Álvaro Reischak de Oliveira

Effects of exercise training on autonomic and myocardial dysfunction in streptozotocin-diabetic rats

Several investigators have demonstrated that diabetes is associated with autonomic and myocardial dysfunction. Exercise training is an efficient non-pharmacological treatment for cardiac and metabolic diseases. The aim of the present study was to investigate the effects of exercise training on hemodynamic and autonomic diabetic dysfunction. After 1 week of diabetes induction (streptozotocin, 50 mg/kg, iv), male Wistar rats (222 +/- 5 g, N = 18) were submitted to exercise training for 10 weeks on a treadmill. Arterial pressure signals were obtained and processed with a data acquisition system. Autonomic function and intrinsic heart rate were studied by injecting methylatropine and propranolol. Left ventricular function was assessed in hearts perfused in vitro by the Langendorff technique. Diabetes (D) bradycardia and hypotension (D: 279 +/- 9 bpm and 91 +/- 4 mmHg vs 315 +/- 11 bpm and 111 +/- 4 mmHg in controls, C) were attenuated by training (TD: 305 +/- 7 bpm and 100 +/- 4 mmHg). Vagal tonus was decreased in the diabetic groups and sympathetic tonus was similar in all animals. Intrinsic heart rate was lower in D (284 +/- 11 bpm) compared to C and TD (390 +/- 8 and 342 +/- 14 bpm, respectively). Peak systolic pressure developed at different pressures was similar for all groups, but +dP/dt max was decreased and -dP/dt max was increased in D. In conclusion, exercise training reversed hypotension and bradycardia and improved myocardial function in diabetic rats. These changes represent an adaptive response to the demands of training, supporting a positive role of physical activity in the management of diabetes.

Radicais livres de oxigênio e exercício: mecanismos de formação e adaptação ao treinamento físico

El interes a cerca de los mecanismos de generacion y adaptacion de radicales libres de oxigeno (RLO) al ejercicio aumento significativamente a partir de la demostracion de su relacion con el consumo de oxigeno. Los RLO son formados por la reduccion incompleta de del oxigeno, generando especies que presentan una alta reactividad para otras biomoleculas, principalmente lipidos y proteinas de las membranas celulares y, asi mismo, el DNA. Las injurias provocadas por el estres oxidativo presentan efectos acumulativos y estan relacionados a una serie de enfermedades, como el cancer, la arteriosclerosis o la diabetes. El ejercicio fisico agudo, en funcion del incremento del consumo de oxigeno promueve un aumento en la formacion de los RLO. No en tanto, el entrenamiento fisico es capaz de generar adaptaciones capaces de mitigar los efectos deletereos provocados por los RLO. Estas adaptaciones estan relacionadas a una serie de sistemas de los cuales los mas importantes son los sistemas enzimaticos, compuestos por la peroxido dismutasa, catalasa y glutation peroxidasa y los sistemas no enzimaticos compuestos por ceruloplasmina, hormonas sexuales, la coenzima Q, acido urico, proteinas de choque termico, y otros. Tales adaptaciones, a pesar de las controversias sobre los mecanismos comprendidos, promueven una mayor resistencia tisular a los desafios oxidativos, como son aquellos proporcionados por el ejercicio fisico de alta intensidad y de larga duracion. Las tecnicas de evaluacion del estres oxidativo, la mayoria de las veces, no son capaces de detectar injurias en ejercicios de corta duracion. De esta forma, los esfuerzos estan siendo realizados por largos periodos de tiempo o realizados hasta la extenuacion. Nuevos marcadores de lesion por accion de los RLO estan siendo descubiertos y nuevas tecnicas para su determinacion estan siendo creadas. El objetivo de este trabajo es discutir los mecanismos de formacion de los RLO y de adaptacion al estres oxidativo cronico provocado por el entrenamiento fisico.

Effective force and economy of triathletes and cyclists.

The effective force applied on the crank, the index of pedalling effectiveness, and the economy of movement at 60, 75, 90, and 105 rev/min cadences were examined in nine cyclists and eight triathletes. Tests were performed on two days. Maximal oxygen uptake was measured and the second ventilatory threshold was estimated on day 1 using a stationary bicycle. On day 2, the four different cadences were tested at about 5% below the second ventilatory threshold. A strain gauge instrumented clip-less pedal mounted on the bicycle enabled us to measure the normal and tangential forces exerted on the pedal, while the pedal and crank angles were monitored with the aid of a video system. Based on this information, the effective force and the index of pedalling effectiveness were calculated. Cyclists produced significantly more effective force and a higher index of pedalling effectiveness at 60 and 75 rev/min and were significantly more economic at all cadences than triathletes. The significant and positive correlation between effective force and economy at all cadences suggests that improvement of the effective force would reflect on economy.

