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Yasuo Kawakami - One of the best experts on this subject based on the ideXlab platform.
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in vivo behavior of muscle Fascicles and tendinous tissues in human tibialis anterior muscle during twitch contraction
Journal of Biomechanics, 2007Co-Authors: Ryutaro Himeno, Toshihiko Nagayoshi, Toshiyuki Kurihara, Kentaro Chino, Tetsuo Fukunaga, Hiroaki Kanehisa, Yasuo KawakamiAbstract:Abstract In this study we investigated the time course of length and velocity of muscle Fascicles and tendinous tissues (TT) during isometric twitch contraction, and examined how their interaction relates to the time course of external torque and muscle Fascicle force generation. From seven males, supra-maximal twitch contractions (singlet) of the tibialis anterior muscle were induced at 30°, 10° and −10° plantar flexed positions. The length and velocity of Fascicles and TT were determined from a series of their transverse ultrasound images. The maximal external torque appeared when the shortening velocity of Fascicles was zero. The Fascicle and TT length, and external torque showed a 10–30 ms delay of each onset, with a significant difference in half relaxation times at −10°. The time course of TT elongation, and Fascicle and tendinous velocities did not differ between joint angles. Curvilinear length–force properties, whose slope of quasi-linear part was ranged from −15.0 to −5.9 N/mm for Fascicles and 5.4 to 14.3 N/mm for TT, and a loop-like pattern of velocity–force properties, in which the mean power was ranged from 0.14 to 0.80 W for Fascicles, and 0.14 to 0.81 W for TT were also observed. These results were attributed to the muscle–tendon interaction, depending on the slack and non-linearity of length–force relationship of compliant TT. We conclude that the mechanical interaction between Fascicles and TT, are significant determinants of twitch force and time characteristics.
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in vivo behavior of muscle Fascicles and tendinous tissues in human tibialis anterior muscle during twitch contraction
Journal of Biomechanics, 2007Co-Authors: Toshiaki Oda, Toshihiko Nagayoshi, Toshiyuki Kurihara, Kentaro Chino, Ryutaro Himeno, Tetsuo Fukunaga, Hiroaki Kanehisa, Dean C Hay, Yasuo KawakamiAbstract:In this study we investigated the time course of length and velocity of muscle Fascicles and tendinous tissues (TT) during isometric twitch contraction, and examined how their interaction relates to the time course of external torque and muscle Fascicle force generation. From seven males, supra-maximal twitch contractions (singlet) of the tibialis anterior muscle were induced at 30 degrees , 10 degrees and -10 degrees plantar flexed positions. The length and velocity of Fascicles and TT were determined from a series of their transverse ultrasound images. The maximal external torque appeared when the shortening velocity of Fascicles was zero. The Fascicle and TT length, and external torque showed a 10-30 ms delay of each onset, with a significant difference in half relaxation times at -10 degrees . The time course of TT elongation, and Fascicle and tendinous velocities did not differ between joint angles. Curvilinear length-force properties, whose slope of quasi-linear part was ranged from -15.0 to -5.9 N/mm for Fascicles and 5.4 to 14.3N/mm for TT, and a loop-like pattern of velocity-force properties, in which the mean power was ranged from 0.14 to 0.80 W for Fascicles, and 0.14 to 0.81 W for TT were also observed. These results were attributed to the muscle-tendon interaction, depending on the slack and non-linearity of length-force relationship of compliant TT. We conclude that the mechanical interaction between Fascicles and TT, are significant determinants of twitch force and time characteristics.
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behavior of Fascicle and tendinous tissue of medial gastrocnemius muscle during rebound exercise of ankle joint
International Journal of Sport and Health Science, 2005Co-Authors: Norihide Sugisaki, Yasuo Kawakami, Hiroaki Kanehisa, Tetsuo FukunagaAbstract:This study aimed to investigate the mechanisms of mechanical work and power enhancement of muscle-tendon complex (MTC) in rebound exercise by quantifying in vivo behavior of Fascicle and tendinous tissue of human medial gastrocnemius muscle (MG). Subjects jumped on a sledge apparatus using only ankle joint with the following two conditions: plantar flexion without counter movement (PFJ) and rebound jumping from a height of 26 cm (RJ). The behavior of Fascicle and tendinous tissue of MG in vivo was determined using ultrasonography. The relative contribution of tendinous tissue to the mechanical work of MTC during plantar flexion phase (PF phase) was 85% in RJ. The maximal mechanical power of tendinous tissue during the PF phase in RJ was about three times greater compared to that in PFJ. There was no significant difference in the mechanical power of Fascicle during PF phase between the two conditions, while the mechanical work of Fascicle in PFJ was less than that in the PF phase of RJ. In RJ, Fascicle was stretched during the dorsiflexion phase. These findings indicated that, in rebound exercise using ankle joint, (1) the enhancement of mechanical work and power of MTC was due to the reuse of elastic energy stored in tendinous tissue during dorsiflexion phase, and (2) Fascicles were stretched during dorsiflexion phase.
