Comparison of Skull Shape in Marsupial and Placental Carnivores

1986 ◽  
Vol 34 (2) ◽  
pp. 109 ◽  
Author(s):  
L Werdelin
Keyword(s):  
Canis Lupus ◽  
Muscle Force ◽  
Red Fox ◽  
Tasmanian Devil ◽  
Moment Arm ◽  
Muscle Attachment ◽  
Temporal Fossa ◽  
Skull Shape ◽  
Moment Arms ◽  
Large Muscle

A set of 11 measurements on 40 species of placental (Order Carnivora) and marsupial (Order Dasyurida) carnivores is analysed by means of correspondence analysis. Dasyurida have long mandibles and tooth rows, large muscle attachment areas on the mandible, long moment arms of the temporalis and masseter, and a low occiput and short temporal fossa. Skull shape is uniform in Dasyurida, with about the same variability as in a family of Carnivora. The temporalis of Dasyurida is relatively small, but this may be compensated for by the more rounded shape and longer moment arm. The Tasmanian tiger, Thylacinus cynocephalus, is more similar in skull shape to the red fox, Vulpes vulpes, than to the placental wolf, Canis lupus. The M5 of Dasyurida occupies the same geometric position as the MI in Carnivora, providing a possible explanation for the greater variability in cheek teeth in Carnivora. The Tasmanian devil, Sarcophilus harrisii, is similar to the Hyaenidae in having a shorter distance between the ultimate sectorial molar and the condyle. It is suggested that this is an adaptation to cracking open bones, as this mandible geometry brings the main bone-cracking teeth closer to the region of greatest muscle force.

Morphology and digestive efficiency of red foxes (Vulpes vulpes) and grey foxes (Urocyon cinereoargenteus) in relation to diet

1987 ◽  
Vol 65 (1) ◽  
pp. 72-79 ◽  
Author(s):  
Carolyn Renzulli Jaslow
Keyword(s):  
Vulpes Vulpes ◽  
Red Fox ◽  
Masticatory Muscles ◽  
Moment Arm ◽  
Urocyon Cinereoargenteus ◽  
Digestive Efficiency ◽  
Red Foxes ◽  
Dietary Preference ◽  
Moment Arms ◽  
Resistance Moment

Measurements of the skull and dentition, and digestive efficiency of red foxes (Vulpes vulpes) and grey foxes (Urocyon cinereoargenteus) were compared to determine whether differences in morphology and digestive ability could be associated with dietary preference. The longer jaws of the more carnivorous red fox increase the resistance moment arm when biting at the canines and carnassials, but greater size and mechanical leverage of the masticatory muscles in this species compensate for this, enabling the red fox to bite with forces that should be comparable to or exceed those of the grey fox. The relatively shorter masticatory moment arms of the more omnivorous–insectivorous grey fox should increase bite speed. Both fox species digested mice with equal efficiency, but the more omnivorous grey foxes had higher digestive efficiencies than red foxes when fed a diet of fruit. These morphological and physiological differences observed between sympatric red foxes and grey foxes may allow each species to exploit different foods more effectively.

Achilles Tendon Moment Arms Computed Using Ultrasound and Motion Analysis: In Vivo Estimates for Male Subjects

2008 ◽  
Author(s):  
Justin D. Cowder ◽  
Thomas S. Buchanan ◽  
Kurt T. Manal
Keyword(s):  
Achilles Tendon ◽  
Motion Capture ◽  
Hybrid Method ◽  
Lower Limb ◽  
Muscle Force ◽  
Average Weight ◽  
Moment Arm ◽  
Moment Arms ◽  
Male Subjects

Accurate estimates for Achilles tendon moment arm (MA) are essential when computing gastroc-soleus force from the net plantarflexion moment. Errors in approximating the Achilles tendon MA will adversely affect the muscle force estimate. We have noted that Achilles tendon MAs reported by Maganaris [1] and others are significantly greater (> 1 cm) than values used by Delp et al. computed using SIMM [2]. It is important to note that the stature of Delp’s lower limb model was almost identical to the average weight and height of the subjects in a study by Maganaris. This led us to question which MA profiles were more anatomically meaningful. To address this, we calculated Achilles tendon MAs for 10 male subjects using a previously described method. The method combines ultrasound and video-based motion capture, and referred to as the hybrid method. Subjects in our study were chosen to ensure they were of a similar stature to those tested by Maganaris, thereby minimizing confounding effects of subject anthropometrics.

