Free body analysis,beam mechanics,and finite element modeling of the mandible of Alligator mississippiensis

The mechanical behavior of mammalian mandibles is well‐studied, but a comprehensive biomechanical analysis (incorporating detailed muscle architecture, accurate material properties, and three‐dimensional mechanical behavior) of an extant archosaur mandible has never been carried out. This makes it unclear how closely models of extant and extinct archosaur mandibles reflect reality and prevents comparisons of structure–function relationships in mammalian and archosaur mandibles. We tested hypotheses regarding the mechanical behavior of the mandible of Alligator mississippiensis by analyzing reaction forces and bending, shear, and torsional stress regimes in six models of varying complexity. Models included free body analysis using basic lever arm mechanics, 2D and 3D beam models, and three high‐resolution finite element models of the Alligator mandible, incorporating, respectively, isotropic bone without sutures, anisotropic bone with sutures, and anisotropic bone with sutures and contact between the mandible and the pterygoid flange. Compared with the beam models, the Alligator finite element models exhibited less spatial variability in dorsoventral bending and sagittal shear stress, as well as lower peak values for these stresses, suggesting that Alligator mandibular morphology is in part designed to reduce these stresses during biting. However, the Alligator models exhibited greater variability in the distribution of mediolateral and torsional stresses than the beam models. Incorporating anisotropic bone material properties and sutures into the model reduced dorsoventral and torsional stresses within the mandible, but led to elevated mediolateral stresses. These mediolateral stresses were mitigated by the addition of a pterygoid‐mandibular contact, suggesting important contributions from, and trade‐offs between, material properties and external constraints in Alligator mandible design. Our results suggest that beam modeling does not accurately represent the mechanical behavior of the Alligator mandible, including important performance metrics such as magnitude and orientation of reaction forces, and mediolateral bending and torsional stress distributions. J.Morphol. 2011. © 2011 Wiley‐Liss, Inc.     

Flexural and Creep Properties of Human Jaw Compact Bone for FEA Studies

The aim of this work was to improve the constitutive model of the human mandible and dentition system by taking into account the non-linear material properties of the structural boney matrix that forms the human jaw bone or mandible. Due to the specific structure of the jaw bone the time dependence of the mechanical properties also forms an important stage of the quantification process. The lack of specific experimental data of this type of material prevents the implementation of these properties into finite element simulations which results in poor quality modelling. Here an attempt was made to determine elastic and viscoelastic mechanical characteristics of the compact bone tissue forming the mandible. The elastic properties of compact bone were determined experimentally from 3 point bending tests and the viscoelastic properties were evaluated from creep tests in compression. A particular human jaw from this complex study was used to reconstruct a geometric model for further numerical experiments.     

Flexural and creep properties of human jaw compact bone for FEA studies

The aim of this work was to improve the constitutive model of the human mandible and dentition system by taking into account the non-linear material properties of the structural boney matrix that forms the human jaw bone or mandible. Due to the specific structure of the jaw bone the time dependence of the mechanical properties also forms an important stage of the quantification process. The lack of specific experimental data of this type of material prevents the implementation of these properties into finite element simulations which results in poor quality modelling. Here an attempt was made to determine elastic and viscoelastic mechanical characteristics of the compact bone tissue forming the mandible. The elastic properties of compact bone were determined experimentally from 3 point bending tests and the viscoelastic properties were evaluated from creep tests in compression. A particular human jaw from this complex study was used to reconstruct a geometric model for further numerical experiments.     

Analysis of arch‐like bones: The rodent mandible as a case study

Bone strength is determined by the mechanical properties of bone material, and the size and shape of the whole bone, i.e., its architecture. The mandible of vertebrates has been traditionally regarded as a beam oriented in relation to main masticatory loads, i.e., the longer dimension of its cross‐section being parallel to the load. Rodents follow this pattern but, in addition, their mandible possesses an intriguing arch‐like shape that is apparent when seen in the lateral view. Little attention was given to the structural capacity of this trait. The advantage of an arch is that it can withstand a greater load than a horizontal beam. The objective of this study was to model the rodent mandible like an arch to evaluate its structural strength. The bending moment in an arch‐like mandible was 15–25% lower with respect to a beam‐like mandible. Further, bending varies with mandible “slenderness” and incisor procumbency, a functionally relevant rodent trait. In the rodent Ctenomys talarum (Caviomorpha; Ctenomyidae), bone stress was substantially reduced when the mandible was modeled as an arch‐like structure as compared with a beam‐like structure, and safety factors were 15–34% higher. The shape of rodents' mandible might confer a functional advantage to high and repeatedly applied loads resulting from a unique feeding mode: gnawing. J. Morphol. 277:879–887, 2016. © 2016 Wiley Periodicals, Inc.     

