Efectos de dos protocolos de entrenamiento sobre el lactato sanguíneo en caballos de paso fino / Effects of two training protocols on blood lactate in paso fino horses

RESUMEN Objetivo: comparar los efectos de un protocolo de entrenamiento de resistencia (ER) con un protocolo tradicional (ET) sobre la concentración sanguínea de lactato (L) y la creatin kinasa (CK). Materiales y Métodos: se aplicaron dos protocolos de entrenamiento durante 6 meses divididos en tres etapas. Se realizaron pruebas de esfuerzo antes de comenzar los protocolos de entrenamiento y al finalizar cada una de las etapas. En cada prueba se tomaron muestras de sangre venosa en reposo, durante el ejercicio y en recuperación para medir el lactato (L) y al inicio y al final para medir la creatin kinasa (CK) e inferir las adaptaciones metabólicas y musculares. Se calculó la diferencia de medianas del lactato basal por medio de la U Mann Whitney y se comparó la diferencia de medias del porcentaje de aclaramiento entre los grupos a través de la T de Students. Resultados: se encontró una diferencia significativa en el porcentaje de depuración de lactato entre ER y ET. También hubo un aumento significativo de los valores de CK intra-grupos, antes y después de las pruebas, pero manteniéndose dentro de los rangos de referencia. Discusión: el ER aumentó la capacidad de metabolizar el lactato pos-ejercicio en potros con entrenamiento de resistencia, aunque no hubo diferencias entre la máxima producción de L entre el grupo ER y ET. El comportamiento de la CK dentro de los rangos de referencia indica que no hubo daño muscular en los potros de ambos grupos.

ABSTRACT Objective: To compare the effects of a resistance training protocol (ER) with a traditional protocol (ET) on blood lactate concentration and CK. Materials and methods: Two training protocols were applied for 6 months divided into three stages. Effort tests were performed before beginning the training protocols and at the end of each stage. In each test, samples of venous blood were taken at rest, during exercise and in recovery to measure lactate (L), and at the beginning and at the end to measure creatine kinase (CK) and infer metabolic and muscular adaptations. The difference in baseline lactate medians was calculated using Mann Whitney U and the mean difference in the percentage of clearance between the groups was compared through the Students' T test. Results: A significant difference in the percentage of lactate clearance between ER and ET was found. There was also a significant increase in intra-group CK values, before and after the tests, but remaining within the reference ranges. Discussion: ER increased the ability to metabolize post-exercise lactate in foals with resistance training, although there was no difference between the maximum production of L between the ER group and ET. The behavior of CK within the reference ranges indicates that there was no muscle damage in the foals of both groups of foals.

Effect of pre-exercise carbohydrate availability on fat oxidation and energy expenditure after a high-intensity exercise

The aim of this study was to test the hypothesis that reduced pre-exercise carbohydrate (CHO) availability potentiates fat oxidation after an exhaustive high-intensity exercise bout. Eight physically active men underwent a high-intensity exercise (∼95% V̇O2max) until exhaustion under low or high pre-exercise CHO availability. The protocol to manipulate pre-exercise CHO availability consisted of a 90-min cycling bout at ∼70% V̇O2max + 6 × 1-min at 125% V̇O2max with 1-min rest, followed by 48 h under a low- (10% CHO, low-CHO availability) or high-CHO diet (80% CHO, high-CHO availability). Time to exhaustion was shorter and energy expenditure (EE) lower during the high-intensity exercise in low- compared to high-CHO availability (8.6±0.8 and 11.4±1.6 min, and 499±209 and 677±343 kJ, respectively, P<0.05). Post-exercise EE was similar between low- and high-CHO availability (425±147 and 348±54 kJ, respectively, P>0.05), but post-exercise fat oxidation was significantly higher (P<0.05) in low- (7,830±1,864 mg) than in high-CHO availability (6,264±1,763 mg). The total EE (i.e., exercise EE plus post-exercise EE) was similar between low- and high-CHO availability (924±264 and 1,026±340 kJ, respectively, P>0.05). These results suggest that a single bout of high-intensity exercise performed under low-CHO availability increased post-exercise fat oxidation, and even with shorter exercise duration, both post-exercise EE and total EE were not impaired.

