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Moment Arms (moment + arm)

Distribution by Scientific Domains

Life Sciences	100%

Kinds of Moment Arms

muscle moment arm

Selected Abstracts

In vivo determination of muscle viscoelasticity in the human leg

ACTA PHYSIOLOGICA, Issue 4 2001
S. Fukashiro
The purpose of this study was to examine the methodological validity of the free vibration technique for determining individual viscoelastic characteristics of the human triceps surae muscle-tendon complex (MTC) in vivo. Six subjects sat with first phalangeal joint of the forefoot on the edge of a force-plate. The special frame on the knee was loaded with weight (0,40 kg) for testing. Oscillations of the triceps surae MTC system were initiated with a hand-held hammer by tapping the weight. In order to keep the same posture, the output of the force plate was displayed on the oscilloscope and subjects were asked to maintain the beam on the oscilloscope at a particular location in relation to a reference line. The damped oscillations in conjunction with the equation of motion of a damped mass-spring model were used to calculate the viscosity of muscle (b) and the elasticity of muscle fibres and tendon (k) in each subject, considering moment arm of the ankle joint. With this arrangement, we have obtained high reproducibility in this method. The coefficient of variations (CVs) of b and k in five trials at each weight were quite small (range: 0.5,18.7% in b and 1.0,15.1% in k). There were no significant differences in viscoelastic coefficients between right and left legs. Therefore, it appears that free vibration technique, used here, is adequate in describing the viscoelastic characteristics of the triceps surae in vivo in humans. [source]

DNA damage and repair measurements from cryopreserved lymphocytes without cell culture,A reproducible assay for intervention studies

ENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 7 2006
Jyh-Lurn Chang
Abstract Single-cell gel electrophoresis (the Comet assay) can be used to measure DNA damage and DNA repair capacity (DRC). However, to test DRC of cryopreserved lymphocytes, published methods include steps for cell culturing and phytohemagglutinin stimulation, which may limit use of this assay in intervention studies. We developed a modified Comet assay protocol that allows us to measure DRC from cryopreserved lymphocytes without these in vitro manipulations. Assay reproducibility was evaluated by performing the assay six times on different dates using six aliquots from one blood draw of one individual. The interindividual variation was assessed by performing the assay using one aliquot from six individuals. When ,-irradiation was used as the mutagen, intra-assay coefficients of variation (CVs.) for baseline DNA damage, damage after ,-irradiation exposure, and DRC,measured as tail moment,were 8, 31, and 10%, respectively. Interindividual CVs. were higher. When H2O2 was used as the mutagen, intra-assay CVs. for damage measurements were lower for a protocol modification that included damage and repair at 37°C (CVs. ranging from 8 to 35%) than for the more standard 4°C protocol. Analyzing moment arm,the average distance of DNA migration within the tail,yielded similar results. DNA repair was successfully detected in each experiment. Comparing freshly isolated lymphocytes to cryopreserved lymphocytes from the same individuals' blood draw indicated that DRC was highly correlated when determined using moment arm values. This modified protocol extends the use of the Comet assay to measuring DRC in intervention studies (e.g., dietary interventions) in that it assesses cellular response after cryopreservation without cell culture or other extensive manipulation. Environ. Mol. Mutagen., 2006. © 2006 Wiley-Liss, Inc. [source]

Muscle moment arms of the gibbon hind limb: implications for hylobatid locomotion

JOURNAL OF ANATOMY, Issue 4 2010
Anthony J. Channon
Abstract Muscles facilitate skeletal movement via the production of a torque or moment about a joint. The magnitude of the moment produced depends on both the force of muscular contraction and the size of the moment arm used to rotate the joint. Hence, larger muscle moment arms generate larger joint torques and forces at the point of application. The moment arms of a number of gibbon hind limb muscles were measured on four cadaveric specimens (one Hylobates lar, one H. moloch and two H. syndactylus). The tendon travel technique was used, utilizing an electro-goniometer and a linear voltage displacement transducer. The data were analysed using a technique based on a differentiated cubic spline and normalized to remove the effect of body size. The data demonstrated a functional differentiation between voluminous muscles with short fascicles having small muscle moment arms and muscles with longer fascicles and comparatively smaller physiological cross-sectional area having longer muscle moment arms. The functional implications of these particular configurations were simulated using a simple geometric fascicle strain model that predicts that the rectus femoris and gastrocnemius muscles are more likely to act primarily at their distal joints (knee and ankle, respectively) because they have short fascicles. The data also show that the main hip and knee extensors maintain a very small moment arm throughout the range of joint angles seen in the locomotion of gibbons, which (coupled to voluminous, short-fascicled muscles) might help facilitate rapid joint rotation during powerful movements. [source]