The variation in the orientations and moment arms of the knee extensor and flexor muscle tendons with increasing muscle force: A mathematical analysis

2000 ◽  
Vol 214 (3) ◽  
pp. 277-286 ◽  
Author(s):  
A Imran ◽  
R A Huss ◽  
H Holstein ◽  
J J O'Connor
Keyword(s):  
Muscle Force ◽  
Sagittal Plane ◽  
Knee Extensor ◽  
Flexion Angle ◽  
Moment Arm ◽  
Flexor Muscle ◽  
Moment Arms ◽  
Maximum Change ◽  
Knee Muscle ◽  
Hamstrings Tendon

The orientations and moment arms of the knee extensor and flexor muscle tendons are evaluated with increasing values of muscle force during simulated isometric exercises. A four-bar linkage model of the knee in the sagittal plane was used to define the motion of the joint in the unloaded state during 0–120° flexion. The cruciate and collateral ligaments were represented by arrays of elastic fibres, which were recruited sequentially under load or remained buckled when slack. A bi-articular model of the patello-femoral joint was used. Simple straight-line representation was used for the lines of action of the forces transmitted by the model muscle tendons. The effects of tissue deformation with increasing muscle force were considered. During quadriceps contraction resisted by an external flexing load, the maximum change in moment arm of the patellar tendon was found to be 2 per cent at 0° flexion when the quadriceps force was increased tenfold, from 250 to 2500 N. The corresponding maximum change in orientation of the tendon was 3° at 120° flexion. During hamstrings contraction resisted by an external extending load, the maximum change in moment arm of the hamstrings tendon was 8 per cent at 60° flexion when the hamstrings force was increased tenfold, from 100 to 1000 N. During gastrocnemious contraction, the corresponding maximum change for the gastrocnemious tendon was 3 per cent at 0°. The orientations of the flexor muscle tendons in this range of force either remained constant or changed by 1° or less at any flexion angle. The general trend at any flexion angle was that, as the muscle force was increased, the moment arms and the orientations approached nearly constant values, showing asymptotic behaviour. It is concluded that experimental simulations of knee muscle action with low values of the externally applied load, of the order of 50 N, can provide reliable estimates of the relationships between muscle forces and external loads during activity.

Development of a Computational Model to Study Effects of Rotator Cuff Tear Size and Location on Muscle Moment Arms

2007 ◽  
Author(s):  
Corinne R. Adams ◽  
Mark A. Baldwin ◽  
Peter J. Laz ◽  
Paul J. Rullkoetter ◽  
Joseph E. Langenderfer
Keyword(s):  
Rotator Cuff ◽  
Rotator Cuff Tear ◽  
Muscle Fiber ◽  
Joint Strength ◽  
Muscle Force ◽  
Fatty Infiltration ◽  
Moment Arm ◽  
Moment Arms ◽  
Cuff Tear ◽  
Tear Size

Rotator cuff tendon tear causes alterations to cuff muscle architecture and tendons including muscle fascicle contracture and increased tendon length, fatty infiltration of the muscle fibers, muscle fiber pennation angle changes, asymmetric muscle atrophy, and altered muscle fiber type composition, e.g. [1]. These changes ultimately result in a reduction in muscle force, and frequently lead to a reduction of shoulder strength and a loss of functionality. Recently, division of the cuff tendons in a manner related to cuff tear has been shown to alter tendon excursions and cause muscle moment arms reductions in a cadaver experiment [2] and a computational study [3]. Evaluations of the effects of cuff tear size and location on cuff muscle moment arms have not been conducted. Consequently, the mechanisms by which the muscle force and moment arm changes affect joint strength are not well understood. An improved understanding of these relationships would increase potential for rehabilitation of joint strength following cuff repair. Models for evaluating rotator cuff tear are non-existent since subject-specific models have focused on healthy normal shoulders. Consequently, models have not been used to quantify the effects of clinically observed changes in muscle and tendon architecture on muscle moment arm and force generating capacity.

Analysis of the mero-carpopodite joint of the American lobster and snow crab. II. Kinematics, morphometrics and moment arms

2003 ◽  
Vol 83 (6) ◽  
pp. 1249-1259 ◽  
Author(s):  
S.C. Mitchell ◽  
M.E. DeMont
Keyword(s):  
Joint Angle ◽  
Snow Crab ◽  
Moment Arm ◽  
Scaling Effects ◽  
Joint Angles ◽  
Positive Allometry ◽  
Moment Arms ◽  
Arm Reaching ◽  
Flexion Extension ◽  
The Moment

This research reports on the kinematics of lobster and snow crab walking, documents changes in the moment arms of the mero-carpopodite joint during rotation, and examines scaling effects of morphological and mechanical variables in these crustacean species. Forward walking lobsters and lateral walking crabs were recorded and images analysed to describe the kinematics of these animals, and subsequently morphometric and moment arm measurements made. During forward walking the lobster maintains fixed mero-carpopodite joint angles during both the power and recovery strokes, though each of the walking legs maintains different joint angles. Legs 3 and 5 are maintained at angles which appear to equalize the flexor and extensor moment arms, and leg 4 joint angle appears to maximize the extensor moment arm. The snow crab has a joint excursion angle of between approximately 50° to 150° and, during flat bed walking, the leading and trailing legs move through similar excursion angles. The length of the meropodite for both species are longer for the anterior two leg pairs relative to the posterior two pairs and the rate of growth of the meropodite is largely isometric for the lobster while consistently increases with positive allometry in the crab. The flexor and extensor moment arms generated as the joint undergoes flexion/extension show two distinct patterns with the extensor moment arm being maximized at relatively low joint angles (55°–115°) and the flexor moment arm reaching a plateau at joint extension with angles between 95° and 155°. The flexor apodeme possesses the largest moment arms in all legs for both species, suggesting the flexors are able to generate greater torques. It appears that, mechanically, these laterally moving animals may be ‘pulling’ with the leading legs to a greater extent than ‘pushing’ with the trailing legs.

