16 research outputs found

    Possible effect of the supplementation of branched chain aminoacids, aspartate and asparagine on anaerobic threshold

    Get PDF
    Recently, the concept of "Anaerobic Threshold” has been widely criticized. The most important critiques are about the mccanisms involved in the concentration of blood lactate increment, mainly muscular hipoxia, and about the supposed aclion-and-reaction relation between the metabolic and ventilatory threshold. In spite of the criticisms the Anaerobic Threshold has been found to have wide aplicabilities, thus, many researches had been done in order to facilitate its measurement, not in a invasive way, but with ventilator)' parameters and using the heart rate deflection curve. Recently, the amount of people who practices motor activities using aminoacids has been widely spread, and this fact became an issue of discussion to many researches. It was proposed that suplemcntation with branched chain aminoacids, aspartate and asparagine results in increased resistance to prolonged exercise, due to an increase of the muscle glycogen content and oxaloacetatc synthesis to sustain the Krebs cycle activity and oxidative metabolism. Thus, glucose transport to inner muscle cell decreases, delaying the depletion of muscle glycogen content and metabolic acidosis, the evident causes of fatigue. In consequence, the oxidation of fatty acids during continuous and moderate exercise increases, delaying the lactate accumulation in muscles and blood. This would delay the metabolic stimulus for the H C 03‘ buffering process and consequent C 02 ventilator)' compensation, and may dissociate the metabolic threshold from ventilator)' threshold. This dissociation of thresholds would reinforce critiques about the concept of Anaerobic Threshold and it would, other, also, make difficult its identification through methods such as the heart rale deflection curveRecentemente o conceito “Limiar Anacróbio” tem sido muito criticado. As principais críticas repousam sobre os mecanismos considerados para o aumento da concentração de laclato sangüíneo, hipóxia muscular principalmente, c sobre a suposta relação de causa-c-cfeito entre os limiares mctabólico e ventilatório. Apesar de criticado, o conceito Limiar Anacróbio encontrou muitas aplicações, c por esta razão, vários estudos foram realizados para facilitar a sua determinação não invasivamente, a partir de parâmetros ventilatórios c da dcílexão da curva de freqüência cardíaca. Recentemente o uso de aminoácidos tem se difundido largamente entre os praticantes de atividades motoras, tornando-se objeto de estudo para vários pesquisadores. Foi proposto que a suplementação de aminoácidos de cadeia ramificada, aspartalo c asparagina promove aumento da resistência ao esforço físico prolongado, em decorrência do aumento do conteúdo de glicogênio muscular c síntese de oxaloacetato para manutenção da atividade do ciclo de Krebs c do própio metabolismo oxidativo. Com isto o transporte de glicose para o interior da célula muscular diminui, retardando a dcplcção de glicogênio muscular e a acidose metabólica, causas evidentes de fadiga. Em conseqüência, a oxidação de AGLs durante o exercício contínuo moderado aumenta, retardando o acúmulo de lactato sangüíneo c muscular. Isto retardaria o estímulo mctabólico para o processo de tamponamento pelo H C 03' c a conseqüente compensação venlilalória para C 0 2, podendo dissociar os limiares mctabólico c ventilatório. A dissociação dos limiares reforçaria as críticas sobre o conceito Limiar Anacróbio c poderia, inclusive, prejudicar a sua identificação através de outros métodos, como por exemplo, a dcílexão da curva de freqüência cardíac

    Substrate oxidation pattern during cardiorespiratory exercise prescribed by different methods

