Analyse de la sollicitation physiologique lors de la navigation en Laser

Objectifs. – Évaluer le niveau de sollicitation physiologique imposée au sportif dans des conditions proches de celles de la régate et vérifier si l'utilisation de la fréquence cardiaque de réserve (ΔFC) est un témoin valide de la consommation d'oxygène lors de la navigation en Laser^®.Protocole expérimental. – Neuf sujets de sexe masculin, et de niveau international, ont effectué deux parcours successifs de 30 minutes de navigation (avec virement de bord toutes les 2 minutes) séparés de 15 minutes de repos. Les mesures de et FC étaient réalisées en continu. Une mesure de lactatémie était effectuée avant le départ de chaque parcours puis à l'arrêt des 30 minutes de navigation.Résultats. – Les valeurs moyennes de , de ΔFC et de lactatémie sont respectivement pour les parcours 1 et 2 de : 58,7 et 54,5 % , 59,1 et 55,3 % ΔFC, 2,57 et 2,77 mmol/l^–1 observés, quels que soient l'intensité du vent et le parcours réalisé. Dans ce cadre, une relation significative est objectivée pour chaque sujet entre les valeurs moyennes de la réserve de fréquence cardiaque et de la consommation d'oxygène.Conclusion. – Lors d'un parcours d'une durée proche de celle de la régate, la consommation d'oxygène lors de la navigation en Laser^® est significativement plus élevée que celle communément relevée dans la littérature scientifique. Dans ce cadre, nos résultats montrent que la dépense énergétique moyenne d'un effort en Laser^® peut être estimée grâce à la fréquence cardiaque de réserve.Purpose. – The first aim of this study was to evaluate the physiological demand during Laser^®sailing in a situation closed to competition. The second one is to analyse the validity of relative heart rate (ΔHR) to assess energy expenditure during Laser^®sailing.Protocol. – Nine male international dinghy sailors performed two successive 30-min sailing tests tacking every 2 min with a 15 min rest in between each test. Measurements of , HR were performed during the whole test. [La]_b levels were measured just prior to the test and immediately after each 30 min of sailing.Results. – Mean values of , ΔHR and [La]_b were, respectively, 58.7% and 54.5% , 59.1% and 55.3% ΔHR, 2.57 and 2.77 mmol l^–1 for test 1 and 2 whatever the speed of the wind. Furthermore a significant relationship was observed between mean relative heart rate value and oxygen consumption in each subject.Conclusions. – In our study closed to regatta condition in Laser^®sailing, energy expenditure values recorded is higher than those classically reported in scientific literature during simulated conditions. Furthermore in this study, our results indicate that relative heart rate can be used as an useful tool to assess energy spending during Laser^® sailing.     

Effet de l'instruction sur la régulation de la raideur des membres inférieurs lors de sauts de contre-haut

Goal. – We tested in this study the possibility of influencing leg stiffness through instructions on the knee flexion in drop jump (30 and 60 cm).Method. – Twelve basket players were instructed to jump with three different instructions: 1) “jump as high as you can”; 2) jump high with a larger knee flexion at touch-down and 3) jump high with a smaller knee flexion at touch-down. The ground reaction force were measured with an AMTI force plate (500 Hz). The kinematics of the jump was recorded using two digital cameras (50 Hz).Results. – The results show that the ground reaction force pattern depended more on the instruction than on the height of the box. The active peak decreased from 6 times the body weight (BW) to 2.9 times BW. Bending the knee appears to be an efficient strategy to increase the leg stiffness [R =0.86; P <0.05].Conclusion. – The instructions high knee flexion decreases the leg stiffness. The same vertical jump performance could be achieved with different values of stiffness. The maximum knee flexion does not modify the vertical performance.     

Effets d'un entraînement en endurance sur des patients atteints de la maladie de McArdle

Objectives. – This study assesses on patients with myophosphorylase deficiency (McArdle’s disease) the effects of a moderate aerobic training program (8 weeks, 3 sessions of 45 minutes per week at 60–70% of maximal heart rate) on the physiological response during exercise.Methods. – The cardiorespiratory, electromyographic (EMG) and metabolic responses are evaluated on four patients before and after training to an acute exercise (1 h) on an ergometric bicycle (20–35 Watts) followed by 30 minutes recovery.Results. – Before training, the EMG activity is very high during the first ten minutes of exercise while oxygen uptake (VO₂) remains stable over the 60 minutes of exercise. The heart rate (FC) and the rate of perceived exertion (RPE) are markedly increased. Patients highly use circulatory glucose and free fatty acids for oxidation. During exercise, the 8-week training program reduces EMG activity, FC, RPE and the time of second-wind apparition whereas it has any effect on VO₂. At the end of exercise recovery, patients use more circulatory glucose and product lactate; moreover, their respiratory exchange ratio is increased.Conclusion. - Patients with McArdle disease show an exacerbation of cardiorespiratory, electromyographic and metabolic responses to exercise. A moderate aerobic training program induces muscle, cardiac and metabolic adaptations to physical strain and improves the tolerance of the patients to the physical exercise.     