Mechanical characteristics of the human mandible and study of in vivo behavior of compact bone tissue, a contribution to the description of biomechanics of the mandible--II

On the basis of the investigation of fresh bone in Part I, results are presented that show the influence of ageing, location and direction on the characteristics of the mandible. A comparison with the results of the earlier report, reveals the extent of degradation. The test results of 56 specimens of the left halves of the mandibles L 01, 02 and 03 indicate a so-called self-splint effect within the bony cross-section in the vicinity of structure possibly diseased or attenuated areas. Investigation of the "in-vivo" behavior of the compact bone was performed on the thigh bone of a freshly slaughtered cow. The influence of the loading velocity on Young's modulus was evaluated, and revealed an elastic and a viscid component, and that an asymptotic limit applies. It was also shown that the loading velocity of 0.2 mm/min, which was used for the tests, provides values very close to the asymptotic limit. Changes in condition, associated with progressive demineralisation and drying out of the bone tissue during the preparation of the specimens have an influence on Young's modulus. Specimens were tested under dry and wet conditions, and a variation of 20% caused by moisture was found. In general, the stiffness of dry specimens is higher than that of specimens in a physiological condition.     

Mechanics of the right whale mandible: Full scale testing and finite element analysis

In an effort to better understand the mechanics of ship-whale collision and to reduce the associated mortality of the critically endangered North Atlantic right whale, a comprehensive biomechanical study has been conducted by the Woods Hole Oceanographic Institution and the University of New Hampshire. The goal of the study is to develop a numerical modeling tool to predict the forces and stresses during impact and thereby the resulting mortality risk to whales from ship strikes.Based on post-mortem examinations, jaw fracture was chosen as a fatal endpoint for the whales hit by a vessel. In this paper we investigate the overall mechanical behavior of a right whale mandible under transverse loading and develop a finite element analysis model of the bone. The equivalent elastic modulus of the cortical component of right whale mandible is found by comparing full-scale bending tests with the results of numerical modeling. The finite element model of the mandible can be used in conjunction with a vessel-whale collision event model to predict bone fracture for various ship strike scenarios.     

Multiscale, structure-based modeling for the elastic mechanical behavior of arterial walls

Passive elastic behavior of arterial wall remains difficult to model. Although phenomenological and structural models exist, the question of how the three-dimensional network structure of the collagen in the artery determines its mechanical properties is still open. A model is presented that incorporates a collagen network as well as the noncollagenous material that comprise the artery. The collagen architecture is represented as a network of interconnected fibers, and a neo-Hookean constitutive equation is used to describe the contribution of the noncollagenous matrix. The model is multiscale in that volume-averaging theory is applied to the collagen network, and it is structural in that parameters of the microstructure of the collagen network were considered instead of a macroscopic constitutive law. The computational results provided a good fit to published experimental data for decellularized porcine carotid arteries. The model predicted increased circumferential compliance for increased axial stretch, consistent with previously published reports, and a relatively small sensitivity to open angle. Even at large extensions, the model predicted that the noncollagenous matrix would be in compression, preventing collapse of the collagen network. The incorporation of fiber-fiber interactions led to an accurate model of artery wall behavior with relatively few parameters. The counterintuitive result that the noncollagenous component is in compression during extension and inflation of the tissue suggests that the collagen is important even at small strains, with the noncollagenous components supporting the network, but not resisting the load directly. More accurate representation of the microstructure of the artery wall is needed to explore this issue further.     

