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.     

Évolution des erreurs techniques et de quelques variables physiologiques pendant la course d'orientation

During orienteering, the accumulation of technical errors (TE) can be an important factor of handicap at the arrival. In the same conditions of championships, ten voluntary national runners (age: 29.2 ± 3 years, height: 176.8 ± 3.5 cm, body mass: 65.0 ±6.8) participed to the study. Firstly in laboratory the subjects performed a treadmill test in order to study their physical capacity (aerobic fitness and oxygen consumption). The initial speed (12 km·h⁻¹) increased by 1 km·h⁻¹ every 4 minutes. During the last minute of each step a blood sample (50 μl) was taken on a finger for lactate analyze (Kontron). Two days later the subjects participed in an orienteering race (OR) of four loops (Bi₁, B₂, B₃, B₄) stepping in a central point; the first and third loops (B₁, B3) were technical orienteering while the second and the fourth (B₂, B₄) were rough orienteering. During the race the heart rate (HR) was recorded by means of a Sport Tester PE 4 000. The nature, the number and the moment of TE were determined with the help of the map area of each subject and time keeping. During OR the subject's physical capacity (running speed, HR, lactates, carbohydrate) was evaluated when the runners arrived at the crossing point of the loops. The results give some evidence that the anaerobic threshold quickly is reached during technical orienteering (B₁) and stay at a level hihger than 4 mmoles.l⁻¹ during the whole field test, suggesting that the energy expenditure was very high. It is difficult to compare the physical capacity and the psychological behavior of the subjects during OR yet two distinctive critical pediods have been observed for TE in OR (B₃, B₄); nevertheless our study confirms that the number of TE (which is a picture of the mental performance) is linked to the decrease of the physical capacity. Indeed the increase of HR (HRmax-HRmin) during OR stabilized in the first three loops (B₁, B₂, B₃) at 25 beats, min⁻¹, then the increase of HR was about 31 beats.min⁻¹ in B4. This increase of HR (HRmax-HRmin), is due to the muscular fatigue, the subjects must have some rest and they run slowly because the carbohydrates decrease, excepted for the best runners. Thus the consequences of an insufficient warm-up in the first quarter of the race and/or supply of energetics substrates during the whole OR has been brought to attention.     

Modification de la lipolyse du tissu adipeux après un entraînement en endurance chez des sujets obèses

This study investigates the effect of a 3 month endurance training on in vitro adipose tissue lipolysis in 13 obese men (body mass index: 36.9 ± 1.3 kg/m²). Training decreased body fat mass percentage (P < 0.05), without body weight change. Lipolytic effects of epinephrine, isoproterenol (β-adrenoceptor agonist) and dobutamine (β₁-adrenoceptor agonist) were significantly increased (P< 0.05). Antilipolytic effects of α₂-adrenoceptor and insulin were significantly decreased (P < 0.05). Endurance training in obese men enhances adipose tissue lipolysis through β-adrenergic pathway, and decreases antilipolytic activity.     

Comparaison de l'oxydation de glucose, d'un mélange de glucose et de fructose, et de saccharose ingérés en bolus ou en doses fractionnées au cours de l'exercice

The purpose of this study was to compare the oxidation rates ofisocaloric amounts of glucose (G), of a mixture of glucose and fructose (G+F), and of sucrose (S) ingested during prolonged exercise (120 min, 58 % V0₂max). The mode of ingestion, that is in a bolus at the onset of exercise or in fractionated doses during the exercise, was also investigated. Six young male subjects ingested a placebo (P), 100 g of G, 50 g of G + 50 g of F, or 95 g of S (13 % concentration) in fractionated doses during exercise, and 100 g of G and 50 g of G + 50 g of F in a bolus at the beginning of exercise. Blood samples were taken before and during the last minute of exercise period. Ingestion of carbohydrates (CHO) does not influence the blood glucose and insulin levels, but decreases by 50% the response of plasma free fatty acid concentration. During the 120-min exercise period, the amounts of ingested carbohydrates which were oxidized were similar for G (53 ± 5 g), G+F (57 ± 6 g) and S (50 ± 7 g). Exogenous CHO oxidation contributed to increasing the total CHO utilization (from 181 to 200 g/120 min) and to reducing fat oxidation (from 86 to 72 g/120 min). Ingestion of CHO as a bolus at the beginning of exercise does not influence G oxidation (58 ± 6 g) but significantly increased the oxidation of the mixture G+F (67 ± 6), probably by favoring fructose utilization which requires a delay. From a practical viewpoint, these results show that the oxidation of S, which is the most widely available oligosaccharide, is similar to that of G or a mixture of G+F. Moreover, in order to maximize exogenous CHO oxidation during exercise, CHO should be ingested early in the exercise period, and not in fractionated doses throughout the exercise period.     

