Cordillera Zealandia: A Mesozoic arc flare-up on the palaeo-Pacific Gondwana Margin.

Two geochemically and temporally distinct components of the Mesozoic Zealandia Cordilleran arc indicate a shift from low to high Sr/Y whole rock ratios at c. 130 Ma. Recent mapping and a reappraisal of published Sr-Nd data combined with new in-situ zircon Hf isotope analyses supports a genetic relationship between the two arc components. A reappraisal of geophysical, geochemical and P-T estimates demonstrates a doubling in thickness of the arc to at least 80 km at c. 130 Ma. Contemporaneously, magmatic addition rates shifted from ~14 km3/my per km of arc to a flare-up involving ~100 km3/my per km of arc. Excursions in Sr-Nd-Hf isotopic ratios of flare-up rocks highlight the importance of crust-dominated sources. This pattern mimics Cordilleran arcs of the Americas and highlights the importance of processes occurring in the upper continental plates of subduction systems that are incompletely reconciled with secular models for continental crustal growth.

Determinação do limiar de anaerobiose de idosos saudáveis: comparação entre diferentes métodos / Determination of anaerobic threshold in healthy elderly people: comparison between different methods

OBJETIVO: Determinar o limiar de anaerobiose (LA) pelo método ventilatório (visual gráfico), pelos modelos matemáticos, Heteroscedástico e Hinkley, aplicados aos conjuntos de dados de freqüência cardíaca (FC), RMS do sinal mioelétrico (Root Mean Square) e VCO2 e comparar o LA obtido pelos três métodos. METODOLOGIA: Foram estudados 9 idosos ativos (61,4±1,8 anos) durante teste de exercício físico dinâmico contínuo do tipo rampa, em cicloergômetro, com incrementos de potência variando de 10 a 15 Watts/min. Foram coletados os dados de FC batimento a batimento, eletromiografia de superfície do músculo vasto lateral e variáveis ventilatórias respiração a respiração. Após a aplicação dos modelos matemáticos e identificados os pontos de quebra de comportamento, foram registrados neste momento os valores de potência, VO2 e FC, comparados e correlacionados aos obtidos pelo método visual gráfico (padrão ouro). Foi utilizado o teste de Friedman para comparações múltiplas e o teste de correlação de Spearman (nível de significância de 5 por cento). RESULTADOS: Não foram encontradas diferenças significantes, em relação ao padrão ouro, entre os valores de potência, VO2 e FC, no momento do LA identificado pelos diferentes modelos. Foram encontradas correlações significantes entre os valores de FC identificados pelos modelos matemáticos entre os valores de VO2 quando identificados pela freqüência cardíaca e de potência somente quando identificada pelo modelo de Hinkley aplicado aos dados de RMS do sinal mioelétrico. CONCLUSÕES: No grupo estudado, os modelos matemáticos mostraram-se adequados na determinação não-invasiva do LA, sendo que ambos ajustaram-se melhor aos dados de FC, seguido pela VCO2 e RMS.

OBJECTIVE: To determine the anaerobic threshold by the graphic visual ventilatory method and the Hinkley and heteroscedastic mathematical models, applied to heart rate, myoelectric root mean square (RMS) signal and VCO2 datasets, and to compare the anaerobic threshold obtained by the three methods. METHOD: Nine active elderly subjects were studied (aged 61.4 ± 1.8 years) during a ramp-load continuous dynamic physical exercise test on a cycle ergometer, with power ranging from 10 to 15 Watts/min. Beat-to-beat heart rate data, electromyographic data from the surface of the vastus lateralis muscle, and breath-to-breath ventilatory data were collected. After applying mathematical models and identifying the behavioral shift points, these power levels, heart rates and VO2 values were noted and these were compared and correlated with those obtained by the graphic visual model (gold standard). The Friedman test for multiple comparisons and the Spearman correlation test were utilized (significance level: 5 percent). RESULTS: No significant differences were found in relation to the gold standard, between the power levels, VO2 values and heart rates at the anaerobic threshold identified by the different models. Significant correlations were found between the heart rates identified by the mathematical models, between the VO2 values identified by the heart rates, and between power rates only when identified by the Hinkley model applied to myoelectric RMS signal data. CONCLUSION: In this study group, the mathematical models were shown to be adequate for non-invasively determining the anaerobic threshold. Both models worked best on the heart rate data, followed by VCO2 and RMS.

Avaliação do controle autonomico da frequencia cardiaca e determinação do limiar de anaerobiose em homens saudaveis e coronariopatias / Evaluation of autonomic heart rate control and determination of anaerobic threshold among healthy and coronary heart-disead men

Avaliar a frequencia cardiaca (FC) e sua variabilidade (VFC) em repouso e durante teste de exercicio fisico dinamico descontinuo tipo degrau (TEFDD-d) em homens saudaveis sedentarios (SS) e infartados ativos (IA); determinar e comparar o limiar de anaerobiose (LA) dos grupos estudados. Metodologia: forma estudados 10 SS (52,5 anos)e 6 IA (59,2 anos) em repouso nas posicoes supino e sentado e em TEFDD-d realizado em cicloergometro, iniciando na potencia com decrescimo de 5 W e acrescimo de 5 W. A Fc (bpm) e os intervalos R-R (iR-R) em ms foram captados batimento a batimento em repouso e em TEFDD-d. Foram calculados os indices RMSSD dos iR_r e a FC media das condicoes de repouso e do trecho estavel de cada nivel de potencia. O LA foi determinado aplicando o modelo semiparametrico aos dados de Fc. Os testes estatisticos utilizados forma Wilcoxon, Mann Whitney e Friedmann, nivel de significancia p < 0,05. Resultados: Em repouso os valores de RMSSD dos iR-R e da FC nao atingiram diferencas estatisticas significativas entre os grupos, ja os SS apresentaram diferencas significativas nos valores de Fc durante a mudanca postural. No nivel potencia do LA ambos os grupos nao apresentaram reducoes significativas da VFC em comparacao com 25 W. Conclusao: nossos resultados sugerem que a atividade fisica regular realizada pelos IA contribuiu para manter a capacidade aerobica como modulacao autonomica da FC similares a dos SS

