Cancellous bone and theropod dinosaur locomotion. Part II—a new approach to inferring posture and locomotor biomechanics in extinct tetrapod vertebrates

This paper is the second of a three-part series that investigates the architecture of cancellous bone in the main hindlimb bones of theropod dinosaurs, and uses cancellous bone architectural patterns to infer locomotor biomechanics in extinct non-avian species. Cancellous bone is widely known to be highly sensitive to its mechanical environment, and therefore has the potential to provide insight into locomotor biomechanics in extinct tetrapod vertebrates such as dinosaurs. Here in Part II, a new biomechanical modelling approach is outlined, one which mechanistically links cancellous bone architectural patterns with three-dimensional musculoskeletal and finite element modelling of the hindlimb. In particular, the architecture of cancellous bone is used to derive a single ‘characteristic posture’ for a given species—one in which bone continuum-level principal stresses best align with cancellous bone fabric—and thereby clarify hindlimb locomotor biomechanics. The quasi-static approach was validated for an extant theropod, the chicken, and is shown to provide a good estimate of limb posture at around mid-stance. It also provides reasonable predictions of bone loading mechanics, especially for the proximal hindlimb, and also provides a broadly accurate assessment of muscle recruitment insofar as limb stabilization is concerned. In addition to being useful for better understanding locomotor biomechanics in extant species, the approach hence provides a new avenue by which to analyse, test and refine palaeobiomechanical hypotheses, not just for extinct theropods, but potentially many other extinct tetrapod groups as well

The influence of speed and size on avian terrestrial locomotor biomechanics: predicting locomotion in extinct theropod dinosaurs

How extinct, non-avian theropod dinosaurs moved is a subject of considerable interest and controversy. A better understanding of non-avian theropod locomotion can be achieved by better understanding terrestrial locomotor biomechanics in their modern descendants, birds. Despite much research on the subject, avian terrestrial locomotion remains little explored in regards to how kinematic and kinetic factors vary together with speed and body size. Here, terrestrial locomotion was investigated in twelve species of ground-dwelling bird, spanning a 1,780-fold range in body mass, across almost their entire speed range. Particular attention was devoted to the ground reaction force (GRF), the force that the feet exert upon the ground. Comparable data for the only other extant obligate, striding biped, humans, were also collected and studied. In birds, all kinematic and kinetic parameters examined changed continuously with increasing speed, while in humans all but one of those same parameters changed abruptly at the walk-run transition. This result supports previous studies that show birds to have a highly continuous locomotor repertoire compared to humans, where discrete ‘walking’ and ‘running’ gaits are not easily distinguished based on kinematic patterns alone. The influences of speed and body size on kinematic and kinetic factors in birds are developed into a set of predictive relationships that may be applied to extinct, non-avian theropods. The resulting predictive model is able to explain 79–93% of the observed variation in kinematics and 69–83% of the observed variation in GRFs, and also performs well in extrapolation tests. However, this study also found that the location of the whole-body centre of mass may exert an important influence on the nature of the GRF, and hence some caution is warranted, in lieu of further investigation

Optimizing exercise intensity in training programs to prevent bone loss in elderly

Exercise programs can positively affect bone and muscle. However, the optimal type, intensity, frequency and duration of exercise to enhance bone and/or muscle mass are still largely unknown, particularly in the elderly population. The main aim of the project isto obtain both fundamental and clinical data that should allow us tooptimize response to exercise programs in elderly subjects. To achieve that, this project consists of three modules: a) quantify the loading on the hip joint during different exercise types in elderly subjects using 3D inverse dynamics and finite element analysis, b) muscle loading during different exercise regimens in elderly individuals will be measured and modeled, c) based on the results of the two previous modules, an optimized training protocol will be designed and implemented in a population of community-dwelling elderly above 70 years of age, in order to assess the clinical implications of the protocol.status: publishe

