Analysis of Two-Dimensional Kinetic Shape Systems

2017 ◽  
Author(s):  
Ismet Handžić ◽  
Haris Muratagić ◽  
Fatemeh Rasouli ◽  
Kyle B. Reed
Keyword(s):  
Mechanical Force ◽  
Ground Reaction Forces ◽  
Ground Contact ◽  
Two Dimensional ◽  
Kinetic Behavior ◽  
Continuous Curve ◽  
Reaction Forces ◽  
Shape Curve

A Kinetic Shape has a physical and continuous curve with a changing radius that is exactly defined by its kinetic behavior. A Kinetic Shape curve is defined by specifying the force applied to the Kinetic Shape and the force with which the Kinetic Shape subsequently reacts at ground contact. This concept allows for predictable, position-dependent, and purely mechanical force redirection which make it broadly applicable. Kinetic Shapes have been previously used in several applications to predict the redirection of forces applied to the shape into ground reaction forces. Here, we analyze various ways 2D Kinetic Shapes interact and show how different mechanical force-based computational operations can be performed using these interconnected Kinetic Shapes, which we call Kinetic Shape Systems.

Predicting ground reaction and tibiotalar contact forces after total ankle arthroplasty during walking

2020 ◽  
Vol 234 (12) ◽  
pp. 1432-1444
Author(s):  
Yanwei Zhang ◽  
Zhenxian Chen ◽  
Yinghu Peng ◽  
Hongmou Zhao ◽  
Xiaojun Liang ◽  
...  
Keyword(s):  
Motion Capture ◽  
Multibody Dynamics ◽  
Contact Forces ◽  
Total Ankle Arthroplasty ◽  
Contact Model ◽  
Patient Specific ◽  
Ground Reaction Forces ◽  
Ground Contact ◽  
Ankle Arthroplasty ◽  
Reaction Forces

The motion capture and force plates data are essential inputs for musculoskeletal multibody dynamics models to predict in vivo tibiotalar contact forces. However, it could be almost impossible to obtain valid force plates data in old patients undergoing total ankle arthroplasty under some circumstances, such as smaller gait strides and inconsistent walking speeds during gait analysis. To remove the dependence of force plates, this study has established a patient-specific musculoskeletal multibody dynamics model with total ankle arthroplasty by combining a foot-ground contact model based on elastic contact elements. And the established model could predict ground reaction forces, ground reaction moments and tibiotalar contact forces simultaneously. Three patients’ motion capture and force plates data during their normal walking were used to establish the patient-specific musculoskeletal models and evaluate the predicted ground reaction forces and ground reaction moments. Reasonable accuracies were achieved for the predicted and measured ground reaction forces and ground reaction moments. The predicted tibiotalar contact forces for all patients using the foot-ground contact model had good consistency with those using force plates data. These findings suggested that the foot-ground contact model could take the place of the force plates data for predicting the tibiotalar contact forces in other total ankle arthroplasty patients, thus providing a simplified and valid platform for further study of the patient-specific prosthetic designs and clinical problems of total ankle arthroplasty in the absence of force plates data.

Dynamic-joint-strength-based two-dimensional symmetric maximum weight-lifting simulation: Model development and validation

2020 ◽  
Vol 234 (7) ◽  
pp. 660-673
Author(s):  
Ritwik Rakshit ◽  
Yujiang Xiang ◽  
James Yang
Keyword(s):  
Joint Strength ◽  
Reaction Force ◽  
Weight Lifting ◽  
Ground Reaction Forces ◽  
Two Dimensional ◽  
Joint Angles ◽  
Maximum Weight ◽  
Strength Based ◽  
Optimization Formulation ◽  
Reaction Forces