Effects of cyclic mechanical stretch stimulation on proliferation and aerobic capacity of C2C12 myoblasts / 医用生物力学

Objective To investigate the influence of mechanical stretch at different frequencies on proliferation and aerobic capacity of mice myoblast cells C2C12. Methods C2C12 cells cultured in vivo were exposed to mechanical strain with the magnitude of 15% at the frequency of 1 and 2 Hz, respectively, for 2 hours per day over a period of 4 days by using Flexercell Cell Tension System, while in control group C2C12 cells were cultured statically. The C2C12 cells were observed by inverted phase contrast microscope. CCK-8 Cell Counting Kit was used to estimate the proliferation of cells. After the experiment, the cells were obtained by trypsin digestion. MitoXpress-Xtra system with oxygen sensitive probe was induced to detect the extracellular oxygen consumption level. Results The morphology of C2C12 cells presented a typical long spindle under the microscope following the mechanical stretch stimulation. The cells were arranged in a certain direction, parallel to the direction of tension stimulation and growing in good condition. Compare with the control group, the cell numbers in 1 Hz group and 2 Hz group were significantly increased (P0.05). Conclusions Cyclic mechanical stretch stimulation can effectively induce proliferation of C2C12 cells, which is related to the frequency of mechanical stretch, with the frequency of 1 Hz being optimum. But stretch stimulation has no significant impact on the aerobic ability of C2C12 cells.

Energy system contribution in a maximal incremental test: correlations with pacing and overall performance in a 10-km running trial

This study aimed to verify the association between the contribution of energy systems during an incremental exercise test (IET), pacing, and performance during a 10-km running time trial. Thirteen male recreational runners completed an incremental exercise test on a treadmill to determine the respiratory compensation point (RCP), maximal oxygen uptake (V˙O2max), peak treadmill speed (PTS), and energy systems contribution; and a 10-km running time trial (T10-km) to determine endurance performance. The fractions of the aerobic (WAER) and glycolytic (WGLYCOL) contributions were calculated for each stage based on the oxygen uptake and the oxygen energy equivalents derived by blood lactate accumulation, respectively. Total metabolic demand (WTOTAL) was the sum of these two energy systems. Endurance performance during the T10-km was moderately correlated with RCP, V˙O2maxand PTS (P<@0.05), and moderate-to-highly correlated with WAER, WGLYCOL, and WTOTAL (P<0.05). In addition, WAER, WGLYCOL, and WTOTAL were also significantly correlated with running speed in the middle (P<0.01) and final (P<0.01) sections of the T10-km. These findings suggest that the assessment of energy contribution during IET is potentially useful as an alternative variable in the evaluation of endurance runners, especially because of its relationship with specific parts of a long-distance race.

Mitochondrial cardiomyopathy / 临床儿科杂志

Mitochondria are the energy factory of all the cells, the center of aerobic metabolism, and essential for the me-tabolism of cells. Mitochondrial cardiomyopathy refers to myocardial damage caused by mitochondrial dysfunction and is char-acterized by cardiac structural and (or) functional abnormalities. The typical clinical feature of mitochondrial cardiomyopathy is hypertrophic cardiomyopathy, dilated cardiomyopathy, arrhythmias, noncompaction of left ventricular and heart failure. This article focuses on the pathophysiology, clinical manifestations and possible treatments of mitochondrial cardiomyopathy.

