Effect of caffeine intake on critical power model parameters determined on a cycle ergometer

The aim of this study was to evaluate the effect of caffeine intake on critical power model parameters determined on a cycle ergometer. Eight male subjects participated in this study. A double-blind protocol consisting of the intake of pure caffeine (6 mg/kg) or placebo (maltodextrin) 60 min before testing was used. Subjects were submitted to four constant-load tests on a cycle ergometer. These tests were conducted randomly in the caffeine and placebo groups [checar] at intensities of 80, 90, 100 and 110% maximum power at a rate of 70 rpm until exhaustion to determine the critical power. As a criterion for stopping the test was adopted any rate fall without recovery by more than five seconds. The critical power and anaerobic work capacity were obtained by nonlinear regression and fitting of the curve to a hyperbolic power-time model. The Shapiro-Wilk test and paired Student t-test were used for statistical analysis. No significant differences in critical power were observed between the caffeine and placebo groups (192.9 ± 31.3 vs 197.7 ± 29.4 W, respectively). The anaerobic work capacity was significantly higher in the caffeine group (20.1 ± 5.2 vs 16.3 ± 4.2 W, p<0.01). A high association (r²) was observed between the caffeine and placebo conditions (0.98 ± 0.02 and 0.99 ± 0.0, respectively). We conclude that caffeine intake did not improve critical power performance but increased anaerobic work capacity by influencing performance at loads of higher intensity and shorter duration.O objetivo do presente estudo foi verificar o efeito da ingestão de cafeína sobre os parâmetros do modelo de potência crítica determinado em cicloergômetro. Participaram do estudo oito sujeitos do sexo masculino. A ingestão de cafeína pura (6 mg.kg-1) ou placebo (maltodextrina) foi realizada através de protocolo duplo-cego, 60 minutos antes dos testes. Para determinação da potência crítica, os sujeitos foram submetidos a quatro testes de cargas constantes em cicloergômetro, realizados aleatoriamente, nos momentos cafeína e placebo, nas intensidades de 80, 90, 100 e 110% da potência máxima, a uma cadência de 70 rpm até a exaustão. A potência crítica e a capacidade de trabalho anaeróbio foram obtidas através de regressão não linear e ajuste de curva para o modelo hiperbólico potência-tempo. Para o tratamento estatístico, utilizaram-se-se o teste de Shapiro Wilk e o teste t de Student pareado. Não foram encontradas diferenças significativas na potência crítica nas condições cafeína e placebo (192,9 ± 31,3 vs 197,7 ± 29,4 W, respectivamente). A capacidade de trabalho anaeróbio foi significativamente maior na condição cafeína (20,1 ± 5,2 vs 16,3 ± 4,2 W, p< 0,01). Foi, ainda, obtido um alto valor de associação (r²) entre as condições cafeína e placebo (0,98± 0,02 e 0,99± 0,0). Através dos resultados obtidos, concluiu-se que a ingestão de cafeína não proporcionou melhorias no desempenho da potência crítica, entretanto, elevou os valores da capacidade de trabalho anaeróbio por influenciar o desempenho nas cargas de maior intensidade e menor duração.495

Fatores psicológicos e sociais são fontes de estresse subjetivo em árbitros de Futebol

Psychological and social factors are subjective stress source in football refereesReferees play one of the most important aspects of competition and often, according to athletes and managers, are responsible for their failures and for causing stress. The objective was to analyze the perception of stress in referees of Liga Uberabense of Soccer after a match. Twenty Six football referees of different sports levels, who play in the championships held by the Uberaba Football League, were part of the study. The stress test for referees, TEPA was used. The results show that the main stressor factors were: places with no safety, lack of proper planning of the competition, no payment, unprepared colleagues, delays, irresponsible co-workers, lack of recognition and appreciation, and comments of those who do not know the rules of the game among others. We conclude that the perception of referee's stress investigated comes from mistakes in decision making during the match, social factors related to lack of safety before, during and after the match, and the playing field structure.A arbitragem é um dos aspectos mais importantes envolvidos na competição, sendo frequentemente citada por atletas e dirigentes como responsáveis por seus insucessos e fonte de estresse. O objetivo foi analisar a percepção de estresse em árbitros da Liga Uberabense de Futebol após uma partida de futebol. Participaram do estudo 26 árbitros de futebol de diferentes níveis esportivos, que atuam nos campeonatos realizados pela Liga Uberabense de Futebol. Foi utilizado o Teste de estresse para árbitros (TEPA). Os resultados mostram que os principais fatores causadores de estresse foram: locais com ausência de segurança, desorganização da competição, falta de pagamento, delegado despreparado, chegar tarde ou atrasado no local da partida, irresponsabilidade do colega, falta de reconhecimento e valorização, comentários de quem não sabe as regras do jogo, entre outros. Concluímos que a percepção de estresse dos árbitros investigados é proveniente de erros na tomada de decisão durante a partida e de fatores sociais relacionados a ausência de segurança antes, durante e depois da partida, estrutura dos campos