This article presents an optimization formulation and experimental validation of a dynamic-joint-strength-based two-dimensional symmetric maximum weight-lifting simulation. Dynamic joint strength (the net moment capacity as a function of joint angle and angular velocity), as presented in the literature, is adopted in the optimization formulation to predict the symmetric maximum lifting weight and corresponding motion. Nineteen participants were recruited to perform a maximum-weight-box-lifting task in the laboratory, and kinetic and kinematic data including motion and ground reaction forces were collected using a motion capture system and force plates, respectively. For each individual, the predicted spine, shoulder, elbow, hip, knee, and ankle joint angles, as well as vertical and horizontal ground reaction force and box weight, were compared with the experimental data. Both root-mean-square error and Pearson’s correlation coefficient ( r) were used for the validation. The results show that the proposed two-dimensional optimization-based motion prediction formulation is able to accurately predict all joint angles, box weights, and vertical ground reaction forces, but not horizontal ground reaction forces.

Optimization-Based Prediction of Aiming and Kneeling Military Tasks Performed by a Soldier

2012 ◽  
Author(s):  
Mahdiar Hariri ◽  
Jasbir Arora ◽  
Karim Abdel-Malek
Keyword(s):  
Degrees Of Freedom ◽  
Optimization Problem ◽  
Human Model ◽  
Ground Reaction Forces ◽  
Optimization Approach ◽  
Ground Contact ◽  
Digital Human Model ◽  
Reaction Forces ◽  
Digital Human ◽  
The Given

The objective of this study is to predict the “Aiming While Standing” and “Aiming While Kneeling” motion tasks for a soldier (human) using a full-body, three dimensional digital human model. The digital human is modeled as a 55 degree of freedom branched mechanism. Six degrees of freedom specify the global position and orientation of the coordinate frame attached to the pelvis of the digital human and 49 degrees of freedom represent the revolute joints which model the human joints and determine the kinematics of the entire digital human. Motion is generated by a multi-objective optimization approach minimizing the mechanical energy and joint discomfort simultaneously. A sequential quadratic programming (SQP) algorithm in SNOPT is used to solve the nonlinear optimization problem. The optimization problem is subject to constraints which represent the limitations of the environment, the digital human model and the motion task. Design variables are the joint angle profiles. All the forces, inertial, gravitational as well as external, are known, except the ground reaction forces. The feasibility of the generation of that arbitrary motion by using the given ground contact areas is ensured by using the well known Zero Moment Point (ZMP) constraint. During the kneeling motion, different parts of the body come in contact and lose contact with the ground which is modeled using a general approach. The ground reaction force on each transient ground contact area is determined using the equations of motion. It is assumed that enough friction exists that allow the human to generate reaction forces as determined by the ZMP constraint. Using these ground reaction forces, the required torques at all joints are calculated by the recursive Lagrangian formulation. Using the given method, we can predict realistic motions for the “Aiming While Standing” and “Aiming While Kneeling” tasks. The optimization approach is able to very well predict the “Natural Point of Aim” which is a well known concept for soldiers. In other words, the approach is able to predict the most comfortable final orientation of the feet on the ground for engaging a specific target. We also predict cases where the orientation of the soldier’s feet are enforced. Many virtual experiments have been conducted by changing the target location in the 3D space, changing the anthropometry of the soldier, adding armor to different joints, changing the variable parameters of the rifle, adding backpack and using different weapons.

scholarly journals Adaptation of Running Biomechanics to Repeated Barefoot Running: A Randomized Controlled Study

2019 ◽  
Vol 47 (8) ◽  
pp. 1975-1983 ◽  
Author(s):  
Karsten Hollander ◽  
Dominik Liebl ◽  
Stephanie Meining ◽  
Klaus Mattes ◽  
Steffen Willwacher ◽  
...  
Keyword(s):  
Passive Control ◽  
Loading Rate ◽  
Control Group ◽  
Ground Reaction Forces ◽  
Ground Contact ◽  
Barefoot Running ◽  
Loading Rates ◽  
Foot Strike ◽  
Reaction Forces ◽  
Running Biomechanics

