Does stroke volume increase during an incremental exercise? A systematic review

Introduction: Cardiac output increases during incremental-load exercise to meet metabolic skeletal muscle demand. This response requires a fast adjustment in heart rate and stroke volume. The heart rate is well known to increase linearly with exercise loadhowever, data for stroke volume during incremental-load exercise are unclear. Our objectives were to (a) review studies that have investigated stroke volume on incremental load exercise and (b) summarize the findings for stroke volume, primarily at maximal-exercise load. Methods: A comprehensive review of the Cochrane Library's, Embase, Medline, SportDiscus, PubMed, and Web of Sci-ence databases was carried out for the years 1985 to the present. The search was performed between February and June 2014 to find studies evaluating changes in stroke volume during incremental-load exercise. Controlled and uncontrolled trials were evaluated for a quality score. Results: The stroke volume data in maximal-exercise load are inconsistent. There is evidence to hypothesis that stroke volume increases during maximal-exercise load, but other lines of evidence indicate that stroke volume reaches a plateau under these circumstances, or even decreases. Conclusion: The stroke volume are unclear, include contradictory evidence. Additional studies with standardized reporting for subjects (e.g., age, gender, physical fitness, and body position), exercise test protocols, and left ventricular function are required to clarify the characteristics of stroke volume during incremental maximal-exercise load.National Council for Scientific [479395/2012-8]Universidade Federal de São Paulo, Laboratório de Fisiologia e Fisiopatologia Cardíaca, São Paulo, SP, BrazilUniversidade Nove de Julho, Programa de Pós-Graduação em Biofotônica Aplicada a Ciências da Saúde, São Paulo, SP, BrazilLaboratorio de Fisiologia Transacional dos Programas de Pos Graduacao em Educacao Fisica e Ciências do En-velhecimento, São Paulo, SP, BrasilUniversidade Nove de Julho, Programa de Pós-Graduação em Medicina, São Paulo, SP, BrazilUniversidade Federal do Mato Grosso, Programa de Mestrado em Educação Física, Cuiabá, MT, BrazilUniversidade Federal de São Paulo, Laboratório de Fisiologia e Fisiopatologia Cardíaca, São Paulo, SP, BrazilNational Council for Scientific: 479395/2012-8Web of Scienc

Decomposição de serrapilheira em bosque de sabiá na Zona da Mata de Pernambuco Litter decomposition under a sabiá canopy in the Forest Zone in Pernambuco

Objetivou-se avaliar a decomposição de frações de serrapilheira de sabiá (Mimosa caesalpiniifolia Benth) utilizando-se a técnica de sacos de náilon. Foram incubadas as seguintes frações de serrapilheira: folha senescente, folha no início da mineralização e ramos com até 20 mm de diâmetro. A incubação foi realizada nos períodos de 0, 4, 8, 16, 64, 100 e 256 dias nos anos de 2006 e 2007. As frações foram distribuídas em blocos ao acaso com cinco repetições. Foram avaliados os desaparecimentos de biomassa, nitrogênio (N) e fósforo (P), as concentrações de nitrogênio e fósforo e a relação carbono/ nitrogênio da serrapilheira ao longo dos períodos de incubação. De modo geral, o modelo exponencial negativo explicou o desaparecimento de biomassa, nitrogênio e fósforo, todavia, houve variação entre anos e, em alguns casos, apesar de significativos, os modelos apresentaram baixa correlação entre dados observados e preditos. A taxa de desaparecimento de biomassa foi lenta, uma vez que apenas 30% de biomassa de folhas foi mineralizada após 256 dias de incubação. A mineralização líquida de nitrogênio apresentou ampla variação entre anos e diferiu entre as frações estudadas. O teor de nitrogênio da serrapilheira incubada aumentou, em média, até os 32 dias (folhas) e até os 64 dias (ramos) de incubação, estabilizando-se em seguida. Foi usado o modelo platô linear para explicar esse processo. Com o passar dos períodos de incubação, a relação carbono/ nitrogênio diminuiu. Apesar de elevado teor de nitrogênio, a decomposição da serrapilheira de sabiá é lenta, o que pode reduzir as perdas de nutrientes no bosque, aumentando sua sustentabilidade e reduzindo os possíveis efeitos deletérios ao ambiente.<br>The research aimed to evaluate the decomposition of sabiá (Mimosa caesalpiniifolia Benth) litter fractions by using the nylon bag technique. The following litter fractions were incubated: senescent leaves, leaves at the beginning of mineralization, and branches with diameter up to 20 mm. Incubation was performed during periods of 0, 4, 8, 16, 64, 100, and 256 days in 2006 and 2007. The fractions were distributed in a random block design with five replications. It was evaluated the disappearance of biomass, nitrogen (N), and phosphorus (P), concentrations of nitrogen and phosphorus and the carbon/ nitrogen ratio of litter during the periods of incubation. In general, the negative exponential model explained the disappearance of biomass, nitrogen, and phosphorus, however, there was a variation among years and, in some cases, despite of being significant, the models showed a low correlation between predicted and observed data. Biomass disappearance rate was slow because only 30% of leaf biomass was mineralized after 256 days of incubation. Net nitrogen mineralization showed large variation among years, and it differed among the studied fractions. Nitrogen content of the litter increased, on average, until 32 days (leaves) and until 64 days (branches) of incubation followed by stabilization. The linear plateau model was used to explain that process. In the course of the incubation periods, the carbon/nitrogen ration decreased. Despite of the high content of nitrogen, the decomposition of sabiá litter is slow, what might reduce the loss of nutrients in the forest, increasing its sustainability and reducing the possible deleterious effects to the environment