Exploration of the Validity of the Two-Dimensional Sagittal Plane Standing Long Jump Model

Most previous standing long jump studies have been based on the assumption of two-dimensional sagittal plane motion. The purpose of this study was to investigate the validity of this assumption. Standing long jump trials were collected using six adult male subjects. Each subject stood with a foot on each of two force plates and performed eight standing long jumps for maximal distance. Inverse dynamics analyses were performed for the two-dimensional (2D) and three-dimensional (3D) models and the joint moments, powers, and work values were compared. The differences between these models with respect to the validity of the common planar jumping assumption were analyzed. Good agreement was observed between the 2D and 3D methods for the lower body, with little difference in the moments, power, and work for the ankle, knee, hip, and lower back. For the upper body, the moments and work were similar, however significant differences were observed in power generation resulting from the two methods. There were also significant moments and power generated about the abduction/adduction axis for the shoulder. An approximately equal amount of work was found to be performed about the abduction/adduction and flexion/extension axes at the shoulder. The 3D model was also found to capture significant differences between the left and right sides of the body that were not able to be observed with the 2D model. The results of this study show that a planar motion assumption should be sufficient for most studies of the standing long jump. However, in cases where upper body motion is being studied or small increases in performances are vital, a 3D model may be more appropriate as it more accurately represents the motion of the upper body and is better able to show the differences in performance between the two sides of the body

Automated shape analysis and visualization of the human back.

Spinal and back deformities can lead to pain and discomfort, disrupting productivity, and may require prolonged treatment. The conventional method of assessing and monitoring tile de-formity using radiographs has known radiation hazards. An alternative approach for monitoring the deformity is to base the assessment on the shape of back surface. Though three-dimensional data acquisition methods exist, techniques to extract relevant information for clinical use have not been widely developed. Thi's thesis presentsthe content and progression of research into automated analysis and visu-alization of three-dimensional laser scans of the human back. Using mathematical shape analysis, methods have been developed to compute stable curvature of the back surface and to detect the anatomic landmarks from the curvature maps. Compared with manual palpation, the landmarks have been detected to within accuracy of 1.15mm and precision of 0.8111m.Based on the detected spinous process landmarks, the back midline which is the closest surface approximation of the spine, has been derived using constrained polynomial fitting and statistical techniques. Three-dimensional geometric measurementsbasedon the midline were then corn-puted to quantify the deformity. Visualization plays a crucial role in back shape analysis since it enables the exploration of back deformities without the need for physical manipulation of the subject. In the third phase,various visualization techniques have been developed, namely, continuous and discrete colour maps, contour maps and three-dimensional views. In the last phase of the research,a software system has been developed for automating the tasks involved in analysing, visualizing and quantifying of the back shape. The novel aspectsof this research lie in the development of effective noise smoothing methods for stable curvature computation; improved shape analysis and landmark detection algorithm; effective techniques for visualizing the shape of the back; derivation of the back midline using constrained polynomials and computation of three dimensional surface measurements.

Development and Biodynamic Simulation of a Detailed Musculo-Skeletal Spine Model

Ph.DDOCTOR OF PHILOSOPH

Towards the use of 2-dimensional video-based markerless motion capture to objectively evaluate kinematics during functional capacity evaluation

Backgrounds Workability, the capacity to perform work, is a concept highly regarded in a return-to-work context and typically measured using functional capacity evaluation (FCE). The aim of FCE is to determine the capacity of an individual such that they can be appropriately matched with job demands. Further, the usage of FCE is popularly used in attempt to proactively reduce the risk of injury in the workplace. Capacity is measured using tests, including maximum safe load tests and manual materials handling tolerance tests. However, the ability to predict workability using FCE has been questioned. Functional capacity evaluation administrators determine workability, in part, by using a priori parameters such as “the subject maintains balance," that are determined via subjective observations. Use of subjective observation may explain why the ability to reliably determine effort and capacity by using FCE remain in debate (Trippolini et al., 2014). However, a markerless motion-capture based solution may permit direct measurement of important movement features, and in turn, may improve the predictive utility and reliability of FCE outcomes. But, first, it remains important to evaluate if a 2-dimensional (2D) video-based markerless motion capture solution can generate objective outcomes that match with those generated using existing 3-dimensional (3D) motion capture. Objective. To determine the agreement of kinematic outputs calculated from motion data collected via a 2D video-based pose-estimation (markerless motion capture) software and a laboratory-based 3D motion capture for floor-to-waist height lifting task. The kinematic outputs calculated include peak knee flexion angle, peak trunk flexion angle, peak shoulder flexion and abduction angles, functional stability limits in the anterior-posterior and medial-lateral direction, the distance of the load relative to the center of gravity and mean absolute relative phase angles. Methods. Three floor-to-waist height lifts were used for analysis for each participant (N = 20). Participants’ lifts were captured using 3D motion capture (Vicon, Oxford, UK) and simultaneously recorded using 2D video (camcorder) in the sagittal plane. The participants lifts were each completed using a light, medium and heavy load dependent on the participants’ individual subjective capacities. Post-collection, motion data from 3D motion capture and video-based markerless motion capture were used separately to calculate the specific kinematic metrics of interest. The outcome measures calculated were peak knee flexion angle, peak trunk flexion angle, peak shoulder flexion and abduction angles, center of gravity relative to the load handled, base of support relative to the center of gravity in the anterior-posterior and medial-lateral directions, as well as mean absolute relative phase angles of the hip-knee for the flexion and extension phases of the lift separately. Bland-Altman analysis and plots were used to calculate agreement as a form of concurrent validity between the two methods. Results. For all outcome measures, Bland-Altman analysis did not suggest agreement between outcomes calculated using the 2D pose-estimation method and 3D motion capture method. Conclusions. Due to the lack of agreement between the two methods, it is advised that video-based markerless motion capture and 2D pose-estimation be further enhanced prior to use in calculating objective measures of FCE performance