Background: Previous studies have shown that changing acutely from shod to barefoot running induces several changes to running biomechanics, such as altered ankle kinematics, reduced ground-reaction forces, and reduced loading rates. However, uncertainty exists whether these effects still exist after a short period of barefoot running habituation. Purpose/Hypothesis: The purpose was to investigate the effects of a habituation to barefoot versus shod running on running biomechanics. It was hypothesized that a habituation to barefoot running would induce different adaptations of running kinetics and kinematics as compared with a habituation to cushioned footwear running or no habituation. Study Design: Controlled laboratory study. Methods: Young, physically active adults without experience in barefoot running were randomly allocated to a barefoot habituation group, a cushioned footwear group, or a passive control group. The 8-week intervention in the barefoot and footwear groups consisted of 15 minutes of treadmill running at 70% of VO2 max (maximal oxygen consumption) velocity per weekly session in the allocated footwear. Before and after the intervention period, a 3-dimensional biomechanical analysis for barefoot and shod running was conducted on an instrumented treadmill. The passive control group did not receive any intervention but was also tested prior to and after 8 weeks. Pre- to posttest changes in kinematics, kinetics, and spatiotemporal parameters were then analyzed with a mixed effects model. Results: Of the 60 included participants (51.7% female; mean ± SD age, 25.4 ± 3.3 years; body mass index, 22.6 ± 2.1 kg·m-2), 53 completed the study (19 in the barefoot habituation group, 18 in the shod habituation group, and 16 in the passive control group). Acutely, running barefoot versus shod influenced foot strike index and ankle, foot, and knee angles at ground contact ( P < .001), as well as vertical average loading rate ( P = .003), peak force ( P < .001), contact time ( P < .001), flight time ( P < .001), step length ( P < .001), and cadence ( P < .001). No differences were found for average force ( P = .391). After the barefoot habituation period, participants exhibited more anterior foot placement ( P = .006) when running barefoot, while no changes were observed in the footwear condition. Furthermore, barefoot habituation increased the vertical average loading rates in both conditions (barefoot, P = .01; shod, P = .003) and average vertical ground-reaction forces for shod running ( P = .039). All other outcomes (ankle, foot, and knee angles at ground contact and flight time, contact time, cadence, and peak forces) did not change significantly after the 8-week habituation. Conclusion: Changing acutely from shod to barefoot running in a habitually shod population increased the foot strike index and reduced ground-reaction force and loading rates. After the habituation to barefoot running, the foot strike index was further increased, while the force and average loading rates also increased as compared with the acute barefoot running situation. The increased average loading rate is contradictory to other studies on acute adaptations of barefoot running. Clinical Relevance: A habituation to barefoot running led to increased vertical average loading rates. This finding was unexpected and questions the generalizability of acute adaptations to long-term barefoot running. Sports medicine professionals should consider these adaptations in their recommendations regarding barefoot running as a possible measure for running injury prevention. Registration: DRKS00011073 (German Clinical Trial Register).

scholarly journals How do prosthetic stiffness, height and running speed affect the biomechanics of athletes with bilateral transtibial amputations?

2017 ◽  
Vol 14 (131) ◽  
pp. 20170230 ◽  
Author(s):  
Owen N. Beck ◽  
Paolo Taboga ◽  
Alena M. Grabowski
Keyword(s):  
Treadmill Running ◽  
Ground Reaction Forces ◽  
Ground Contact ◽  
Step Frequency ◽  
Running Speed ◽  
Leg Stiffness ◽  
Reaction Forces ◽  
Ground Contact Time ◽  
Available Information ◽  
Distance Running Performance

Limited available information describes how running-specific prostheses and running speed affect the biomechanics of athletes with bilateral transtibial amputations. Accordingly, we quantified the effects of prosthetic stiffness, height and speed on the biomechanics of five athletes with bilateral transtibial amputations during treadmill running. Each athlete performed a set of running trials with 15 different prosthetic model, stiffness and height combinations. Each set of trials began with the athlete running on a force-measuring treadmill at 3 m s −1 , subsequent trials incremented by 1 m s −1 until they achieved their fastest attainable speed. We collected ground reaction forces (GRFs) during each trial. Prosthetic stiffness, height and running speed each affected biomechanics. Specifically, with stiffer prostheses, athletes exhibited greater peak and stance average vertical GRFs ( β = 0.03; p < 0.001), increased overall leg stiffness ( β = 0.21; p < 0.001), decreased ground contact time ( β = −0.07; p < 0.001) and increased step frequency ( β = 0.042; p < 0.001). Prosthetic height inversely associated with step frequency ( β = −0.021; p < 0.001). Running speed inversely associated with leg stiffness ( β = −0.58; p < 0.001). Moreover, at faster running speeds, the effect of prosthetic stiffness and height on biomechanics was mitigated and unchanged, respectively. Thus, prosthetic stiffness, but not height, likely influences distance running performance more than sprinting performance for athletes with bilateral transtibial amputations.