Real-Time Prediction of Joint Forces by Motion Capture and Machine Learning

Conventional biomechanical modelling approaches involve the solution of large systems of equations that encode the complex mathematical representation of human motion and skeletal structure. To improve stability and computational speed, being a common bottleneck in current approaches, we apply machine learning to train surrogate models and to predict in near real-time, previously calculated medial and lateral knee contact forces (KCFs) of 54 young and elderly participants during treadmill walking in a speed range of 3 to 7 km/h. Predictions are obtained by fusing optical motion capture and musculoskeletal modeling-derived kinematic and force variables, into regression models using artificial neural networks (ANNs) and support vector regression (SVR). Training schemes included either data from all subjects (LeaveTrialsOut) or only from a portion of them (LeaveSubjectsOut), in combination with inclusion of ground reaction forces (GRFs) in the dataset or not. Results identify ANNs as the best-performing predictor of KCFs, both in terms of Pearson R (0.89–0.98 for LeaveTrialsOut and 0.45–0.85 for LeaveSubjectsOut) and percentage normalized root mean square error (0.67–2.35 for LeaveTrialsOut and 1.6–5.39 for LeaveSubjectsOut). When GRFs were omitted from the dataset, no substantial decrease in prediction power of both models was observed. Our findings showcase the strength of ANNs to predict simultaneously multi-component KCF during walking at different speeds—even in the absence of GRFs—particularly applicable in real-time applications that make use of knee loading conditions to guide and treat patients

Βελτιστοποίηση έντασης προγραμμάτων άσκησης για την αντιμετώπιση απώλειας οστικής μάζας σε ηλικιωμένους

The main objective of the study was to assess the effectiveness of specific exercises in terms of peak loading and their possible effect on bone structure in order to counteract osteoporosis at the hip area. This was accomplished by capturing adults performing ordinary sport activities through MOCAP system (Vicon), calculate peak hip loading through inverse dynamics algorithms (Opensim) and calculate peak strains at the femoral neck area (Finite element analysis). Finally, potentially osteogenic exercises were classified in regards to the peak mechanical loading/deformation induced at the hip area. This knowledge can be used for optimizing training programs to address osteoporosis in elderly population or for rehabilitation purposes.Ο κύριος στόχος της έρευνας ήταν η μελέτη της αποτελεσματικότητας ενός δυνητικά ‘οστεγενετικού’ προγράμματος άσκησης για ηλικιωμένους, σε συνάρτηση της μέγιστης μηχανικής επιβάρυνσης και της ακόλουθης συνέπειας της στην οστική δομή, με σκοπό την αντιμετώπιση της οστεοπόρωσης της άρθρωσης του ισχίου. Αυτός κατέστη δυνατός κυρίως μέσω της λεπτομερής εμβιομηχανικής ανάλυσης συνηθισμένων αθλητικών δραστηριοτήτων (βάδιση, ασκήσεις με αντιστάσεις κ.α.) μέσω καταγραφής και ανάλυσης κίνησης με τη βοήθεια ανεπτυγμένων οπτικών συστημάτων, χρήσης λογισμικού μυοσκελετικής προσομοίωσης (Opensim) και ανάλυσης απειροστικού λογισμού (FEM) για τον υπολογισμό τοπικών τάσεων – παραμορφώσεων, ειδικά στη περιοχή του αυχένα του μηριαίου οστού. Τελικά, οι διάφορες ασκήσεις κατηγοριοποιήθηκαν σε σχέση με τη μηχανική επιβάρυνση που επιφέρουν στον αυχένα το μηριαίου οστού και στην ευρύτερη περιοχή της άρθρωσης του ισχίου. Αυτή η γνώση μπορεί να οδηγήσει στη βελτιστοποίηση των προγραμμάτων άσκησης για τη καταπολέμηση της οστεοπόρωσης σε ηλικιωμένους πληθυσμούς

Less hip joint loading only during running rather than walking in elderly compared to young adults