Effets du repas précompétitif sur la perception de l'effort et sur la glycémie lors d'un exercice de pédalage

The first purpose of the present study was to investigate the effect of three different preexercise meals on perceived exertion and glycaemia during a one-hour bicycle exercise at 80% VO₂ max. The second purpose of this study was to determine the relationship between glycaemia and perceived exertion. Eight athletes (age: 24.6 ± 2.7 years, weight: 78.0 ±6.8 kg, height: 182.6 ± 9.9 cm) completed three assessment sessions, each being preceeded by one of the following meals, ingested 3 h before exercise: 400 mL of water, 400 mL of water and 75 g of glucose, and 100 mL of water and 375 g of potatoes. The subjects 'perceived exertion were measured at times 6, 15, 30, 45, 60 min and glycaemia at 0, 30, 60 min of the exercise. The results showed that perceived exertion (RPE and ETL) of each meal increased as a function of time (P <- 0.05) whereas glycaemia did not differ except for the glucose meal between 30 min and 1 h(P < 0.02). There was no significant difference in ratings of perceived exertion among any meal whereas glycaemia was different between the three conditions only at the beginning and the middle of the exercises (P < 0.04 and P < 0.02, respectively). Moreover, the vectorial angles between the variables ofperceived exertion and the glycaemia are close to 90 °. These results would suggest that perceived exertion does not seem to be affected by the three preexercise meals used in our study. Perceived exertion is not correlated to glycaemia changes during one-hour high intensity exercise. The results would, therefore, suggest that glycaemia is not a contributor signal of perceived exertion in this study. It seems that physiological factors other than glycaemia may have mediated the perceptual intensity at exhaustion. The respiratory-metabolic signals of exertion which are most pronounced at high relative exercise intensity are suggested to influence the perceptual signal of exertion.     

Uchi-komi avec charge,une approche physiologique d'un nouveau test spécifique au judo

Objective

The aim of this study was to elaborate and validate a specific test to evaluate the physical condition of judo players.

Subjects and methods

Twenty-three volunteers, males, aged 22 ± 3.62 years old took part in our experiment. They did the progressive test of Leger et al. (1984), vertical Jump test (Sargent test), Australian shuttle run test and a specific judo test.

Results

The observed results showed significant correlations between muscular power and the number of Uchi-komi on the judo test reference scale (R = 0.52, P < 0.01). Furthermore, there were other correlations between the number of Uchi-komi at the two first sets of specific judo test and the anaerobic power represented by the distance covered in 30s at the Australian shuttle test (R = 0.86, P < 0.01), also between the anaerobic capacity represented by the whole distance covered and the total number of Uchi-komi achieved at the judo test (R = 0.88, P < 0.01).

Conclusion

The test reproduces the physiological characteristics of judo fight. It is a good indicator of the judoka's physical fitness and their cardiovascular adaptation in a physical effort.     

Facteurs biologiques influençant les concentrations urinaires en stéroïdes anabolisants lors de contrôles antidopage

ObjectiveTo review the biological factors that may influence the urinary concentrations of anabolic steroids in doping controls.TopicsAccording to the World Anti-Doping Agency statistics, the use of anabolic steroids represents the main offence carried out by the athletes. The use of substances naturally produced by the body (such as testosterone, nandrolone) makes the interpretation of urine analyses very difficult. Furthermore, many biological factors (age, diet, menstrual cycle, oral contraceptives…) may modify these concentrations.PerspectivesThe search of indirect markers of doping through the setting of the biological passport offers a powerful alternative to the current anti-doping method. Detecting the presence of the exogenous substances in biological matrices would not be the main purpose in that kind of strategy, but rather the examination of the spectra of biological variances that can be affected by doping substances.     

Influence d'un triathlon courte distance sur la performance des muscles respiratoires

Objectives – The aim of the present study was to investigate the influence of a short distance triathlon (1.5 km swim, 40 km cycle, and 10 km run) on respiratory muscle performance.Methods and results – Nine male triathletes underwent the measurement of respiratory muscle strength (maximal expiratory and inspiratory pressures), and respiratory muscle endurance (Time limit), before the competition (Pre-T), at the end (Post-T) and 24 h later (post-T-24 h). The results showed, 1) the absence of significant difference in maximal expiratory pressure (P > 0.05), 2) a significant decrease in maximal inspiratory pressure and time limit at Post-T and Post-T-24 h (P < 0.05).Conclusion – We concluded that a short distance triathlon induced an inspiratory muscle fatigue, showed by a significant decrease in strength and endurance of these muscles.     