Cocontraction and economy of triathletes and cyclists at different cadences during cycling motion

The purpose of this study was to compare the cycling technique of triathletes and cyclists on the basis of the cocontraction of selected muscles of the lower limbs and economy at different cadences. The economy (EC) and percent cocontraction from nine triathletes and eight cyclists were compared at 60, 75, 90 and 105 rpm cadences. Tests were performed on two separate days. The maximal oxygen uptake was measured and the second ventilatory threshold (VO(2VT)) was estimated on the first day using a stationary bicycle. On the second day the four different cadences were tested at approximately 5% below the VO(2VT). The EMG activity of the rectus femoris (RF), biceps femoris (BF) and vastus lateralis (VL) was recorded and the EMG signal was normalized using the 60 rpm dynamic contraction. The percent cocontractions were calculated from RF/BF and VL/BF muscles. The EC was also calculated. The results showed that cyclists were significantly more economic, indicating that they exerted more power with less VO(2), and presented significantly lower percent cocontraction than triathletes (p<0.05). Thus, the results suggest that the cyclists had a better technique than the triathletes. The simultaneous use of the percent cocontraction and economy seems to be a good performance indicator for cyclists and triathletes.

Effect of biological maturation on maximal oxygen uptake and ventilatory thresholds in soccer players: An allometric approach

Abstract In this study, we investigated the effect of biological maturation on maximal oxygen uptake ([Vdot]O2max) and ventilatory thresholds (VT1 and VT2) in 110 young soccer players separated into pubescent and post-pubescent groups.. Maximal oxygen uptake and [Vdot]O2 corresponding to VT1 and VT2 were expressed as absolute values, ratio standards, theoretical exponents, and experimentally observed exponents. Absolute [Vdot]O2 (ml · min−1) was different between groups for VT1, VT2, and [Vdot]O2max. Ratio standards (ml · kg−1 · min−1) were not significantly different between groups for VT1, VT2, and [Vdot]O2max. Theoretical exponents (ml · kg−0.67 · min−1 and ml · kg−0.75 · min−1) were not properly adjusted for the body mass effects on VT1, VT2, and [Vdot]O2max. When the data were correctly adjusted using experimentally observed exponents, VT1 (ml · kg−0.94 · min−1) and VT2 (ml · kg−0.95 · min−1) were not different between groups. The experimentally observed exponent for [Vdot]O2max (ml · kg−0.90 · min−1) was different between groups (P = 0.048); however, this difference could not be attributed to biological maturation. In conclusion, biological maturation had no effect on VT1, VT2 or [Vdot]O2max when the effect of body mass was adjusted by experimentally observed exponents. Thus, when evaluating the physiological performance of young soccer players, allometric scaling needs to be taken into account instead of using theoretical approaches.

O estresse oxidativo e o exercício físico em indivíduos HIV positivo

Human immunodeficiency virus (HIV) infection is characterized by functional and structural changes related to the immunological system. Moreover, increase in oxidative stress (OS) in HIV patients, characterized by a reduction in the glutathione (GSH) levels, increases in glutathione disulfide (GSSG), in the ratio GSSG/GSH and in lipid peroxidation, as well as a reduction in antioxidant enzymes - catalase, superoxid dismutase (SOD) and gluthatione peroxidase (GPx) - is a consequence of the evolution in HIV-infected patients. Higher levels of antioxidant activity are necessary to maintain the immunological system cells redox balance and preserve their function. In an antioxidant depleted state, there is a reduction in the immunological response and an increase in HIV replication. The use of highly active antiretroviral therapy (HAART) has improved the clinical evolution of these patients. However, some patients remain showing higher OS and other effects of HAART, such as changes in lipidic and muscle metabolism. Exercise training has been used as a non pharmacological treatment in HIV-infected patients to promote improvements in anthropometrics, aerobic, muscle and psychological outcomes; however, there are insufficient data about the effects of exercise training in OS. This review analyzes the topics related to the oxidative stress in HIV-infected patients and the possible benefits of the physical exercise in the antioxidant capacity. Physical training is a complementary procedure for the patients, with or without use of the HAART, since it improves the cardiorespiratory, muscle, anthropometrics and psychological performance without inducing immunodepression. In relation to oxidative stress, it is inferred, from the data obtained in non-HIV individuals, that the physical training could promote adaptations that minimize the deleterious effect induced by OS through improvements in the activity of the enzymatic and non-enzymatic antioxidant defenses.

