An official website of the United States government
The ‘sprawling–parasagittal’ transition was a major postural shift that occurred in the ancestors of mammals, [PSE1] underpinned by musculoskeletal reorganization of the limbs. However, ‘when’ and ‘how’ this important postural shift occurred is unknown. While the anatomical changes characterizing this transition can be traced through the fossil record, how these relate to functional changes, and the acquisition of parasagittal posture, remains poorly understood. Here, we produced three-dimensional musculoskeletal models of the forelimbs of extant (n=3) and fossil (n=8) taxa that phylogenetically and functionally span the sprawling–parasagittal transition. We calculated joint range of motion (ROM) to determine a 3D pose space, using the novel APSE algorithm (Accelerated Pose Searching with Electrostatics). We then estimated muscle moment arms (MMAs) across the entire pose space for all muscles crossing the shoulder and elbow joints. Models of extant species were validated against empirical measures of ROM and MMA derived from ex vivo XROMM (X-ray reconstruction of moving morphology). Among extant species, our parasagittal taxon occupied a distinct region of pose-space, with more retracted and depressed shoulder joint angles. MMA data show increased emphasis on shoulder elevation associated with a parasagittal posture, but greater shoulder depression in sprawlers. Results from the fossil species show complex, non-linear patterns of forelimb transformation, demonstrating that the ‘sprawling-parasagittal’ transition is characterized by homoplasy and postural variation within the mammalian lineage.
more »
« less
Validation of an Echidna Forelimb Musculoskeletal Model Using XROMM and diceCT
In evolutionary biomechanics, musculoskeletal computer models of extant and extinct taxa are often used to estimate joint range of motion (ROM) and muscle moment arms (MMAs), two parameters which form the basis of functional inferences. However, relatively few experimental studies have been performed to validate model outputs. Previously, we built a model of the short-beaked echidna ( Tachyglossus aculeatus ) forelimb using a traditional modelling workflow, and in this study we evaluate its behaviour and outputs using experimental data. The echidna is an unusual animal representing an edge-case for model validation: it uses a unique form of sprawling locomotion, and possesses a suite of derived anatomical features, in addition to other features reminiscent of extinct early relatives of mammals. Here we use diffusible iodine-based contrast-enhanced computed tomography (diceCT) alongside digital and traditional dissection to evaluate muscle attachments, modelled muscle paths, and the effects of model alterations on the MMA outputs. We use X-ray Reconstruction of Moving Morphology (XROMM) to compare ex vivo joint ROM to model estimates based on osteological limits predicted via single-axis rotation, and to calculate experimental MMAs from implanted muscles using a novel geometric method. We also add additional levels of model detail, in the form of muscle architecture, to evaluate how muscle torque might alter the inferences made from MMAs alone, as is typical in evolutionary studies. Our study identifies several key findings that can be applied to future models. 1) A light-touch approach to model building can generate reasonably accurate muscle paths, and small alterations in attachment site seem to have minimal effects on model output. 2) Simultaneous movement through multiple degrees of freedom, including rotations and translation at joints, are necessary to ensure full joint ROM is captured; however, single-axis ROM can provide a reasonable approximation of mobility depending on the modelling objectives. 3) Our geometric method of calculating MMAs is consistent with model-predicted MMAs calculated via partial velocity, and is a potentially useful tool for others to create and validate musculoskeletal models. 4) Inclusion of muscle architecture data can change some functional inferences, but in many cases reinforced conclusions based on MMA alone.