Effet d'un exercice de sprint de 30 s sur le statut antioxydant plasmatique

Introduction. – A recent study (Groussard et al., personal communication) demonstrated that a single sprint exercise (30 s) induced an increase in lipid radical production and an alteration of blood enzymatic antioxidant system. So we hypothesised that the same exercise may also affect plasma non enzymatic antioxidant status.Method and results. – Eight students in physical education performed a Wingate test. Plasma nonenzymatic antioxidant status (uric acid, vitamins C and E, β-carotene) was determined at rest (R), after the warm up (E), after the exercise (P₀), and at 5 (P₅), 10 (P₁₀), 20 (P₂₀) and 40 (P₄₀) minutes of recovery. We observed an increase in plasma uric acid and vitamin C respectively since P₁₀ et P₂₀. Inversely, the Wingate test induced a decrease in plasma vitamin E concentration at P₅ and P₁₀ which then return to basal values and a decrease in plasma β-carotene concentration since P_5.Conclusion. – These results demonstrated that a short (30 s) single sprint exercise alters plasma non-enzymatic antioxidant status.     

Evolution des taux plasmatiques des LDH (lacticodeshydrogénase), CPK (créatine phosphokinase) et de la myoglobine à l'issue d'une course de 100 km et d'un triathlon

The elevation of plasma levels of lactate dehydrogense (LDH), creatine phosphokinase (CPK) and myoglobin under the effect of prolonged physical exercise is considered as a biochemical index of muscle cell destruction. These biochemical parameters were used to evaluate the comparative effects of a 100 km race and a triathlon of the same duration upon muscle function. Venous blood samples were drawn from 8 long distance runners (the 100 km race at Belvès) and 8 participants in the Nice triathlon (swim 3 km, cycle 120 km, run 32 km) before the events, at the end and 4 days after. Leg muscle function was evaluated, using an isokinetic dynamometer CYBEX II before both events and 4 days later.The results show significant increases in these three parameters at the end of the competitive events. The plasma levels observed were higher at the end of the 100 km run (CPK: 700 ± 200 VS 180 ± 90; LDH: 411 ± 30 VS 200 ± 5; myoglobin 1100 ± 100 VS 730 + 400). The measurements made 4 days after these sporting events with the CYBEX revealed no change in the maximal effort of leg extensors and flexors. However, a slight reduction in the duration of exertion at this maximal level was noted. Foru days after these events, the CPK levels remained above the resting level for both groups studied, whereas the myoglobin values returned to basal levels in the triathletes, and the LDH values were the same as those observed at rest for both populations. These findings suggest that for a physical exertion lasting between 9 h 8 min and 8 h 20 min, the 100 km race causes more muscular lesions than the triathlon. The reduced time of exertion at maximal effort during the recovery period noted for both groups is an index representing a perturbation of the muscle function capacity, in spite of the normalization of the two biochemical parameters, LDH and myoglobin. The persistence of the slightly elevated CPK values suggests that this parameter is a better index of muscular lesions during the recovery phase.     

Coordination musculaire lors du coup droit lifté chez les jeunes joueurs de tennis

Purpose

The aim of this study was to assess the timing of muscle activation during the acceleration phase of topspin forehand drives in young tennis players.

Synthesis

The activity of six muscles was recorded using surface electromyography during topspin forehand drives in 22 players (9–17 years). The timing of muscle activation was characterized by the onset of EMG bursts during the acceleration stage.

Conclusion

The proximal-to-distal sequential muscle activity was observed for the agonist muscles while the antagonist muscles were recruited at the end of the acceleration stage. This sequential muscle activity was common to all participants whatever their abilities.     

Répercussions d'une prise chronique de salbutamol au cours d'un exercice supramaximal

Introduction. – The aim of the study is to assess the effects of chronic therapeutical β₂-agonist intake on performance during supramaximal dynamic exercise.Synthesis. – We studied, according to a double-blind, randomized cross-over protocol, the effects of chronic salbutamol intake (Sal) during a supramaximal anaerobic Wingate test in 15 healthy male volunteers. Body composition and performance were monitored in this study. Sal increases significantly maximal anaerobic power whereas no change is found in body composition.Conclusion. – These results rule out any implication of an anabolic effect of β₂-agonist in this improvement in performance with salbutamol during supramaximal exercise.     

Effet d’une hyperventilation volontaire préexercice sur la performance lors de l’épreuve de Wingate

Aim

To determine the effect of a preexercise hyperventilation (HV) on performance measured during the Wingate test.

Protocol

Seven subjects realized the Wingate test whether in normal condition or after the realization of six maximal respiration cycles realized in 30 s. Gas exchanges were recorded breath by breath throughout the test.

Results

Pic power measured during the test was not significantly different after HV. In opposite, the fatigability index (FI) was significantly higher after HV.

Conclusion

A HV does not affect maximal power, but seems to reduce aerobic contribution, which may explain the higher FI observed after HV.     

Imagerie des troubles de ventilation

Atelectasis is one of the most commonly encountered abnormalities in chest radiology. The presence of such abnormality must be considered on the basis of a standard face chest X-ray, eventually helped by a lateral view. These disorders of ventilation may be related to a decrease (atelectasis or collapse) or an increase (air trapping) of the lung volume. In this article, following a brief review of the different radiological techniques and radio anatomy of lung segmentation, we describe the pathophysiology, mechanisms and radiological signs of ventilation disorders. We underline the essential role of CT scanning and the recently highlighted potentialities of multiplan reconstruction.