    Get PDF
    The American College of Sports Medicine recommends intensities of between 55% and 70% heart rate reserve (HRR) for prescription of endurance exercise (EEx) aiming the body composition change. However, several studies have found that the maximal lipid oxidation (LIPox) is directly related to anaerobic threshold (AT) and occurs at intensities around 60% maximal heart rate (HRmax) and 55% maximal oxygen uptake (VO2max). The aim of this study was to compare the substrate oxidation rates from EEx prescribed by AT (direct method, mDR) and HRR (indirect method, mIND). Seven untrained healthy male subjects performed 60min of EEx at AT and 55% HRR for substrates oxidation rates by indirect calorimetry, after 8-h fasting followed by maltodextrin intake (2g/kg, 6% solution) 30-min before the onset of exercise. Our results showed dissimilar patterns of LIPox (0,23 ± 0,01 e 0,10 ± 0,01 g/min; mDR e mIND, respectively; p < 0,05); as a consequence, the relative contribution of LIP oxidation to total energy expenditure was 1.8 times higher in AT than in HRR trial (25,9 ± 0,9 e 14,6 ± 1,0 %; mDR e mIND, respectively; p < 0,05). Despite HRR underestimate the LIPox, this method indicated for applicability approaching the scientifically recommended criteria, which for strength indication in field situations may result in lower margin of error.O Colégio Americano de Medicina Esportiva recomenda intensidades de 55 a 70% da freqüência cardíaca de reserva (FCrs) para prescrição do exercício de resistência cardiorespiratória (ECr) objetivando a alteração da composição corporal. Entretanto, vários estudos verificaram que a oxidação de lipídeos (LIPox) máxima está diretamente relacionada ao primeiro limiar anaeróbio (LAn1) e ocorre em intensidades por volta de 60% da frequência cardíaca máxima (FCmax) e 55% do consumo máximo de oxigênio (VO2 max). O objetivo do presente estudo foi verificar e comparar as taxas de oxidação de substratos resultantes do ECr prescrito pelos métodos dos limiares anaeróbios ventilatórios (método “direto”, mDR) e da reserva da frequência cardíaca (método “indireto”, mIND). Sete indivíduos ativos não treinados foram submetidos a 60min de ECr nas intensidades do LAn1 e 55% da FCrs para determinação das taxas de oxidação de lipídeos (LIP) e carboidratos (CHO) por calorimetria indireta, após jejum noturno de 8h seguido de ingestão de maltodextrina (2g/kg, solução a 6%) 30min antes do início da atividade. Nossos resultados demonstraram que os métodos de prescrição promoveram padrões distintos de LIPox (0,23 ± 0,01 e 0,10 ± 0,01 g/min; mDR e mIND, respectivamente; p < 0,05); como conseqüência, a contribuição relativa de LIP para o dispêndio calórico durante a sessão mDR foi aproximadamente 1,8 vezes maior em comparação a mIND (25,9 ± 0,9 e 14,6 ± 1,0 %; mDR e mIND, respectivamente; p < 0,05). Apesar da prescrição por método da reserva da frequência cardíaca subestimar a LIPox, este método indicou para uma aplicabilidade que se aproxima dos critérios cientificamente preconizados, o que para uma indicação de intensidade em situações de campo poderá acarretar em menor margem de erro

    Influencia da suplementação de Aspartato e Asparagina sobre a associação entre os limiares metabolicos e ventilatorios e sobre a taxa de oxidação de nutrientes durante o exercicio