more »
« less
- Award ID(s):
- 1754459
- PAR ID:
- 10338131
- Date Published:
- Journal Name:
- Frontiers in Bioengineering and Biotechnology
- Volume:
- 9
- ISSN:
- 2296-4185
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
The ‘sprawling-parasagittal’ transition was a major postural shift in the ancestors of mammals, resulting in musculoskeletal reorganization of the forelimbs that underpins modern mammal locomotor diversity. However, ‘when’ and ‘how’ this important postural shift occurred is unknown. While the anatomical changes characterizing this transition can be traced through the fossil record, how these relate to functional changes, and the acquisition of parasagittal posture, remains poorly understood. We produced three-dimensional musculoskeletal models of the forelimbs of extant (n=3) and fossil (n=8) taxa that phylogenetically and functionally span the sprawling–parasagittal transition. We calculated joint range of motion (ROM) to determine a 3D pose-space, using the novel APSE algorithm (Accelerated Pose Searching with Electrostatics). We then estimated muscle moment arms (MMAs) across the entire pose space for all muscles crossing the shoulder and elbow joints. Models of extant species were validated against empirical measures of ROM and MMA derived from ex vivo XROMM (X-ray reconstruction of moving morphology). Among extant species, in both models and experiments, our parasagittal taxon occupied a distinct region of pose-space, with more retracted and depressed shoulder joint angles. MMA data show increased emphasis on shoulder elevation associated with a parasagittal posture, but greater shoulder depression in sprawlers. We hypothesised the fossil taxa would follow trends in these postural variables – e.g., increasing shoulder retraction and elevation MMAs through time – but they instead showed complex, non-linear patterns of forelimb transformation. We demonstrate that the ‘sprawling-parasagittal’ transition is characterized by considerable homoplasy and continuous postural variation throughout mammalian evolution.more » « less
-
In this study, a 3D asymmetric lifting motion is predicted by using a hybrid predictive model to prevent potential musculoskeletal lower back injuries for asymmetric lifting tasks. The hybrid model has two modules: a skeletal module and an OpenSim musculoskeletal module. The skeletal module consists of a dynamic joint strength based 40 degrees of freedom spatial skeletal model. The skeletal module can predict the lifting motion, ground reaction forces (GRFs), and center of pressure (COP) trajectory using an inverse dynamics-based motion optimization method. The musculoskeletal module consists of a 324-muscle-actuated full-body lumbar spine model. Based on the predicted kinematics, GRFs and COP data from the skeletal module, the musculoskeletal module estimates muscle activations using static optimization and joint reaction forces through the joint reaction analysis tool in OpenSim. The predicted asymmetric motion and GRFs are validated with experimental data. Muscle activation results between the simulated and experimental EMG are also compared to validate the model. Finally, the shear and compression spine loads are compared to NIOSH recommended limits. The differences between asymmetric and symmetric liftings are also compared.more » « less
-
Abstract Cerebrovascular accidents like a stroke can affect the lower limb as well as upper extremity joints (i.e., shoulder, elbow, or wrist) and hinder the ability to produce necessary torque for activities of daily living. In such cases, muscles’ ability to generate forces reduces, thus affecting the joint’s torque production. Understanding how muscles generate forces is a key element to injury detection. Researchers have developed several computational methods to obtain muscle forces and joint torques. Electromyography (EMG) driven modeling is one of the approaches to estimate muscle forces and obtain joint torques from muscle activity measurements. Musculoskeletal models and EMG-driven models require necessary muscle-specific parameters for the calculation. The focus of this study is to investigate the EMG-driven approach along with an upper extremity musculoskeletal model to determine muscle forces of two major muscle groups, biceps brachii and triceps brachii, consisting of seven muscle-tendon units. Estimated muscle forces are used to determine the elbow joint torque. Experimental EMG signals and motion capture data are collected for a healthy subject. The musculoskeletal model is scaled to match the geometric parameters of the subject. Then, the approach calculates muscle forces and joint moment for two tasks: simple elbow flexion extension and triceps kickback. Individual muscle forces and net joint torques for both tasks are estimated. The study also has compared the effect of muscle-tendon parameters (optimal fiber length and tendon slack length) on the estimated results.more » « less
-
A three‐dimensional musculoskeletal model of the pelvis and lower limb of Australopithecus afarensisAbstract ObjectivesMusculoskeletal modeling is a powerful approach for studying the biomechanics and energetics of locomotion.Australopithecus (A.) afarensisis among the best represented fossil hominins and provides critical information about the evolution of musculoskeletal design and locomotion in the hominin lineage. Here, we develop and evaluate a three‐dimensional (3‐D) musculoskeletal model of the pelvis and lower limb ofA. afarensisfor predicting muscle‐tendon moment arms and moment‐generating capacities across lower limb joint positions encompassing a range of locomotor behaviors. Materials and MethodsA 3‐D musculoskeletal model of an adultA. afarensispelvis and lower limb was developed based primarily on the A.L. 288‐1 partial skeleton. The model includes geometric representations of bones, joints and 35 muscle‐tendon units represented using 43 Hill‐type muscle models. Two muscle parameter datasets were created from human and chimpanzee sources. 3‐D muscle‐tendon moment arms and isometric joint moments were predicted over a wide range of joint positions. ResultsPredicted muscle‐tendon moment arms generally agreed with skeletal metrics, and corresponded with human and chimpanzee models. Human and chimpanzee‐based muscle parameterizations were similar, with some differences in maximum isometric force‐producing capabilities. The model is amenable to size scaling from A.L. 288‐1 to the larger KSD‐VP‐1/1, which subsumes a wide range of size variation inA. afarensis. DiscussionThis model represents an important tool for studying the integrated function of the neuromusculoskeletal systems inA. afarensis. It is similar to current human and chimpanzee models in musculoskeletal detail, and will permit direct, comparative 3‐D simulation studies.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3389/fbioe.2021.751518