The development and validation of a movement evaluation system for children with cerebral palsy

The development of objective assessment tools for evaluation in physiotherapy is vital. Currently, the outcomes resulting from an intervention are generated by clinical assessments that are almost exclusively based on subjective criteria which rely upon the assessor’s expertise and consistency. The aim of this project was to develop an objective clinical tool to measure head and trunk postural control in sitting for children with cerebral palsy (CP). It is preferable for any objective measurement tool to be useable with as wide a range of patients and conditions as possible. Ideally, the tool should also be ‘clinically-friendly’ for both therapist and patient. This project took children with CP as a starting point, as representing one of the most challenging groups to assess and to quantify. The project was specifically focused on head-trunk control in sitting because of the importance of this posture for activities of daily living. The Literature Reviews confirmed that head-trunk control status in sitting could be defined by an aligned sitting posture without any external support for the head, trunk and upper limbs. The Method selected was video-based (Dartfish) to meet the requirement of ‘clinically-friendly’ and developed to quantify alignment (and deviations from alignment) of the head and trunk with small errors when compared to a 3D motion capture system (Vicon). The Dartfish method was also used to classify the positions of the upper limbs in comparison with the standard clinical classification; it showed that a simplified representation of the hands and elbows can reflect the clinical judgement. The combination of both these elements enabled the quantification of head/trunk control in children with CP for the first time. The work presented in this thesis makes a new and major contribution to postural assessment. It also provides the basis for the development of a fully automated system for the objective assessment of control using 2D-video recording. This work confirmed that clinical assessments can be objectively replicated, representing a major advance in the validation of physiotherapy interventions

Biomechanical modelling of the whole human spine for dynamic analysis

Developing computational models of the human spine has been a hot topic in biornechanical research for a couple of decades in order to have an understanding of the behaviour of the whole spine and the individual spinal parts under various loading conditions. The objectives of this thesis are to develop a biofidefic multi-body model of the whole human spine especially for dynamic analysis of impact situations, such as frontal impact in a car crash, and to generate finite element (FE) models of the specific spinal parts to investigate causes of injury of the spinal components. As a proposed approach, the predictions of the multi-body model under dynamic impact loading conditions, such as reaction forces at lumbar motion segments, were utilised not only to have a better understanding of the gross kinetics and kinematics of the human spine, but also to constitute the boundary conditions for the finite element models of the selected spinal components. This novel approach provides a versatile, cost effective and powerful tool to analyse the behaviour of the spine under various loading conditions which in turn helps to develop a better understanding of injury mechanisms

Fetus safety in motor vehicle accidents

Motor vehicle accidents are statistically the major cause of accidental severe injuries for pregnant women and fetuses fatality. Volunteers, post mortem human surrogates, anthropomorphic crash test devices and computational occupant models are used to improve human safety in motor vehicle accidents. However, due to the ethical issues, pregnant women and their fetuses cannot be used as volunteers or post mortem human surrogates to investigate the effects of crashes on them. The only anthropomorphic test device representing pregnant women is very limited in design and lacks a fetus. There is no computational pregnant occupant model with a fetus other than 'Expecting'. This thesis focuses on understanding the risk of placental abruption for pregnant drivers involved in road accidents, hence assessing the risk to fetus fatality. An extensive review of existing models in general and pregnant women models in particular is reported. The time line of successive development of crash test dummies and their positive effect on automotive passive safety design are examined. 'Expecting', the computational pregnant occupant model with a finite element uterus and a multibody fetus, is used in this research to determine the strain levels in the uteroplacental interface. External factors, such as the effect of restraint systems and crash speeds are considered. Internal factors, such as the effect of placental location in the uterus, and the inclusion and exclusion of a fetus are investigated. The head of the multibody fetus is replaced with a deformable head model to investigate the effects of a deformable fetus head on strain levels. The computational pregnant driver model with a fetus offers a more realistic representation of the response to crash impact hence provides a useful tool to investigate fetus safety in motor vehicle accidents. Seat belt, airbag and steering wheel interact directly with the pregnant abdomen and play an important role on fetus safety in motor vehicle accidents. The results prove that the use of a three-point seat belt with the airbag offer the greatest protection to the fetus for frontal crash impacts. The model without a fetus underestimates the strain levels. The outcome of this research should assist automobile manufacturers to address the potential safety issues at the design level