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Tytuł:
A longitudinal assessment of myoelectric activity, postural sway, and low-back pain during pregnancy
Autorzy:
Moreira, L. S.
Elias, L. A.
Gomide, A. B.
Vieira, M. F.
Do Amaral, W. N.
Powiązania:
https://bibliotekanauki.pl/articles/307463.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
elektromiografia
stabilność postawy
bóle kręgosłupa
electromyography
low back pain
postural balance
pregnancy trimesters
stabilometry
Opis:
The present study aimed at investigating the control of upright quiet standing in pregnant women throughout pregnancy, and whether low-back pain exerts influence on this motor task. Methods: Myoelectric signals from postural muscles and stabilometric data were collected from 15 non-pregnant and 15 pregnant women during upright quiet standing. Electromyogram envelopes and center of pressure metrics were evaluated in the control group, as well as in pregnant women in their first and third trimester of pregnancy. A correlation analysis was performed between the measured variables and a low-back pain disability index. Results: Pregnant women exhibited a decreased maximum voluntary isometric activity for all postural muscles evaluated. Additionally, the activity of lumbar muscles during the postural task was significantly higher in the pregnant women in comparison to the non-pregnant controls. The soleus muscle maintained its activity at the same level as the gestation progressed. Higher postural oscillations were observed in the anteroposterior direction while mediolateral sway was reduced in the third trimester of pregnancy. No correlation was detected between the lowback pain disability index and neuromechanical variables. Conclusion: This study provides additional data regarding the functioning and adaptations of the postural control system during pregnancy. Also, we provide further evidence that postural control during quiet standing cannot be used to predict the occurrence of low-back pain. We hypothesize that the modifications in the neural drive to the muscles, as well as in postural sway may be related to changes in the biomechanics and hormonal levels experienced by the pregnant women.
Źródło:
Acta of Bioengineering and Biomechanics; 2017, 19, 3; 77-83
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Absolute and relative reliability of several measures of static postural stability calculated using a GYKO inertial sensor system
Autorzy:
Jaworski, Janusz
Ambroży, Tadeusz
Lech, Grzegorz
Spieszny, Michał
Bujas, Przemysław
Żak, Michał
Chwała, Wiesław
Powiązania:
https://bibliotekanauki.pl/articles/27324151.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
balance
postural stability
accelerometer
test-retest reliability
intraclass correlation coefficient
balans
stabilność postawy
akcelerometr
niezawodność testu-retestu
współczynnik korelacji wewnątrzklasowej
Opis:
The aim of this study was to analyse absolute and relative reliability of a number of postural static stability measures obtained from a GYKO inertial sensor system in young adults. Methods: The study examined 29 healthy non-athlete young adults. A test was performed for 30 s while standing on one foot, without moving, with eyes open and arms relaxed along the sides of the body. The examinations were performed twice, with a one-week interval. Relative reliability was measured using the intraclass correlation coefficient (ICC) and the 95% confidence interval (95% CI), whereas the absolute reliability was evaluated based on the standard error of measurement (SEM) and the minimal detectable change (MDC). Results: The results of this study showed moderate to good relative reliability scores for all the postural stability measures, with ICC values ranging from 0.62 to 0.70. For most of the analysed variables, SEM% ranged from ca. 10 to 14%. Relatively high SEM% values were obtained only for two variables (Area, Convex Hull Area). Conclusions: The low costs of GYKO inertial sensor systems, the fast and easy installation, the mobility and high reliability of the measurement of postural stability show that it can be effective alternative to stabilographic platforms.
Źródło:
Acta of Bioengineering and Biomechanics; 2020, 22, 2; 93--99
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Acute effects of core stability exercises on balance control
Autorzy:
Szafraniec, R.
Barańska, J.
Kuczyński, M.
