Vieillissement et désaturation oxyhémoglobinée du sportif

A extreme athlete can be defined as an athlete able to exceed the limit of one function in such a way that failure of another function appears. For example extreme athletes in endurance events are able to exceed the normal limits of cardiac output but show a hemoglobin desaturation by the end of exhaustive exercise. Usually, these athletes have had a maximal oxygen uptake (O₂ max) greater than 65 ml·min⁻¹. The aim of this study was to determine whether hemoglobin desaturation occurs in master athletes and whether aging facilitates this phenomenon. Nine master athletes aged 62–75 participated to this study. They practised leisure cycling 5000 to 14000 km per year. Hemoglobin saturation was measured non-invasively using the transcutaneous method during both incremental exercise until exhaustion and constant load exercise at 70% and 90% of O₂ max for a 15 min period. We considered that there was a desaturation if SaO₂ decreased by 4%. During maximal incremental exercise we observed desaturation in six subjects. These results were confirmed during constant load exercise at 90% of O₂ max. It is interesting to note that one of the subjects, whose desaturation was 8% during incremental exercise, showed a desaturation of 16% at the 15th minute of constant load exercise at 90% O₂ max. In our master athletes this desaturation was observed for O₂ max and pulse oxygen values respectively equal to 1/2 and 2/3 of the values of young athletes. Aging thus seems to facilitate the mechanisms of athlete's desaturation. These mechanisms are highly speculative. One can, however, suspect the role of relative hypoventilation, a ventilation-perfusion inequality, and a diffusion limitation. A decrease of red blood cell transit time in the pulmonary capillary may also play a role, as there is a decrease in pulmonary capillary volume in master athletes over 60 years and that maximal cardiac output does not seem to decrease with age.     

Isometric handgrip exercise during cardiovascular magnetic resonance imaging: Set‐up and cardiovascular effects

Purpose:

To establish a suitable setup for combining isometric handgrip exercise with cardiovascular magnetic resonance (CMR) imaging and to assess cardiovascular effects.

Materials and Methods:

Fifty‐three healthy volunteers (31 males, mean age 45 ± 17 years) underwent handgrip exercise in a 3T scanner using a prototype handgrip system and a custom‐made feedback system that displayed the force. Handgrip was sustained at 30% of the maximal contraction for 6–8 minutes. Heart rate, blood pressure (BP), and double product were determined sequentially. Stroke volume was quantified in a subgroup (n = 21) at rest and stress using phase contrast acquisitions.

Results:

Heart rate increased significantly between rest and stress by 20 ± 13%, systolic / diastolic / mean BP by 15 ± 11% / 20 ± 18% / 17 ± 13%, double product by 37 ± 21%, and cardiac output by 27 ± 16% (each P < 0.001). Stroke volume did not significantly increase (3 ± 9%; P = 0.215). Higher age was associated with reduced increase of stroke volume (P = 0.022) and cardiac output (P < 0.001). Overweight subjects showed less increases in heart rate (P = 0.021) and cardiac output (P = 0.002).

Conclusion:

The handgrip exercise during CMR with the presented set‐up leads to considerable hemodynamic changes in healthy volunteers. J. Magn. Reson. Imaging 2013;37:1342–1350. © 2013 Wiley Periodicals, Inc.     

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.     

Le questionnaire de surentraînement de la Société française de médecine du sport : reproductibilité à court termeOvertraining questionnaire of the Société française de médecine du sport (French Society of Sport Medicine): short term reproducibility

Purpose. – To assess the short-term stability, over time, of a slightly modified version of the overtraining questionnaire proposed by the SFMS.Methods. – Three or 7-day test–retest of the questionnaire was completed in 30 high level athletes. In a first stage analysis, the score obtained during the first test was compared to and correlated with that obtained during the second one. Then, in a second stage analysis, the individual reproducibility of each item was assessed using a similitude index: a value of 100% meant that all the athletes gave an identical response for the two trials.Results. – Scores were not different between the two tests and intra-class correlation coefficients were r = 0.82. Overall reproducibility of the similitude index was quite good even if six items of 52 displayed a lower similitude index (around 80%).Conclusion. – The short-term reproducibility of the overtraining questionnaire is quite good. This result reinforces its reliability and warrants its use in a longitudinal follow-up framework aimed to detect precociously an overtraining syndrome.