Elastic properties and masticatory bone stress in the macaque mandible

One important limitation of mechanical analyses with strain gages is the difficulty in directly estimating patterns of stress or loading in skeletal elements from strain measurements. Because of the inherent anisotropy in cortical bone, orientation of principal strains and stresses do not necessarily coincide, and it has been demonstrated theoretically that such differences may be as great as 45 degrees (Cowin and Hart, 1990). Likewise, relative proportions of stress and strain magnitudes may differ. This investigation measured the elastic properties of a region of cortical bone on both the buccal and lingual surfaces of the lower border of the macaque mandible. The elastic property data was then combined with macaque mandibular strain data from published and a new in vivo strain gage experiment to determine directions and magnitudes of maximum and minimum principal stresses. The goal was to compare the stresses and strains and assess the differences in orientation and relative magnitude between them. The main question was whether these differences might lead to different interpretations of mandibular function. Elastic and shear moduli, and Poisson's ratios were measured using an ultrasonic technique from buccal and lingual cortical surfaces in 12 macaque mandibles. Mandibular strain gage data were taken from a published set of experiments (Hylander, 1979), and from a new experiment in which rosette strain gauges were fixed to the buccal and lingual cortices of the mandibular corpus of an adult female Macaca fascicularis, after which bone strain was recorded during mastication. Averaged elastic properties were combined with strain data to calculate an estimate of stresses in the mandibular corpus. The elastic properties were similar to those of the human mandibular cortex. Near its lower border, the macaque mandible was most stiff in a longitudinal direction, less stiff in an inferosuperior direction, and least stiff in a direction normal to the bone's surface. The lingual aspect of the mandible was slightly stiffer than the buccal aspect. Magnitudes of stresses calculated from average strains ranged from a compressive stress of -16.00 GPa to a tensile stress of 8.84 GPa. The orientation of the principal stresses depended on whether the strain gage site was on the working or balancing side. On the balancing side of the mandibles, maximum principal stresses were oriented nearly perpendicular to the lower border of the mandible. On the working side of the mandibles, the orientation of the maximum principal stresses was more variable than on the balancing side, indicating a larger range of possible mechanisms of loading. Near the lower border of the mandible, differences between the orientation of stresses and strains were 12 degrees or less. Compared to ratios between maximum and minimum strains, ratios between maximum and minimum stresses were more divergent from a ratio of 1.0. Results did not provide any major reinterpretations of mandibular function in macaques, but rather confirmed and extended existing work. The differences between stresses and strains on the balancing side of the mandible generally supported the view that during the power stroke the mandible was bent and slightly twisted both during mastication and transducer biting. The calculated stresses served to de-emphasize the relative importance of torsion. On the working side, the greater range of variability in the stress analysis compared to the strain analysis suggested that a more detailed examination of loadings and stress patterns in each individual experiment would be useful to interpret the results. Torsion was evident on the working side; but in a number of experiments, further information was needed to interpret other superimposed regional loading patterns, which may have included parasagittal bending and reverse parasagittal bending.     

Numerical estimation of bone density and elastic constants distribution in a human mandible

In this paper, we try to predict the distribution of bone density and elastic constants in a human mandible, based on the stress level produced by mastication loads using a mathematical model of bone remodelling. These magnitudes are needed to build finite element models for the simulation of the mandible mechanical behavior. Such a model is intended for use in future studies of the stability of implant-supported dental prostheses. Various models of internal bone remodelling, both phenomenological and more recently mechanobiological, have been developed to determine the relation between bone density and the stress level that bone supports. Among the phenomenological models, there are only a few that are also able to reproduce the level of anisotropy. These latter have been successfully applied to long bones, primarily the femur. One of these models is here applied to the human mandible, whose corpus behaves as a long bone. The results of bone density distribution and level of anisotropy in different parts of the mandible have been compared with various clinical studies, with a reasonable level of agreement.     

单端固定式下颌骨修复体的应力分析

目的:针对包括一侧髁状突的下颌骨缺损,通过有限元应力分析,了解单端固定式下颌骨修复体在功能运动时的受力与变形规律,以期寻求更加合理的修复体的设计和固定方式。方法:建立下颌骨断端和修复体的简易三维模型,模拟咀嚼运动,施加垂直方向载荷,进行有限元法应力分析,计算出该模型各组成部分的应力分布和受力变形。结果:在该模型加载时,延伸板基部和近断端处上部的螺钉颈部是应力集中的部位,近断端处下部的螺钉颈部和修复体的远端舌侧为形变最大的部位。结论:单端固定式下颌骨修复体在加载时,延伸板的基部和靠近断端的固定螺钉是应力集中的部位,修复体远离固定的一侧是变形最大的部位,提示我们应将延伸板形态设计为尽可能加宽,并应增加下颌骨下缘处的固定,使修复体与下颌骨断端受力更加合理,变形也尽可能缩小。     

A composite micromechanical model for connective tissues: Part II--Application to rat tail tendon and joint capsule.