Powiązania:
https://bibliotekanauki.pl/articles/307089.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
stabilność postawy
posturografia
mięśnie tułowia
postural stability
motor learning
posturography
balance training
trunk muscles
sway entropy
Opis:
The aim of this study was to investigate whether a single bout of core stability exercises improves body balance immediately after the bout of exercise and during a retention test. Methods: The study involved 16 women (age 22–25 years, body weight 60.5 ± 5.2 kg, height 166 ± 5.4 cm). Postural stability was assessed in the mediolateral (ML) and anteroposterior (AP) planes separately on a force plate (Kistler 9286 AA) during quiet standing on a soft support surface with the eyes closed. Subjects were measured 4 times: just before (T0), 1 minutes after (T1 m), 30 minutes after (T30 m), and 24 hours after the workout (T24 h). Postural balance was evaluated by five parameters based on the center of pressure (COP) signal: variability (VAR), mean velocity (VEL), sample entropy (ENT), frequency (FRE), and fractal dimension (FRA). Results: We observed a decrease in VAR and VEL in the ML plane at T30 m and T24 h, compared to T0. The COP entropy significantly increased in the ML plane at T24 h, compared to T0. Conclusions: A single bout of core stability exercises improved the control of the mediolateral body balance. This effect was evident within 30 minutes after exercise, and remained for at least 24 hours. In addition, 24 hours after exercise we observed an increased automaticity in the strategy to maintain a stable upright stance.
Źródło:
Acta of Bioengineering and Biomechanics; 2018, 20, 3; 145-151
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analiza przebiegu pracy turbogeneratora po wystąpieniu samoczynnego ponownego załączenia linii
Analysis of the turbogenerator work after appearance of automatic switching line
Autorzy:
Gozdowiak, A.
Kisielewski, P.
Powiązania:
https://bibliotekanauki.pl/articles/1817703.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
turbogenerator
stabilność
system elektroenergetyczny
samoczynne ponowne załączenie linii
metoda elementów skończonych
Opis:
The investigations were prepared using a valid field-circuit model of the turbogenerator. The analysis refer to an appearance of the faults in the transmission line. During this study the physical phenomena existing in turbogenerator during the faults were analyzed.
Źródło:
Prace Naukowe Instytutu Maszyn, Napędów i Pomiarów Elektrycznych Politechniki Wrocławskiej. Studia i Materiały; 2014, 70, 34; 295--302
1733-0718
Pojawia się w:
Prace Naukowe Instytutu Maszyn, Napędów i Pomiarów Elektrycznych Politechniki Wrocławskiej. Studia i Materiały
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Assessment of dynamic balance during step initiation in Parkinson’s disease patients and elderly – a validity study
Autorzy:
Juras, Grzegorz
Kamieniarz, Anna
Michalska, Justyna
Słomka, Kajetan
Powiązania:
https://bibliotekanauki.pl/articles/307381.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
choroba Parkinsona
wiek starszy
stabilność postawy
Parkinson’s disease
elderly
postural stability
validity
step initiation
Opis:
The aim of this study was to evaluate the reliability of the novel posturographic procedure and to investigate the relationships between parameters of this procedure and clinical tests. We hypothesised the proposed step initiation procedure to be reliable method of balance and motor disability assessment, especially in patients with neurological deficits. Also, we assumed high significant correlation between parameters of step initiation procedures and clinical tests. Methods: The 35 subjects with idiopathic PD and 35 agedmatched healthy controls participated in this study. The gait initiation was measured using two force platforms. The procedure consisted of three phases: (1) quiet standing on a first platform (2) crossing on the second platform, (3) quiet standing on a second platform. Testing was carried out in four conditions: unperturbed trial, obstacle crossing, step-up and step-down. Results: In the proposed gait initiation procedure, the vCOP, raCOP and rmsCOP showed an excellent reliability (ICC > 0.80). For transit phase, reliability of all variables in all conditions also was excellent (ICC = 0.8–0.9). There were only a few associations between Tinetti scores and posturographic variables in controls, but in PD patients the significant correlations were found between the proposed measures and the UPDRS, Tinetti, FRT, TUG and with the BBS. Conclusions: The proposed gait initiation procedure is reliable and very suitable for the assessment of patients with Parkinson’s disease. It can be used as an objective assessment of the clinical condition and dynamic balance, and help in the designing and programming of the appropriate rehabilitation and treatment.