Walking and running have been found to increase hip bone mass in postmenopausal women. However, the optimal speed to trigger osteogenesis is still under debate because the exact loading during different speeds is poorly characterized. Moreover, age related differences in gait kinematics/kinetics can potentially result in differences in peak hip loading, making extrapolation of results based on young populations to the elderly misleading. Using integrated 3D motion capture and musculoskeletal modeling, peak hip contact forces (HCFs) were calculated during walking and running from 3 to 9km/h in 14 female young (21.4±1.6years old) and elderly (69.8±3.4years old) participants. Peak HCFs were similar during walking in both groups, whereas elderly loaded their hip less than young during running, through reducing their stride length and hip adduction angle at peak loading. Moreover, hip adduction moment was found to best predict peak HCF during impact in walking and running whereas hip extension and external rotation moment can predict the second peak HCF during walking in the elderly and young group respectively. Comparison between same speeds in walking and running revealed that in contrast to young no additional hip loading is imposed during running in elderly. The present study offers an insight into the differences in hip loading profile in postmenopausal women during walking and running at different speeds. Such information is crucial to medical experts that target site-specific bone loading through exercise in elderly populations in order to prevent hip bone loss.publisher: Elsevier articletitle: Less hip joint loading only during running rather than walking in elderly compared to young adults journaltitle: Gait & Posture articlelink: http://dx.doi.org/10.1016/j.gaitpost.2017.01.020 content_type: article copyright: © 2017 Elsevier B.V. All rights reserved.status: publishe

Loading of hip measured by hip contact forces at different speeds of walking and running

Exercise plays a pivotal role in maximizing peak bone mass in adulthood and maintaining it through aging, by imposing mechanical loading on the bone that can trigger bone mineralization and growth. The optimal type and intensity of exercise that best enhances bone strength remains however poorly characterized, partly because the exact peak loading of the bone produced by the diverse types of exercises is not known. By means of integrated motion capture as an input to dynamic simulations, contact forces acting on the hip of 20 young healthy adults were calculated during walking and running at different speeds. During walking, hip contact forces (HCFs) have a two peak profile whereby the first peak increases from 4.22 BW to 5.41 BW and the second from 4.37 BW to 5.74 BW, by increasing speed from 3 to 6 km/h. During running, there is only one peak HCF that increases from 7.49 BW to 10.01 BW, by increasing speed from 6 to 12 km/h. Speed related profiles of peak HCFs and ground reaction forces (GRFs) reveal a different progression of the two peaks during walking. Speed has a stronger impact on peak HCFs rather than on peak GRFs during walking and running, suggesting an increasing influence of muscle activity on peak HCF with increased speed. Moreover, results show that the first peak of HCF during walking can be predicted best by hip adduction moment whereas the second peak of HCF by hip extension moment. During running, peak HCF can be best predicted by hip adduction moment. The present study contributes hereby to a better understanding of musculoskeletal loading during walking and running in a wide range of speeds, offering valuable information to clinicians and scientists exploring bone loading as a possible non-pharmacological osteogenic stimulus. This article is protected by copyright. All rights reserved.status: publishe

LOADING OF HIP MEASURED BY HIP CONTACT FORCES AT DIFFERENT SPEEDS OF WALKING AND RUNNING

status: accepte

Real-Time Musculoskeletal Kinematics and Dynamics Analysis Using Marker- and IMU-Based Solutions in Rehabilitation

This study aims to explore the possibility of estimating a multitude of kinematic and dynamic quantities using subject-specific musculoskeletal models in real-time. The framework was designed to operate with marker-based and inertial measurement units enabling extensions far beyond dedicated motion capture laboratories. We present the technical details for calculating the kinematics, generalized forces, muscle forces, joint reaction loads, and predicting ground reaction wrenches during walking. Emphasis was given to reduce computational latency while maintaining accuracy as compared to the offline counterpart. Notably, we highlight the influence of adequate filtering and differentiation under noisy conditions and its importance for consequent dynamic calculations. Real-time estimates of the joint moments, muscle forces, and reaction loads closely resemble OpenSim’s offline analyses. Model-based estimation of ground reaction wrenches demonstrates that even a small error can negatively affect other estimated quantities. An application of the developed system is demonstrated in the context of rehabilitation and gait retraining. We expect that such a system will find numerous applications in laboratory settings and outdoor conditions with the advent of predicting or sensing environment interactions. Therefore, we hope that this open-source framework will be a significant milestone for solving this grand challenge

EFFECT OF THE HOUNSFIELD-DENSITY AND DENSITY-ELASTICITY RELATIONSHIPS ON THE STRAINS AT THE FEMUR NECK

status: publishe