<b>The influence of different distances on determination of critical velocity in swimmers </b>

The purpose of this study was to determine the influence of different distance combinations on critical velocity (CV) and anaerobic work capacity (AWC). Nineteen swimmers experienced in this training modality participated in the study. CV was calculated by the angular coefficient of the linear regression line between distance and time obtained for each repetition. Five distances (50, 100, 200, 400 and 800 m) performed at an interval of 24 hours were used for the determination of CV, followed by the following four combinations of distances: CV1 (50, 100 and 200 m), CV2 (100, 200 and 400 m), CV3 (200, 400 and 800 m), and CV4 (50, 100, 200, 400 and 800 m). The Shapiro-Wilk test was used to determine the normality of the data. One-way ANOVA was used for comparisons between CV and the different combinations of shots (p < 0.05). The combination of smaller distances (CV1) resulted in an increase of CV (1.47 ± 0.13) and a decrease of AWC (11.91 ± 2.61). The use of shots of medium and long distance resulted in a lower CV (1.38 ± 0.10, 1.34 ± 0.09 and 1.36 ± 0.09 for CV2, CV3 and CV4, respectively) and higher AWC (19.84 ± 6.74, 27.44 ± 6.91 and 18.43 ± 5.21) when compared to short shots. The results suggest that shot distance influences CV and AWC, overestimating or underestimating the speed corresponding to maximum lactate steady state

Effect of caffeine intake on critical power model parameters determined on a cycle ergometer

The aim of this study was to evaluate the effect of caffeine intake on critical power model parameters determined on a cycle ergometer. Eight male subjects participated in this study. A double-blind protocol consisting of the intake of pure caffeine (6 mg/kg) or placebo (maltodextrin) 60 min before testing was used. Subjects were submitted to four constant-load tests on a cycle ergometer. These tests were conducted randomly in the caffeine and placebo groups [checar] at intensities of 80, 90, 100 and 110% maximum power at a rate of 70 rpm until exhaustion to determine the critical power. As a criterion for stopping the test was adopted any rate fall without recovery by more than five seconds. The critical power and anaerobic work capacity were obtained by nonlinear regression and fitting of the curve to a hyperbolic power-time model. The Shapiro-Wilk test and paired Student t-test were used for statistical analysis. No significant differences in critical power were observed between the caffeine and placebo groups (192.9 ± 31.3 vs 197.7 ± 29.4 W, respectively). The anaerobic work capacity was significantly higher in the caffeine group (20.1 ± 5.2 vs 16.3 ± 4.2 W, p< 0.01). A high association (r2) was observed between the caffeine and placebo conditions (0.98 ± 0.02 and 0.99 ± 0.0, respectively). We conclude that caffeine intake did not improve critical power performance but increased anaerobic work capacity by influencing performance at loads of higher intensity and shorter duration

Description and performance of track and primary-vertex reconstruction with the CMS tracker

A description is provided of the software algorithms developed for the CMS tracker both for reconstructing charged-particle trajectories in proton-proton interactions and for using the resulting tracks to estimate the positions of the LHC luminous region and individual primary-interaction vertices. Despite the very hostile environment at the LHC, the performance obtained with these algorithms is found to be excellent. For tbar t events under typical 2011 pileup conditions, the average track-reconstruction efficiency for promptly-produced charged particles with transverse momenta of p(T) > 0.9GeV is 94% for pseudorapidities of |η| < 0.9 and 85% for 0.9 < |η| < 2.5. The inefficiency is caused mainly by hadrons that undergo nuclear interactions in the tracker material. For isolated muons, the corresponding efficiencies are essentially 100%. For isolated muons of p(T) = 100GeV emitted at |η| < 1.4, the resolutions are approximately 2.8% in p(T), and respectively, 10μm and 30μm in the transverse and longitudinal impact parameters. The position resolution achieved for reconstructed primary vertices that correspond to interesting pp collisions is 10–12μm in each of the three spatial dimensions. The tracking and vertexing software is fast and flexible, and easily adaptable to other functions, such as fast tracking for the trigger, or dedicated tracking for electrons that takes into account bremsstrahlung