Źródło:
Acta of Bioengineering and Biomechanics; 2020, 22, 1; 3-10
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Assessment of gait stability and preferred walking speed in virtual reality
Autorzy:
Wodarski, Piotr
Jurkojć, Jacek
Polechoński, Jacek
Bieniek, Andrzej
Chrzan, Miłosz
Michnik, Robert
Gzik, Marek
Powiązania:
https://bibliotekanauki.pl/articles/306508.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
stabilność chodu
chód na bieżni
prędkość marszu
gait stability
gait on treadmill
preferred walking speed
gait variability
Opis:
Analysis of human gait as well as diagnosis of human locomotion organ should always be conducted with velocity of gait equal to Preferred Walking Speed (PWS). The literature review shows that the PWS value is not the same in real and virtual environment. The aim of this study was to determine PWS values in both environments and to specify values of parameters used in equations enabling PWS calculations on the basis of lower limb length. Methods: Research-related tests involved 40 subjects walking on the treadmill and wearing HMD goggles. The spatial scenery made participants feel like during a walk in the park. The tests included measurements of displacements of the COP, allowing for the calculation of the Lyapunov exponent and Floquet Multiplier. Both coefficients were used to identify stability at various gait velocities. Results: The analysis revealed that the PWS in relation to gait on the treadmill with VR was lower than the PWS without VR. The final stage of research involved the determination of new values of coefficients of the formula enabling the identification of the velocity of comfort of gait in VR. Conclusions: Obtained results proved that PWS in real and virtual environment are different. The lower values were obtained for measurements in VR. On the basis of these results, value of the “a” coefficient, used in PWS calculations on the basis of lower limb length, was re-determined. The new value makes it possible to assess PWS for gait conducted on treadmill in virtual environment, what can be very important in gait evaluation.
Źródło:
Acta of Bioengineering and Biomechanics; 2020, 22, 1; 127-134
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Assessment of postural stability in patients after reconstruction of the anterior cruciate ligament with LARS and autogenous graft
Autorzy:
Plocki, J.
Kotela, I.
Bejer, A.
Pelikan, P.
Granek, A.
Krawczyk-Suszek, M.
Powiązania:
https://bibliotekanauki.pl/articles/307030.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
postural stability
knee
ACL reconstruction
LARS
knee function
stabilność postawy
kolano
ACL
Opis:
The aim of the study was to assess static balance after reconstruction of the anterior cruciate ligament (ACL), using gracialis tendons graft (GR) or semi-tendinosus (ST), compared to patients treated with the Ligament Advanced Reinforcement System (LARS). The study was performed within 36 to 48 months after the surgery. Methods: The study included 96 patients. The LARS group consisted of 44 patients, control group operated with ST/GR tendons included 52 patients. The stabilometric platform Alpha was used to assess the static balance. Two 30-second trials in the double-leg stance position with eyes opened and closed were performed. The distribution of loads in a free standing was also assessed. Results: In the test with open eyes the subjects from the LARS group had a significantly longer center of pressure (COP) path, a higher mean velocity, a greater mean COP sway in foot in the lateral direction and a larger path area occupied by the COP graph. During the tests with eyes closed, a significant difference occurred in the mean displacement of COP in lateral direction – greater in the LARS group. In addition, all parameters deteriorated during the tests with eyes closed in both groups. Conclusions: In static balance assessed with eyes closed, more proprioceptive deficits may appear in the LARS group.
Źródło:
Acta of Bioengineering and Biomechanics; 2018, 20, 4; 9-14
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Assessment of postural stability in patients with lumbar spine chronic disc disease
Autorzy:
Truszczyńska, A.
Dobrzyńska, M.
Trzaskoma, Z.
Drzał-Grabiec, J.
Tarnowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/307493.pdf
Data publikacji:
2016
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
postawa ciała
ból przewlekły
stabilność
dysk
degenerative disc disease
postural stability
chronic pain
Lumbar intervertebral disc
Opis:
Purpose: The pain, motor and sensory deficits are common symptoms of the lumbar disc disorder, and they can significantly affect human postural control. The aim of this study was to assess postural stability in patients with severe symptoms of lumbar spine disc disease qualifying them for surgical treatment and to compare them with a control group. Methods The study involved 103 subjects: 54 patients and 49 healthy subjects. Patient’s mean age was 46.4 ± 11.3 years, mean body height 172.2 ± 10.3 cm, mean body mass was 83.1 ± 18.9 kg and mean body mass index (BMI) was 27.9 ± 5.2 kg m-2. The mean time of their recent pain episode was 9.7 ± 8.5 month. Results: We found statistically significant differences between postural stability in patients with lumbar spine disc disease and the control group. The measurements taken with eyes closed, as compared with the clinical control group, revealed higher and statistically significant values of the mean amplitude of COP, mean amplitude of COP on sagittal plane, and maximal sway in sagittal plane parameters. The analysis of pressure value differences between the right and left lower limbs in both groups revealed statistical significance. In the study population the difference was significantly greater in comparison to the control group. The patients has significantly greater asymmetry of lower limb load. Conclusions: 1. Patients with lumbar spine discogenic pain had decreased postural control. 2. The patients had significant asymmetry in foot pressure, resultant from pain radiating to a lower limb.
Źródło:
Acta of Bioengineering and Biomechanics; 2016, 18, 4; 71-77
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Assessment of the impact of geomechanical parameters variability on underground excavations stability using response surface method
Autorzy:
Pytel, W.
Świtoń, J.
Powiązania:
https://bibliotekanauki.pl/articles/178429.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
parametry geomechaniczne
stabilność wyrobiska
górotwór
górnictwo
wyrobisko górnicze
wyrobisko podziemne
parametry geomechaniczne górotworu
geomechanical parameters
rock mass
underground excavation
excavation
excavation stability
Opis:
Recognition of properties of the rock mass surrounding a mineral deposit is particularly important for the mining operations at greater depths. Since the rock mass is usually not homogeneous, and its parameters have characteristics of randomness, underground workings safety issue should always be analysed taking into account the dispersion of the values of these parameters around their mean values. In order to assess the impact of geotechnical parameters uncertainty on the excavation stability one uses the appropriate statistical approach. In this paper, by analysing successive combinations of geomechanical parameters of the rock in the measured range, we examined the effect of their variability on risk of underground excavation instability using response surface method.
Źródło:
Studia Geotechnica et Mechanica; 2013, 35, 1; 183-194
0137-6365
2083-831X
Pojawia się w:
Studia Geotechnica et Mechanica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Biological stability of water in water distribution systems. The effect of water treatment trials
Autorzy:
Wolska, M.
Powiązania:
https://bibliotekanauki.pl/articles/206902.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
water treatment
carbon
groundwater
microorganisms
nitrogen removal
organic carbon
surface waters
water aeration
water distribution systems
water supply systems
biological stability
inorganic nitrogen
uzdatnianie wody
węgiel
wody gruntowe
mikroorganizmy
usuwanie azotu
węgiel organiczny
wody powierzchniowe
napowietrzanie wody
systemy dystrybucji wody
wodociągi
stabilność biologiczna
stężenie dwutlenku węgla
azot nieorganiczny
Opis:
Research into the removal efficiency of biogenic substances, necessary for the growth of heterotrophic microorganisms, was carried out for the following water treatment trials: surface water, infiltrative water and mixed surface water after microsieving with aerated underground water. The results have shown that the efficiency of removal of organic substances, independently of the type of treated water, increased along with the organic carbon concentrations in raw water. The average effectiveness of phosphate removal was: 92.1%, 88.8% and 83.7% for surface, infiltrative and mixed water, respectively. In all analyzed systems, presence of phosphates was an limiting factor for the regrowth of microorganisms in the distribution system. In none of the water treatment trials, effective removal of inorganic nitrogen has been recorded.
