The aim of the present study was to identify potential gender differences in leg stiffness and reactive strength during hopping tasks in 13 to16-year old team sports players. Reactive strength index (RSI) and leg stiffness were obtained in two consecutive seasons from 51 girls (U14: n = 31, U16: n = 20) and 65 boys (U14: n = 32, U16: n = 33). A significant main effect on absolute (U14: p = 0.022, η2= 0.084; U16: p < 0.001, η2= 0.224) and relative leg stiffness (U14 p<0.001; η2= 0.195; U16; p = 0.008, η2= 0.128) for gender was found in both groups with values higher in boys than in girls. For absolute and relative stiffness gender differences in the U14 group were significant in the 1st year only (p=0.027 and p=0.001), and for the U16s in the 2nd year only (p < 0.001 and p = 0.022). For RSI, a significant main effect for gender was observed in the U16 group only (p < 0.001 η2= 0.429) with values significantly higher in boys than in girls in both years of measurement (p = 0.001; p < 0.001). Results of this study support previous limited findings, mostly related to non-athletes, suggesting lower stretch-shortening cycle capability in adolescence female compared to male, however our data only partly supports the theory that quality of neuromuscular functions increases with age until post puberty.

• Publikační typ
• časopisecké články MeSH

• MeSH
• dýchání MeSH
• funkční vyšetření srdce MeSH
• fyziologický stres MeSH
• hygiena práce MeSH
• krevní tlak MeSH

BACKGROUND: This study was designed to evaluate the effects of low-frequency electrical stimulation (LFES) on muscle strength and blood flow in patients with advanced chronic heart failure (CHF). METHODS AND RESULTS: Patients with CHF (n=15; age 56.5 +/- 5.2 years; New York Heart Association III - IV; ejection fraction 18.7 +/- 3.3%) were examined before and after 6 weeks of LFES (10 Hz) of the quadriceps and calf muscles of both legs (1 h/day, 7 days/week). Dynamometry was performed weekly to determine maximal muscle strength (F(max); N) and isokinetic peak torque (PT(max); Nm); blood flow velocity (BFV) was measured at baseline and after 6 weeks of LFES using pulsed-wave Doppler velocimetry of the right femoral artery. Six weeks of LFES significantly increased F(max) (from 224.5 +/- 96.8 N to 340.0 +/- 99.4 N; p<0.001), and also PT(max) (from 94.5 +/- 41.5 Nm to 135.3 +/- 28.8 Nm; p<0.01). BFV in the femoral artery increased after 6 weeks from 35.7 +/- 15.4 cm/s to 48.2 +/- 18.1 cm/s (p<0.05); BFV values at rest before and after 6 weeks of LFES did not differ significantly. CONCLUSIONS: LFES may improve muscle strength and blood supply, and could be recommended for the treatment of patients with severe CHF.

• MeSH
• biologické markery krev   MeSH
• C-reaktivní protein analýza   MeSH
• chronická nemoc MeSH
• elektrická stimulace * MeSH
• funkce levé komory srdeční MeSH
• index tělesné hmotnosti MeSH
• koronární cirkulace * fyziologie   MeSH
• kosterní svaly krevní zásobení   patofyziologie   MeSH
• lidé středního věku MeSH
• lidé MeSH
• pevnost ve smyku * MeSH
• rychlost toku krve MeSH
• srdce * patofyziologie   MeSH
• srdeční selhání krev   patofyziologie   terapie   MeSH
• Check Tag
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• práce podpořená grantem MeSH

Lipid peroxidation induced by oxidants leads to the formation of highly reactive metabolites. These can affect various immune functions, including reactive oxygen species (ROS) and nitric oxide (NO) production. The aim of the present study was to investigate the effects of lipid peroxidation products (LPPs) - acrolein, 4-hydroxynonenal, and malondialdehyde - on ROS and NO production in RAW 264.7 macrophages and to compare these effects with the cytotoxic properties of LPPs. Macrophages were stimulated with lipopolysaccharide (0.1 μg/ml) and treated with selected LPPs (concentration range: 0.1-100 μM). ATP test, luminol-enhanced chemiluminescence, Griess reaction, Western blotting analysis, amperometric and total peroxyl radical-trapping antioxidant parameter assay were used for determining the LPPs cytotoxicity, ROS and NO production, inducible nitric oxide synthase expression, NO scavenging, and antioxidant properties of LPPs, respectively. Our study shows that the cytotoxic action of acrolein and 4-hydroxynonenal works in a dose- and time-dependent manner. Further, our results imply that acrolein, 4-hydroxynonenal, and malondialdehyde can inhibit, to a different degree, ROS and NO production in stimulated macrophages, partially independently of their toxic effect. Also, changes in enzymatic pathways (especially NADPH-oxidase and nitric oxide synthase inhibition) and NO scavenging properties are included in the downregulation of reactive species formation.