A micromechanical model of fibrous soft tissue has been developed which predicts upper and lower bounds on mechanical properties based on the structure and properties of tissue components by Ault and Hoffman [3, 4]. In this paper, two types of biological tissue are modeled and the results compared to experimental test data. The highly organized structure of rat tail tendon is modeled using the upper bound aggregation rule which predicts uniform strain behavior in the composite material. This model fits the experimental data and results in a correlation coefficient of 0.98. Applied to cat knee joint capsule, the lower bound aggregation rule of the model correlates with the data and predicts uniform stress within this more loosely organized tissue structure. These studies show that the nature of the interactions between the components in tissue differs depending upon its structure and that the biomechanical model is capable of analyzing such differences in structure.     

单端固定式下颌骨修复体的应力分析

目的：针对包括一侧髁状突的下颌骨缺损,通过有限元应力分析,了解单端固定式下颌骨修复体在功能运动时的受力与变形规律,以期寻求更加合理的修复体的设计和固定方式。方法：建立下颌骨断端和修复体的简易三维模型,模拟咀嚼运动,施加垂直方向载荷,进行有限元法应力分析,计算出该模型各组成部分的应力分布和受力变形。结果：在该模型加载时,延伸板基部和近断端处上部的螺钉颈部是应力集中的部位,近断端处下部的螺钉颈部和修复体的远端舌侧为形变最大的部位。结论：单端固定式下颌骨修复体在加载时,延伸板的基部和靠近断端的固定螺钉是应力集中的部位,修复体远离固定的一侧是变形最大的部位,提示我们应将延伸板形态设计为尽可能加宽,并应增加下颌骨下缘处的固定,使修复体与下颌骨断端受力更加合理,变形也尽可能缩小。     

Effect of bone graft characteristics on the mechanical behavior of the lumbar spine

There is little information about the influence of bone graft size, position and elasticity on the mechanical behavior of the lumbar spine. Intersegmental motion, intradiscal pressure and stresses in the lumbar spine were calculated using a three-dimensional, nonlinear finite element model which included an internal spinal fixation device and a bone graft. Cross-sectional area, position, and elastic modulus of the graft were varied in this study. Bone grafts, especially very stiff ones, increase stresses on adjacent endplates. Though larger grafts lead to less contact pressure, it is difficult to judge the quality of different bone graft positions. In general, ventral flexion results in lower maximum contact pressure than lateral bending. There is always little intersegmental rotation in the bridged region compared with that of an intact spine.A larger graft with low stiffness should be favored from a mechanical point of view. Patients should avoid lateral bending of the upper body shortly after surgery.     

The relationships among physical,geometrical and mechanical properties of bone,with a note on the properties of nonhuman primate bone

Since bone reacts to imposed loads by formation and resorption of tissue, analysis of tissue distribution within a bone provides evidence of the adaptation of that bone to a given mechanical function. Definition of these structure-function relationships permits the physical anthropologist to clarify the wide variety of behavioral/morphological adaptations to specific ecological niches in extant primates. From this information, behavior and locomotor function can ultimately be inferred in fossil primates. This paper reviews research which shows the relationships between the physical, geometrical and mechanical properties of bone, so that researchers who are investigating the properties of bone are aware of the numerous interpretations which may be made about structure and function from basic data. In addition, this paper is an attempt to apprise investigators working with primates that comparative data on the properties of primate bone are available, though sparse.     

Numerical modeling of bone tissue adaptation—A hierarchical approach for bone apparent density and trabecular structure

In this work, a three-dimensional model for bone remodeling is presented, taking into account the hierarchical structure of bone. The process of bone tissue adaptation is mathematically described with respect to functional demands, both mechanical and biological, to obtain the bone apparent density distribution (at the macroscale) and the trabecular structure (at the microscale). At global scale bone is assumed as a continuum material characterized by equivalent (homogenized) mechanical properties. At local scale a periodic cellular material model approaches bone trabecular anisotropy as well as bone surface area density. For each scale there is a material distribution problem governed by density-based design variables which at the global level can be identified with bone relative density. In order to show the potential of the model, a three-dimensional example of the proximal femur illustrates the distribution of bone apparent density as well as microstructural designs characterizing both anisotropy and bone surface area density. The bone apparent density numerical results show a good agreement with Dual-energy X-ray Absorptiometry (DXA) exams. The material symmetry distributions obtained are comparable to real bone microstructures depending on the local stress field. Furthermore, the compact bone porosity is modeled giving a transversal isotropic behavior close to the experimental data. Since, some computed microstructures have no permeability one concludes that bone tissue arrangement is not a simple stiffness maximization issue but biological factors also play an important role.     