Efeitos do consumo prévio de carboidratos sobre a resposta glicêmica e desempenho

Bases and Objective: Nutrition is an important tool for the sport practice. Among the nutrients, the carbohydrates are one of the most important. In that way the aim of this study was analyze the influence of glycaemic response on performance of healthy subjects, after intake of different carbohydrate solutions. Methods: Ten healthy male subjects, 23 ± 2.1 years old, were asked to answer a three days nutritional and physical activity recordatory. Anthropometric data were collected and a progressive test in cycle ergometer was performed to measure the maximal oxygen uptake and ventilatory thresholds. Each subject performed three submaximal tests at the intensity of second ventilatory threshold. Thirty minutes before each submaximal test, 250 ml of each drink: maltodextrin (Malto), glucose (Glicose) plus sport drink or dietetic juice (Placebo) was ingested. Venous blood was collected to determine the glycaemic index and lactate. Results and Conclusion: There was a significant increase after 30 minutes when the subjects ingested maltodextrin solution (87.4 ± 11.2 to 116.9 ± 19.6 ml.dl -1). After 15 minutes of exercise, there was a decrease in the glycaemia after the consumption of Malto (116.9 ± 19.6 to 77.6 ± 14.5 ml.dl -1) and Glicose (113.2 ± 23.5 to 81.8 ± 13.1 ml.dl -1) plus sport drink solutions when compared with Placebo solution. The glucose plus sport drink solution induced a significant increase in the heart rate during exercise (167.7 ± 14.2 and 177.1 ± 10.4 bpm). The consumption of different carbohydrate solutions with high glycaemic index before exercise was not capable to change the performance of the volunteers. However it induced changes in the glycaemia and heart rate during exercise. Thus the oscillations on glycaemia during exercise may affect negatively the long distance performance, this fact was not verified in our study.INTRODUCAO E OBJETIVO: A nutricao e uma importante ferramenta dentro da pratica desportiva. Dentre os nutrientes, os carboidratos destacam-se como uma fonte energetica importante. Dessa forma, o objetivo deste trabalho foi verificar a influencia da resposta glicemica no desempenho de individuos saudaveis, apos a ingestao de bebidas com diferentes tipos de carboidratos. METODOS: Foram avaliados 10 voluntarios, do sexo masculino, com idade de 23 ± 2,1 anos. Os voluntarios preencheram recordatorio alimentar de tres dias e de atividade fisica. Foram realizadas avaliacoes antropometricas e teste de cargas progressivas em cicloergometro para determinacao do consumo maximo de oxigenio e limiares ventilatorios. Cada voluntario realizou tres testes submaximos na intensidade do 2o limiar ventilatorio. Trinta minutos antes de cada teste submaximo, foram ingeridos 250ml de uma das bebidas compostas por: maltodextrina (malto), glicose (glicose), ou suco dietetico (placebo). Foram realizadas puncoes de sangue capilar para determinacao dos niveis glicemicos e lactato sanguineo. RESULTADOS E CONCLUSAO: Houve aumento significativo na glicemia apos 30 minutos do consumo da bebida malto (87,4 ± 11,2 para 116,9 ± 19,6ml.dl1). Aos 15 minutos do exercicio, houve diminuicao nos niveis glicemicos apos o consumo das bebidas malto (116,9 ± 19,6 para 77,6 ± 14,5ml.dl1) e glicose (113,2 ± 23,5 para 81,8 ± 13,1ml.dl1) em comparacao com o placebo. A ingestao da bebida glicose provocou aumento significativo na frequencia cardiaca durante o exercicio (167,7 ± 14,2 e 177,1 ± 10,4bpm). O consumo de bebidas com diferentes tipos de carboidratos e de alto indice glicemico antes do exercicio nao foi capaz de alterar o desempenho dos voluntarios; entretanto, ocasionou alteracoes na glicemia e na frequencia cardiaca durante o exercicio. Embora se especule que oscilacoes na glicemia durante o exercicio possam prejudicar o desempenho em exercicios de longa duracao, esse fato nao foi verificado em nosso estudo.

