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1
Content available remote Jumping Impairs Visual Feedback Control of Body Position
100%
Human Movement
|
2011
|
tom 12
|
nr 3
248-253
EN
Purpose. The aim of this study was to evaluate the effects of maximal rebound jumping on sensorimotor tasks that required visual feedback control in positioning the body. Methods. A group of 14 university students (age 23.7 ± 2.6 y, height 178.6 ± 9.2 cm, and weight 70.6 ± 11.4 kg) had to hit a target that randomly appeared on one side of a screen by horizontally shifting their centre of mass (COM) in the appropriate direction prior to (as a baseline) and after six 60-second maximal jump exercises. Each response test consisted of 60 targets. The time, distance, and the velocity of the centre of pressure (COP) trajectory between the stimulus's appearance and its hit, by visually-guiding the COM movement on the screen, were registered by means of a FiTRO Sway Check system using a dynamometric platform. During the sets of jumps, the power of the concentric phase of take off was registered using a FiTRO Jumper recorder. Results. Results found that after each set of jumping (of around 110 jumps per set), mean response time significantly (p ≤ 0.05) increased from an initial value of 1616 ± 506 ms to 1825 ± 562 ms till the 4th set, with no further increase towards the 6th set. Similarly, the mean distance of COP covered during the response time increased significantly (p ≤ 0.05) from a pre-exercise value of 0.449 ± 0.298 m to 0.550 ± 0.295 m after the 4th set which then plateaued towards the 6th set. However, no significant changes in mean COP velocity were detected. Conclusion. Rebound jumping negatively affected the visual feedback control in positioning the body. However, after the proprioceptive functions deteriorated to a certain level, there was no further impairment on sensorimotor parameters.
EN
The strengths of interpersonal dyads formed by the attacker and defender in one-on-one situations are crucial for performance in team ball sports such as soccer. The purpose of this study was to analyze the kinematics of one-on-one defensive movements in soccer competitions, and determine the relationships between lower limb kinematics and the center of mass translation during cutting actions. Six defensive scenes in which a player was responding to an offender’s dribble attack were selected for analysis. To reconstruct the three-dimensional kinematics of the players, we used a photogrammetric model-based image-matching technique. The hip and knee kinematics were calculated from the matched skeleton model. In addition, the center of mass height was expressed as a ratio of each participant’s body height. The relationships between the center of mass height and the kinematics were determined by the Pearson’s product-moment correlation coefficient. The normalized center of mass height at initial contact was correlated with the vertical center of mass displacement (r = 0.832, p = 0.040) and hip flexion angle at initial contact (r = −0.823, p = 0.044). This suggests that the lower center of mass at initial contact is an important factor to reduce the downwards vertical center of mass translation during defensive cutting actions, and that this is executed primarily through hip flexion. It is therefore recommended that players land with an adequately flexed hip at initial contact during one-on-one cutting actions to minimize the vertical center of mass excursion.
PL
W artykule opisano stanowisko do wyznaczania położenia środka masy ciała człowieka. Konstrukcję stanowiska oparto na dźwigni jednostronnej. Metodę tę jako pierwszy zastosował i opisał Emil du Bois-Reymond. Stanowisko jest elementem wyposażenia laboratorium posturografii Wyższej Szkoły Oficerskiej Sił Powietrznych w Dęblinie, w której są prowadzone badania zdolności do utrzymania równowagi statycznej kandydatów na pilotów wojskowych. Informację ilościową określającą funkcjonowanie układu utrzymania równowagi można uzyskać przez badania posturograficzne. Obejmują one wyznaczenie położenia środka masy ciała badanej osoby, co jest niezbędne do oceny podstawowych parametrów opisujących równowagę człowieka w postawie stojącej. Uzyskane wyniki pozwoliły na wyznaczenie parametrów rozkładu statystycznego względnej wysokości środka masy ciała dla licznej grupy młodych mężczyzn i kilku kobiet. Grupa ta ma charakter specyficzny, gdyż są to osoby w podobnym wieku, których potencjalna przydatność do zawodu pilota została już wcześniej potwierdzona przez szczegółowe badanie stanu zdrowia, sprawności fizycznej i psychotechnicznej.
EN
The article describes the measuring device for determining the location of the center of human body mass, the construction of which is based on the properties of a one-sided lever. This device is a part of the posturograph laboratory of the Air Force Academy in Dęblin, where research is conducted on the ability to maintain static balance of candidates for military pilots. Quantitative information describing the functioning of the balance maintenance system can be obtained through posturographic research. It includes determination of the location of the center of body mass of the examined person. The measuring device was subjectedto the linear calibration process. The obtained results allowed to determine the parameters of the statistical distribution of the relative height of the body mass center for a large group of young men and a few women. This group is specific in nature, because they are people of similar age, whose potential fitness for the military pilot profession has already been confirmed by a detailed examination of the state of health, physical and psychotechnical skills.
PL
W artykule przedstawiono model symulacyjny układu przeładunkowego żurawia samojezdnego, opracowany w zintegrowanym środowisku CAD/CAE, umożliwiający badanie jego stateczności dla wybranych konfiguracji i warunków pracy. Dodatkowo są obliczane wartości sił nacisku żurawia na podłoże, co daje możliwość takiego sterowania ruchami roboczymi maszyny, że w trakcie ruchu nie pojawi się zagrożenie utraty stateczności. Jako wyniki badań symulacyjnych przedstawiono zmiany warunków stateczności w zależności od: położenia kątowego kolumny obrotowej z wysięgnikami oraz ramionami teleskopowymi, położenia ramion teleskopowych, masy składowych elementów układu nośnego, a także od jego obciążenia ładunkiem.
EN
The article presents a simulation model of the handling of a mobile crane, developed in a CAD/CAE integrated environment, enabling testing of its stability for selected configurations and operating conditions. In addition, the crane’s pressure force on the ground is calculated, which enables such controlling of the movements of the working crane that during the movement does not appear a risk of loss of its stability. As the results of the simulation are shown changes in the conditions of stability depending on: the angular position of the rotating column with booms and telescopic arms, the position of telescopic arms, the masses of the constituent elements for lifting, as well as its cargo load.
EN
In the article we put some recommendations on the possibilities to provide to talented math students push out beyond the program material. We propose relatively closed system of educational material on the center of mass. In this paper we propose a relatively closed system of educational material about the center of mass points (centroid), the center of mass of material points (barycenter) and barycenteric geometric method for solving problems for students who are interested in geometry, its methods and connections with physics and for future mathematics teachers that are the students of pedagogical universities studying methods for solving problems of plane geometry and principles of their harmonization. This system includes the theorem of existence and uniqueness of the center of mass and its location and also proofs of basic properties of barycenter. The presentation of theoretical material is complete and strict accompanied by examples and counterexamples, the selection of problems of educational and research character is also available. We justify the expediency of pupils and students of pedagogical universities with barycenteric method of solving problems of plane geometry. Also we base efficiency of vector and coordinate geometry method of building mass, highlights the relationship of physical and metric approaches to key concepts topics including depending optimization and Lagrange and Jacobi identity. We propose order of introduction of concepts (including alternative definition, discusses the sequence of presentation of factual material, give succinct formulation essentially of barycenteric method for solving positional and metric problems and discussed motivational bases of learning etc. Finally we analyse some risk zones and propose some methodological and methodical caveats.
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