    No full text
    Orientador: Antonio Herbert Lancha JuniorTese (doutorado) - Universidade Estadual de Campinas, Instituto de BiologiaResumo: o "Limiar Anaeróbio" (LAn) apresenta-se, nas últimas décadas, como um dos CONCEITOS mais polêmicos e controversos dentro da história recente da fisiologia do esforço. O LAn, definido como a intensidade crítica para a atividade oxidativa máxima e manutenção do exercício cardio-respiratório, baseia-se na relação causaefeito entre limiares distintos, metabólico (LM) e ventilatório (LV), resultante do aumento da atividade anaeróbia. No entanto, ainda existem dúvidas relacionadas aos mecanismos que explicam o acúmulo sanguíneo e muscular de lactato e relatos de dissociação dos limiares em determinadas situações. Os objetivos deste trabalho foram avaliar a influência da suplementação de aspartato e asparagina (AA) sobre a associação entre LMs e L Vs (experimento 1, n = 6) e a taxa de oxidação de substratos (experimento 2, n = 18). Os sujeitos de ambos experimentos foram suplementados, durante 7 dias em cada tratamento, com 150mg/kg/dia de aspartato + 150mglkg/dia de asparagina (AA) e 300mglkgldia de lactose (PLC), em protocolo duplo-cego. No experimento 1, os sujeitos realizaram três testes descontínuos progressivos (TDPs) para a determinação dos LMs e LVs (testes BASAL, sem suplementação; AA e PLC). No experimento 2, os sujeitos foram divididos em três grupos e submetidos a 28 minutos de exercício contínuo (28M), após a determinação dos LMs. As intensidades utilizadas durante os 28M em cada grupo, correspondentes à carga (watts) do LM2 foram: 75% (SUB; n = 6), 100% (SPI; n = 6) e 115% (SPII; n = 6). O dispêndio de energia e as taxas de oxidação de substratos foram determinados por calorimetria indireta, somente para o grupo SUB, aos 8, 13, 18, 23 e 28 minutos (períodos) de exercício. Não foram observadas diferenças significativas entre as intensidades relativas de exercício correspondentes aos LMs e L Vs durante os testes descontínuos progressivos com suplementação de AA ou PLC, expressas a partir de diferentes parâmetros (CARGA, V02, FC e LA). As relações LMlILV1 e LM2ILV2 durante os testes com suplementação de AA ou PLC foram mantidas e semelhantes entre os grupos (experimento 1). Não foram observadas diferenças significativas para concentrações sanguíneas de lactato entre os tratamentos em nenhum dos grupos (SUB, SPI e SPII) ao longo dos 28M. A suplementação de AA, no entanto, promoveu alterações nas taxas de oxidação de substratos - aumentando a energia derivada de carboidratos em 2,284% (97,531 :I: 4,241% para 99,759 :I: 0,720%; P < 0,05) e diminuindo a energia derivada de lipídeos em -90,239% (2,469:1: 4,241% para 0,241 :I: 0,720%; P < 0,05), durante os 28Ms do grupo sua (experimento 2). Sugerimos um modelo hipotético que considera os aumentos da relação [piruvato]/[Iactato] e da atividade da PDH, determinados pela suplementação de AA, via LMA, para justificar a menor oxidação de lipídeos observada durante os 28M realizados com 75% da intensidade correspondente ao LM2Abstract: The anaerobic threshold (A T), defined as the levei of work or the O2 consumption (V02) just below that at which metabolic acidosis and associated changes in gas exchange occur, is composed of a supposed cause-effect association of 2 individual thresholds - lactate or metabolic (MT) and ventilatory (VT). However the proposed mechanisms to explain musclelblood lactate accumulation and cause-effect association of MTNT has been rejected. The aim of this study was to verify the influence of aspartate and asparagine (AA) supplementation on MTNT association (experiment 1; n = 6) and substrate oxidation rates (experiment 2; n = 18). The subjects of both experiments were supplemented with 300mg . kg -1 . day -1 of amino acids (150mg aspartate + 150mg asparagine, AA treatment) and 300mg . kg -1 . day-1 of lactose (PLC treatment) in double blind-crossover fashion prior DIT tests, for 7 days. In the experiment 1, the subjects performed three discontinuous incremental tests (DITs) on cycle ergometer for detection of the MTs, VTs (BASAL, AA and PLC tests). In the experiment 2, the subjects were randomly placed into three groups and submitted to 28-min cycling rides (28R) at the 75% (group SUB), 100% (group SPI) or 115% (group SPII) of the AT 11 workload (watts). The energy expenditure and substrate oxidation rates for group SUB were calculated from respiratory measurements collected at 8, 13, 18, 23 and 28 min from 28R. No significant differences were observed in absolute or relative values for WR, VENT, HR and LA for the comparisons between MTINTI and MTIINTII relationships among test groups (experiment 1). No significant differences were observed for LA during 28R between treatments for the same group. The AA treatment increases the rei ative CHO energy expenditure in 2.284 % (97.531 :!: 4.241% to 99.759 :!: 0.720%; P < .05%) and decreases the relative LlP energy expenditure in -90.239% (2.469:!:: 4.241% to 0.241 : 0.720%, P < .05%) in comparison with PLC treatment, during the SUB28R (experiment 2). We suggest a hypothetic model that involves the increases of [pyruvate]/[Iactate] ratio and PDH activity, promoted for the AA supplementation, to justify the lower LlP oxidation rate during the 28R performed below anaerobic threshold intensityDoutoradoBioquimicaDoutor em Biologia Funcional e Molecula

    A note on motor skill acquisition in mild and moderate Down syndrome individuals

    Get PDF
    Abstract This study investigated the acquisition of a serial motor skill in individuals with Down syndrome with two levels of handicap, mild group (mean age = 14.5 years, SD = 2.3, 7 individuals) and moderate group (mean age = 15.2 years, SD = 3.2, 7 individuals). The task involved single-arm sequential movements to five. The measures to access performance were overall sequence error, reaction time, and total movement time. To evaluate action program, formation variability of sequencing and relative timing variability were considered. Although there was no clear practice effect, the results showed that the level of handicap led to different strategies to plan and control the actions. The moderate group presented a less stable action program expressed in the variability in sequencing and timing. Their longer reaction times also suggest a heavy demand on central processing in accord with the one-target advantage hypothesis and also due to memory deficits to select and plan movements

