Biomedical subjects

E Oggero

Publications and source records attributed to E Oggero.

12 recordsLinked to original sources

PubMed2001

Muscular contractions and their effect on the vertical ground reaction force during quiet stance--Part I: Hypothesis and experimental investigation.

There is no consensus as to the origins of the oscillations of the vertical ground reaction force during quiet stance. The concept of a cardiovascular origin is supported by many ballistocardiographic studies, but its exclusivity has never been proven. A new hypothesis was formulated to explain their genesis: there is a neuromuscular postural control system, possibly different from the well-investigated mechanisms controlling the macroscopic sway, responsible for compensating the small endogenous forces perturbing the posture by causing some muscles to contract proportionately to the magnitude of perturbation. These contractions contribute to the ground reaction force oscillations. To verify this hypothesis, a series of experiments simultaneously recording the electrocardiogram, the electromyogram of several muscles, and the ground reaction forces were conducted on ten informed and consenting human subjects. The experimental results confirmed that the hypothesized muscular activity in response to the perturbation induced by the cardiac contraction and subsequent blood movement does in fact exist. The signal detected by electromyography is not a cardioelectric artifact, but an actual myoelectrical activity. Several interesting patterns of muscular activity emerged in this investigation. These results provide the needed background and justification for investigating the use of the vertical ground reaction force, not only in the study of posture, but also in the study of clinical conditions affecting the neuromuscular control and the musculature of the trunk.

Adult↗

PubMed2001

Muscular contractions and their effect on the vertical ground reaction force during quiet stance--Part II: Mathematical model.

A one-dimensional lumped-parameters mathematical model of the standing human was developed to specifically investigate how the muscular activity and the cardiovascular forces originated by the heart movement and the blood ejection in the ascending aorta affect the ground reaction force in the head-to-toes direction. The forces produced by the cardiovascular activity were modeled by a time-varying force actuator connected to the torso whose characteristics were obtained from the literature. The muscles identified as active during Part I of this work, mainly the erector spinae and oblique abdominal muscles, were modeled as a single force actuator acting with equal and opposite force between the pelvis and the thoracic spine. The force versus time data were obtained from the electromyographic signals obtained in Part I. Although the model of the human body used in this investigation was simple, the results of the simulations clearly showed that the cardiovascular forces alone are not sufficient for generating the large negative (i.e., upward) peak observed in the vertical ground reaction force. The peaks were mainly the result of a very modest muscular contraction of the spinal muscles. The simulations offer further evidence to support the hypothesis that trunk muscles contractions are capable of generating vertical ground reaction force oscillations that are consistent with the experimental results. These oscillations are apparently generated by a combination of cardiovascular and muscular forces.

Adult↗

PubMed2001

Force transducer design: a new approach combining nonlinear finite element analysis and robust design.

Designing a strain gage based force transducer is considered more of an art than an engineering process. Only general guidelines are available, and many trial and error iterations are needed to optimize the geometry and minimize the errors caused by nonlinear behavior of the structure. A new method, based on nonlinear finite element analysis and robust design principles, is proposed. A matrix of experiments considers relevant geometric and loading parameters. The behavior of the structure under different combinations of these parameters is determined by calculating the strain at different locations (suitable for strain gage installation) using finite element models. The nonlinear behavior of the transducer is identified by comparing the results of the nonlinear finite element analysis with those obtained using a linear finite element analysis. A signal-to-noise ratio is defined to quantify the nonlinearities and how the considered parameters affect them. An analysis of variance is employed to determine their relative influence. Based on the results of the statistical analysis, it is possible to identify the best value for each geometric parameter that would reduce, if not eliminate the nonlinearities. Once these optimal geometric parameters are chosen, a prototype can be built, instrumented with strain gages, and tested, to validate the obtained design. To illustrate this new proposed methodology, and appreciate its advantages over current practice of designing a force transducer, an example of the step-by-step procedure is illustrated considering a thin-wall cylindrical transducer.

Equipment Design↗

PubMed2000

Numerical simulation of a child restraint system in an aircraft crash-test.

