1,244 research outputs found

    Time-motion characteristics and physiological responses of small-sided games in elite youth players: The influence of player number and rule changes

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    The aim of this study was to examine acute physiological responses and time-motion characteristics associated with 4 soccer-specific small-sided game (SSG) formats (3 vs. 4 players, 3 vs. 3 players + floater, 5 vs. 6 players, and 5 vs. 5 players + floater) and 4 rule changes in elite youth soccer players. Sixteen male youth soccer players (mean ± SD: age = 15.6 ± 0.8 years, stature = 170.8 ± 6.6 cm, body mass = 67.5 ± 6.2 kg, and 20-m shuttle run estimated V̇2 max = 57.4 ± 3.7 ml·kg-1-min-1) participated in the study, in which heart rate (HR), rating of perceived exertion (RPE), blood lactate (La -), and time-motion characteristics were recorded. The rule change requiring extra sprint running had a greater effect on the time-motion characteristics than all other rule modifications but no effect on acute %HRmax, La-, and RPE. Rule changes had no effect on RPE. Fixed underload teams (i.e., lower number of players compared with the opponent team) recorded a significantly higher RPE compared with the fixed overload teams, although there were no differences in %HRmax and La-. The major practical findings are that subtle changes in SSGs playing rules can influence the physiological, perceptual, and time-motion responses in young elite soccer players. Rules that are related to a team's chances of scoring may improve player motivation and thereby increase training intensity during SSGs. There were no differences between fixed and variable formats in terms of physiological and perceptual responses, although both may provide useful technical-tactical training. Coaches should take care in designing different soccer SSGs as each rule or game format change may influence exercise intensity independently. © 2010 National Strength and Conditioning Association

    Efeito do nĂșmero de jogadores sobre a demanda fĂ­sica e respostas fisiolĂłgicas durante jogos com campo reduzido em jogadores de futebol sub-15

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    O objetivo do estudo foi verificar o efeito do nĂșmero de jogadores em jogos com campo reduzido (JCRs) sobre a demanda fĂ­sica e as respostas fisiolĂłgicas em jogadores adolescentes de futebol. Para isso, 14 jogadores de uma equipe de nĂ­vel estadual (idade 14,4 ± 0,5 anos; massa corporal 56,2 ± 7,0 kg; estatura 1,7 ± 0,1 m; IMC 20,3 ± 1,4 kg∙m-2) foram submetidos a dois formatos (3 vs 3 e 7 vs 7) de JCRs. Foram analisadas as repostas de frequĂȘncia cardĂ­aca (FC), percepção subjetiva de esforço (PSE) e lactato sanguĂ­neo ([La]), alĂ©m da demanda fĂ­sica por meio do sistema de posicionamento global (GPS). Embora nĂŁo tenha havido diferença estatĂ­stica nas distĂąncias percorridas em diferentes zonas de velocidade entre os formatos de JCRs, a distĂąncia total percorrida, a distĂąncia percorrida em alta velocidade, a quantidade de açÔes em alta intensidade e a quantidade de aceleraçÔes > 1 m∙s-2 foram maiores (p < 0,05) no JCR 3 vs 3 (1794 m; 885 m; 69; 87, respectivamente) em relação ao JCR 7 vs 7 (1663 m; 712 m; 57; 68). O percentual da frequĂȘncia cardĂ­aca mĂĄxima (FCmĂĄx), PSE e [La] foram superiores (p < 0,05) no JCR 3 vs 3 quando comparado ao 7 vs 7 (91,3%; 6,1 u.a.; 5,0 mmol∙L-1 vs 85,1%; 5,1 u.a.; 2,1 mmol∙L-1, respectivamente). Os resultados demonstram que a intensidade Ă© maior durante o JCR 3 vs 3 do que no JCR 7 vs 7; alĂ©m disso, a demanda fĂ­sica Ă© influenciada pelo nĂșmero de jogadores, com uma maior distĂąncia total e distĂąncia em alta velocidade, alĂ©m de maior quantidade de atividades em alta intensidade e aceleraçÔes no JCR 3 vs 3

    Avaliação da intensidade do treinamento técnico-tåtico e da fadiga causada em jogadores de futebol da categoria sub-20