Comparação dos niveis de potencia e da frequencia cardiaca no limiar de anaerobiose determinado por dois metodos indiretos / Comparasion of power output and heart rate levels in anaerobic threshold determinations by two indirect methods

Analisar se protocolos individualizados do tipo rampa podem ser melhor que os do tipo degrau na determinacao do limiar de anaerobiose (LA). Metodo: 10 homens de meia idade (54+-3,25 anos) saudaveis e sedentarios foram submetidos a 2 testes de exercicio fisico dinamico em cicloergometro de frenagem eletromagnetica (Quinton Corival 400). O primeiro teste foi continuo do tipo rampa (TC-R), com incrementos de 15 W/min, ate a exaustao fisica. O segundo teste foi descontinuo do tipo degrau (TD-D). A frequencia cardiaca (FC) foi captada batimento a batimento e as variaveis ventilatorias e metabolicas, respiracao a respiracao, em tempo real. No TC-R o LA foi determinado pela metodlogia visual (media de 3 observadores) de analise das variaveis ventilatorias e metabolicas. Para determinacao do LA no TD-D foi aplicado o modelo matematico e estatistico semiparametrico ao conjunto de dados da FC. Analise estatistica Teste de wilcoxon para amostras pareadas com nivel de significancia (= 5 por cento). Resultados: foi observada diferenca estatisticamente significativa (p< 0,05) entre os valores de potencia no LA determinando no TC-R (66,5w) e no TD-D (45w). Os valores de FC nao foram estatisticamente diferentes (p > 0,05) entre 2 protocolos. Conclusoes: nossos dados mostram que no protocolo com cargas descontinuas, os voluntarios atingem o LA em niveis de potencia inferiores, porem com resposta do trabalho ardiaco similar a do exercicio realizado com protocolo continuo do tipo rampa. Isso sugere que a carga de trabalho durante o treinamento fisico para esses voluntarios devem ser a do protocolo descontinuo

Effects of aerobic exercise training on heart rate variability during wakefulness and sleep and cardiorespiratory responses of young and middle-aged healthy men.

The purpose of the present study was to evaluate the effects of aerobic physical training (APT) on heart rate variability (HRV) and cardiorespiratory responses at peak condition and ventilatory anaerobic threshold. Ten young (Y: median = 21 years) and seven middle-aged (MA = 53 years) healthy sedentary men were studied. Dynamic exercise tests were performed on a cycloergometer using a continuous ramp protocol (12 to 20 W/min) until exhaustion. A dynamic 24-h electrocardiogram was analyzed by time (TD) (standard deviation of mean R-R intervals) and frequency domain (FD) methods. The power spectral components were expressed as absolute (a) and normalized units (nu) at low (LF) and high (HF) frequencies and as the LF/HF ratio. Control (C) condition: HRV in TD (Y: 108, MA: 96 ms; P<0.05) and FD - LFa, HFa - was significantly higher in young (1030; 2589 ms2/Hz) than in middle-aged men (357; 342 ms2/Hz) only during sleep (P<0.05); post-training effects: resting bradycardia (P<0.05) in the awake condition in both groups; VO2 increased for both groups at anaerobic threshold (P<0.05), and at peak condition only in young men; HRV in TD and FD (a and nu) was not significantly changed by training in either groups. The vagal predominance during sleep is reduced with aging. The resting bradycardia induced by short-term APT in both age groups suggests that this adaptation is much more related to intrinsic alterations in sinus node than in efferent vagal-sympathetic modulation. Furthermore, the greater alterations in VO2 than in HRV may be related to short-term APT.

Effects of aerobic exercise training on heart rate variability during wakefulness and sleep and cardiorespiratory responses of young and middle-aged healthy men

The purpose of the present study was to evaluate the effects of aerobic physical training (APT) on heart rate variability (HRV) and cardiorespiratory responses at peak condition and ventilatory anaerobic threshold. Ten young (Y: median = 21 years) and seven middle-aged (MA = 53 years) healthy sedentary men were studied. Dynamic exercise tests were performed on a cycloergometer using a continuous ramp protocol (12 to 20 W/min) until exhaustion. A dynamic 24-h electrocardiogram was analyzed by time (TD) (standard deviation of mean R-R intervals) and frequency domain (FD) methods. The power spectral components were expressed as absolute (a) and normalized units (nu) at low (LF) and high (HF) frequencies and as the LF/HF ratio. Control (C) condition: HRV in TD (Y: 108, MA: 96 ms; P<0.05) and FD - LFa, HFa - was significantly higher in young (1030; 2589 ms²/Hz) than in middle-aged men (357; 342 ms²/Hz) only during sleep (P<0.05); post-training effects: resting bradycardia (P<0.05) in the awake condition in both groups; VO2 increased for both groups at anaerobic threshold (P<0.05), and at peak condition only in young men; HRV in TD and FD (a and nu) was not significantly changed by training in either groups. The vagal predominance during sleep is reduced with aging. The resting bradycardia induced by short-term APT in both age groups suggests that this adaptation is much more related to intrinsic alterations in sinus node than in efferent vagal-sympathetic modulation. Furthermore, the greater alterations in VO2 than in HRV may be related to short-term APT