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muscle fiber and tendon length changes in the human vastus lateralis during slow pedaling
Journal of Applied Physiology, 2001Co-Authors: Tetsuro Muraoka, Yasuo Kawakami, Masanobu Tachi, T FukunagaAbstract:Muscle Fascicle lengths of vastus lateralis (VL) muscle were measured in five healthy men during slow pedaling to investigate the interaction between muscle fibers and tendon. Subjects cycled at a pedaling rate of 40 rpm (98 W). During exercise, Fascicle lengths changed from 91 ± 7 (SE) to 127 ± 5 mm. It was suggested that Fascicles were on the descending limb of their force-length relationship. The average shortening velocity of Fascicle was greater than that of muscle-tendon complex in the first half of the knee extension phase and was less in the second half. The maximum shortening velocity of Fascicle in the knee extension phase was less than that of muscle-tendon complex by 22 ± 9%. These discrepancies in velocities were mainly caused by the elongation of the tendinous tissue. It was suggested that the elasticity of VL tendinous tissue enabled VL Fascicles to develop force at closer length to their optimal length and kept the maximum shortening velocity of VL Fascicles low during slow pedaling.
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estimation of active force length characteristics of human vastus lateralis muscle
Cells Tissues Organs, 1997Co-Authors: Y Ichinose, Yasuo Kawakami, T FukunagaAbstract:The length and angles of Fascicles were determined for the vastus lateralis muscle (VL) using ultrasonography in 6 subjects performing ramp isometric knee extension. The subject increased torque from zero (relax) to maximum (MVC) with the knee positioned every 15°, from 10° to 100° flexion (0° = full extension). As the knee was positioned closer to extension, Fascicle length was shorter [116+4.7 (mean ± SEM) mm at 100° vs. 88+4.1 mm at 10° (relax)]. The Fascicle length of the VL decreased with increasing torque at each knee position [116+4.7 (relax) to 92 ± 4.3 mm (MVC) at 100°]. On the other hand, Fascicle angles increased with an increase in torque. These changes reflected the compliance of the muscle-tendon complex which increased as the knee reached a straight position. The estimated muscle force of the VL was maximal (2,052 ± 125 N) for a Fascicle length of 78 ± 2.7 mm (i.e. optimum length) with the knee positioned at 70° of flexion. The relationship between muscle force and Fascicle length indicated that the VL uses the ascending (knee 70°) of the force-length curve.
Paavo V Komi - One of the best experts on this subject based on the ideXlab platform.
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muscle Fascicle and tendon behavior during human locomotion revisited
Exercise and Sport Sciences Reviews, 2008Co-Authors: Masaki Ishikawa, Paavo V KomiAbstract:High-speed ultrasonography has revealed that, in human locomotion, the nature of Fascicle and tendon length changes varies depending on the task, contraction intensity, and the muscles involved. The findings emphasize that the active Fascicles of the gastrocnemius muscle are suddenly stretched, although they are shortening. This short-lasting stretch triggers the stretch reflex, timing of which is dependent on running speed.
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effects of contraction intensity on muscle Fascicle and stretch reflex behavior in the human triceps surae
Journal of Applied Physiology, 2008Co-Authors: Neil J Cronin, Masaki Ishikawa, Paavo V Komi, Jussi Peltonen, Janne Avela, Thomas Sinkjaer, Michael VoigtAbstract:The aims of this study were to examine changes in the distribution of a stretch to the muscle Fascicles with changes in contraction intensity in the human triceps surae and to relate Fascicle stret...