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    Resumo Visto que o calendĂĄrio atual do futebol nĂŁo disponibiliza um tempo hĂĄbil para a devida recuperação dos atletas, fadiga e recuperação tĂȘm sido amplamente estudadas por pesquisadores. O que levou ao surgimento de alguns instrumentos com o propĂłsito de fornecer informaçÔes e dar suporte aos profissionais visando a alta performance. O objetivo deste estudo foi analisar a intensidade do Treinamento TĂ©cnico-tĂĄtico e a fadiga causada em jogadores de futebol da categoria sub-20, atravĂ©s do desempenho em testes de salto vertical e horizontal e da percepção subjetiva de esforço da sessĂŁo (PSE da sessĂŁo). Os jogadores (n = 25) realizaram o salto vertical contra movimento (SCM) e horizontal (SH), antes e apĂłs a uma sessĂŁo de Treinamento TĂ©cnico-tĂĄtico (TTT), sendo a intensidade avaliada pela Escala de Borg (CR 10). O SCM nĂŁo apresentou diferença significativa (p > 0,05), enquanto que o SH foi maior no PĂłs-TTT em relação ao PrĂ©-TTT (p = 0,02). Quanto a PSE da sessĂŁo, 92% dos jogadores classificaram a intensidade do TTT como sendo de fĂĄcil Ă  moderada. Os resultados deste estudo indicam que o TTT de baixa intensidade nĂŁo compromete a potĂȘncia nos testes de salto vertical e horizontal. Sugere-se que alĂ©m de proporcionar a operacionalização dos padrĂ”es de comportamento tĂĄticos coletivos, o TTT de baixa intensidade possa ser utilizado em treinamentos de carĂĄter regenerativo ou em momentos que o calendĂĄrio esportivo nĂŁo possibilite a recuperação completa dos jogadores

    Inhibition of IL-10 Production by Maternal Antibodies against Group B Streptococcus GAPDH Confers Immunity to Offspring by Favoring Neutrophil Recruitment

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    Group B Streptococcus (GBS) is the leading cause of neonatal pneumonia, septicemia, and meningitis. We have previously shown that in adult mice GBS glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is an extracellular virulence factor that induces production of the immunosuppressive cytokine interleukin-10 (IL-10) by the host early upon bacterial infection. Here, we investigate whether immunity to neonatal GBS infection could be achieved through maternal vaccination against bacterial GAPDH. Female BALB/c mice were immunized with rGAPDH and the progeny was infected with a lethal inoculum of GBS strains. Neonatal mice born from mothers immunized with rGAPDH were protected against infection with GBS strains, including the ST-17 highly virulent clone. A similar protective effect was observed in newborns passively immunized with anti-rGAPDH IgG antibodies, or F(ab')2 fragments, indicating that protection achieved with rGAPDH vaccination is independent of opsonophagocytic killing of bacteria. Protection against lethal GBS infection through rGAPDH maternal vaccination was due to neutralization of IL-10 production soon after infection. Consequently, IL-10 deficient (IL-10−/−) mice pups were as resistant to GBS infection as pups born from vaccinated mothers. We observed that protection was correlated with increased neutrophil trafficking to infected organs. Thus, anti-rGAPDH or anti-IL-10R treatment of mice pups before GBS infection resulted in increased neutrophil numbers and lower bacterial load in infected organs, as compared to newborn mice treated with the respective control antibodies. We showed that mothers immunized with rGAPDH produce neutralizing antibodies that are sufficient to decrease IL-10 production and induce neutrophil recruitment into infected tissues in newborn mice. These results uncover a novel mechanism for GBS virulence in a neonatal host that could be neutralized by vaccination or immunotherapy. As GBS GAPDH is a structurally conserved enzyme that is metabolically essential for bacterial growth in media containing glucose as the sole carbon source (i.e., the blood), this protein constitutes a powerful candidate for the development of a human vaccine against this pathogen

    Could futsal hold the key to developing the next generation of youth soccer players?

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    The identification and development of talented players is a priority within elite soccer clubs and national governing bodies. Small-sided games training methods are commonly used in aiding player development. Yet the potential role for futsal (indoor 5 a-side equivalent to 11 a-side soccer) as part of contemporary youth player conditioning and skills acquisition training has received insufficient consideration. This absence might be linked to a lack of understanding due to a paucity of scientific evidence underpinning the potential role for futsal in aiding player development. While highlighting these issues, the present point-counterpoint article argues how futsal could impact positively on contemporary youth talent development processes

    Jet energy measurement with the ATLAS detector in proton-proton collisions at root s=7 TeV

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    The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of √s = 7TeV corresponding to an integrated luminosity of 38 pb-1. Jets are reconstructed with the anti-kt algorithm with distance parameters R=0. 4 or R=0. 6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta pT≄20 GeV and pseudorapidities {pipe}η{pipe}<4. 5. The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations. The jet energy uncertainty is less than 2. 5 % in the central calorimeter region ({pipe}η{pipe}<0. 8) for jets with 60≀pT<800 GeV, and is maximally 14 % for pT<30 GeV in the most forward region 3. 2≀{pipe}η{pipe}<4. 5. The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon pT, the sum of the transverse momenta of tracks associated to the jet, or a system of low-pT jets recoiling against a high-pT jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response. The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-pT jets. Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating from light quarks, heavy quarks or gluons are also discussed and the corresponding uncertainties are determined. © 2013 CERN for the benefit of the ATLAS collaboration

    Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

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    The inclusive and dijet production cross-sections have been measured for jets containing b-hadrons (b-jets) in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV, using the ATLAS detector at the LHC. The measurements use data corresponding to an integrated luminosity of 34 pb^-1. The b-jets are identified using either a lifetime-based method, where secondary decay vertices of b-hadrons in jets are reconstructed using information from the tracking detectors, or a muon-based method where the presence of a muon is used to identify semileptonic decays of b-hadrons inside jets. The inclusive b-jet cross-section is measured as a function of transverse momentum in the range 20 < pT < 400 GeV and rapidity in the range |y| < 2.1. The bbbar-dijet cross-section is measured as a function of the dijet invariant mass in the range 110 < m_jj < 760 GeV, the azimuthal angle difference between the two jets and the angular variable chi in two dijet mass regions. The results are compared with next-to-leading-order QCD predictions. Good agreement is observed between the measured cross-sections and the predictions obtained using POWHEG + Pythia. MC@NLO + Herwig shows good agreement with the measured bbbar-dijet cross-section. However, it does not reproduce the measured inclusive cross-section well, particularly for central b-jets with large transverse momenta.Comment: 10 pages plus author list (21 pages total), 8 figures, 1 table, final version published in European Physical Journal

    Search for the standard model Higgs boson at LEP

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    Measurement of the Forward-Backward Asymmetry in the B -> K(*) mu+ mu- Decay and First Observation of the Bs -> phi mu+ mu- Decay

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    We reconstruct the rare decays B+→K+ÎŒ+Ό−B^+ \to K^+\mu^+\mu^-, B0→K∗(892)0ÎŒ+Ό−B^0 \to K^{*}(892)^0\mu^+\mu^-, and Bs0→ϕ(1020)ÎŒ+Ό−B^0_s \to \phi(1020)\mu^+\mu^- in a data sample corresponding to 4.4fb−14.4 {\rm fb^{-1}} collected in ppˉp\bar{p} collisions at s=1.96TeV\sqrt{s}=1.96 {\rm TeV} by the CDF II detector at the Fermilab Tevatron Collider. Using 121±16121 \pm 16 B+→K+ÎŒ+Ό−B^+ \to K^+\mu^+\mu^- and 101±12101 \pm 12 B0→K∗0ÎŒ+Ό−B^0 \to K^{*0}\mu^+\mu^- decays we report the branching ratios. In addition, we report the measurement of the differential branching ratio and the muon forward-backward asymmetry in the B+B^+ and B0B^0 decay modes, and the K∗0K^{*0} longitudinal polarization in the B0B^0 decay mode with respect to the squared dimuon mass. These are consistent with the theoretical prediction from the standard model, and most recent determinations from other experiments and of comparable accuracy. We also report the first observation of the Bs0→ϕΌ+Ό−decayandmeasureitsbranchingratioB^0_s \to \phi\mu^+\mu^- decay and measure its branching ratio {\mathcal{B}}(B^0_s \to \phi\mu^+\mu^-) = [1.44 \pm 0.33 \pm 0.46] \times 10^{-6}using using 27 \pm 6signalevents.Thisiscurrentlythemostrare signal events. This is currently the most rare B^0_s$ decay observed.Comment: 7 pages, 2 figures, 3 tables. Submitted to Phys. Rev. Let

    Search for a New Heavy Gauge Boson Wprime with Electron + missing ET Event Signature in ppbar collisions at sqrt(s)=1.96 TeV

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    We present a search for a new heavy charged vector boson Wâ€ČW^\prime decaying to an electron-neutrino pair in ppˉp\bar{p} collisions at a center-of-mass energy of 1.96\unit{TeV}. The data were collected with the CDF II detector and correspond to an integrated luminosity of 5.3\unit{fb}^{-1}. No significant excess above the standard model expectation is observed and we set upper limits on σ⋅B(Wâ€Č→eÎœ)\sigma\cdot{\cal B}(W^\prime\to e\nu). Assuming standard model couplings to fermions and the neutrino from the Wâ€ČW^\prime boson decay to be light, we exclude a Wâ€ČW^\prime boson with mass less than 1.12\unit{TeV/}c^2 at the 95\unit{%} confidence level.Comment: 7 pages, 2 figures Submitted to PR
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