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.     

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.     

Influence de l''hydratation sur la sécrétion d''hormone de croissance induite par l''exerciceHydration influence on exercise-induced growth hormone secretion

Aim – Study was then to investigate hydration influence on exercise-induced GHh secretion.Methods and results – Seven healthy men underwent a submaximal rectangular cycling exercise for 30 minutes to 150 watts during two sessions. A first one without any water intake and a second one with ingestion of spring water corresponding to the volume of water lost during the first session. Plasma volume decrease was significantly higher during the first session (p < 0.05). Total GH secretion was significantly lower during this session (p < 0.05).Conclusion – A moderate dehydration decreases exercise-induced GH response. Thus, hypovolemia may exert a negative feed back on GH secretion, during exercise.     

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.     

Influence d’une compétition de rugby sur le taux de cortisol salivaireInfluence of an international rugby mah upon the concentration of salivary cortisol

Introduction – Measure the influence of a sporting event (in this case an international rugby match) upon the concentration of salivary cortisol.Synthesis of facts – In order to take our study to a successful conclusion, we took salivary samples from the players during the event as well as at the time of a rest day. These concentrations are measured thanks to a radio immunoassay technique. The sporting event  has resulted in a 75% cortisol level rise. This increase reflects both a physiological and a psychological response to a stressful stimulation. The value of the cortisol before the event is also higher (85%) than the one measured at the same time of day during the rest day.Conclusion – This result shows that the sporting event has a positive correlation with the level of the salivary cortisol that it is to say a cognitive anticipation of the subjects.     

Intérêt du questionnaire de surentraînement de la Société française de médecine du sport lors d’un suivi de sportifsOvertraining questionnaire of Société française de médecine du sport for a continuous observation in a sport population

Aim. – Verify the sensibility of a standardised overtraining questionnaire during a weekly observation in a sport population.Methods and results. – The experiment was carried out in 12 athletes, 20–23 years old, students at the University in Licence STAPS, with a standardised overtraining questionnaire given every week during 8 weeks. Results were analysed individually and for the total population. Those showed that overtraining questionnaire could allow individualised training programs, and could provide some pertinent information on sleep quality and physical condition for each athlete. For the coach, the overtraining questionnaire permits to identify some fatigue state, consecutively to training variations. On the total population, the analysis of overtraining questionnaire showed some items more reliable than other.Conclusion. – This questionnaire was very interesting for coaches, allowing a good individualisation of the training program. Nevertheless, this questionnaire presents intricate statistical analysis when given at high frequency.     

Les effets d''une exposition répétée à l''oxygène hyperbare (OHB) sur la performance physique du sportif

Objectifs. – Le but de cette étude a été de vérifier que l'hyperoxie permettait d'augmenter les performance d'un exercice physique.Méthodes. – Vingt-deux sportifs de spécialités différentes, « explosif » (musculation) et « endurance » (cyclisme) ont été étudiés. Les groupes « explosif » et « endurance » comportaient respectivement six sujets hyperoxie + trois contrôles et six sujets hyperoxie + sept contrôles. Douze séances d'entraînement de 90 minutes ont été réalisées : groupe hyperoxie = 100 % d'oxygène à 1,6 b (PO2 = 160 kPa), groupe témoin = pression atmosphérique normale (PO2 = 21 kPa). Des paramètres anthropométriques et biologiques , la force utile maximale (groupe « explosif ») et la VO2 max (groupe « endurance ») ont été mesurés avant et après les 12 séances. L'évolution des puissances développées à la fréquence cardiaque correspondant au seuil de 4 mmol d'acide lactique a été suivie dans le groupe « endurance ».Résultats. – Il n'existait pas de différence significative entre les groupes pour les paramètres anthropométriques, sanguins et la VO2 max. Le groupe « explosif » hyperoxie présentait à la fin des séances, une force utile maximale plus importante (p = 0,03) que celle des témoins. Le groupe « endurance » présentait une augmentation plus importante (p < 0,05) des puissances sous-maximales que le groupe témoin.Conclusion. – L'hyperoxie permet une optimisation de l'entraînement du sportif.Aims. – Evaluate the effect of hyperbaric oxygen on physical exercise performance.Methods. – Twenty two athletes with different specialties: “explosive” (musculation) and “endurance” (cycling), were studied. The “explosive” and “endurance” groups included respectively 6 “hyperoxy” subjects + 3 controls and 6 “hyperoxy” subjects + 7 controls. Twelve 90 min-sessions of training were scheduled: “hyperoxy” group = 100% oxygen at 1.6 b (PO₂ = 160 kPa), control group = atmospheric pressure (PO₂ =21 kPa). Anthropometric and biologic parameters, useful maximum strength (“explosive” group) and VO_2max (“endurance” group) were assessed before and after the 12 sessions. Modifications of strength developed at the cardiac frequency corresponding to the 4 mmol threshold of lactic acid were noted in the “endurance” group.Results. – No difference was noted between the two groups in the variations of the anthropometric and biologic parameters as well as in the VO_2max determinations. The “explosive/hyperoxy” group developed, at the end of the sessions, a more important (P = 0.03) increase of the useful maximum strength that controls. The “endurance” group developed a more important increase (P < 0.05) of sub maximum powers that controls.Conclusion. – Hyperbaric oxygen optimize athletic training.     

