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.
Highlights
O efeito ergogênico da cafeína está bem documentado para eventos de resistência, observando-se aumento significativo no tempo de exaustão e na produção média de potência[1,2,3,4]
Estudos também evidenciam que a cafeína poderia exercer influência sobre o desempenho em atividades de alta intensidade e curta duração[7,8,9]
As possibilidades incluem: alteração de íons, particularmente, sódio e potássio; inibição da fosfodiesterase (PDE), possibilitando um aumento na concentração de adenosina monofosfato cíclica (AMPc); e aumento na mobilização de cálcio através do retículo sarcoplasmático, com consequente aumento dos níveis intracelulares de cálcio nos músculos, aumentando a eficiência da contração muscular[1,10]
Summary
Effect of caffeine intake on critical power model parameters determined on a cycle ergometer. 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. 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. Embora os mecanismos responsáveis pelos efeitos ergogênicos da cafeína ainda não estejam esclarecidos[2,11], acredita-se que a potência crítica (PC), por fornecer parâmetros sobre a capacidade aeróbia e anaeróbia, possa ser adequada para verificar sua ação sobre estes metabolismos. O objetivo do presente estudo foi investigar o efeito da ingestão de cafeína sobre os parâmetros do modelo de Potência Crítica determinados em cicloergômetro
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