Biomechanics

Biomechanics is a vast discipline within the field of Biomedical Engineering. It explores the underlying mechanics of how biological and physiological systems move. It encompasses important clinical applications to address questions related to medicine using engineering mechanics principles. Biomechanics includes interdisciplinary concepts from engineers, physicians, therapists, biologists, physicists, and mathematicians. Through their collaborative efforts, biomechanics research is ever changing and expanding, explaining new mechanisms and principles for dynamic human systems. Biomechanics is used to describe how the human body moves, walks, and breathes, in addition to how it responds to injury and rehabilitation. Advanced biomechanical modeling methods, such as inverse dynamics, finite element analysis, and musculoskeletal modeling are used to simulate and investigate human situations in regard to movement and injury. Biomechanical technologies are progressing to answer contemporary medical questions. The future of biomechanics is dependent on interdisciplinary research efforts and the education of tomorrow’s scientists

Articular human joint modelling

Copyright @ Cambridge University Press 2009.The work reported in this paper encapsulates the theories and algorithms developed to drive the core analysis modules of the software which has been developed to model a musculoskeletal structure of anatomic joints. Due to local bone surface and contact geometry based joint kinematics, newly developed algorithms make the proposed modeller different from currently available modellers. There are many modellers that are capable of modelling gross human body motion. Nevertheless, none of the available modellers offer complete elements of joint modelling. It appears that joint modelling is an extension of their core analysis capability, which, in every case, appears to be musculoskeletal motion dynamics. It is felt that an analysis framework that is focused on human joints would have significant benefit and potential to be used in many orthopaedic applications. The local mobility of joints has a significant influence in human motion analysis, in understanding of joint loading, tissue behaviour and contact forces. However, in order to develop a bone surface based joint modeller, there are a number of major problems, from tissue idealizations to surface geometry discretization and non-linear motion analysis. This paper presents the following: (a) The physical deformation of biological tissues as linear or non-linear viscoelastic deformation, based on spring-dashpot elements. (b) The linear dynamic multibody modelling, where the linear formulation is established for small motions and is particularly useful for calculating the equilibrium position of the joint. This model can also be used for finding small motion behaviour or loading under static conditions. It also has the potential of quantifying the joint laxity. (c) The non-linear dynamic multibody modelling, where a non-matrix and algorithmic formulation is presented. The approach allows handling complex material and geometrical nonlinearity easily. (d) Shortest path algorithms for calculating soft tissue line of action geometries. The developed algorithms are based on calculating minimum ‘surface mass’ and ‘surface covariance’. An improved version of the ‘surface covariance’ algorithm is described as ‘residual covariance’. The resulting path is used to establish the direction of forces and moments acting on joints. This information is needed for linear or non-linear treatment of the joint motion. (e) The final contribution of the paper is the treatment of the collision. In the virtual world, the difficulty in analysing bodies in motion arises due to body interpenetrations. The collision algorithm proposed in the paper involves finding the shortest projected ray from one body to the other. The projection of the body is determined by the resultant forces acting on it due to soft tissue connections under tension. This enables the calculation of collision condition of non-convex objects accurately. After the initial collision detection, the analysis involves attaching special springs (stiffness only normal to the surfaces) at the ‘potentially colliding points’ and motion of bodies is recalculated. The collision algorithm incorporates the rotation as well as translation. The algorithm continues until the joint equilibrium is achieved. Finally, the results obtained based on the software are compared with experimental results obtained using cadaveric joints

Biomechanical consequences of variation in shoulder morphology in the Hominoidea

Studies of comparative morphology clearly distinguish the shoulder morphology of Homo from that of the other hominoids. While the shoulder morphology of non-human hominoids is thought to signal adaptations to arboreal locomotion, human shoulder morphology is understood to have lost this adaptation during hominin evolution. Ideas how non-human hominoid shoulder morphology is advantageous in an arboreal context suggest that the specific shoulder morphological traits enhance the arm-raising mechanism. However, this idea has not been biomechanically tested. This thesis constitutes the first analysis of the biomechanical consequences of two distinct shoulder morphologies within Hominoidea by comparing the glenohumeral muscle capabilities of Gorilla to Homo. The biomechanical capabilities are evaluated by constructing a computational musculoskeletal model of a gorilla thorax, shoulder girdle and upper arm, which is used to predict relevant biomechanical metrics such as muscle moments and moment arms. Muscle moments and moment arms are predicted for two important mechanisms, arm-raising and arm-lowering. The predictions are compared to those of an already existing human musculoskeletal model in order to evaluate differences in arm-raising and arm-lowering capability based on the two distinct thorax and shoulder girdle morphologies. The results of the biomechanical analyses show that the arm-lowering mechanism is enhanced in Gorilla compared to Homo, instead of the arm-raising mechanism. The enhanced arm-lowering mechanism is evident by greater moment capacities of two important arm-lowering muscles, pectoralis major and teres major. The greater moments are the result of greater muscle force capacities and greater moment arms, due to the beneficial musculoskeletal geometry of Gorilla. The results highlight that a more distal muscle insertion along the humerus has the greatest enhancing effect on the arm-lowering moment arms of teres major and pectoralis major. Furthermore, thorax and shoulder girdle morphological traits that are well known to distinguish non-human apes from humans were found to contribute to the enhancement of the arm-lowering mechanism. The more cranially oriented glenoid, obliquely oriented scapular spine and cranial scapula position on the thorax enabled certain muscles to act as arm-lowering muscles in Gorilla, contrary to the arm-raising action capability that is predicted for Homo. The enhanced arm-lowering capability is likely advantageous for the arboreal locomotion of apes. During hoisting behaviours that are known to occur during suspension and vertical climbing, arm-lowering is used to lift the heavy body of the apes upward. The results of this thesis in conjunction with earlier EMG studies suggest those muscles which are highly activated during these hoisting behaviours also have enhanced arm-lowering capacities in Gorilla and potentially other non-human hominoids compared to Homo. As such, the results highlight shoulder morphological traits that are biomechanically important for the arboreal locomotor behaviour of apes. By this, the thesis demonstrates a link between the conformation of shoulder morphological traits and their biomechanical capability, which will aid future functional interpretations of extant and extinct species.:Acknowledgements Bibliographische Darstellung Summary Zusammenfassung Chapter 1: Exploring the functional morphology of the Gorilla shoulder through musculoskeletal modelling Chapter 2: Comparison of the arm-lowering performance between Gorilla and Homo through musculoskeletal modeling Conclusion Appendix A: Supplementary Information for Chapter 1 Appendix B: Supplementary Information for Chapter 2 Appendix C: Curriculum Vitae Appendix D: Author Contribution