Architectural properties of the first dorsal interosseous muscle

JOURNAL OF ANATOMY, Issue 4 2010
Benjamin W. Infantolino
Abstract Muscle architecture is considered to reflect the function of muscle in vivo, and is important for example to clinicians in designing tendon-transfer and tendon-lengthening surgeries. The purpose of this study was to quantify the architectural properties of the FDI muscle. It is hypothesized that there will be consistency, that is low variability, in the architectural parameters used to describe the first dorsal interosseous muscle because of its clear functional role in index finger motion. The important architectural parameters identified were those required to characterize a muscle adequately by modeling. Specifically the mass, cross-sectional area, and length of the tendon and muscle were measured in cadavers along with the muscle fiber optimum length and pennation angle, and the moment arm of the first dorsal interosseous at the metacarpophalangeal joint. These parameters provide a characterization of the architecture of the first dorsal interosseous, and were used to indicate the inherent variability between samples. The results demonstrated a large amount of variability for all architectural parameters measured; leading to a rejection of the hypothesis. Ratios designed to describe the functioning of the muscles in vivo, for example the ratio of tendon to fiber optimum lengths, also demonstrated a large variability. The results suggest that function cannot be deduced from form for the first dorsal interosseous, and that subject-specific architectural parameters may be necessary for the formulation of accurate musculoskeletal models or making clinical decisions. [source]

Effect of acute tensile loading on gender-specific tendon structural and mechanical properties

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2009
Katherine E. Burgess
Abstract Stretching is commonly used prior to exercise, as it is thought to reduce the risk of injury, and it is also used in the preconditioning of tendon grafts. As tendon properties have been shown to be different between genders, it is proposed that stretching will differentially affect the structure. Here we examine the effect of acute stretch on the mechanical properties of both male and female medial gastrocnemius tendon. Female [20 years,±,1 (SEM), n,=,17] and male (22 years,±,1, n,=,18) subjects underwent a 5-min passive dorsiflexion stretch. Prior to and post stretch medial gastrocnemius tendon stiffness (K), length (l) and cross-sectional area (csa) were measured using ultrasonography and dynamometry. Stiffness and Young's modulus (,) were significantly reduced with stretch for both genders (p,<,0.05). Females showed significantly (p,<,0.05) greater pre- to poststretch decreases in K (22.4 vs. 8.8%) and , (20.5 vs. 8.4%) in comparison to males. The present results show that stretching acutely reduces stiffness of the medial gastrocnemius tendon in females and males, with females showing significantly greater change. The observed disparity between genders may be due in part to variations in tendon moment arm and intrinsic differences in tendon composition. These differential changes in tendon mechanical properties have functional, motor control, and injury risk implications, as well as possible implications for preconditioning of tendon grafts. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27: 510,516, 2009 [source]

Ecomorphological analysis of the masticatory apparatus in the seed-eating bats, genus Chiroderma (Chiroptera: Phyllostomidae)

