patients with chronic hemiparesis, a daily self-stretch program of soleus and medial gastrocnemius through Guided Self-rehabilitation Contract over one year increased muscle fascicle length and thickness more than conventional rehabilitation. [ABSTRACT FROM AUTHOR]