ABSTRACT
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.
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.
ABSTRACT
O objetivo do presente estudo foi verificar a influência da utilização de diferentes combinações de distâncias sobre os valores da Velocidade Crítica (VC) e Capacidade de Trabalho Anaeróbio (CTAn). Participaram do estudo dezenove nadadores com experiência em treinamento na modalidade. A VC foi determinada através do coeficiente angular da reta de regressão linear entre a distância e o tempo obtido em cada repetição. Para a determinaçãoda VC, foram utilizadas cinco distâncias (50, 100, 200, 400 e 800m) com intervalo de 24 horas entre elas. Posteriormente, foram feitas quatro combinações entre as distâncias: VC1 (50, 100 e 200m), VC2 (100, 200 e 400m), VC3 (200, 400 e 800m) e VC4 (50, 100, 200, 400 e 800m). O teste de Shapiro-Wilk foi utilizado para determinar a normalidade das amostras. Para comparações entre a VC e as diferentes combinações de tiros, utilizou-se ANOVA one way (p<0,05). A combinação com distâncias menores (VC1) proporcionou maiores valores da VC (1,47 ± 0,13), causando com isso uma diminuição na CTAn (11,91 ± 2,61). A utilização de tiros de média e longa distância proporcionou um valor mais baixo para a VC (1,38 ± 0,10, 1,34 ± 0,09 e 1,36 ± 0,09) e maior para a CTAn (19,84 ± 6,74, 27,44 ± 6,91 e 18,43 ± 5,21) quando comparados com os tiros curtos, respectivamente para VC2, VC3 e VC4. Através dos dados obtidos, conclui-se que a distância dos tiros possui grande influência sobre os valores da VC e da CTAn, podendo com isso superestimar ou subestimar a velocidade correspondente à máxima fase estável do lactato.
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.