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.     

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.     

Le « syndrome des jambes lourdes » chez les athlètes surentraînés est-il le reflet de désordres hémorhéologiques ?Is the feeling of heavy legs in overtrained athletes related to impaired hemorheology?

Introduction. – The aim of this work is to evaluate if the feeling of heavy legs in athletes is correlated with overtraining syndrome-related hemorheological disturbances.Results. – The subjects who quoted the item: “I have the feeling of heavy legs” had higher plasma viscosity and higher red cell aggregation parameters. The overtraining score was correlated positively with plasma viscosity, and aggregability parameters. The feeling of heavy legs was correlated with plasma viscosity and aggregability.Conclusion. – These findings suggest that the feeling of heavy legs in overtrained athletes is related to overtraining syndrome-related hemorheologic disturbances, namely mild plasma hyperviscosity and mild erythrocyte hyperaggregability.     

Étude comparative de l'analyse spectrale de la fréquence cardiaque au cours de l'exercice sur ergocycle et de l'entraînement en judoHeart rate comparative study by spectral analysis between two exercises: ergocycle vs judo randori

Aim – Heart rate comparative study by spectral analysis between a 6 minutes judo randori et a 4 minutes ergocycle exercise at .Materials and methods – By ten male judokas, both time series were analyzed by short term Fourier transform (time/frequency analysis). Each 512 RR time series drawn from ECG was subdivided by Hanning windowing in 13 samples of 128 values (32 RR periods step). For each sample, both exercise types, means of the ten spectrograms have been computed, yielding two mean spectrograms for each sample.Results – 1) Despite a near maximal heart rate (HR) level between the two exercise types, the spectral energy computed from judo randori was significantly more important than ergocycle spectral energy. This phenomenon yields a qualitative effect of the exercise type (judo or ergocycle) on HRV. 2) the normalized spectral powers of low frequency and high frequency bands respectively, were not significantly different between both exercise types.Conclusion – The autonomie nervous control on HR would depend rather on exercise load than on exercise type.     

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.     

Fécondité féminine et activité physique intense et répétéeFemale fertility and intensive physical activity

Aims – To estimate the effects of intensive physical activity on female fertility.Current knowledge – Since twenty to thirty years ago, women have regularly participated in intense physical sports. The first Olympic Marathon for women took place at Los Angeles (United-States) in 1984 and many clinical studies concerning the incidence of menstrual disturbances among sportswomen, were concomitant of the dramatic increase in female participation in endurance sports, either as recreational or professional sportswomen. Most of these studies were focused on secondary amenorrhea. Later, etiological studies have shown that a range of disturbances, from an apparently normal menstrual cycle, irregular menstruation, oligomenorrhea to the complete blockage of the ovarian function were observed.Points of views and plans – It is very likely that the physiological process leading to menstrual troubles among sportswomen include disturbances of GnRH pulsatility at hypothalamic level. It has been shown that a session of training at an intensity greater than 60% during at least 40 min leads to the secretion of neuromediators able to interfere with GnRH pulsatility. Repetitiveness of daily sessions of training (i.e., more than five sessions a week) associated with marginal energy intake or strictly vegetarian food may contribute to disturb the hypothalamo-pituitary-ovarian axis in female athletes.     

Réponses corticotropes à un stress intense en fonction de l'entraînement chez deux souches de rats. Résultats préliminairesCorticotropic responses to acute stress according to exercise training in different rat strains: preliminary results

Aims – Determine the corticotropic responses to acute stress with or without prior exercise training and following the corticotropic phenotype of the rats.Methods and results – Lewis and SHR strains were selected for their opposite corticotropic responsiveness characteristics (high and low in SHR and Lewis strain, respectively). This study shows that exercise training induces opposite adrenal responses in SHR strain and in Lewis strain (which decrease increase its corticosterone concentration, respectively).Conclusion – This suggests that genetic may play an key role in pituitary-adrenal adaptations to exercise training.     

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.     

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.     

Suivi de l’entraînement de nageurs de haut niveau par questionnaire de fatigue, dosages hormonaux et variabilité de la fréquence cardiaqueTraining follow up by questionnaire fatigue, hormones and heart rate variability measurements

Introduction. – A short questionnaire of fatigue, urinary cortisol/cortisone ratio and heart rate variability were measured in 14 elite swimmers during heavy, light and moderate training periods.Results. – The questionnaire was strongly related to the variations of training and performance (r > 0.70). Correlations were lower with the hormonal ratio and insignificant with the heart rate variability.Conclusion. – The questionnaire and the hormonal ratio were good markers of the variations of training and performance contrary to the heart rate variability.     

Les effets indésirables de la créatine exogène: de la fiction à la réalité

Summary

Objectives

For the last six years the consumption of exogenous creatine monohydrate has been extended more and more. Despite numerous publications on the ergogenic effects of this naturally occurring substance, there is almost no information on the deleterious effects of this supplement. The objectives of this review are to point out facts which are often in contradiction with allegations introduced by the media.

Topics

In athletes, exogenous creatine supplements amount to 20 g per day during five days followed by 1 to 10 g per day, every day, for weeks, months, and even years. Usually consumers do not report side-effects, with the exception of body weight increase. However, gastro-intestinal disturbances and muscle cramps have been reported occasionally. Liver and kidney dysfunction have also been hypothesized but real facts are missing for this. From a theoretical point of view, exogenous creatine supplementation suppresses its hepatic synthesis (maximum 2 g per day for vegetarians). Its destination is mainly (95–98%) skeletal muscle and all excess is excreted in urine (on average 60% of the supplement). Scientific publications on the undesirable effects of exogenous creatine are almost non-existent, but newspapers and the media do not hesitate to publish false information or wrong interpretations based on one individual case of an individual with nephropathy who, later on, consumed creatine monohydrate. In addition, we did not find any side-effects on renal function after short-term (five days), medium-term (nine weeks) or long-term (up to five years) creatine supplementation in small cohorts of athletes.

Future prospects

We have no intention to validate or not the supplementation of exogenous creatine by athletes, but apparently there are no real deleterious effects on the body of healthy consumers. Nevertheless, one has to be careful about individual reactions when excess food are taken up. We are convinced that regular biological check-ups are needed to avoid any abnormal reaction under creatine supplementation.