Effets de la reprise d’une activité physique régulière sur les capacités physiques et la qualité de vie d’hommes atteints du syndrome métabolique

Objective

To assess the effects of aerobic training on physical capacities and quality of life in men with metabolic syndrome (Mets), using field evaluation tools.

Synthesis

The physical capacities and the quality of life of eight men with Mets (59.5 ± 4.8 years old) was assessed before and after 8 weeks of aerobic exercise training by the 6 minutes walking test and the quality of life, obesity and dietetics scale.

Conclusion

Aerobic exercise training of 8 weeks improves physical capacities and the psychosocial impact dimension of quality of life in men with Mets, without generating anthropometric modification.     

Effets en miroir de l''entraînement et du surentraînement sur la fonction somatotrope et la balance glucidolipidique à l''exerciceEffects out of mirror of the drive and overtraining on the somatotropic function and the glucido-lipidic balance with the exercise

Objective. – To confirm the assumption whereby overtraining would have opposite effects on the utilisation of the substrates and the somatotropic function.Exposed facts. – The drive has different effects according to its characteristics and its level. It seems y to have two types of drive: that which amplify the aptitude to oxidize lipids (low powers) and that which accroit the aptitude to oxidize glucides (high powers and/or intermittent exercise). Overtraining reverses these two effects. The somatotropic axis has an evolution parallel with these processes and seems implied in those.Conclusion. – This diagram deserves to be confirmed by additional studies.     

L''hémorhéologie permet-elle de comprendre le « paradoxe de l''hématocrite » lors de l’entraînement et du surentraînement ?Does hemorheology explain the paradox of hematocrit in training and overtraining?

Purpose. – Doping with EPO increases both hematocrit and performance. On the opposite, training reduces hematocrit due to plasma volume extension and overtraining both increases hematocrit and decreases performance. This apparent paradox seems to be explained by a new concept proposed interpreting the interactions between viscosity factors and blood flow.Facts. – Viscosity factors exert a non linear “all or none” effect that can be described according to the “ percolation theory”. Blood viscosity has no hemodynamic relevance by its own, but viscosity factors (hematocrit, red cell deformability and aggregability, plasma viscosity) can result according to flow conditions in self-potentiating phenomena of quick transition between a state of high fluidity and a state of red cell aggregate clumping. In muscle, this model predicts that: (a) during exercise the only viscosity factor that could influence flow is plasma viscosity; (b) at rest all viscosity factors (including high hematocrit) may induce a self-potentiating “viscidation” process.Conclusion. – According to these concepts, supraphysiologic hematocrit values are probably unable to disturb muscular perfusion at exercise, but are likely to promote self-potentiated stasis at rest and thus to increase the risk of thrombosis.     