Studies conducted at the FAA Civil Aeromedical Institute have shown that when used in aircraft, automotive child restraint devices do not always provide the level of safety desired. Various factors that contribute to poor performance, such as seat belt anchor location, cushion stiffness, and child restraint device design features, were evaluated by a dynamic impact test program. To efficiently continue the research, a computer model was developed using MADYMO. Results of two of the impact tests were used to validate the model. Both test configurations utilized a typical commercial transport airplane passenger seat and a popular automotive child restraint device. These tests were considered representative of the extremes of child restraint device and occupant kinematics due to variance in seat belt anchor location. Details are presented of the test parameters and geometry, as well as cushion and restraint system properties. Test and modelling results for these two impact conditions are summarized and compared. Parametric studies were then conducted that used the model to investigate the effect of cushion stiffness, belt anchor spacing, and initial belt tension.

Accidents, Aviation↗

PubMed2000

Inertially compensated force plate: a means for quantifying subject's ground reaction forces in non-inertial conditions.

A system for the measurement of forces in noninertial reference systems, and a possible solution to compensate force plate readings by means of accelerometers were investigated. If the force plate can be considered a rigid body, six linear accelerometers can measure all linear and angular accelerations of the instrument in 3-D space. However, by using nine accelerometers in a proper layout, the force and moment generated by the movement of the plate can be quantified in a way that eliminates the errors due to the time integration of the accelerations. By doing so, no temporal limits are imposed to the compensation. A one degree of freedom numerical model was implemented to evaluate the importance of main error sources in the estimation of inertial forces using accelerometers with different technical characteristics. The inertial compensation of the force plate along one axis was tested, and the performances of a piezoelectric accelerometer and a capacitive accelerometer were compared. With the proposed inertially compensated force plate, accelerations up to 5 g's in amplitude and frequencies from 0 to 100 Hz can be compensated by means of capacitive accelerometers. Such a device can be used for force measurements in moving vehicles, or any situation where the surface on which the instrument is mounted is moving or vibrating.

Acceleration↗

PubMed1999

How force plate size influences the probability of valid gait data acquisition.

Acquiring valid data is one of the major difficulties in gait analysis. Our previous study proved that, using the currently commercially available force plates, there is a low probability that every trial will be successful, and some subjects will have to alter their gait pattern to have a successful trial. In the present study the possibility of using an instrumented floor consisting of more than two force places of small size was investigated. This appears as the most promising solution to simultaneously solve the contrasting requirements of avoiding double contact on each element while acquiring complete gait cycles. In this work the set of mathematical equations previously developed for systems of two force plates was extended to consider any number of plates. Using gait data of 280 subjects from The Ohio State University Gait Laboratory, a software simulation was developed and performed to analyze different combinations of element and system sizes, and to calculate the probability of a successful gait analysis trial.

Biomechanical Phenomena↗

PubMed1999

Design and testing of a 6-component ballistocardiographic bed.

Ballistocardiography is a non-invasive technique for the assessment of the cardiac function. It consists in studying the resultant forces generated by the blood mass flowing in the cardio-circulatory system while the subject lies on an instrumented bed. In the past, ballistocardiography was in large part limited by the signal processing and data acquisition capabilities. Technology improvements have countered these limitations. Previous studies by the authors using a regular size force plate have shown the capability of detecting cardiac activity in the human body. However, many patients with severe disorders cannot stand on a force plate for the duration required to acquire adequate data. Thus, a force plate, which performs as a ballistocardiographic bed, would allow patients to lie down in a stable position while body tremor data are acquired. To evaluate this idea, a highly sensitive ballistocardiographic bed was built using strain gage technology. Then, using high-resolution data acquisition software, the sensitivity of the instrument and the capability to obtain ballistocardiographic data were tested. Future developments include the analysis of ballistocardiographic data obtained from the bed to search their possible relation with cardio-circulatory and neurologic pathologies.

Ballistocardiography↗

PubMed1997

Average power spectral density of physiological tremor in normal subjects.

