Influência da cafeína na resposta pressórica ao exercício aeróbio em sujeitos hipertensos Caffeine influence on blood pressure response to aerobic exercise in hypertensive subjects

A redução da pressão arterial (PA) promovida pelo exercício físico é evidente segundo a literatura atual. Mecanismos neuro-humorais explicam essa resposta hipotensora, em que a diminuição da atividade simpática apresenta-se como um dos principais mecanismos. Porém, a ingestão de alimentos ricos em cafeína (CA) pode suprimir esta atenuação simpática. O objetivo desse estudo foi elucidar o impacto da ingestão de CA na resposta pressórica ao exercício em pessoas hipertensas. Sete hipertensos (52,3 ± 3,3 anos), sendo cinco mulheres, realizaram duas sessões de caminhada com 40 minutos de duração, em dois dias de treinamento, tendo previamente ingerido CA (4mg/kg de peso corporal) ou placebo (PL). A PA e a frequência cardíaca foram verificadas anteriormente a ingestão, após 15, 30, 45, 60 minutos da ingestão em estado de repouso e com 10, 20 e 30 minutos após o exercício. Os dados foram tratados por meio de estatística descritiva, e pelo teste não paramétrico de Wilcoxon (p < 0,05). A média da PA aumentou de 124,9/80,9mmHg antes da ingestão de CA para 129,4/84,3mmHg 60 minutos após, ainda no repouso (p < 0,05). Trinta minutos após o exercício observou-se resposta hipotensora no procedimento PL (queda da PA de 122,6/79,4mmHg para 115,7/78,6mmHg), enquanto que no procedimento com CA, a PA mostrou-se significativamente mais alta em relação aos valores de repouso (aumento de 124,9/80,9mmHg para 136,9/90,9mmHg, p < 0,05). Conclui-se que a ingestão de CA não só suprime a resposta hipotensora do exercício, como provoca uma hipertensão pós-exercício.<br>Blood pressure reduction (BP) promoted by physical exercise is evident according to the current literature. Neurohumoral mechanisms explain this hypotensive response, in which decrease of the sympathetic activity appears as one of its main mechanisms. However, the ingestion of caffeine-rich food (CA) can suppress this sympathetic attenuation. The objective of this study was to elucidate the impact of CA ingestion in BP after exercise, in hypertensive individuals. Seven hypertensive subjects (52.3 +/-3.3 years), being 5 women, accomplished two walk sessions with 40 minutes of duration, in two days of training, having previously ingested CA (4 mg/kg of body weight) or placebo (PL). BP and heart rate were verified previously to the ingestion, after 15, 30, 45, 60 minutes of the ingestion, at rest and with 10, 20 and 30 minutes after exercise. Data were treated through descriptive statistics and by the non-parametric Wilcoxon test (p<0.05). BP mean increased from 124.9/80.9 mmHg before ingestion to 129.4/84.3 mmHg 60 minutes later (p< 0.05). In the recovery period, after 30 minutes of exercise, hypotensive answer was observed in the PL procedure (decrease of 122.6/79.4 mmHg to 115.7/78.6 mmHg), while in the procedure with CA, BP was significantly higher than at rest (increase of 124.9/80.9 mmHg to 136.9/90.9 mmHg, p<0.05). It was concluded that CA not only suppresses the hypotensive response to exercise, but also provokes post-exercise hypertension

CO2 Degassing from Volcanic Lakes

Measurements of CO2 flux emitted at the surface of volcanic lakes have been performed using the so-called floating accumulation chamber method. Two statistical methods are used to process data: the graphical statistical and stochastic simulation methods. The results of graphical statistical approach allow the quantification of two degassing processes acting at the lake surface: one corresponding to CO2 fluxes resulting from rising bubbles and the second corresponding to equilibrium diffusion of dissolved CO2 at the water-air surface. The sequential Gaussian simulation method has been used for mapping the CO2 flux and estimating the total CO2 emission rate at the surface of volcanic lakes. The study of two volcanic lakes is presented in this chapter: Kelud, Indonesia and El Chichón, Mexico. Before a lava dome appeared in the middle of Kelud Lake on the 4th November 2007, the lake contained near neutral waters with a pH of 6. The total CO2 emission rate estimated by stochastic simulation ranged from 105 t day−1 for 2001 to 35 t day−1 for 2006. In early July 2007, the total flux for the lake area was estimated at 307 t day−1, showing that CO2 flux monitoring at the surface of volcanic lakes is a powerful tool in the improvement of early warning systems of volcanic eruptions. A significant change in CO2 flux was not detected for El Chichón lake during the period of survey (2007-2008) but the mapping of the CO2 flux on the lake area highlighted lineaments reflecting structures controlled by the main local and regional tectonic patterns.SCOPUS: ch.binfo:eu-repo/semantics/publishe