Źródło:
Environment Protection Engineering; 2015, 41, 2; 147-157
0324-8828
Pojawia się w:
Environment Protection Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparative study of phenol degradation with a wild-type and genetically modified P. vesicularis (pBR322). plasmid stability and fame profiling
Autorzy:
Mrozik, A.
Swędzioł, Ż.
Miga, S.
Powiązania:
https://bibliotekanauki.pl/articles/207456.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
biodegradation
phenols
comparative studies
fatty acid methyl ester
phenol degradation
plasmid stability
biodegradacja
kwasy tłuszczowe
fenole
badania porównawcze
ester metylowy kwasu tłuszczowego
degradacja fenolu
stabilność plazmidu
Opis:
It was evidenced that P. vesicularis is an efficient degrader of phenol but does not have a reporter system for monitoring bacterial survival in the environment. Therefore, P. vesicularis (pBR322) has been constructed. In this study we experimentally confirmed that introduction of plasmid pBR322 into P. vesicularis did not change its ability to degrade phenol in liquid media and after its inoculation into sterile soil. Moreover, it has been shown that plasmid pBR322 was stable in P. vesicularis during all experiments. Additionally, the pattern of fatty acid methyl esters for P. vesicularis (pBR322) looked similar to that of P. vesicularis under phenol exposure. Some fatty acids, especially branched and cyclopropane ones were sensitive markers of phenol utilization. These findings indicate that P. vesicularis (pBR322) due to the presence of plasmid could be used instead of P. vesicularis in bioaugmentation of phenol-contaminated areas.
Źródło:
Environment Protection Engineering; 2015, 41, 1; 137-155
0324-8828
Pojawia się w:
Environment Protection Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Differences in evaluation methods of trunk sway using different MoCap systems
Autorzy:
Kutilek, P.
Socha, V.
Cakrt, O.
Svoboda, Z.
Powiązania:
https://bibliotekanauki.pl/articles/306317.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
trunk
postural stability
camera system
orientation tracker
convex hull
confidence ellipse
pitch versus roll
tułów
stabilność
powłoka wypukła
Opis:
The position of the trunk can be negatively influenced by many diseases. Several methods can be used for identifying defects in balance and coordination as a result of pathology of the musculoskeletal or nervous system. The aim of this article is to examine the relationship between the three methods used for analysis of trunk sway and compare two fundamentally different MoCap systems. We used a camera system and a 3DOF orientation tracker placed on subject’s trunk, and measured inclination (roll) and flexion (pitch) during quiet stance. Ten healthy participants in the study were measured with eyes open and closed. The pitch versus roll plots of trunk were formed, and the area of the convex hull, area of confidence ellipse and total length of the trajectory of the pitch versus roll plot were calculated. The statistical analysis was performed and strong correlation between the area of the convex hull and area of the confidence ellipse was found. Also, the results show moderate correlation between the area of the confidence ellipse and total length of the trace, and moderate correlation between the area of the convex hull and total length of the trace. In general, the different MoCap systems show different areas and lengths but lead to the same conclusions. Statistical analysis of the participants with eyes open and eye closed did not show significant difference in the areas and total lengths of the pitch versus roll plots.
Źródło:
Acta of Bioengineering and Biomechanics; 2014, 16, 2; 85-94
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effects of anthropometric factors on postural stability in individuals with hearing impairment
Autorzy:
Zdrodowska, A.
Wiszomirska, I.
Kaczmarczyk, K.
Kosmol, A.