Electromyographic normalization procedures for determining exercise intensity of closed chain exercises for strengthening the quadriceps femoris muscles

The purpose of this study was to compare the electromyographic (EMG) amplitudes of the quadriceps femoris (QF) muscles during a maximum voluntary isometric contraction (MVIC) to submaximal and maximal dynamic concentric contractions during active exercises. A secondary purpose was to provide information about the type of contraction that may be most appropriate for normalization of EMG data if one wants to determine if a lower extremity closed chain exercise is of sufficient intensity to produce a strengthening response for the QF muscles. Sixty-eight young healthy volunteers (39 female, 29 male) with no lower extremity pain or injury participated in the study. Surface electrodes recorded EMG amplitudes from the vastus medialis obliquus (VMO), rectus femoris (RF), and vastus lateralis (VL) muscles during 5 different isometric and dynamic concentric exercises. The last 27 subjects performed an additional 4 exercises from which a second data set could be analyzed. Maximum isokinetic knee extension and moderate to maximum closed chain exercises activated the QF significantly more than a MVIC. A 40-cm. lateral step-up exercise produced EMG amplitudes of the QF muscles of similar magnitude as the maximum isokinetic knee extension exercises and would be an exercise that could be considered for strengthening the QF muscles. Most published EMG studies of exercises for the QF have been performed by comparing EMG amplitudes during dynamic exercises to a MVIC. This procedure can lead one to overestimate the value of a dynamic exercise for strengthening the QF muscles. We suggest that when studying the efficacy of a dynamic closed chain exercise for strengthening the QF muscles, the exercise be normalized to a dynamic maximum muscle contraction such as that obtained with knee extension during isokinetic testing.     

Estimation of stature from the skeletal reconstruction of an immature Neandertal from Dederiyeh cave, Syria

Skeletal reconstruction of a child Neandertal unearthed at Dederiyeh Cave, Syria in 1993, is undertaken and the acquired stature discussed. Although the skeletal remains were well preserved, the reconstruction required several assumptions to be made because of the immature status of the specimen. The assumptions were mainly concerned with distances between bones in the inter-vertebral spaces and in the joints of the hip, knee, and ankle. These were estimated from X-ray films of modern children and data from previous studies. Stature was directly measured on the reconstruction, and found to be 79.2 cm. After corrections for soft tissue thickness and shrinkage of the casts, the stature became 81.7 cm. This estimate is consistent with estimates based on regression equations of long bone lengths, especially from those of the lower extremity. In comparison with longitudinal data for white American boys, the assessment of stature for Dederiyeh varied according to the estimated age. For a younger estimated age, the stature falls in the lower half of the white American range of variation, but with an older estimated age, it falls below the lower limit of the range of variation. Other immature Neandertals including two European specimens, Roc de Marsal and La Ferrassie 6, fall below the lower limit of the 5th to 95th percentile range based on the estimated statures from their long bone lengths. More comprehensive age assessment covering both fossil and modern humans is required before accurate conclusions in relation to Neandertal growth can be drawn.     

A customized fixation plate with novel structure designed by topological optimization for mandibular angle fracture based on finite element analysis

Background

The purpose of this study was to design a customized fixation plate for mandibular angle fracture using topological optimization based on the biomechanical properties of the two conventional fixation systems, and compare the results of stress, strain and displacement distributions calculated by finite element analysis (FEA).

Methods

A three-dimensional (3D) virtual mandible was reconstructed from CT images with a mimic angle fracture and a 1 mm gap between two bone segments, and then a FEA model, including volume mesh with inhomogeneous bone material properties, three loading conditions and constraints (muscles and condyles), was created to design a customized plate using topological optimization method, then the shape of the plate was referenced from the stress concentrated area on an initial part created from thickened bone surface for optimal calculation, and then the plate was formulated as “V” pattern according to dimensions of standard mini-plate finally. To compare the biomechanical behavior of the “V” plate and other conventional mini-plates for angle fracture fixation, two conventional fixation systems were used: type A, one standard mini-plate, and type B, two standard mini-plates, and the stress, strain and displacement distributions within the three fixation systems were compared and discussed.

Results

The stress, strain and displacement distributions to the angle fractured mandible with three different fixation modalities were collected, respectively, and the maximum stress for each model emerged at the mandibular ramus or screw holes. Under the same loading conditions, the maximum stress on the customized fixation system decreased 74.3, 75.6 and 70.6% compared to type A, and 34.9, 34.1, and 39.6% compared to type B. All maximum von Mises stresses of mandible were well below the allowable stress of human bone, as well as maximum principal strain. And the displacement diagram of bony segments indicated the effect of treatment with different fixation systems.