JOURNAL OF ZOOLOGY, Issue 4 2005
Marcelo R. Nogueira
Abstract Recent data have shown that owing to their seed-predator capacity Chiroderma doriae and Chiroderma villosum trophically depart from all previously studied species within the canopy fruit-bat ensemble. In this paper, the hypothesis that morphological adaptations related to granivory have evolved in these bats is investigated and discussed. A canonical variate analysis was used to search for possible divergent trends between the masticatory apparatus of Chiroderma and other stenodermatines currently recognized in the same ensemble. A total of 142 specimens representative of eight species was included in the analysis. Species of Chiroderma can be discriminated from all other species in the sample based on the increased development of masseter-related variables (height of the anterior zygomatic arch, masseter moment arm, and masseter volume), which, in conjunction with other morphological characteristics (dentition and gape angle) discussed herein, corroborates the evolution of durophagy in this group. A complementary analysis based on a Mantel test revealed that the pattern of morphological differentiation that emerged from the canonical variate analysis does not agree with the one expected based solely on the phylogenetic relationships adopted for the canopy fruit-bats studied here. This result is consistent with the hypothesis that morphological adaptations related to granivory have evolved in Chiroderma. [source]

Muscle moment arms of the gibbon hind limb: implications for hylobatid locomotion

Functional anatomy and muscle moment arms of the pelvic limb of an elite sprinting athlete: the racing greyhound (Canis familiaris)

JOURNAL OF ANATOMY, Issue 4 2008
S. B. Williams
Abstract We provide quantitative anatomical data on the muscle,tendon architecture and geometry of the pelvic limb of an elite sprint athlete, the racing greyhound. Specifically, muscle masses, muscle lengths, fascicle lengths, pennation angles and muscle moment arms were measured. Maximum isometric force and power of muscles, the maximum muscle torque at joints and tendon stress and strain were estimated. We compare data with that published for a generalized breed of canid, and other cursorial mammals such as the horse and hare. The pelvic limb of the racing greyhound had a relatively large volume of hip extensor muscle, which is likely to be required for power production. Per unit body mass, some pelvic limb muscles were relatively larger than those in less specialized canines, and many hip extensor muscles had longer fascicle lengths. It was estimated that substantial extensor moments could be created about the tarsus and hip of the greyhound allowing high power output and potential for rapid acceleration. The racing greyhound hence possesses substantial specializations for enhanced sprint performance. [source]

Functional anatomy and muscle moment arms of the thoracic limb of an elite sprinting athlete: the racing greyhound (Canis familiaris)

JOURNAL OF ANATOMY, Issue 4 2008
S. B. Williams
Abstract We provide quantitative muscle,tendon architecture and geometry data for the racing greyhound thoracic limb. Muscle mass, belly length, fascicle lengths, pennation angles and moment arms were measured, as were tendon masses and lengths. Maximum isometric force and maximum power were estimated for muscles, and maximum stress and strain were estimated for tendons. Results are compared with other fast quadrupedal runners, and to previously published data in mixed-breed dogs. The implications of the functional adaptations of the greyhound thoracic limb for sprinting performance are discussed. The thoracic limb was found to benefit from a similar proportion of locomotor muscle mass to the pelvic limb, suggesting that it may be used to some extent in propulsion, or alternatively that stabilisation is very important in this animal. Extrinsic muscles, especially latissimus dorsi and pectoralis profundus, were predicted to be powerful and important for generating net positive work during accelerations. Proximal biarticular muscles show specialisation toward preventing collapse of the shoulder and elbow joints to enable strut-like limb function, or some form of dynamic control. Distal muscles did not appear specialised for elastic energy storage, a functional difference to pelvic limb muscles, and the equivalents in horse thoracic limbs. The greyhound thoracic limb appears to possess substantial differences from both that of more ,sub-maximal specialist' quadrupeds, and from the greyhound pelvic limb. [source]

The interplay between speed, kinetics, and hand postures during primate terrestrial locomotion

