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

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

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

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

Incidence of injuries to the lower limbs joints in kung fu athletes

Background and Study Aim: This study evaluated the influence of competitive practice and training aspects on incidence of injuries to the lower limbs joints in formalized (taolu) and combat (sanshou) kung fu athletes. Material/Methods: One hundred and twenty-seven kung fu athletes (taolu, n=82; sanshou, n=45) were interviewed about kung fu practice (practice time, competition time and competition level), training volume (days of training per week and hours per training session) and injury profiles (incidence and type). Continuous variables were compared by non-parametric Kolmogorov-Smirnov test (disciplines and competition levels as grouping variables). The effects of categorical variables (kung fu practice) on injury profiles were analyzed using the Pearson`s chi-square test. The level of significance was set at p<0.05. Results: Our data exhibited large frequency of injury reports (70.1%) and significantly differences on injury profiles between disciplines and competition levels. Taolu athletes, despite the lower practice/competition time (-51.5 and -41.8%, respectively), presented frequency of injury reports twofold greater, longer daily training volume (23.3%) and higher incidence of lower limbs joints injuries than sanshou athletes (35.4% and 11.8%, respectively). Conclusions: Our results suggest a link between injury profiles (incidence and type) and specific characteristics of kung fu disciplines

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

Abstract 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.</p

A nova Lei do Mandado de Segurança no Direito Tributário

Divulgação dos SUMÁRIOS das obras recentemente incorporadas ao acervo da Biblioteca Ministro Oscar Saraiva do STJ. Em respeito à Lei de Direitos Autorais, não disponibilizamos a obra na íntegra. 336.2:347.919.6(81) N935l STJ0008777

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

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

Abstract 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