Conclusions

The customized fixation system with topological optimized structure has good biomechanical behavior for mandibular angle fracture because the stress, strain and displacement within the plate could be reduced significantly comparing to conventional “one mini-plate” or “two mini-plates” systems. The design methodology for customized fixation system could be used for other fractures in mandible or other bones to acquire better mechanical behavior of the system and improve stable environment for bone healing. And together with SLM, the customized plate with optimal structure could be designed and fabricated rapidly to satisfy the urgent time requirements for treatment.

     

The biomechanics of human femurs in axial and torsional loading: comparison of finite element analysis, human cadaveric femurs, and synthetic femurs

To assess the performance of femoral orthopedic implants, they are often attached to cadaveric femurs, and biomechanical testing is performed. To identify areas of high stress, stress shielding, and to facilitate implant redesign, these tests are often accompanied by finite element (FE) models of the bone/implant system. However, cadaveric bone suffers from wide specimen to specimen variability both in terms of bone geometry and mechanical properties, making it virtually impossible for experimental results to be reproduced. An alternative approach is to utilize synthetic femurs of standardized geometry, having material behavior approximating that of human bone, but with very small specimen to specimen variability. This approach allows for repeatable experimental results and a standard geometry for use in accompanying FE models. While the synthetic bones appear to be of appropriate geometry to simulate bone mechanical behavior, it has not, however, been established what bone quality they most resemble, i.e., osteoporotic or osteopenic versus healthy bone. Furthermore, it is also of interest to determine whether FE models of synthetic bones, with appropriate adjustments in input material properties or geometric size, could be used to simulate the mechanical behavior of a wider range of bone quality and size. To shed light on these questions, the axial and torsional stiffness of cadaveric femurs were compared to those measured on synthetic femurs. A FE model, previously validated by the authors to represent the geometry of a synthetic femur, was then used with a range of input material properties and change in geometric size, to establish whether cadaveric results could be simulated. Axial and torsional stiffnesses and rigidities were measured for 25 human cadaveric femurs (simulating poor bone stock) and three synthetic "third generation composite" femurs (3GCF) (simulating normal healthy bone stock) in the midstance orientation. The measured results were compared, under identical loading conditions, to those predicted by a previously validated three-dimensional finite element model of the 3GCF at a variety of Young's modulus values. A smaller FE model of the 3GCF was also created to examine the effects of a simple change in bone size. The 3GCF was found to be significantly stiffer (2.3 times in torsional loading, 1.7 times in axial loading) than the presently utilized cadaveric samples. Nevertheless, the FE model was able to successfully simulate both the behavior of the 3GCF, and a wide range of cadaveric bone data scatter by an appropriate adjustment of Young's modulus or geometric size. The synthetic femur had a significantly higher stiffness than the cadaveric bone samples. The finite element model provided a good estimate of upper and lower bounds for the axial and torsional stiffness of human femurs because it was effective at reproducing the geometric properties of a femur. Cadaveric bone experiments can be used to calibrate FE models' input material properties so that bones of varying quality can be simulated.     

Effect of arm swing direction on forward and backward jump performance

This study quantified and compared how the directional differences in arm swing affected mechanical and physiological parameters during forward and backward jumping. Seven subjects maximally performed three types of forward and backward squat jumps-no arm swing (FJ, BJ), forward arm swing (FJF, BJF), and backward arm swing (FJB, BJB) from a force platform. All performances were captured with a 3-D motion capture system. Electromyograms (EMGs) of the lower extremity muscles were obtained. Variables were calculated by combining kinematic and kinetic data. The jump displacement and center of mass velocity at take-off were significantly larger in FJF than in FJ or FJB and larger in BJB than in BJ or BJF, suggesting that the best performance was obtained by employing the same arm swing direction as a given jump direction. The total work by three lower and two upper extremity joints was significantly larger in FJF than in FJ or FJB and larger in BJB than in BJ or BJF. For the lower extremity joints, hip work was the greatest in FJF and BJB. The integrated EMG of the biceps femoris when the hip power was produced was significantly larger in FJF and BJB than under other conditions. These results suggest that if the arm swing direction is the same as a given jump direction, the activation level of the hip extensor is greater to counter large loads which make the hip joint flex during the push-off phase, which result in increased hip extension torque, power, and work.