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medial gastrocnemius muscle behavior during human running and walking
Gait & Posture, 2007Co-Authors: M Ishikawa, J Pakaslahti, Paavo V KomiAbstract:Utilization of elastic energy in the tendinous tissues (TT) of the human skeletal muscle may be task dependent. The present study was designed to investigate this problem by comparing the Fascicle-TT interaction of the medial gastrocnemius muscle (MG) during ground contact of running and walking. Seven subjects ran and walked with a natural cadence. Ankle and knee joint angular data were recorded by electrogoniometers for estimating the entire MG muscle-tendon unit (MTU) length, together with the ground reaction forces. The MG Fascicle length was measured by using the high-speed ultrasound image scanning during movements. The results showed that in running, after the rapid early Fascicle stretching (0-10% of the contact period), the Fascicles shortened throughout the ground contact while TT was stretched prior to shortening. In walking, the Fascicles shortened initially (0-15% of the contact period) due to sudden plantar-flexion. Thereafter, the Fascicles and TT lengthened slowly until the end of single support (15-70% of the contact period.). The Fascicles then shorted during the push-off phase (70-100% of the contact period). These results demonstrate that the MG Fascicles behaved differently between running and walking and did not follow the length change pattern of the MTU during the ground contact period. The estimated working range of active muscle fibers in force-length relationship could shift more to an ascending limb (shorter length) phase in running than in walking. These results suggest that MG Fascicles can work within the optimal working range of the sarcomeres in the force-length relation but are responsible for the effective utilization of the TT elasticity during human running.
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intensity and muscle specific Fascicle behavior during human drop jumps
Journal of Applied Physiology, 2007Co-Authors: F Sousa, M Ishikawa, Joao Paulo Vilasboas, Paavo V KomiAbstract:The present study was designed to examine Fascicle-tendon interaction in the synergistic medial gastrocnemius (MG) and soleus (Sol) muscles during drop jumps (DJ) performed from different drop heights (DH). Eight subjects performed unilateral DJ with maximal rebounds on a sledge apparatus from different DH. During the exercises, Fascicle lengths (using ultrasonography) and electromyographic activities were recorded. The results showed that the Fascicles of the MG and Sol muscles behaved differently during the contact phase, but the whole muscle-tendon unit and its tendinous tissue lengthened before shortening in both muscles. The Sol Fascicles also lengthened before shortening during the ground contact in all conditions. During the braking phase, the Sol activation increased with increasing DH. However, the amplitude of Sol Fascicle lengthening was not dependent on DH during the same phase. In the MG muscle, the Fascicles primarily shortened during the braking phase in the lower DH condition. However, in the higher DH conditions, the MG Fascicles either behaved isometrically or were lengthened during the braking phase. These results suggest that the Fascicles of synergistic muscles (MG and Sol) can behave differently during DJ and that, with increasing DH, there may be specific length change patterns of the Fascicles of MG but not of Sol.
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muscle tendon interaction and elastic energy usage in human walking
Journal of Applied Physiology, 2005Co-Authors: Masaki Ishikawa, Paavo V Komi, Michael James Grey, Vesa Lepola, Gertpeter BruggemannAbstract:The present study was designed to explore how the interaction between the Fascicles and tendinous tissues is involved in storage and utilization of elastic energy during human walking. Eight male subjects walked with a natural cadence (1.4 ± 0.1 m/s) on a 10-m-long force plate system. In vivo techniques were employed to record the Achilles tendon force and to scan real-time Fascicle lengths for two muscles (medial gastrocnemius and soleus). The results showed that tendinous tissues of both medial gastrocnemius and soleus muscles lengthened slowly throughout the single-stance phase and then recoiled rapidly close to the end of the ground contact. However, the Fascicle length changes demonstrated different patterns and amplitudes between two muscles. The medial gastrocnemius Fascicles were stretched during the early single-stance phase and then remained isometrically during the late-stance phase. In contrast, the soleus Fascicles were lengthened until the end of the single-stance phase. These findings suggest that the elastic recoil takes place not as a spring-like bouncing but as a catapult action in natural human walking. The interaction between the muscle Fascicles and tendinous tissues plays an important role in the process of release of elastic energy, although the leg muscles, which are commonly accepted as synergists, do not have similar mechanical behavior of Fascicles in this catapult action.
Glen A Lichtwark - One of the best experts on this subject based on the ideXlab platform.
