Short duration exhaustive aerobic exercise induces oxidative stress: a novel play-oriented volitional fatigue test

Aim. Exercise is associated with the generation of reactive oxygen and nitrogen species. This study examined the oxidative stress in response to a novel volitional fatigue test. Methods. Eleven male college students performed a volitional fatigue test consisting of shuttle runs with a tennis racquet in the hand towards the left and right sidelines within the tennis singles court in an attempt to hit tennis balls until exhaustion. A tennis ball serving machine was adjusted to alternate feeds to the forehand and backhand sides of the subjects, standing at the baseline, at a frequency of 20 balls per minute. Results. Mean time to volitional fatigue was 5.9 +/- 1.3 min and mean heart rate at volitional fatigue was 189 +/- 8.1 beats.min(-1). The volitional fatigue test resulted in significant increases in blood thiobarbituric acid-reactive substances (22%), protein carbonyls (58%), catalase activity (143%), total antioxidant capacity (34%) and oxidized glutathione (GSSG, 81%) concentration, as well as significant decreases in reduced glutathione (GSH, 15%) concentration and GSH/GSSG ratio (56%) immediately postexercise, as compared to the pre-exercise concentration. Conclusion. The data provide evidence that acute short duration exhaustive aerobic exercise in the form of a novel volitional fatigue test is capable of inducing oxidative stress. This novel test could serve as an alternative exercise modality to study oxidative stress

Association between ankle muscle strength and postural sway in older adults

Our study aimed to investigate the relationship between the strength of ankle muscles and postural sway in older adults during upright standing tasks of varying difficulty. Forty-three elderly participants (20 women) performed maximal isometric contractions and three distinct postural tasks: normal quiet stance (60 s), tandem stance (20 s), and one-legged stance (10 s) on a pressure platform. Postural sway was comprehensively assessed, considering center of pressure velocity, peak-to-peak amplitude, and standard deviation of center of pressure displacement in both anterior/posterior and medio/lateral directions. Additionally, weight distribution asymmetry in both directions served as a quantifiable index. Surface electromyographic (EMG) activity of the Tibialis Anterior, Medial Gastrocnemius, Rectus Femoris, and Semitendinosus was recorded during the postural tasks. Throughout the balance tasks, isometric plantar and dorsiflexion torque exhibited a consistent decrease as posture variables increased (p < 0.001). Narrowing the base of support led to significant increases in all postural variables and EMG activity (p < 0.01), with a more pronounced effect on ankle muscles compared to hip muscles (p < 0.0005). In the normal quiet stance (r =.683) and tandem stance (r =.641), greater center of pressure velocity correlated with a more symmetrical weight distribution between the legs. These results suggest that ankle muscle strength serves as a reliable predictor of static balance control, particularly in postures involving a narrow stance. Therefore, the enhancement of plantar flexors and dorsiflexors, rather than an exclusive focus on symmetrical weight distribution, is more likely to contribute to improved static balance control in older adults

Protonation of key acidic residues is critical for the K+-selectivity of the Na/K pump

The sodium-potassium (Na/K) pump is a P-type ATPase that generates Na+ and K+ concentration gradients across the cell membrane. For each hydrolyzed ATP molecule, the pump extrudes three Na+ and imports two K+ by alternating between outward- and inward-facing conformations that preferentially bind K+ or Na+, respectively. Remarkably, the selective K+ and Na+ binding sites share several residues, and how the pump is able to achieve the selectivity required for the functional cycle is unclear. Here, free energy–perturbation molecular dynamics (FEP/MD) simulations based on the crystal structures of the Na/K pump in a K+-loaded state (E2·Pi) reveal that protonation of the high-field acidic side chains involved in the binding sites is crucial to achieving the proper K+ selectivity. This prediction is tested with electrophysiological experiments showing that the selectivity of the E2P state for K+ over Na+ is affected by extracellular pH

Treinamento físico: considerações práticas e científicas Physical training: scientific and practical considerations

O treinamento físico é uma importante área de atuação profissional da Educação Física e do Esporte. Ela tem por objetivo precípuo, a melhoria do desempenho físico-esportivo através da aplicação de um processo organizado e sistemático composto por exercícios físicos. Nos últimos anos, os progressos tecnológicos e nos métodos de investigação científica nas diferentes subáreas relacionadas ao treinamento físico trouxeram um avanço significativo na obtenção deste objetivo. Neste artigo será discutido, do ponto de vista acadêmico-científico e também da prática profissional, o estado da arte do conhecimento associado à avaliação do treinamento, ao controle da carga de treinamento, aos modelos de organização da carga de treinamento e ao desenvolvimento das capacidades motoras. Esperamos que ao final, o leitor possa ter um bom entendimento destes diferentes componentes, como eles contribuem para a modificação do desempenho motor e como aplicá-los para a elaboração, implementação, avaliação e reformulação de programas de treinamento físico.<br>Physical training is an important field of work for the Physical Education and Sport professional. Its main goal is to develop the physical capacity and sports performance of an individual by means of an organized and systematic application of physical exercises. In the past years, the technological progress in the scientific investigation within the different disciplines related to physical training have contributed a great deal towards the accomplishment of such goal. In this manuscript we discuss, from both an academic-scientific and from a practical application point-of-view, the state of the art of the knowledge associated with the physical training evaluation, loading control, loading scheming, and the development of physical abilities. Our goal is to provide a comprehensive overview of the different components of the physical training and how they contribute to the development of the physical performance as well as how to apply these concepts in the elaboration, implementation, and evaluation of physical training programs