Effects of repeated sprint training on isocapnic buffering phase in volleyball players [Efeitos de treinos de sprint repetidos na faixa de tamponamento ısocápnıco em jogadores de voleibol] [Efectos del entrenamiento de sprint repetido en la fase de tamponamiento isocápnico en jugadores de voleibol]

Introduction: The region between the ventilatory threshold (VT) and respiratory compensation point (RCP) is defined as the isocapnic buffering (ICB) phase and represents a phase of compensation for exercise-induced metabolic acidosis. There is sparse literature examining the effects of physical training on ICB phase in athletes. Objectives: The purpose of this study was to examine the effects of a repeated sprint training program on the ICB phase of college volleyball players. Methods: Eighteen male volleyball players were randomly assigned to either an experimental group (n=9) or a control group (n=9) and followed a traditional volleyball training program three times per week for six weeks. The experimental group additionally performed a repeated sprint training protocol immediately before each volleyball training session. Before and after the 6-week training period, all participants performed an incremental treadmill test to determine VT, RCP, and maximal oxygen uptake (VO2max). The ICB phases were calculated as VO2 (ml/kg/min) and sprint speed (km/h). Results: The experimental group showed significant improvements in ICB phase, RCP, VO2max and maximal sprint speed after training (p<0.01). There were no significant changes in VT after training in the experimental group (p>0.05). None of these variables changed significantly in the control group (p>0.05). Conclusions: These findings indicate that repeated sprint training can enhance the ICB phase of volleyball players, which may be attributable to an improvement in buffering capacity leading to a shift in RCP towards higher intensities without any change in VT. The increase in the ICB phase may an important factor in terms of improvement in the high-intensity exercise tolerance of athletes. Level of Evidence II; Therapeutic studies - Investigating the results of treatment. © 2018, Redprint Editora Ltda. All rights reserved

An Investigation into the Oil Leakage Effect Inside the Electronic Servo-valve for an H∞/LPV Active Anti-roll Bar System

La version déposée sur le site est une version soumise, ce n'est pas la version acceptée le 15 juin 2019 (version ayant fait l'objet de nombreuses modifications à la suite des retours des reviewers.International audienceThe Electronic Servo-Valve Hydraulic (ESVH) actuator is commonly used in the industrial sector and engineering practice. This paper investigates the robustness of the H ∞ /LPV active anti-roll bar system when the presence of an oil leakage inside the electronic servo-valve is taken into account. We propose a fully integrated model, including four ESVH actuators in a single unit heavy vehicle. Then, an H ∞ /LPV controller is synthesized in order to satisfy simultaneously the two main objectives of enhancing roll stability and the saturation of the actuators. Survey results indicate that the oil leakage has a positive effect in protecting the active anti-roll bar system if the controller stops working and it is indispensable for this system. At each design point of the LPV system, the µ-tool method is used to test the robustness analysis in the frequency domain. It is shown that the active anti-roll bar system is always robust with the maximum uncertain level of the total flow pressure coefficient being 41%, when the forward velocity is considered to be over 130 km/h