Évaluation d''une batterie de tests pour la sélection des jointeurs d''une firme hydroélectrique

The purpose of this study was to evaluate the specificity, the reliability and the discriminative power of 12 tests that could be used to select electrical utility workers-splicers. The work of electrical utility workers-splicers consists of building, repair and modification of the underground power grid or lines. The first requirement to retain a test was its reliability (standard error of the estimate arbitrarily set to or lower than 12%). With 13 unexperienced subjects, only four tests met that criterion. The remaining original tests, although specific to the task, show very high test-retest variability (SEE = 15.7 to 107.7%) and were thus rejected on that basis alone. The test-retest data also showed a learning process for many of the tests. Theoretically, that would have to be considered when choosing a pass or fail criterion. From a practical point of view, however, the learning process was observed mostly in the agility tests, which were the same as those rejected due to their low reliability. In the second phase of this study, the discriminative power of the tests was established in comparing inexperienced male subjects (n = 13) to experienced male workers (n = 16). Again, significant differences were found for agility tests that were already rejected. For the four reliability tests, with high physical requirements regarding strength or muscular endurance, there was a significant difference for only one test, indicating a lack of discrimination for the other three. As a result, a logical decision would be to reject those tests. However, considering that these tests were “physical” rather than involving “motor abilities”, the experience of the workers did not make any difference. It is important to underline that inexperienced subjects were physically fit physical education students, which may explain why they scored as high as the workers in these tests. In other words, the unexperienced subjects barely passed these tests. Ideally, it would have been preferable to compare poor and good workers but that was not possible due to adminitrative problems. The correlations among test items was determined in order to eliminate tests having high levels of covariance. None of the retained reliability tests were highly correlated but all were retained as valid tests. In general however, this study has shown the difficulties in constructing task-specific tests. Too many of the original tests, mostly “motor abilities” tests, had to be rejected due to low reliability. Other tests would need to be designed and tested again in order to have a complete battery to mimic the essential aspects of this task.     

Effets de l'entraînement sur les potentiels aérobie et anaérobie de jeunes nageurs. Exercice réalisé avec les brasEffect of training on aerobic and anaerobic capacity in young swimmers. Exercise performed with arms

Aims – Investigate the influence of exercise training on the aerobic and anaerobic capacities of young swimmers.Methods – Ten male swimmers aged 15.2 ± 3.8 years participated: five sprint specialists and five middle-distance specialists. Each subject performed, an arm ergocycle, two laboratory tests, a maximal incremental exercise test and a force–velocity test, once in February (T1) and then again in June (T2).Results – For all subjects combined (n=10), the results showed a significant increase in maximal anaerobic power (p < 0.01) between T1 and T2. Aerobic capacity did not change significantly between the two tests in either group.Conclusion – This study demonstrates the interest of evaluating aerobic and anaerobic capacity in young swimmers during arm exercise. The change in results over the 5-month period between the two tests indicates the importance of scheduling exercise tests during the course of athletic training programs.     

Pratique sportive et oligoéléments: conséquences nutritionnelles

Trace elements are scarce in our body, where as some of them are implicated in various metabolic processes. Regular exercise alters the levels and increases outputs and requirements of some of them. Zinc losses through sweat, urine and feces are increased in response to chronic and acute exercise. Chromium losses, mainly via the urinary tract, increase following training and simple carbohydrate intake, a common situation among sportsmen. Copper losses increase in sweat. Recommended daily allowances are not always satisfied, depending upon the trace element being considered. Zinc and chromium intakes are often marginal, while copper does not seem to be present in sufficient amounts in a high percentage of athletes. It is not the same for manganese, always delivered in sufficient amounts. Selenium intake mainly depends on its rate in the soil, this factor varying the most from one country (and one average diet) to another. So precise recommendations such as three servings of meat per week seem to be justified. Some diets are not adequate towards some trace element intakes, and this abnormality enhances the probability that deficiencies appear. Complex interrelationships enhance or impede supplementation. For instance, copper, zinc and iron inhibit each other's absorption at gut's level. These interrelationships make nutritional strategy harder to implement. Some trace elements (selenium, zinc, copper or manganese — the latter at the mitochondrion level) act as free radical scavengers. Thus increased intakes at appropriate levels may be required. Changes in dietary habits, improving “nutritional density” is one possible strategy. But for some elements, the required amounts are not currently available in our diet. Thus supplementation becomes necessary in some cases. As far as vanadium and silicon are concerned, and though they are implicated in some physiological processes linked to sports, it is not possible to recommend at present precise amounts, even though future research will certainly show that their intake is to be increased.