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medial gastrocnemius and soleus muscle tendon unit Fascicle and tendon interaction during walking in children with cerebral palsy
Developmental Medicine & Child Neurology, 2017Co-Authors: Lee Barber, Christopher P Carty, Luca Modenese, John P Walsh, Roslyn N Boyd, Glen A LichtwarkAbstract:Aim This study investigates the in vivo function of the medial gastrocnemius and soleus muscle-tendon units (MTU), Fascicles, and tendons during walking in children with cerebral palsy (CP) and an equinus gait pattern. Method Fourteen children with CP (9 males, 5 females; mean age 10y 6mo, standard deviation [SD] 2y 11mo; GMFCS level I=8, II=6), and 10 typically developing (6 males, 4 females; mean age 10y, SD 2y 1mo) undertook full body 3D gait analysis and simultaneous B-mode ultrasound images of the medial gastrocnemius and soleus Fascicles during level walking. Fascicle lengths were analysed using a semi-automated tracking algorithm and MTUs using OpenSim. Statistical parametric mapping (two-sample t-test) was used to compare differences between groups (p<0.05). Results In the CP group medial gastrocnemius Fascicles lengthened during mid-stance gait and remained longer into late-stance compared to the typically developing group (p<0.001). CP medial gastrocnemius Fascicles shortened less during stance (1.16mm [SD 1.47mm]) compared to the typically developing group (4.48mm [SD 1.94mm], p<0.001). In the CP group the medial gastrocnemius and soleus MTU and tendon were longer during early- and mid-stance (p<0.001). Ankle power during push-off (p=0.015) and positive work (p<0.002) and net work (p<0.001) were significantly lower in the CP group. Interpretation Eccentric action of the CP medial gastrocnemius muscle Fascicles during mid-stance walking is consistent with reduced volume and neuromuscular control of impaired muscle. Reduced ankle push-off power and positive work in the children with CP may be attributed to reduced active medial gastrocnemius Fascicle shortening. These findings suggest a reliance on passive force generation for forward propulsion during equinus gait.
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ultratrack software for semi automated tracking of muscle Fascicles in sequences of b mode ultrasound images
Computer Methods and Programs in Biomedicine, 2016Co-Authors: Dominic James Farris, Glen A LichtwarkAbstract:Abstract Background Dynamic measurements of human muscle Fascicle length from sequences of B-mode ultrasound images have become increasingly prevalent in biomedical research. Manual digitisation of these images is time consuming and algorithms for automating the process have been developed. Here we present a freely available software implementation of a previously validated algorithm for semi-automated tracking of muscle Fascicle length in dynamic ultrasound image recordings, “UltraTrack”. Methods UltraTrack implements an affine extension to an optic flow algorithm to track movement of the muscle Fascicle end-points throughout dynamically recorded sequences of images. The underlying algorithm has been previously described and its reliability tested, but here we present the software implementation with features for: tracking multiple Fascicles in multiple muscles simultaneously; correcting temporal drift in measurements; manually adjusting tracking results; saving and re-loading of tracking results and loading a range of file formats. Results Two example runs of the software are presented detailing the tracking of Fascicles from several lower limb muscles during a squatting and walking activity. Conclusion We have presented a software implementation of a validated Fascicle-tracking algorithm and made the source code and standalone versions freely available for download.
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in vivo behavior of the human soleus muscle with increasing walking and running speeds
Journal of Applied Physiology, 2015Co-Authors: Nicholas A.t. Brown, Anthony G Schache, Glen A Lichtwark, Adrian K M Lai, Yichung Lin, Marcus G PandyAbstract:The interaction between the muscle Fascicle and tendon components of the human soleus (SO) muscle influences the capacity of the muscle to generate force and mechanical work during walking and running. In the present study, ultrasound-based measurements of in vivo SO muscle Fascicle behavior were combined with an inverse dynamics analysis to investigate the interaction between the muscle Fascicle and tendon components over a broad range of steady-state walking and running speeds: slow-paced walking (0.7 m/s) through to moderate-paced running (5.0 m/s). Irrespective of a change in locomotion mode (i.e., walking vs. running) or an increase in steady-state speed, SO muscle Fascicles were found to exhibit minimal shortening compared with the muscle-tendon unit (MTU) throughout stance. During walking and running, the muscle Fascicles contributed only 35 and 20% of the overall MTU length change and shortening velocity, respectively. Greater levels of muscle activity resulted in increasingly shorter SO muscle Fascicles as locomotion speed increased, both of which facilitated greater tendon stretch and recoil. Thus the elastic tendon contributed the majority of the MTU length change during walking and running. When transitioning from walking to running near the preferred transition speed (2.0 m/s), greater, more economical ankle torque development is likely explained by the SO muscle Fascicles shortening more slowly and operating on a more favorable portion (i.e., closer to the plateau) of the force-length curve.