• MeSH
• akrolein toxicita   MeSH
• aktivace makrofágů MeSH
• aldehydy toxicita   MeSH
• časové faktory MeSH
• down regulace účinky léků   MeSH
• dusitany metabolismus   MeSH
• lipopolysacharidy imunologie   MeSH
• makrofágy imunologie   metabolismus   MeSH
• malondialdehyd toxicita   MeSH
• myši MeSH
• NADPH-oxidasy antagonisté a inhibitory   MeSH
• osmolární koncentrace MeSH
• oxid dusnatý antagonisté a inhibitory   metabolismus   MeSH
• peroxidace lipidů MeSH
• reaktivní formy kyslíku antagonisté a inhibitory   metabolismus   MeSH
• scavengery volných radikálů farmakologie   MeSH
• synthasa oxidu dusnatého, typ II metabolismus   MeSH
• transformované buněčné linie MeSH
• viabilita buněk účinky léků   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH

BACKGROUND: Table tennis is considered as a reaction sport, in which reaction speed is the key factor of sports performance. However, in addition to the quality of sensory (or cognitive) functions, it also requires a rapid motor response. Reactive agility is one of the most important qualities of table tennis performance. It comprises both sensory and motor components. Therefore, the aim of this study was to find the relationship between reactive agility performance and reaction speed (sensory part), sprint and change of direction speed, and muscle strength parameters (motor part) and thus to identify determinants of reactive agility in table tennis players. METHODS: Fifteen male competitive table tennis players (26.3 ± 4.0 years, 179.4 ± 6.0 cm, 77.2 ± 6.4 kg) performed the Reactive Agility Test (RAT), three reaction time tests (simple and choice reaction, reaction to four visual stimuli), sprint for 5 m, 505 Agility test, countermovement and drop jumps. RESULTS: Pearson correlation coefficient revealed a significant relationship between RAT performance and reaction time to four visual stimuli (r = 0.801, p < 0.001). Nonsignificant, but the medium correlation was found between RAT performance and choice reaction time (r = 0.404) and decision-making time, which was calculated as a difference between choice and simple reaction time (r = 0.410). These results showed that reactive agility is determined by the cognitive component (reflected by the reaction time) in table tennis players. CONCLUSION: It seems that fast reactions associated with hand movements are more important than explosive strength and speed abilities in table tennis performance. Therefore, the trainers should focus primarily on the development of reaction-speed abilities in their training program. Secondary, they should focus on more specific movements (e.g., lateral change of direction or speed of first steps) rather than linear sprint speed or changing of direction under angles higher than 90°. Additionally, it seems that explosive strength training has only supportive character in relationship to the sports performance.

CONTEXT: Obesity is characterized by a low-grade inflammatory state, which could play a role in insulin resistance. Dynamic strength training improves insulin sensitivity. OBJECTIVE: The objective of this study was to investigate, in obese subjects, whether the insulin sensitizing effect of dynamic strength training is associated with changes in plasma levels and gene expression of adipokines potentially involved in the development of insulin resistance. DESIGN: Twelve obese male subjects were investigated before and at the end of 3 months of dynamic strength training. Insulin sensitivity was evaluated using euglycemic-hyperinsulinemic clamp. Blood samples and needle biopsy samples of sc abdominal adipose tissue were obtained. The plasma levels and adipose tissue mRNA levels of adiponectin, leptin, IL-1beta, IL-6, and TNF-alpha were determined. RESULTS: The training induced an increase in the whole-body glucose disposal rate by 24% (P = 0.04). The body weight was not altered during the training. Plasma levels of leptin decreased during the training (16.6 +/- 6.3 vs. 13.1 +/- 5.7 ng/ml) by 21% (P < 0.02), whereas no change in plasma levels of other adipokines and C-reactive protein was observed. Gene expression of the investigated adipokines was not changed in sc adipose tissue during the training. CONCLUSIONS: In obese subjects, the dynamic strength training resulted in an improvement of whole-body insulin sensitivity. The increase in insulin sensitivity was not associated with training-induced modifications of plasma levels or adipose tissue gene expression of adipokines supposedly involved in the development of insulin resistance.

• MeSH
• adiponektin krev   metabolismus   MeSH
• cvičení * fyziologie   MeSH
• cytokiny * krev   metabolismus   MeSH
• exprese genu MeSH
• interleukin-1beta krev   metabolismus   MeSH
• interleukin-6 krev   metabolismus   MeSH
• inzulinová rezistence * fyziologie   MeSH
• leptin krev   metabolismus   MeSH
• lidé středního věku MeSH
• lidé MeSH
• obezita krev   metabolismus   MeSH
• podkožní tuk * metabolismus   MeSH
• svalová síla fyziologie   MeSH
• TNF-alfa krev   metabolismus   MeSH
• Check Tag
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• klinické zkoušky MeSH
• práce podpořená grantem MeSH

• MeSH
• chůze (způsob) MeSH
• diabetes mellitus MeSH
• hyperglykemie MeSH
• hypoglykemie MeSH
• lidé MeSH
• posturální rovnováha MeSH
• senioři MeSH
• svalová atrofie MeSH
• Check Tag
• lidé MeSH
• senioři MeSH