scholarly journals Prosthetic model, but not stiffness or height, affects the metabolic cost of running for athletes with unilateral transtibial amputations

2017 ◽  
Vol 123 (1) ◽  
pp. 38-48 ◽  
Author(s):  
Owen N. Beck ◽  
Paolo Taboga ◽  
Alena M. Grabowski
Keyword(s):  
Lower Limb ◽  
Metabolic Cost ◽  
Ground Reaction Forces ◽  
Ground Contact ◽  
Limb Stiffness ◽  
Leg Stiffness ◽  
In Series ◽  
Reaction Forces ◽  
Vertical Ground ◽  
Vertical Ground Reaction Forces

Running-specific prostheses enable athletes with lower limb amputations to run by emulating the spring-like function of biological legs. Current prosthetic stiffness and height recommendations aim to mitigate kinematic asymmetries for athletes with unilateral transtibial amputations. However, it is unclear how different prosthetic configurations influence the biomechanics and metabolic cost of running. Consequently, we investigated how prosthetic model, stiffness, and height affect the biomechanics and metabolic cost of running. Ten athletes with unilateral transtibial amputations each performed 15 running trials at 2.5 or 3.0 m/s while we measured ground reaction forces and metabolic rates. Athletes ran using three different prosthetic models with five different stiffness category and height combinations per model. Use of an Ottobock 1E90 Sprinter prosthesis reduced metabolic cost by 4.3 and 3.4% compared with use of Freedom Innovations Catapult [fixed effect (β) = −0.177; P < 0.001] and Össur Flex-Run (β = −0.139; P = 0.002) prostheses, respectively. Neither prosthetic stiffness ( P ≥ 0.180) nor height ( P = 0.062) affected the metabolic cost of running. The metabolic cost of running was related to lower peak (β = 0.649; P = 0.001) and stance average (β = 0.772; P = 0.018) vertical ground reaction forces, prolonged ground contact times (β = −4.349; P = 0.012), and decreased leg stiffness (β = 0.071; P < 0.001) averaged from both legs. Metabolic cost was reduced with more symmetric peak vertical ground reaction forces (β = 0.007; P = 0.003) but was unrelated to stride kinematic symmetry ( P ≥ 0.636). Therefore, prosthetic recommendations based on symmetric stride kinematics do not necessarily minimize the metabolic cost of running. Instead, an optimal prosthetic model, which improves overall biomechanics, minimizes the metabolic cost of running for athletes with unilateral transtibial amputations.NEW & NOTEWORTHY The metabolic cost of running for athletes with unilateral transtibial amputations depends on prosthetic model and is associated with lower peak and stance average vertical ground reaction forces, longer contact times, and reduced leg stiffness. Metabolic cost is unrelated to prosthetic stiffness, height, and stride kinematic symmetry. Unlike nonamputees who decrease leg stiffness with increased in-series surface stiffness, biological limb stiffness for athletes with unilateral transtibial amputations is positively correlated with increased in-series (prosthetic) stiffness.