Powiązania:
https://bibliotekanauki.pl/articles/306452.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
budowa ciała
stabilność postawy
uszkodzenie słuchu
antropometria
body composition
postural stability
balance
hearing impairment
anthropometry
Opis:
Identification of factors that affect postural stability may help to improve diagnostic accuracy and enhance the quality of treatment and rehabilitation. This study sought to assess the relationship between postural stability parameters and anthropometric factors of persons with hearing impairment (HI). Methods: The study included 128 individuals – 42 subjects with HI and 86 without HI (healthy controls). Research methodology included an interview and a medical examination, anthropometric measurements and stabilometric tests on platforms with stable and unstable surfaces. Results: In the group of female study participants with HI, significant correlations were only noted between body height and the Fall Risk Index (FRI). In the group of male subjects with HI, the study revealed significant correlations between FRI and body mass, BMI, % MM (muscle mass percentage) and % FAT (fat percentage). Moreover, moderate correlation was found between COP path with eyes open and body mass, while high correlation was observed between COP path with eyes open and BMI, % MM and % FAT. No significant correlation was noted between FRI and body height in men with HI. Conclusions: The examination of correlations between postural stability and body build of persons with HI did not confirm the effects of body height on postural stability in the examined group of individuals with HI, but revealed a greater influence of somatic parameters (body mass, BMI, % MM, % FAT) on postural stability in hearing-impaired men.
Źródło:
Acta of Bioengineering and Biomechanics; 2018, 20, 1; 109-115
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Evaluation of the accuracy of the postural stability measurement with the Y-Balance Test based on the levels of the biomechanical parameters
Autorzy:
Walaszek, R.
Chwała, W.
Walaszek, K.
Burdacki, M.
Błaszczuk, J.
Powiązania:
https://bibliotekanauki.pl/articles/306519.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
biomechanika
staw kolanowy
stabilność postawy
testy
biomechanics
motor control
postural stability
Y-Balance Test
structure test
Opis:
The testing of dynamic balance involves tests that assess the muscle control of spatial changes of the position of the centre of gravity over the base of support. The purpose of this work was to determine the structure of the Y-balance test and its accuracy based on the measurements of strength performance of the muscles acting on the knee joint, as well as the flexibility and balance in boys aged 14 years. Methods: The study included 43 schoolboys regularly participating in physical education lessons. The examination of postural stability was conducted with the use of the Y-balance test. The measurements of muscle strength and of resistance to fatigue of the extensors and flexors of knee joints in isometric contraction were performed on a measurement stand in a standard position with the use of tensometric sensors. The measurement of mobility range of the lower extremity joints was performed according to the SFTR. The examination of balance was performed with the use of the modified ‘Flamingo balance test’. Results: The factor structure of the Y-balance test results for the left and right lower extremities is similar and includes five principal independent factors that characterise the structure of analysed variables. They explain 76% and 74% of communality in total for the left and the right extremity, respectively. Conclusions: The extracted factor structure points to a hybrid structure of the Y-balance test and shows its accuracy in the measurements of the lower limb joint mobility and strength performance of knee joint extensors.
Źródło:
Acta of Bioengineering and Biomechanics; 2017, 19, 2; 121-128
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Global stability for thermal convection in a couple-stress fluid with temperature and pressure dependent viscosity
Autorzy:
Choudhary, S. S.
Bharti, P. K.
Powiązania:
https://bibliotekanauki.pl/articles/178230.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
konwekcja
konwekcja cieplna
stabilność
płyn nieniutonowski
convection
thermal convection
stability
non-Newtonian fluid
Opis:
We show that the global nonlinear stability threshold for convection in a couple-stress fluid with temperature and pressure dependent viscosity is exactly the same as the linear instability boundary. This optimal result is important because it shows that linearized instability theory has captured completely the physics of the onset of convection. It has also been found that the couplestress fluid is more stable than the ordinary viscous fluid and then the effect of couple-stress parameter (F) and variable dependent viscosity (Γ) on the onset of convection is also analyzed.
Źródło:
Studia Geotechnica et Mechanica; 2013, 35, 3; 85-102
0137-6365
2083-831X
Pojawia się w:
Studia Geotechnica et Mechanica
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 30

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