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muscle Fascicle and series elastic element length changes along the length of the human gastrocnemius during walking and running
Journal of Biomechanics, 2007Co-Authors: Glen A Lichtwark, A M Wilson, K BougouliasAbstract:Ultrasound imaging has recently been used to distinguish the length changes of muscle Fascicles from those of the whole muscle tendon complex during real life movements. The complicated three-dimensional architecture of pennate muscles can however cause heterogeneity in the length changes along the length of a muscle. Here we use ultrasonography to examine muscle Fascicle length and pennation angle changes at proximal, distal and midbelly sites of the human gastrocnemius medialis (GM) muscle during walking (4.5 km/h) and running (7.5 km/h) on a treadmill. The results of this study have shown that muscle Fascicles perform the same actions along the length of the human GM muscle during locomotion. However the distal Fascicles tend to shorten more and act at greater pennation angles than the more proximal Fascicles. Muscle Fascicles acted relatively isometrically during the stance phase during walking, however during running the Fascicles shortened throughout the stance phase, which corresponded to an increase in the strain of the series elastic elements (SEEs) (consisting of the Achilles tendon and aponeurosis). Measurement of the Fascicle length changes at the midbelly level provided a good approximation of the average Fascicle length changes across the length of the muscle. The compliance of the SEE allows the muscle Fascicles to shorten at a much slower speed, more concomitant with their optimal speed for maximal power output and efficiency, with high velocity shortening during take off in both walking and running achieved by recoil of the SEE.
Ingvars Birznieks - One of the best experts on this subject based on the ideXlab platform.
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muscle spindles in human tibialis anterior encode muscle Fascicle length changes
Journal of Neurophysiology, 2017Co-Authors: Leah R Bent, Ingvars Birznieks, Vaughan G Macefield, Andrew G CresswellAbstract:Muscle spindles provide exquisitely sensitive proprioceptive information regarding joint position and movement. Through passively driven length changes in the muscle-tendon unit (MTU), muscle spindles detect joint rotations because of their in-parallel mechanical linkage to muscle Fascicles. In human microneurography studies, muscle Fascicles are assumed to follow the MTU and, as such, Fascicle length is not measured in such studies. However, under certain mechanical conditions compliant structures can act to decouple the Fascicles, and therefore the spindles, from the MTU. Such decoupling may reduce the fidelity by which muscle spindles encode joint position and movement. The aim of the present study was to measure, for the first time, both the changes in firing of single muscle spindle afferents and changes in muscle Fascicle length in vivo from the tibialis anterior muscle (TA) during passive rotations about the ankle. Unitary recordings were made from 15 muscle spindle afferents supplying TA via a microelectrode inserted into the common peroneal nerve. Ultrasonography was used to measure the length of an individual Fascicle of TA. We saw a strong correlation between Fascicle length and firing rate during passive ankle rotations of varying rates (0.1-0.5Hz) and amplitudes (1-9°). In particular, we saw responses observed at relatively small changes in muscle length that highlight the sensitivity of the TA muscle to small length changes. This study is the first to measure spindle firing and Fascicle dynamics in vivo and provides an experimental basis for further understanding the link between Fascicle length, MTU length and spindle firing patterns.
James M Wakeling - One of the best experts on this subject based on the ideXlab platform.
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3d curvature of muscle Fascicles in triceps surae
Journal of Applied Physiology, 2014Co-Authors: Manku Rana, Ghassan Hamarneh, James M WakelingAbstract:Muscle Fascicles curve along their length, with the curvatures occurring around regions of high intramuscular pressure, and are necessary for mechanical stability. Fascicles are typically considered to lie in Fascicle planes that are the planes visualized during dissection or two-dimensional (2D) ultrasound scans. However, it has previously been predicted that Fascicles must curve in three-dimensional (3D) and thus the Fascicle planes may actually exist as 3D sheets. 3D Fascicle curvatures have not been explored in human musculature. Furthermore, if the Fascicles do not lie in 2D planes, then this has implications for architectural measures that are derived from 2D ultrasound scans. The purpose of this study was to quantify the 3D curvatures of the muscle Fascicles and Fascicle sheets within the triceps surae muscles and to test whether these curvatures varied among different contraction levels, muscle length, and regions within the muscle. Six male subjects were tested for three torque levels (0, 30, and 60% maximal voluntary contraction) and four ankle angles (−15, 0, 15, and 30° plantar flexion), and Fascicles were imaged using 3D ultrasound techniques. The Fascicle curvatures significantly increased at higher ankle torques and shorter muscle lengths. The Fascicle sheet curvatures were of similar magnitude to the Fascicle curvatures but did not vary between contractions. Fascicle curvatures were regionalized within each muscle with the curvature facing the deeper aponeuroses, and this indicates a greater intramuscular pressure in the deeper layers of muscles. Muscle architectural measures may be in error when using 2D images for complex geometries such as the soleus.