The aim of this study was to investigate the restorative connections of composite materials after fracture, under controlled conditions of treating the materials with novel, spherosilicate-based (SS) primers bearing both methacryl (MA) and trimethoxysilyl (TMOS) groups. The chemistry of methacrylate group insertion and reactive groups hydrolysis has been studied with the aid of 1H NMR (Nuclear Magnetic Resonance) spectroscopy. The light-cured resin composites were repaired by activating the connection site with the obtained primers and, for comparison, a silane (methacryloxypropyltrimethoxysilane, MATMOS) as a conventional coupling agent bearing the same reactive groups. The resistance of such a joint was tested in a three-point bending test after 24 h and 28 days period of sample conditioning. The effect of bond application was also studied, showing that spherosilicate-based primers may be used more effectively than MATMOS for two-step (primer-composite) restorative process, while for silane, the three-step process with bond application is crucial for satisfactory joint quality. The joint failure mode was determined by microscopic analysis and it was found that SS-4MA-4TMOS and SS-2MA-6TMOS application resulted in mostly composite, and not joint, failure. After 28 days of conditioning, the flexural strength of the joint repaired with SS-4MA-4TMOS was at 94% of the neat, solid material under the same procedure. However, the strength of the neat composite was observed to decline during the conditioning process by ~30%. The joint behavior was explained on the basis of the gradual hydrolysis effect (the greatest decrease being observed for silane).

• Publikační typ
• časopisecké články MeSH

Soybean (Glycine max L.) has been extensively cultivated in maize-soybean relay intercropping systems in southwest China. However, during the early co-growth period, soybean seedlings suffer from severe shading by maize resulting in lodging and significant yield reduction. The purpose of the present research was to investigate the reasons behind severe lodging and yield loss. Therefore, four different soybean genotypes (B3, B15, B23, and B24) having different agronomic characteristics were cultivated in intercropping and monocropping planting patterns. The results showed that under different planting patterns, the stem resistance varied among genotypes (P < 0.01). The lodging resistance index of B3, B15, B23, and B24 genotypes was 70.9%, 60.5%, 65.2%, and 57.4%, respectively, under intercropping, among which the B24 genotype was less affected by the shade environment as there was little decrease in the lodging resistance index of this genotype under intercropping. The lignin content of B23 and B24 was significantly higher than that of B3 and B15 under both planting patterns. Under intercropping, the hemicellulose content of B23 and B24 stems was significantly higher than that of B3 and B15. Compared to the monocropping, the content of mannose in the structural carbohydrate of soybean stems was decreased in all genotypes except B23, but the difference was not significant. The content of xylose in the structural carbohydrate of soybean stems was significantly higher than that in B3 and B15. Mannose content showed no significant difference among genotypes. The arabinose content of B24 was significantly higher than that of B3, B15, and B23. The effective pod number, seed number per plant, seed weight per plant and yield of soybean plants were significantly decreased under intercropping. Conclusively, manipulation of structural and nonstructural carbohydrate rich soybean genotypes in intercropping systems could alleviate the yield loss due to lodging.

• MeSH
• celulosa genetika   metabolismus   MeSH
• fyziologický stres genetika   fyziologie   MeSH
• genotyp MeSH
• Glycine max genetika   metabolismus   MeSH
• lignin genetika   metabolismus   MeSH
• monosacharidy genetika   metabolismus   MeSH
• polysacharidy genetika   metabolismus   MeSH
• sacharosa metabolismus   MeSH
• stonky rostlin genetika   fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH

The purpose of the study was to analyse the changes in muscle strength, power, and somatic parameters in elite volleyball players after a specific pre-season training programme aimed at improving jumping and strength performance and injury prevention. Twelve junior female volleyball players participated in an 8-week training programme. Anthropometric characteristics, isokinetic peak torque (PT) single-joint knee flexion (H) and extension (Q) at 60º/s and 180º/s, counter movement jump (CMJ), squat jump (SJ), and reactive strength index (RSI) were measured before and after intervention. Significant moderate effects were found in flexor concentric PT at 60º/s and at 180 º/s in the dominant leg (DL) (18.3±15.1%, likely; 17.8±11.2%, very likely) and in extensor concentric PT at 180º/s (7.4%±7.8%, very likely) in the DL. In the non-dominant leg (NL) significant moderate effects were found in flexor concentric PT at 60º/s and at 180º/s (13.7±11.3%, likely; 13.4±8.0%, very likely) and in extensor concentric PT at 180º/s (10.7±11.5%, very likely). Small to moderate changes were observed for H/QCONV in the DL at 60º/s and 180º/s (15.9±14.1%; 9.6±10.4%, both likely) and in the NL at 60º/s (moderate change, 9.6±11.8%, likely), and small to moderate decreases were detected for H/QFUNC at 180º/s, in both the DL and NL (-7.0±8.3%, likely; -9.5±10.0%, likely). Training-induced changes in jumping performance were trivial (for RSI) to small (for CMJ and SJ). The applied pre-season training programme induced a number of positive changes in physical performance and risk of injury, despite a lack of changes in body mass and composition.

• Publikační typ
• časopisecké články MeSH