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2010
Biren A. Patel
Abstract Nonprimate terrestrial mammals may use digitigrade postures to help moderate distal limb joint moments and metapodial stresses that may arise during high-speed locomotion with high-ground reaction forces (GRF). This study evaluates the relationships between speed, GRFs, and distal forelimb kinematics in order to evaluate if primates also adopt digitigrade hand postures during terrestrial locomotion for these same reasons. Three cercopithecine monkey species (Papio anubis, Macaca mulatta, Erythrocebus patas) were videotaped moving unrestrained along a horizontal runway instrumented with a force platform. Three-dimensional forelimb kinematics and GRFs were measured when the vertical force component reached its peak. Hand posture was measured as the angle between the metacarpal segment and the ground (MGA). As predicted, digitigrade hand postures (larger MGA) are associated with shorter GRF moment arms and lower wrist joint moments. Contrary to expectations, individuals used more palmigrade-like (i.e. less digitigrade) hand postures (smaller MGA) when the forelimb was subjected to higher forces (at faster speeds) resulting in potentially larger wrist joint moments. Accordingly, these primates may not use their ability to alter their hand postures to reduce rising joint moments at faster speeds. Digitigrady at slow speeds may improve the mechanical advantage of antigravity muscles crossing the wrist joint. At faster speeds, greater palmigrady is likely caused by joint collapse, but this posture may be suited to distribute higher GRFs over a larger surface area to lower stresses throughout the hand. Thus, a digitigrade hand posture is not a cursorial (i.e. high speed) adaptation in primates and differs from that of other mammals. Am J Phys Anthropol 2010. © 2009 Wiley-Liss, Inc. [source]

Development of an anatomically based whole-body musculoskeletal model of the Japanese macaque (Macaca fuscata)

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2009
Naomichi Ogihara
Abstract We constructed a three-dimensional whole-body musculoskeletal model of the Japanese macaque (Macaca fuscata) based on computed tomography and dissection of a cadaver. The skeleton was modeled as a chain of 20 bone segments connected by joints. Joint centers and rotational axes were estimated by joint morphology based on joint surface approximation using a quadric function. The path of each muscle was defined by a line segment connecting origin to insertion through an intermediary point if necessary. Mass and fascicle length of each were systematically recorded to calculate physiological cross-sectional area to estimate the capacity of each muscle to generate force. Using this anatomically accurate model, muscle moment arms and force vectors generated by individual limb muscles at the foot and hand were calculated to computationally predict muscle functions. Furthermore, three-dimensional whole-body musculoskeletal kinematics of the Japanese macaque was reconstructed from ordinary video sequences based on this model and a model-based matching technique. The results showed that the proposed model can successfully reconstruct and visualize anatomically reasonable, natural musculoskeletal motion of the Japanese macaque during quadrupedal/bipedal locomotion, demonstrating the validity and efficacy of the constructed musculoskeletal model. The present biologically relevant model may serve as a useful tool for comprehensive understanding of the design principles of the musculoskeletal system and the control mechanisms for locomotion in the Japanese macaque and other primates. Am J Phys Anthropol, 2009. © 2008 Wiley-Liss, Inc. [source]

Functional variation of neck muscles and their relation to feeding style in Tyrannosauridae and other large theropod dinosaurs

THE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 8 2007
Eric Snively
Abstract Reconstructed neck muscles of large theropod dinosaurs suggest influences on feeding style that paralleled variation in skull mechanics. In all examined theropods, the head dorsiflexor m. transversospinalis capitis probably filled in the posterior dorsal concavity of the neck, for a more crocodilian- than avian-like profile in this region. The tyrannosaurine tyrannosaurids Daspletosaurus and Tyrannosaurus had relatively larger moment arms for lateroflexion by m. longissimus capitis superficialis and m. complexus than albertosaurine tyrannosaurids, and longer dorsiflexive moment arms for m. complexus. Areas of dorsiflexor origination are significantly larger relative to neck length in adult Tyrannosaurus rex than in other tyrannosaurids, suggesting relatively large muscle cross-sections and forces. Tyrannosaurids were not particularly specialized for neck ventroflexion. In contrast, the hypothesis that Allosaurus co-opted m. longissimus capitis superficialis for ventroflexion is strongly corroborated. Ceratosaurus had robust insertions for the ventroflexors m. longissimus capitis profundus and m. rectus capitis ventralis. Neck muscle morphology is consistent with puncture-and-pull and powerful shake feeding in tyrannosaurids, relatively rapid strikes in Allosaurus and Ceratosaurus, and ventroflexive augmentation of weaker jaw muscle forces in the nontyrannosaurids. Anat Rec, 290:934,957, 2007. © 2007 Wiley-Liss, Inc. [source]