Design and Evaluation of an Adaptive Ground Contact Model

2007 ◽  
Author(s):  
Christian D. Remy ◽  
Darryl G. Thelen
Keyword(s):  
Experimental Data ◽  
Contact Model ◽  
Human Gait ◽  
Ground Reaction Forces ◽  
Ground Contact ◽  
Inverse Dynamic ◽  
Dynamic Analyses ◽  
Reaction Forces

Ground reaction forces are the driving element of human gait. They are — in the form of forceplate measures — included in virtually all inverse dynamic analyses. While it is possible to base forward dynamic analyses on such measurements, it is preferable to model the foot-floor interactions such that simulations can be performed independent of experimental data. Such a representation then facilitates the use of simulations to predict how movement would change in response to an impairment or intervention.

Standardized Lab Shoes Do Not Decrease Loading Rate Variability in Recreational Runners

2020 ◽  
Vol 36 (5) ◽  
pp. 340-344
Author(s):  
Jessica G. Hunter ◽  
Alexander M.B. Smith ◽  
Lena M. Sciarratta ◽  
Stephen Suydam ◽  
Jae Kun Shim ◽  
...  
Keyword(s):  
Contact Time ◽  
Loading Rate ◽  
Ground Reaction Forces ◽  
Ground Contact ◽  
Step Rate ◽  
Running Shoes ◽  
Reaction Forces ◽  
Ground Contact Time ◽  
Recreational Runners ◽  
Running Mechanics

Studies of running mechanics often use a standardized lab shoe, ostensibly to reduce variance between subjects; however, this may induce unnatural running mechanics. The purpose of this study was to compare the step rate, vertical average loading rate, and ground contact time when running in standardized lab shoes versus participants’ normal running shoes. Ground reaction forces were measured while the participants ran overground in both shoe conditions at a self-selected speed. The Student’s t-test revealed that the vertical average loading rate magnitude was smaller in lab shoes versus normal shoes (42.09 [11.08] vs 47.35 [10.81] body weight/s, P = .013), while the step rate (170.92 [9.43] vs 168.98 [9.63] steps/min, P = .053) and ground contact time were similar (253 [25] vs 251 [20] ms, P = .5227) and the variance of all outcomes was similar in lab shoes versus normal shoes. Our results indicate that using standardized lab shoes during testing may underestimate the loads runners actually experience during their typical mileage.

scholarly journals Consistent inconsistencies in braking: a spatial analysis

2021 ◽  
Vol 11 (5) ◽  
pp. 20200058
Author(s):  
Alexandra G. Hammerberg ◽  
Patricia Ann Kramer
Keyword(s):  
Ground Reaction Forces ◽  
Two Dimensional ◽  
Centre Of Pressure ◽  
Experimental Conditions ◽  
Disease Clustering ◽  
Reaction Forces ◽  
Vertical Ground ◽  
Applied Forces ◽  
Vertical Ground Reaction Forces ◽  
Fatigue Failures

The dynamic system that is the bipedal body in motion is of interest to engineers, clinicians and biological anthropologists alike. Spatial statistics is more familiar to public health researchers as a way of analysing disease clustering and spread; nonetheless, this is a practical approach to the two-dimensional topography of the foot. We quantified the clustering of the centre of pressure (CoP) on the foot for peak braking and propulsive vertical ground reaction forces (GRFs) over multiple, contiguous steps to assess the consistency of the location of peak forces on the foot during walking. The vertical GRFs of 11 participants were collected continuously via a wireless insole system (MoticonReGo AG) across various experimental conditions. We hypothesized that CoPs would cluster in the hindfoot for braking and forefoot for propulsion, and that braking would demonstrate more consistent clustering than propulsion. Contrary to our hypotheses, we found that CoPs during braking are inconsistent in their location, and CoPs during propulsion are more consistent and clustered across all participants and all trials. These results add to our understanding of the applied forces on the foot so that we can better predict fatigue failures and better understand the mechanisms that shaped the modern bipedal form.

scholarly journals Generating two dimensional ground reaction forces with a viscoelastic runner model

2011 ◽  
Vol 13 ◽  
pp. 161-167 ◽  
Author(s):  
Harutoshi Yukawa ◽  
Akinori Tokizawa ◽  
Shozo Kawamura
Keyword(s):  
Ground Reaction Forces ◽  
Two Dimensional ◽  
Reaction Forces
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