    Creatine supplementation spares muscle glycogen during high intensity intermittent exercise in rats

    No full text
    Background: The effects of creatine (CR) supplementation on glycogen content are still debatable. Thus, due to the current lack of clarity, we investigated the effects of CR supplementation on muscle glycogen content after high intensity intermittent exercise in rats. Methods: First, the animals were submitted to a high intensity intermittent maximal swimming exercise protocol to ensure that CR-supplementation was able to delay fatigue ( experiment 1). Then, the CR-mediated glycogen sparing effect was examined using a high intensity intermittent sub-maximal exercise test ( fixed number of bouts; six bouts of 30-second duration interspersed by two-minute rest interval) ( experiment 2). For both experiments, male Wistar rats were given either CR supplementation or placebo (Pl) for 5 days. Results: As expected, CR-supplemented animals were able to exercise for a significant higher number of bouts than Pl. Experiment 2 revealed a higher gastrocnemius glycogen content for the CR vs. the Pl group (33.59%). Additionally, CR animals presented lower blood lactate concentrations throughout the intermittent exercise bouts compared to Pl. No difference was found between groups in soleus glycogen content. Conclusion: The major finding of this study is that CR supplementation was able to spare muscle glycogen during a high intensity intermittent exercise in rats.Fundacao de Amparo a Pesquisa do Estado de Sao Paulo - FAPESP[99/07678-3

    Effect of Menstrual Cycle Phase on Fuel Oxidation Post HIT in Women Reproductive Age: A Pilot Study

    No full text
    Women of childbearing age have variations in substrate oxidation rates that can lead to overweight, type II diabetes, and other conditions that may be associated with metabolic inflexibility and the variations in estrogen concentrations observed during the monthly ovarian cycle. Purpose: This study aimed to verify and compare the influence of eight treadmill high-intensity interval training (HIT) sessions on carbohydrate and lipid oxidation rates (CHOox and LIPox, respectively) and intensities of ventilatory anaerobic thresholds (VATs) of women in different phases of the monthly ovarian cycle. Methods: Eleven irregularly active women performed incremental treadmill exercise testing followed by submaximal work-rate running for 45 min to determine VATs, VO2peak, peak velocity (Vpeak), and substrate oxidation rates, before and after a training period, in different phases of their monthly ovarian cycle (follicular phase group, FL, n = 6; luteal phase group, LT, n = 5). The training period consisted of eight HIT sessions, composed each one of eight sets of 60 s running at 100%Vpeak interspersed by 75 s recovery every 48 h. Results: Our results showed no significant differences in VATs intensities between groups. The comparison between groups showed significant differences in relative energy derived from CHO pre- and post-training of −61.42% and −59.26%, respectively, and LIP pre- and post-training of 27.46% and 34.41%, respectively. The relative energy derived from CHO after the training period was 18.89% and 25.50% higher for FL and LT, respectively; consequently, the relative energy derived from LIPox after the training period was 8,45% and 3.46% lower for FL and LT, respectively. Over the training period, Vpeak was ~13.5 km/h, which produced the relative intensities of ~89%VO2peak e ~93%HRpeak for both groups. Conclusion: The monthly ovarian cycle phases promote significant changes in substrate oxidation rates leading to a decrease in CHOox. High-intensity interval training can minimize the differences observed and constitute an alternative intervention

    Tracing thermal history of the central Patagonian Andes withdetrital multi-dating of foreland basin deposits

    No full text
    National audienceDetrital thermochronology in wide foreland basins documents erosion ofdiverse sediment source areas along an adjacent orogen through time. This studypresents new detrital apatite thermochronology data (U-Pb and fission tracks) from thewhole central Patagonian foreland (44°S – 48 °S) that identify at first a persistentvolcanic input from Oligocene to late Miocene. The apatite U-Pb dating was effective todiscriminate AFT ages related to either the exhumation of the source or the volcanicinput, which can easily overtake the exhumation signal along the Patagonian Andes.Lag time, calculated from the youngest AFT component (~30 Ma) and stratigraphicallyconstrained with new zircon U-Pb ages, indicates that the entire central PatagonianCordillera was probably in steady-state erosion at ca. 30 Ma until the resumption ofshortening during the late Neogene. Furthermore, these new detritalthermochronological data emphasize a signal of low rate post-orogenic erosionalprocesses (0.1 – 0.4 km/Ma) corresponding to a significant unroofing of 2 – 4 kmbetween the Oligocene and the late Miocene; a period characterized by a relativetectonic quiescence, subsequent to the late Early Cretaceous – middle Eocene intervalin which significant deformation took place.This study identifies sediment contribution from different source areas to thecentral Patagonian foreland and constrains the timing and rates of the post-orogeniccooling along the central Patagonian Andes, thus defining great sediment sourcing fromthe Andes in spite of tectonic quiescence

