Lenka Hanakova

Quantification of Trunk Postural Stability Using Convex Polyhedron of the Time-Series Accelerometer Data

Techniques to quantify postural stability usually rely on the evaluation of only two variables, that is, two coordinates of COP. However, by using three variables, that is, three components of acceleration vector, it is possible to describe human movement more precisely. For this purpose, a single three-axis accelerometer was used, making it possible to evaluate 3D movement by use of a novel method, convex polyhedron (CP), together with a traditional method, based on area of the confidence ellipse (ACE). Ten patients (Pts) with cerebellar ataxia and eleven healthy individuals of control group (CG) participated in the study. The results show a significant increase of volume of the CP (CPV) in Pts or CG standing on foam surface with eyes open (EO) and eyes closed (EC) after the EC phase. Significant difference between Pts and CG was found in all cases as well. Correlation coefficient indicates strong correlation between the CPV and ACE in most cases of patient examinations, thus confirming the possibility of quantification of postural instability by the introduced method of CPV.

ASSESSMENT OF POSTURAL INSTABILITY IN PATIENTS WITH A NEUROLOGICAL DISORDER USING A TRI-AXIAL ACCELEROMETER

Current techniques for quantifying human postural stability during quiet standing have several limitations. The main problem is that only two movement variables are evaluated, though a better description of complex three-dimensional (3-D) movements can be provided with the use of three variables. A single tri-axial accelerometer placed on the trunk was used to measure 3-D data. We are able to evaluate 3-D movements using a method based on the volume of confidence ellipsoid (VE) of the set of points obtained by plotting three accelerations against each other. Our method was used to identify and evaluate pathological balance control. In this study, measurements were made of patients with progressive cerebellar ataxia, and also control measurements of healthy subjects, and a statistical analysis was performed. The results show that the VEs of the neurological disorder patients are significantly larger than the VEs of the healthy subjects. It can be seen that the quantitative method based on VE is very sensitive for identifying changes in stability, and that it is able to distinguish between neurological disorder patients and healthy subjects.

An evaluation method of complex movement of the arm during walking based on gyroscope data and angle-angle diagram

The article focuses on a technique of gyroscope data processing and quantifying movement patterns of upper limb during walking. Four cheap gyroscopes were used. Using a novel method based on the trajectory length obtained by plotting shoulder and elbow joint angle vs. each other, provides information for a quantification of the complex arm movement as a whole in the sagittal plane. Two parameters for the evaluation of motion, the trajectory length (TL) and traditional range of motion (ROM), were used to analyze a simple rhythmical movement and identified application possibilities of the new parameter. The Pearsons correlation coefficient indicates very strong correlation between the TL and ROM (r>0.8) for both dominant and non-dominant upper limb. Also, the correlation between the body height and TL or ROM was studied. The correlation between the body height and TL or ROM was a negligible (r<;0.2). This shows the versatility of the proposed parameter.

Determining importance of physiological parameters and methods of their evaluation for classification of pilots psychophysiological condition

At present, several studies exist describing the relevance of human factor in air transport with main focus on pilots and flight safety. Within such studies, monitoring of physiological functions is used. There are lot of physiological parameters and methods of their assessment; however, they are mostly based on principles originating from clinical practice. Yet, sensitivity and specificity of these methods with regard to assessment of aviation professionals — pilots is unknown. Therefore, this paper is oriented towards description of the most common methods for physiological parameters assessment. The paper also describes evaluation methods, which are on experimental level in terms of physiological data evaluation, namely recurrent quantification analysis. Within the research carried out, sample group of pilots was subjected to measurement for evaluation of their psychophysiological condition and performance. Selected evaluation methods were applied on the collected data and importance of those parameters and methods, which provided best classification for level of psychophysiological stress, was evaluated by means of statistical analyses. The results indicate that the most important physiological parameter for psychophysiological condition assessment of pilots is heart electrical activity where the possibility to perform signal processing whilst preserving its importance is provided by linear methods in the time and frequency domain, or alternatively by non-linear methods utilizing recurrent quantification analysis.

Effect of High-Induction Magnetic Stimulation on Elasticity of the Patellar Tendon

Nowadays, a high-induction magnetic stimulation is starting to be increasingly applied as a biophysical stimulation in the conservative treatment of the degenerative locomotor system diseases. These are mainly in correlation with the changes in soft tissue elasticity, which should be positively influenced by the flow-induced electrical currents of high current density during high-induction magnetic stimulation. This assumption was verified within the interventional and prospective study using the ultrasound elastography. The group consisted of 6 volunteers, whose elasticity of the patellar tendons was measured using the 2D shear-wave ultrasound elastography. The volunteers were then exposed to a 20-minute high-induction magnetic stimulation session with a frequency of 20 Hz, in 2 s package intervals, with a 5 s pause, and a induced electric current density of 100 Am−2 in the tendons area. A tendon tension was measured five times for all volunteers, where mean tension at the marked area of the tendon, as well as the highest point tension indicated by the Q-Box, was monitored. The measurement results show that high-induction magnetic stimulation has an influence on the patellar tendon tension change, which occurred in the case of all involved volunteers when the patellar tension was decreased.

Perspectives of Use of Alternative Energy Sources in Air Transport

The problem of environmental load is also reflected in air transport. Usage of fossil fuels, which are dominant nowadays, has a negative impact on the environment and also its resources are limited. Therefore, the article focuses on the prospective of use of other energy sources in aviation, such as alternative fuels (synthetic fuels, biofuels, alcohol, methane, hydrogen), solar energy and the use of fuel cells. Also, the paper briefly summarizes the approach of aircraft manufacturers to the use alternative sources.

Prediction of atrial fibrillation and its successful termination based on recurrence quantification analysis of ECG

Atrial fibrillation ranks among the most common heart rhythm disorders. Considering the lack of any trusted method capable of foreseeing possible recurrence of atrial fibrillation after it has been terminated, nonlinear analyses of beat-to-beat heart rate variability demonstrate promising potential. This work focuses on verifying the capability of the nonlinear methods to differentiate patients with early recurrence of atrial fibrillation from those with stable normal sinus rhythm after cardioversion. Both patients groups underwent the active-standing test involving ECG measurement. Recurrence quantification analysis was used to evaluate sequences of intervals between two consecutive heart beats. The data were derived from body surface ECG signal. The results selected those parameters capable of identification of patient groups during the initial phase of the active-standing test prior to cardioversion.

Telemetry System Utilization for Stress Monitoring of Pilots During Training

Air transport development brings an increased focus on the safety of piloting. The safety conditions can be assessed by mental workload. Psychic discomfort or excessive stress on pilots can negatively influence the course of flights. Therefore it appears convenient to monitor such parameters, which represent the mental wellbeing, or discomfort of a pilot. Since physiological measurements can provide a good information about mental workload or stress, this work primarily focuses on the observation of the change in heart rate, as it is an indicator of stress during the training of pilots, using the designed modular telemetry system. Another aim of this study is to evaluate the influence of a change in the avionic data visualization. This can have an unfavorable effect on the piloting of an airplane. This work, based on the evaluation of heart rate shows, that the switch from analog visualization to glass cockpit creates increased levels of stress in pilots, which was proved for all examined subjects except one. Significant level of correlation in the heart beat rate change in subjects in the course of training was also discovered.