Predição da performance de corredores de endurance por meio de testes de laboratório e pista / Performance prediction of endurance runners through laboratory and track tests

Os objetivos deste estudo foram: determinar e comparar índices fisiológicos obtidos em teste de laboratório e pista (teste de pista da Universidade de Montreal - UMTT) em corredores de endurance; analisar a capacidade de predição do VO2max, vVO2max e LAn determinados no laboratório e no UMTT para a performance nas distâncias de 1.500 m, 5.000 m e 10.000 m; analisar os efeitos da distância da prova na relação entre os índices fisiológicos VO2max, vVO2max e LAn com a performance. Participaram deste estudo, 10 corredores moderadamente treinados que realizaram os seguintes testes: provas simuladas nas distâncias de 10.000 m, 5.000 m e 1.500 m; dois testes incrementais máximos (laboratório e pista) para determinar os índices VO2max, vVO2max e LAn. Não houve diferenças significativas entre o VO2max, vVO2max e LAn determinados em ambos os protocolos. De acordo com a análise de regressão múltipla, referente ao teste de laboratório, a vVO2max foi a única variável selecionada para explicar a performance nas provas de 1.500 e 5.000 m (62 e 35%, respectivamente). Do mesmo modo, dentre as variáveis determinadas no UMTT, somente a vVO2max explicou a performance nestas distâncias (78 e 66%, respectivamente). Por outro lado, o LAn determinado no laboratório e no UMTT explicou 38 e 52% da performance nos 10.000 m, respectivamente. Pode-se concluir que a predição da performance aeróbia de corredores de endurance moderadamente treinados, a partir do VO2max, vVO2max e LAn, determinados em laboratório e no UMTT, é dependente da distância da prova analisada.

The objectives of this study were: 1) determine and compare physiological indexes from laboratory and track tests (Université de Montréal Track Test - UMTT) in endurance runners; 2) analyze the predictive capacity of VO2max, vVO2max and AT with the running performance at 1,500 m, 5,000 m and 10,000 m time trials; 3) analyze the effects of running distance on the relationship between the physiological indexes with aerobic performance. The study included 10 moderately trained endurance runners who performed the following series of tests on different days: 10,000 m, 5,000 m, and 1,500 m time trials on a 400 m track; two maximal incremental tests (laboratory and track) to determine the VO2max, vVO2max, and AT. There were no significant differences between VO2max, vVO2max and AT determined in both protocols. The multiple regression analysis revealed that vVO2max was the only index from laboratory associated with running performance at 1,500 and 5,000 m (62 and 35%, respectively). In addition, vVO2max from UMTT explained the running performance for the same previous distance (78 and 66%, respectively). On the other hand, the AT determined in both incremental tests explained 38 and 52% of performance at 10,000 m time trial, respectively. Thus, the prediction of endurance performance of long distance runners using VO2max, vVO2max and AT determined in the laboratory and UMTT tests depends on the running distance.

ACtn3 e desempenho esportivo: um gene candidato ao sucesso em provas de curta e longa duração / ACTN3 gene and sports performance: a candidate gene to success in short and long duration events

O presente estudo revisou evidências acerca da relação entre o polimorfismo R577X do gene ACTN3 e o desempenho esportivo. Foram acessados estudos na base Pubmed através das palavras-chave: ACTN3 gene e sports performance. O gene ACTN3 codifica para uma proteína presente nas fibras musculares esqueléticas tipo II, a α-actinina-3. A maioria dos estudos demonstra uma relação entre a presença da α-actinina-3 e a capacidade de geração de força muscular. Porém, estudos recentes apontam que a ausência da forma funcional dessa proteína pode regular a utilização de substratos durante o exercício, priorizando o metabolismo oxidativo, poupando glicogênio muscular e favorecendo o desempenho em atividades de longa duração. Porém, ainda são necessários mais estudos envolvendo humanos para elucidar melhor esse papel metabólico.

The aim of the present study was to review the evidence on the relationship between the R577X polymorphism of the ACTN3 gene and sports performance. The Pubmed database was searched using ACTN3 gene AND sports performance as keywords. The ACTN3 gene encodes a muscle-specific protein, called α-actinin-3, which is only present in type II fibers. Most studies have demonstrated a relationship between the presence of α-actinin-3 and the ability of muscle to generate force. However, recent studies suggest that the absence of the functional form of this protein may regulate substrate utilization during exercise, giving priority to oxidative metabolism, sparing muscle glycogen, and improving performance in long-duration events. Nevertheless, further studies involving humans are needed to better understand the metabolic role of this protein.