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regional variations in Fascicle curvatures within a muscle belly change during contraction
Journal of Biomechanics, 2012Co-Authors: Ana I L Namburete, James M WakelingAbstract:Abstract During muscle contraction, the Fascicles curve in response to changes in internal pressures within the muscle. Muscle modelling studies have predicted that Fascicles curve to different extents in different regions of the muscle and, as such, curvature is expected to vary along and across the muscle belly. In the present study, the local variations in Fascicle curvature within the muscle belly were investigated for a range of contractile conditions. B-mode ultrasound scans of the medial and lateral gastrocnemii muscles were collected at five ankle positions—ranging from dorsiflexion to plantarflexion. An automated algorithm was applied to the images in order to extract the local curvatures from the muscle belly regions. Significant variations in Fascicle curvature were seen in the superficial-to-deep direction. Curvatures were positive in the superficial layer, negative in the deep layer, and had intermediate values close to zero in the central muscle region. This is indicative of the Fascicles following an S-shaped trajectory across the muscle image. The relation between external pressure and curvature regionalization was also investigated by applying elastic compression bandages on the calf. The application of pressure was associated with greater negative curvatures in the distal and central regions of the middle layer, but appeared to have little effect on the superficial and deep layers. The results from this study showed that (1) Fascicle curvature increases with contraction level, (2) there is curvature regionalization within the muscle belly, (3) curvature increases with pressure, and (4) Fascicles follow an S-shaped trajectory across the muscle images.
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computational methods for quantifying in vivo muscle Fascicle curvature from ultrasound images
Journal of Biomechanics, 2011Co-Authors: Ana I L Namburete, Manku Rana, James M WakelingAbstract:Abstract Muscle Fascicles curve during contraction, and this has been seen using B-mode ultrasound. Curvature can vary along a Fascicle, and amongst the Fascicles within a muscle. The purpose of this study was to develop an automated method for quantifying curvature across the entirety of an imaged muscle, to test the accuracy of the method against synthetic images of known curvature and noise, and to test the sensitivity of the method to ultrasound probe placement. Both synthetic and ultrasound images were processed using multiscale vessel enhancement filtering to accentuate the muscle Fascicles, wavelet-based methods were used to quantify Fascicle orientations and curvature distribution grids were produced by quantifying local curvatures for each point within the image. Ultrasound images of ramped isometric contractions of the human medial gastrocnemius were acquired in a test–retest study. The methods enabled distinct curvatures to be determined in different regions of the muscle. The methods were sensitive to kernel sizes during image processing, noise within the image and the variability of probe placements during retesting. Across the physiological range of curvatures and noise, curvatures calculated from validation grids were quantified with a typical standard error of less than 0.026 m −1 , and this is about 1% of the maximum curvatures observed in Fascicles of contracting muscle.
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automated tracking of muscle Fascicle orientation in b mode ultrasound images
Journal of Biomechanics, 2009Co-Authors: Manku Rana, Ghassan Hamarneh, James M WakelingAbstract:B-mode ultrasound can be used to non-invasively image muscle Fascicles during both static and dynamic contractions. Digitizing these muscle Fascicles can be a timely and subjective process, and usually studies have used the images to determine the linear Fascicle lengths. However, Fascicle orientations can vary along each Fascicle (curvature) and between Fascicles. The purpose of this study was to develop and test two methods for automatically tracking Fascicle orientation. Images were initially filtered using a multiscale vessel enhancement (a technique used to enhance tube-like structures), and then Fascicle orientations quantified using either the Radon transform or wavelet analysis. Tests on synthetic images showed that these methods could identify fascicular orientation with errors of less than 0.061. Manual digitization of muscle Fascicles during a dynamic contraction resulted in a standard deviation of angle estimates of 1.411 across ten researchers. The Radon transform predicted Fascicle orientations that were not significantly different from the manually digitized values, whilst the wavelet analysis resulted in angles that were 1.351 less, and reasons for these differences are discussed. The Radon transform can be used to identify the dominant fascicular orientation within an image, and thus used to estimate muscle Fascicle lengths. The wavelet analysis additionally provides information on the local Fascicle orientations and can be used to quantify Fascicle curvatures and regional differences with Fascicle orientation across an image.