Influence de l''âge sur différents facteurs déterminants de la performance sur ergomètre aviron

The aim of the present work was to study the evolution with age of the maximal oxygen uptake (VO_2max) and gross efficiency on rowing ergometer in a population of 29 elite oarsmen (17 adults and 12 youths). Independently of body mass, VO_2max increases until 23 years of age and very slightly afterwards. This evolution might be explained by the increase of the volume and intensity of training once the subjects become adults. Efficiency increases continuously with age and leave opportunities to improve this parameter even in high level oarsmen.     

Augmentation de la fréquence d’apparition de l’hypoxémie induite par l’exercice chez des rameurs de haut-niveau

Objectifs. – Évaluer la fréquence d’apparition de l’hypoxémie induite par l’exercice (HIE) chez un groupe de rameurs de haut-niveau.Méthodes. – Sept rameurs de haut-niveau ont participé à l’étude (19,14 ± 1,3 ans). Les sujets ont effectué une épreuve d’effort à charge croissante sur un rameur ergométrique lors de laquelle les échanges gazeux et la saturation de l’hémoglobine en oxygène (SpO₂) ont été mesurés.Résultats. – Les sujets avaient une VO₂max de 61,68 ± 1,65 ml/min par kilogramme. Tous ont présenté une HIE avec des chutes de SpO₂ comprises entre 5 et 11 %. Cette chute était significative dès 70 % VO₂max. Le volume d’entraînement réduit des athlètes testés par rapport aux autres athlètes endurants semble indiquer que le phénomène est indépendant du volume d’entraînement.Conclusion. – Cette étude a permis de mettre en évidence que 100 % des rameurs de haut-niveau présentaient une HIE. La limitation ventilatoire et l’importante masse musculaire mise en jeu spécifiques à l’aviron seraient les hypothèses explicatives.Aim. – To access the frequency of exercise-induced hypoxemia (EIH) in elite oarsmen.Method. – Seven elite oarsmen participated (19.14 ± 1.3 year) in this study. Subjects performed an incremental exercise testing on a rowing ergometer. Gas exchanges and pulse oxymetric saturation in oxygen (SpO₂) were measured during exercise.Results. – Subjects exhibited a mean of VO₂max of 61.68 ± 1.65 ml min^–1 kg^–1. All rowers showed an EIH with a SpO₂ ranging between 5% and 11%. This SpO₂ fall was significant from 70% VO₂max. The reduced training volume of our athletes compared with others endurance trained athletes seems indicate that phenomenon is not dependent of training volume.Conclusion. – This study showed that 100% of elite oarsmen exhibit EIH. Mechanical limitation in ventilation and great muscle mass involved in rowing could be the explicative hypothesis.     

Cortisol, testostérone et rapport testostérone/cortisol au cours d''un trimestre scolaire chez des lutteurs de haut niveau comparés à des étudiants non sportifs

This study presents the saliva cortisol and testosterone levels in young high level wrestlers compared to those of students not involved in sporting activities. Measures were realised during the first school term (September to mid-December) at 3-week intervals. Hormonal levels revealed a higher degree of tiredness in sportsmen than in non-sportsmen. It also appeared that a 2-week resting period (All-Saint's Day at the end of October) permitted return to hormonal reference values at the beginning of the school year.