scholarly journals Analyzing Moment Arm Profiles in a Full-Muscle Rat Hindlimb Model

Biomimetics ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 10 ◽  
Author(s):  
Fletcher Young ◽  
Christian Rode ◽  
Alex Hunt ◽  
Roger Quinn
Keyword(s):  
Three Dimensional ◽  
Joint Torque ◽  
Fundamental Aspect ◽  
Moment Arm ◽  
Critical Aspect ◽  
Step Cycle ◽  
Moment Arms ◽  
3D Space ◽  
Torque Generation ◽  
Torque Moment

Understanding the kinematics of a hindlimb model is a fundamental aspect of modeling coordinated locomotion. This work describes the development process of a rat hindlimb model that contains a complete muscular system and incorporates physiological walking data to examine realistic muscle movements during a step cycle. Moment arm profiles for selected muscles are analyzed and presented as the first steps to calculating torque generation at hindlimb joints. A technique for calculating muscle moment arms from muscle attachment points in a three-dimensional (3D) space has been established. This model accounts for the configuration of adjacent joints, a critical aspect of biarticular moment arm analysis that must be considered when calculating joint torque. Moment arm profiles from isolated muscle motions are compared to two existing models. The dependence of biarticular muscle’s moment arms on the configuration of the adjacent joint is a critical aspect of moment arm analysis that must be considered when calculating joint torque. The variability in moment arm profiles suggests changes in muscle function during a step.

Determination of Muscle Orientations and Moment Arms

1984 ◽  
Vol 106 (3) ◽  
pp. 280-282 ◽  
Author(s):  
K. N. An ◽  
K. Takahashi ◽  
T. P. Harrigan ◽  
E. Y. Chao
Keyword(s):  
Muscle Force ◽  
Experimental Techniques ◽  
Force Analysis ◽  
Equilibrium Equations ◽  
Extensive Experience ◽  
Load Measurement ◽  
Moment Arms ◽  
Advantages And Disadvantages ◽  
Geometric Measurement

In muscle force analysis, orientations and moment arms of the muscles about a joint provide essential coefficients in the equilibrium equations. For the determination of these parameters, several experimental techniques, including geometric measurement, tendon-joint displacement measurement and direct load measurement, are available. Advantages and disadvantages associated with each of the techniques are reviewed and compared based on our extensive experience.

Mechanical and photosynthetic constraints on the evolution of plant shape

Paleobiology ◽  
1984 ◽  
Vol 10 (1) ◽  
pp. 79-101 ◽  
Author(s):  
Karl J. Niklas ◽  
Vincent Kerchner
Keyword(s):  
Photosynthetic Efficiency ◽  
Growth Habit ◽  
Three Dimensional ◽  
Main Axis ◽  
Moment Arm ◽  
Total Moment ◽  
Moment Arms ◽  
Branching Patterns ◽  
Upper Silurian ◽  
Lateral Branches

A computer model is presented which is capable of calculating both the photosynthetic efficiency (I) of any specified plant shape and the stress related to the total moment arm (M) imposed on vertical branching patterns. Computer simulations indicate that a flattened plant thallus and an erect branching growth habit are two plant shapes capable of optimizing photosynthetic efficiency during indeterminate growth. These two morphologies have geometric analogues in the dorsiventral thalli of some bryophytes and in the vertical axes of mosses and tracheophytes, respectively.Extension of the model to complex, three-dimensional branching patterns indicates that I and I/M are maximized when branching is overtopped (treelike, with lateral branches on a main axis) and when lateral branching systems are planated (frondlike). Geometric alterations of branching patterns that result in optimization of I and I/M can be simulated by computer and are shown to be similar to morphologic alterations attending the early evolution of vascular land plants. It is suggested that a number of major evolutionary trends seen in Upper Silurian to Upper Devonian times can be expressed in terms of optimizing the display of photosynthetic tissues (I) or the balance between photosynthetic efficiency and incurred moment arms (I/M).

Muscle Strengths and Musculoskeletal Geometry of the Upper Limb

1979 ◽  
Vol 8 (1) ◽  
pp. 41-48 ◽  
Author(s):  
A A Amis ◽  
D Dowson ◽  
V Wright
Keyword(s):  
Upper Limb ◽  
Cross Sections ◽  
Wrist Joint ◽  
Elbow Flexion ◽  
Reliable Data ◽  
Moment Arm ◽  
Joint Replacements ◽  
Moment Arms ◽  
Joint Forces

A survey of past literature has shown that there is a lack of reliable data for use in prediction of joint forces in the upper limb although this is desirable when developing joint replacements. Upper limb geometry has been analysed, leading to muscle moment arm data at the wrist and elbow. The variation of these moment arms during elbow flexion has also been examined. Analysis of the dimensions of muscles has enabled their relative strengths to be predicted, based on their ‘physiological cross-sections’. When used in conjuction with published emg data, this information will enable elbow and wrist joint forces to be estimated more realistically than has previously been possible.

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