The measurement technologies currently available to quantitatively evaluate neurological tremors have several limitations. For this reason the assessment of disorders involving tremor is largely based on subjective clinical evaluation of the patient. The availability of a high-sensitivity, portable and easy to use instrument based on force plate technology, coupled with a customized data analysis protocol could represent a useful tool for the clinician. To verify such a hypothesis, baseline physiological tremor information in a standing posture was collected from normal subjects. A lightweight portable force plate was built and used in collecting vertical ground reaction force data, which was subsequently analyzed for frequency content and power spectral distribution. Repeatability of results in a group of subjects without any diagnosed neurological disorders, and intra-subject repeatability, as well as influence of footwear were investigated.

Adult↗

PubMed1997

Oversampling data acquisition to improve resolution of digitized signals.

The ability to capture analog signals in a digital format suitable for subsequent storage, processing and analysis by a computer has revolutionized many scientific fields, including biomechanics. In the process of going from the analog signal to its digital representation, it is essential to maintain as much of the original signal content as possible. There is always a loss of information associated with the conversion from analog to digital, independently of how it is actually performed. The only possibility to reduce the loss of information is to increase the number of states or the resolution of the digital signal. The method presented here, based on the same theory used in oversampling analog to digital converters, is applicable to digital signals acquired using any converter. In most situations this method provides a feasible and inexpensive technique to significantly improve the amplitude resolution of the analog to digital conversion. This can be of fundamental importance when the information of interest is small in amplitude compared to the overall signal, or when subsequent ill-conditioned operations, like the computation of the derivatives of the signal, are to be performed.

Analog-Digital Conversion↗

PubMed1997

Probability of valid gait data acquisition using currently available force plates.

A major difficulty in using force plates for gait analysis is to have a foot fall completely on the instrument while not having the other foot in contact with the same device. This translates into more trials (and time) required to obtain valid data. In order to estimate the probability of a successful trial, which is related to the overall number of trials required, the dimensional relationships between force plate, foot and gait cycle were investigated. In particular, it was analyzed how the dimensions of the plate, the size of foot, the step length and width affect the probability of having a successful trial when acquiring one or two subsequent foot falls using one or two force plates respectively. The equations obtained can also be used to estimate the force plate dimensions that allow for the minimum number of trials for a specific group of subjects. To illustrate this approach, commercially available force plate sizes were statistically evaluated using gait data collected in recent years at The Ohio State University Gait Laboratory from patients with different pathologies. The force plate length maximizing the probability of a successful trial was identified for this specific population.

Adolescent↗

PubMed1997

The realization of a haptic (force feedback) interface device for the purpose of angioplasty surgery simulation.

Simulation is becoming an increasingly accepted method for training personnel for complex or high risk tasks. With the advent of modern Virtual Reality (VR) technology, such simulations are becoming more and more immersive. One significant limitation to the advance of this science is the challenges associated with simulating the touch or feel of various tasks in conjunction with VR simulations. This work has focused on creating and assessing the feasibility of haptic technology for high fidelity surgery simulation. It has culminated in a prototypical interface device to provide tactile feedback during the simulation of complex interventional radiology procedures such as Angioplasty. This device extends state of the art motion control, distributed computing processes, high resolution sensors for real-time feedback, and modular design techniques to accomplish these goals. The realization of the device, its capabilities, interfacing requirements, its limitations, and future extensions will be presented here.

Angioplasty, Balloon↗

PubMed1997

The mechanics of drop landing on a flat surface--a preliminary study.

In an effort to investigate the mechanics of drop landing on a flat surface, bilateral performance characteristics during the landing were investigated. Two force plates were used as landing surfaces, and the six component kinetic time histories and the path of the center of pressure were measured for both feet. The forces were combined to obtain the resultant ground reaction force, allowing comparison between the global resultant and the forces developed by each leg. The results highlighted an asymmetry, and the presence of one dominant leg during the landing: the contact with the plate occurred with a delay between the dominant and non-dominant legs, and the forces applied to the plate were also unequal. Furthermore, due to the high rate of data acquisition and sensitivity of the force plates used, it was possible to correlate the peaks present in the global vertical reaction force with the impact of the different anatomical segments of each foot. The availability of such high resolution information presents to researchers and clinicians with more key identifiers to quantify various phenomena, potentially injury prevention, pathological diagnosis or quantification, and others.

Adult↗