    Tracing thermal history of the central Patagonian Andes withdetrital multi-dating of foreland basin deposits

    No full text
    National audienceDetrital thermochronology in wide foreland basins documents erosion ofdiverse sediment source areas along an adjacent orogen through time. This studypresents new detrital apatite thermochronology data (U-Pb and fission tracks) from thewhole central Patagonian foreland (44°S – 48 °S) that identify at first a persistentvolcanic input from Oligocene to late Miocene. The apatite U-Pb dating was effective todiscriminate AFT ages related to either the exhumation of the source or the volcanicinput, which can easily overtake the exhumation signal along the Patagonian Andes.Lag time, calculated from the youngest AFT component (~30 Ma) and stratigraphicallyconstrained with new zircon U-Pb ages, indicates that the entire central PatagonianCordillera was probably in steady-state erosion at ca. 30 Ma until the resumption ofshortening during the late Neogene. Furthermore, these new detritalthermochronological data emphasize a signal of low rate post-orogenic erosionalprocesses (0.1 – 0.4 km/Ma) corresponding to a significant unroofing of 2 – 4 kmbetween the Oligocene and the late Miocene; a period characterized by a relativetectonic quiescence, subsequent to the late Early Cretaceous – middle Eocene intervalin which significant deformation took place.This study identifies sediment contribution from different source areas to thecentral Patagonian foreland and constrains the timing and rates of the post-orogeniccooling along the central Patagonian Andes, thus defining great sediment sourcing fromthe Andes in spite of tectonic quiescence

    DESEMPENHO DE INDIVÍDUOS COM DERMOPIGMENTAÇÃO SUBMETIDOS À PRÁTICA DE EXERCÍCIO FÍSICO

    Get PDF
    RESUMO Introdução: A duração e a intensidade dos exercícios provocam diferentes alterações no sistema imunológico, dentre elas a diminuição das respostas imunes, acarretando queda no desempenho físico. Sabe-se também que a dermopigmentação pode colaborar com tais alterações no comportamento deste sistema. Objetivo: Avaliar os efeitos da dermopigmentação sobre o desempenho no exercício físico. Método: Neste ensaio clínico participaram 12 sujeitos, dentre eles seis com dermopigmentação, idade (anos), peso (Kg), estatura (cm) e gordura corporal (%) de 16,5 ± 1,16; 68,10 ± 6,83; 176,29 ± 7,71; 11,49 ± 0,58 respectivamente, divididos em dois grupos, sendo submetidos a teste de esforço máximo com intensidade progressiva em esteira ergométrica para determinação do consumo máximo de oxigênio (VO2máx), limiares anaeróbios (LAns) e economia de corrida (EC 14km/h %), sendo realizadas coletas de lactato pré e 5 minutos pós-teste. Os dados foram tratados por "teste t" para variáveis independentes, tendo como nível de significância adotado α < 0,05. Resultados: Foram observadas diferenças significativas entre os grupos em relação à concentração sanguínea de lactato (CSL) pré-teste (4,6 ± 0,11 e 3,23 ± 0,88 para dermopigmentados e não dermopigmentados, respectivamente; p < 0,05) e 5 minutos pós-teste (5,65 ± 0,49 e 13,13 ± 2,20 para dermopigmentados e não dermopigmentados, respectivamente; p < 0,05). O tempo de teste também foi significativamente superior para o grupo não dermopigmentado em comparação ao grupo com dermopigmentação (8 min 47 seg ± 0,08 e 7 min 39 seg ± 0,03 respectivamente; p < 0,05), bem como análise do WURSS-21 (3,33 ± 3,14 e 2,00 ± 1,09, respectivamente; p > 0,05). Em relação às demais variáveis dependentes (VO2máx, segundo limiar anaeróbio e economia de corrida) não foram encontradas diferenças estatisticamente significativas. Conclusão: A dermopigmentação produziu rendimento inferior no teste de esforço máximo, influenciando o desempenho no exercício físico
    corecore