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Wyszukujesz frazę "Vulovic, R." wg kryterium: Autor


Wyświetlanie 1-4 z 4
Tytuł:
Neuromechanical control in submaximal drop jumps: The effects of volitional effort demands and drop height magnitude on soleus muscle activation
Autorzy:
Mrdakovic, V.
Pazin, N.
Vulovic, R.
Filipovic, N.
Ilic, D.
Powiązania:
https://bibliotekanauki.pl/articles/307166.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
elektromiografia
sprzężenie zwrotne
staw skokowy
biomechanika
electromyography
stretch-shortening cycle
feedback control
pre activation
feedforward control
ankle biomechanics
Opis:
The purpose of this study was to investigate soleus muscle activation during different phases of drop jump performed at submaximal levels of volitional effort and drop height magnitude. Methods: Fifteen professional volleyball players with minimum of eight years of experience in jumping activities participated in the study. Experimental protocol involved executing submaximal drop jumps at three levels of volitional effort (i.e., 65, 80 and 95% of the maximal height of jump). All submaximal drop jumps were done from three drop heights (20, 40 and 60 cm). The soleus muscle activation was monitored during four jump phases: pre-activation phase before touchdown, early contact phase upon touchdown, early and late push-off phase. Results: The results indicate that volitional effort level did not change the muscle activation during pre activation and early contact phase, but only in early and late push-off phase ( p ≤ 0.05). Conversely, it was observed that muscle activation during all phases of drop jump was adapted to the increased intensity of the external load caused by increasing of drop height magnitude ( p ≤ 0.01). Conclusions: The findings of the present study suggested that soleus muscle activation has selective responses to internal load (i.e., volitional effort level) and external load (i.e., drop height magnitude) intensities when drop jump is executing with submaximal effort.
Źródło:
Acta of Bioengineering and Biomechanics; 2018, 20, 4; 101-111
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Leg stiffness adjustment during hopping at different intensities and frequencies
Autorzy:
Mrdakovic, V.
Ilic, D.
Vulovic, R.
Matic, M.
Jankovic, N.
Filipovic, N.
Powiązania:
https://bibliotekanauki.pl/articles/307107.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
połączenie
węzeł podatny
sztywność
skoki
joint stiffness
jumping performance
preferred hopping frequency
spring-mass model
Opis:
Understanding leg and joint stiffness adjustment during maximum hopping may provide important information for developing more effective training methods. It has been reported that ankle stiffness has major influence on stable spring-mass dynamics during submaximal hopping, and that knee stiffness is a major determinant for hopping performance during maximal hopping task. Furthermore, there are no reports on how the height of the previous hop could affect overall stiffness modulation of the subsequent maximum one. The purpose of the present study was to determine whether and how the jump height of the previous hop affects leg and joint stiffness for subsequent maximum hop. Ten participants completed trials in which they repeatedly hopped as high as possible (MX task) and trials in which they were instructed to perform several maximum hops with 3 preferred (optimal) height hops between each of them (P3MX task). Both hopping tasks were performed at 2.2 Hz hopping frequency and at the participant's preferred (freely chosen) frequency as well. By comparing results of those hopping tasks, we found that ankle stiffness at 2.2 Hz (p=0.041) and knee stiffness at preferred frequency (p=0.045) was significantly greater for MX versus P3MX tasks. Leg stiffness for 2.2 Hz hopping is greater than for the preferred frequency. Ankle stiffness is greater for 2.2 Hz than for preferred frequencies; opposite stands for knee stiffness. The results of this study suggest that preparatory hop height can be considered as an important factor for modulation of maximum hop.
Źródło:
Acta of Bioengineering and Biomechanics; 2014, 16, 3; 69-76
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Teaching Efficacy of Preservice Mathematics Teachers: Research in the Republic of Serbia
Autorzy:
Mihajlović, Aleksandra M.
Vulović, Nenad R.
Milikić, Milan P.
Powiązania:
https://bibliotekanauki.pl/articles/1963634.pdf
Data publikacji:
2020-09-30
Wydawca:
Wydawnictwo Adam Marszałek
Tematy:
Teaching effi cacy
mathematics teaching
preservice primary and preschool teachers
MTEBI
Opis:
This research aims to study the psychometric properties and theoretical structure of the Serbian version of the Mathematics Teaching Efficacy Beliefs Instrument (MTEBI) which was developed by Enochs, Smith and Huinker (2000). The sample consisted of 252 preservice primary and preschool teachers from teacher education faculties in Serbia. The original MTEBI indicated acceptable reliability (α=0.779). The results of confirmatory factor analysis indicate that the fit of the original MTEBI model to the data is not acceptable, but the re-specified model (MTEBI12) shows good fit and acceptable reliability (α=0.742). These findings indicate that a short 12 item version of MTEBI possesses adequate psychometric properties and is applicable to the sample of respondents in the Republic of Serbia.
Źródło:
The New Educational Review; 2020, 61; 63-75
1732-6729
Pojawia się w:
The New Educational Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of analytical and the FEM method for deriving the Mode I stress intensity factor of thin-walled beams containing a crack
Autorzy:
Djoković, J. M.
Vulović, S. D.
Nikolić, R. R.
Živković, M. M.
Bujnak, J.
Powiązania:
https://bibliotekanauki.pl/articles/131642.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Komisja Inżynierii Budowlanej PAN Oddział w Katowicach
Tematy:
cracked thin-walled beams
modeI SIF
cross-section warping
FEM
J-EDI
belka cienkościenna
współczynnik intensywności naprężeń
MES
Opis:
The problem considered in this paper is of the cracked thin-walled beams. They are subjected to combined loading by the bending moment and the axial force. The profiles with the I (H), T and U cross-sections were analyzed. The analytical method is based on application of classical expressions for Mode I SIF of such beams with taking into account the cross sections' warping. The classical expressions for SIF for the thin plate are adapted by including the reduced forces and moments characteristic for the thin-walled beams. The numerical simulation for calculating the stress intensity factor of the cracked thin-walled beams consisted of application of the Finite Element Method (FEM) by use of the J-EDI method. It is found that the Mode I SIF of cracked thin-walled beams increases with crack length increase. The conducted comparison of results obtained by application of the two methods confirms the validity of the proposed analytical expressions only for the small crack lengths.
Źródło:
Roczniki Inżynierii Budowlanej; 2015, 15; 43-51
1505-8425
Pojawia się w:
Roczniki Inżynierii Budowlanej
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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