Ergonomic Models of Anthropometry, Human Biomechanics and Operator-Equipment Interfaces

The Committee on Human Factors was established in October 1980 by the Commission on Behavioral and Social Sciences and Education of the National Research Council. The committee is sponsored by the Office of Naval Research, the Air Force Office of Scientific Research, the Army Research Institute for the Behavioral and Social Sciences, the National Aeronautics and Space Administration, and the National Science Foundation. The workshop discussed the following: anthropometric models; biomechanical models; human-machine interface models; and research recommendations. A 17-page bibliography is included

Internal structural loading of the lower extremity during running: Implications for skeletal injury

Running is a popular activity of choice for many, and a necessity for athletes and military personnel. The positive physiological adaptations associated with running are well established, and these adaptations can only be exploited if runners remain free from overuse injury. This dissertation utilized a combination of experimentation, musculoskeletal modeling, and a probabilistic model of bone damage, repair, and adaptation to investigate internal structural loading of the lower extremity during running. Specific emphasis was placed on stress fracture development, a common overuse injury that results, in part, from the mechanical fatigue of bone. A series of studies were conducted that addressed the influence of speed on lower-extremity contact forces during running, the relationship between internal femoral loads and stress fracture development, and changes in the probability of tibial stress fracture with practical alterations in kinematics and running mileage. The findings of these studies can be summarized as follows: 1) musculoskeletal models provide meaningful non-invasive estimations of internal structural loads in healthy young adults; 2) joint contact forces increase with speed, 3) stress fractures tend to occur at femoral locations experiencing the largest mechanical loads; 4) the probability of tibial stress fracture increases with stride length and running mileage for a given speed; and 5) the probability of tibial stress fracture increases with running speed for a given mileage. Ultimately this information can be used to develop running regimens that maximize the positive adaptations associated with running and minimize the potential for overuse injury and stress fracture development

Effects of Pacing When Using Material Handling Manipulators

Common manipulator-assisted materials handling tasks were performed in a laboratory simulation at self-selected and faster (paced) speeds. The effects of pacing on peak hand forces, torso kinematics, spine moments and forces, and muscle antagonism were determined, along with any influences of several task variables on these effects. The faster trials were performed 20% more rapidly than the self-paced trials. It was found that (a) achieving this level of performance required 10% higher hand forces and 5%-10% higher torso moments, (b) consistent torso postures and motions were used for both speed conditions, and (c) the faster trials resulted in 10% higher spine forces and 15% higher levels of lumbar muscle antagonism. On whole, these results suggest a higher risk of musculoskeletal injury associated with performance of object transfers at faster than self-selected speeds with and without a manipulator. Further analysis provided evidence that the use of manipulators involves higher levels of motor coordination than do manual tasks. Several implications regarding the use of material handling manipulators in paced operations are discussed. Results from this investigation can be used in the design, evaluation, and selection of material handling manipulators.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67067/2/10.1518_001872099779591240.pd

Biomechanical behaviors of the human triceps surae during landing activities

The purpose of this study was to investigate biomechanical behaviors of human triceps surae in landing activities using a Hill-type muscle model. Ten healthy male subjects (23±3 yrs) performed five trials of drop landing from a height of 60 cm in each of four conditions: a normal landing (NL); a stiff landing that required the subject to perform a NL but with minimal knee flexion (SL); a SL but landing flat footed (SF); and a stiff landing while landing on the toes only (SC). Sagittal kinematic (120 Hz), ground reaction forces (GRF) and moments (1200 Hz) were recorded simultaneously. Using an inverse dynamics approach, ankle moment and triceps surae muscle forces were computed. In addition, the triceps surae muscle force and ankle moment were estimated using the Hill-type model. A one-way analysis of variance (ANOVA) was used to evaluate selected variables with the significant level set at P \u3c 0.05. The mean peak GRF values for NL, SL, SF and SC were 38.0, 49.2, 35.5 and 58.6 N/kg, respectively. The mean VGRF of peak associated was found to be significantly different between each condition except NL and SC. The Hill model predicted the peak triceps surae forces at 54.6, 65.0, 40.7, and 62.1 N/kg for NL, SL, SF, and SC respectively. The mean peak plantar flexing moments for NL, SL, SF, and SC were 2.2, 4.0, 2.8, and 4.4 Nm/kg respectively while the estimated plantar flexing moment had values of 3.7, 4.6, 4.7 and 3.2 Nm/Kg for the same conditions. Greater discrepancy was observed between the experimental and estimated joint moment and muscle force for SF. The Hill model was considered to be a good predictor of the eccentric muscle force in the landing activity for NL, SL, and SC except for SF