Níveis de beta-endorfina em resposta ao exercício e no sobretreinamento

O sobretreinamento (ST) e um fenomeno esportivo complexo e multifatorial; e atualmente nao existe nenhum marcador independente que possa diagnostica-lo. Interessantemente, alguns sintomas do ST apresentam relacao com os efeitos da b-endorfina (b-end1-31). Alguns de seus efeitos sao importantes para o treinamento, como analgesia, maior tolerância ao lactato e euforia do exercicio. Esses efeitos podem ser revertidos por destreinamento ou por ST, ocasionando diminuicao no desempenho, reducao da tolerância a carga e depressao. O exercicio fisico e o principal estimulo da b-end1-31, pois sua secrecao e volume/intensidade dependente, tanto para exercicios aerobios quanto anaerobios. No entanto, o treinamento excessivo pode diminuir suas concentracoes, alterando assim seus efeitos beneficos para o treinamento. Portanto, a b-end1-31 poderia ser utilizada como um marcador adicional de ST, principalmente porque seus efeitos apresentam extensa relacao com os sintomas do ST.

Oxygen free radicals and exercise: mechanisms of synthesis and adaptation to the physical training *

El interes a cerca de los mecanismos de generacion y adaptacion de radicales libres de oxigeno (RLO) al ejercicio aumento significativamente a partir de la demostracion de su relacion con el consumo de oxigeno. Los RLO son formados por la reduccion incompleta de del oxigeno, generando especies que presentan una alta reactividad para otras biomoleculas, principalmente lipidos y proteinas de las membranas celulares y, asi mismo, el DNA. Las injurias provocadas por el estres oxidativo presentan efectos acumulativos y estan relacionados a una serie de enfermedades, como el cancer, la arteriosclerosis o la diabetes. El ejercicio fisico agudo, en funcion del incremento del consumo de oxigeno promueve un aumento en la formacion de los RLO. No en tanto, el entrenamiento fisico es capaz de generar adaptaciones capaces de mitigar los efectos deletereos provocados por los RLO. Estas adaptaciones estan relacionadas a una serie de sistemas de los cuales los mas importantes son los sistemas enzimaticos, compuestos por la peroxido dismutasa, catalasa y glutation peroxidasa y los sistemas no enzimaticos compuestos por ceruloplasmina, hormonas sexuales, la coenzima Q, acido urico, proteinas de choque termico, y otros. Tales adaptaciones, a pesar de las controversias sobre los mecanismos comprendidos, promueven una mayor resistencia tisular a los desafios oxidativos, como son aquellos proporcionados por el ejercicio fisico de alta intensidad y de larga duracion. Las tecnicas de evaluacion del estres oxidativo, la mayoria de las veces, no son capaces de detectar injurias en ejercicios de corta duracion. De esta forma, los esfuerzos estan siendo realizados por largos periodos de tiempo o realizados hasta la extenuacion. Nuevos marcadores de lesion por accion de los RLO estan siendo descubiertos y nuevas tecnicas para su determinacion estan siendo creadas. El objetivo de este trabajo es discutir los mecanismos de formacion de los RLO y de adaptacion al estres oxidativo cronico provocado por el entrenamiento fisico.

Comparação de respostas fisiológicas absolutas e relativas entre ciclistas e triatletas

BASES AND OBJECTIVE: The ventilatory threshold (VT) has been used as an indicator of the lactate threshold and used as a reference for endurance training. The purpose of this study was to compare the maximal oxygen uptake (VO2MAX) and the VT during a bicycle ergometer test between cyclists and triathletes. METHODS: VO2MAX was determined by open-circuit spirometry in 12 cyclists and 13 triathletes. The ventilatory equivalent for oxygen consumption, the ventilatory equivalent for carbon dioxide production, partial pressure of oxygen and the partial pressure of carbon dioxide (PETCO2) were plotted in function of the workload. The criterion to determinate the VT was when the ventilatories equivalents increased with a concomitant reduction in the PETCO2. RESULTS AND CONCLUSIONS: There was difference (p < 0.05) for the VO2MAX (57.72 ± 3.92 and 49.47 ± 5.96 kg·ml-1·min-1), VO2 at VT (46,91 ± 5,96 and 42,16 ± 4,97 kg·ml-1·min-1), and maximal heart rate (FCMAX) (188.83 ± 12.89 and 174.61 ± 13.79 bpm) between cyclists and triathletes, respectively. Therefore, there was no difference for the %VO2MAX (81.42 ± 7.61 and 85.18 ± 6.87%), the heart rate at VT (168.5 ± 13.79 and 157.23 ± 16.15 bpm), as well as for the %FCMAX at which VT occurred in these athletes (89.23 ± 6.98 and 90.05 ± 1.04%). In conclusion, cyclists and triathletes showed different aerobic capacity because they had unlike physiological adaptations.