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Open access

Michał Kuczyński and Marcin Wieloch

Effects of Accelerated Breathing On Postural Stability

Purpose. The aim of the paper was to determine the effect of respiration on body balance in quiet standing. Basic procedures. Postural performance during quiet standing was compared in 37 young healthy subjects in two trials on a force plate: first with natural breathing, and then with accelerated high-volume breathing at the rate of 1 Hz. Each trial included 20 s quiet standing with eyes open, and the center of pressure (COP) was recorded with the sampling rate of 20 Hz in both anterior-posterior (AP) and mediallateral (ML) planes. Based on the recorded signals the COP dispersion measures and postural frequency were calculated. Main findings. The forced respiration contributed significantly to the increase in all COP stability measures in the AP plane: dispersion (p < 0.01), range (p < 0.001) and mean velocity and frequency (p < 0.00001). In the ML plane only mean velocity (p < 0.001) and frequency (p < 0.01) were affected. Conclusions. In view of the evidence provided by other authors that stress tests increase the amplitude- and frequency-based stability measures, our results indicate that the contribution of natural accelerated breathing after strenuous physical exercise will bias the results of stabilographic studies, rendering them worthless in understanding the role of neuromuscular fatigue in stability deterioration. Such studies must use data collected after the respiration returns to normal rate. However, if the study aims at overall assessment of postural stability post-fatigue, the postural testing may be performed immediately after the stress test.

Open access

Michał Kuczyński, Zbigniew Rektor and Dorota Borzucka

Postural Control in Quiet Stance in the Second League Male Volleyball Players

Purpose. The aim of the present work was to identify factors and neurophysiological mechanisms that may determine a robust and very stable postural control in athletes. Basic procedures. Postural performance in quiet stance was compared in 23 volleyball players from the Polish second league with 24 age-matched healthy physically active male subjects (controls). All participants stood quietly for 20 s on a force plate with their eyes open, while the center of pressure (COP) was recorded with the sampling rate of 20 Hz in both: the anterior-posterior (AP) and medial-lateral (ML) planes. From the recorded signals the COP dispersion measures, postural frequency and stiffness were computed. Main findings. The players displayed lower COP variability in the ML plane (p < 0.05) and lower COP range than controls in both planes (p < 0.01). Their COP mean velocity was higher in the AP plane (p < 0.0001) and the ML plane (p < 0.01) than in controls. Together, these findings indicated the presence of an additional low-amplitude and high-frequency signal superimposed on the COP in athletes but not in controls. Superior body stability and different mode of automatic postural control observed in the players challenge recent views on the relationships between attention resources allocation and its consequences to the selection and implementation of postural strategies. Conclusions. The volleyball players have superior body stability and different mode of automatic postural control as compared with the control group. Postural strategies of athletes may result from slight muscular adjustments that adopt mechanisms similar to stochastic resonance to monitor an instantaneous body vertical with greater efficiently.

Open access

Michał Tadeusiewicz, Stanisław Hałgas and Andrzej Kuczyński

Abstract

The paper is focused on nonlinear analog circuits, with the special attention paid to circuits comprising bipolar and MOS transistors manufactured in micrometer and submicrometer technology. The problem of fault diagnosis of this class of circuits is discussed, including locating faulty elements and evaluating their parameters. The paper deals with multiple parametric fault diagnosis using the simulation after test approach as well as detection and location of single catastrophic faults, using the simulation before test approach. The discussed methods are based on diagnostic test, leading to a system of nonlinear algebraic type equations, which are not given in explicit analytical form. An important and new aspect of the fault diagnosis is finding multiple solutions of the test equation, i.e. several sets of the parameters values that meet the test. Another new problems in this area are global fault diagnosis of technological parameters in CMOS circuits fabricated in submicrometer technology and testing the circuits having multiple DC operating points. To solve these problems several methods have been recently developed, which employ different concepts and mathematical tools of nonlinear analysis. In this paper they are sketched and illustrated. All the discussed methods are based on the homotopy (continuation) idea. It is shown that various versions of homotopy and combinations of the homotopy with some other mathematical algorithms lead to very powerful tools for fault diagnosis of nonlinear analog circuits. To trace the homotopy path which allows finding multiple solutions, the simplicial method, the restart method, the theory of linear complementarity problem and Lemke’s algorithm are employed. For illustration four numerical examples are given

Open access

Tomasz Sipko, Marek Stefanik, Edmund Glibowski, Adam Paluszak and Michał Kuczyński

Abstract

Introduction. To assess the mode of sit-to-stand (STS) task performed in a habitual manner or with flexion or extension pattern transfer in asymptomatic young subjects. It was hypothesized that different initial movements of the lumbar-pelvic region would modify the performance of the STS task: coordination of STS in time and level of vertical ground reaction forces (VGRF).

Methods. A convenience sample of 30 young asymptomatic volunteers, both genders, was recruited. The STS task was performed in a habitual manner or with a flexion or extension pattern. A Kistler platform was used to measure the VGRF and time of STS phases.

Results. ANOVAs analysis revealed the main effect in the total time and in maximum VGRF during the STS manoeuvre in three STS tasks (F(2, 58) = 21.67–30.74; p < 0.00001). In the post-hoc analysis, there was no difference in the total time between flexion and extension pattern of STS (p > 0.05), there was no difference between the flexion and extension pattern in minimum VGRF (p > 0.05), but the latter task was the longest in preparation time (p < 0.001). The lowest maximum VGRF was bound with the extension pattern of STS (p < 0.01).

Conclusions. The extension or flexion movement pattern modified STS performance and displayed different coordination in time and level of VGRF. Young asymptomatic participants performed the STS task longer with flexion or extension pattern than in the habitual pattern. The extension pattern of STS had the capacity to produce the lowest VGRF.