Cardiac Output and Performance during a Marathon Race in Middle-Aged Recreational Runners

Purpose. Despite the increasing popularity of marathon running, there are no data on the responses of stroke volume (SV) and cardiac output (CO) to exercise in this context. We sought to establish whether marathon performance is associated with the ability to sustain high fractional use of maximal SV and CO (i.e, cardiac endurance) and/or CO, per meter (i.e., cardiac cost). Methods. We measured the SV, heart rate (HR), CO, and running speed of 14 recreational runners in an incremental, maximal laboratory test and then during a real marathon race (mean performance: 3 hr 30 min ± 45 min). Results. Our data revealed that HR, SV and CO were all in a high but submaximal steady state during the marathon (87.0 ± 1.6%, 77.2 ± 2.6%, and 68.7 ± 2.8% of maximal values, respectively). Marathon performance was inversely correlated with an upward drift in the CO/speed ratio (mL of CO × m−1) (r = −0.65, P < 0.01) and positively correlated with the runner's ability to complete the race at a high percentage of the speed at maximal SV (r = 0.83, P < 0.0002). Conclusion. Our results showed that marathon performance is inversely correlated with cardiac cost and positively correlated with cardiac endurance. The CO response could be a benchmark for race performance in recreational marathon runners

Limiting factors of endurance at maximal oxygen utpake in human

Le débit maximal d’oxygène (VO2max), aussi appelé consommation maximale d’oxygène, est actuellement l’un des paramètres central pour la compréhension de la physiologie humaine lors d’un effort physique. Plus ce débit est important et plus le sujet, sportif ou non, est capable de fournir une grande quantité d’énergie pour courir, sauter, voir courir plus vite, sauter plus haut… Ainsi, le temps pendant lequel l’homme est capable de soutenir cette valeur de débit maximal (endurance au VO2max) est l’un des facteurs déterminant de la performance. Plus ce temps est long et plus le sujet maintient une haute vitesse de course. C’est pourquoi, de nombreuses études dans le domaine de la physiologie humaine et sportive se sont attachées à analyser les facteurs limitants le VO2max et l’endurance au VO2max. Néanmoins, si les facteurs limitants du VO2max sont aujourd’hui largement acceptés, les facteurs limitant l’endurance au VO2max restent encore à déterminer. La mise en place d’un modèle expérimental innovant utilisant comme variable indépendante la VO2max et non la puissance, comme cela était fait habituellement, a permis de mettre en évidence les facteurs limitant l’endurance au VO2max. Grâce à ce modèle, nous avons démontré que l’endurance au VO2max dépend de variations de puissance (ou de vitesse) durant cet effort au VO2max. Cette variation de puissance permet d’épargner les réserves du métabolisme anaérobie. Ainsi, nous avons montré que ces réserves anaérobies sont également un facteur limitant de l’endurance au VO2max. De plus, l’endurance au VO2max n’est pas corrélée au VO2max des sujets. Autrement dit, un sujet, avec un VO2max bas sera capable de soutenir longtemps son VO2max, s’il a en contre partie une grande capacité anaérobie et s’il est capable d’adapter sa vitesse de façon adéquate lors de sa course. L’endurance au VO2max sera identique au niveau de la mer ou en altitude (3000m) et ne dépendra pas des facteurs cardiovasculaires intervenant dans l’équation de Fick, principaux facteurs limitants de l’amplitude du VO2max. L’ensemble de ses résultats a donc permis, pour la première fois, de déterminer des facteurs limitant l’endurance au 2max qui sont différents des facteurs limitant l’amplitude du VO2max. Ces nouvelles connaissances sur l’endurance trouveront des applications dans la planification des entraînements sportifs afin d’améliorer la qualité des entraînements et en épargnant le surentraînement aux sportifs. De plus, ces données pourraient être également mise en œuvre chez les sujets dont les capacités physiques ont été endommagées par des pathologies (cardiaques, respiratoires par exemple).Maximal Oxygen uptake (VO2max) is currently one of the central parameters for the comprehension of human physiology during a physical activity. Higher is this oxygen uptake is and greater is the energy supply to run or jump for trained or untrained subjects … Thus, the time during which the subject is able to support this maximal oxygen uptake (endurance at VO2max) is one of the factors determining the performance. Longer is this endurance at VO2max Higher is the speed of race maintains by the subjects this is why, Among the numerous studies in the field of human and sporting physiology, the limiting factors of VO2max and the limiting factors of endurance at VO2max were studied. Nevertheless, if the limiting factors of VO2max today are well accepted, the factors limiting the endurance at VO2max still remain to be determined.The development of an innovating experimental model using VO2max as independent variable and not the power, as that was usually done, highlight the factors limiting the endurance at VO2max. Thanks to this model, we showed that the endurance at VO2max depends on variations of power (or speed) during this effort at VO2max. This variation of power minimizes the anaerobic metabolism reserve utilization during the 2max plateau. Thus, we showed that these anaerobic reserves are also a limiting factor of the endurance at VO2max. Moreover, the endurance at VO2max was not correlated with the VO2max. In other words, a subject, with a low VO2max may be able to support VO2max for a long time, if the anaerobic capacity is important and if the speed variation is properly adapted during the race. The endurance at VO2max is identical at sea level and in hypoxic condition (3000m) and that not depend on the cardiovascular factors entering in the Fick equation, known as limiting factors of VO2max amplitude. For the first time, all of these results determine factors limiting the endurance at VO2max which are different from the factors limiting the amplitude of VO2max. This new knowledge about endurance will find applications in the planning of the sport training in order to improve its quality and by saving athletes overtraining. Moreover, these data could also be implemented for subjects whose physical capacities are damaged by pathologies (cardiac, respiratory impairments for example)

Sport et Santé

International audiencerésumé du livre:Cet ouvrage est conçu pour les futurs professionnels des activités physiques et sportives, comprenant des métiers aussi variés que coach sportif, animateur, préparateur physique, entraîneur... Il aborde les problématiques liées au suivi du sportif : psychologie du sportif, travail de la performance, nutrition, santé, dopage, autant de notions qui doivent être parfaitement articulées pour composer un cadre de travail sportif cohérent.STAPS — EPS — BPJEPS — DEJEPS — CQ

A new incremental test for VO2max accurate measurement by increasing VO2max plateau duration, allowing the investigation of its limiting factors

International audienceThe purpose of this study was to (1) validate anew exercise protocol for accurate measurement of VO2max by obtention of a VO2max plateau for all subjects fit and unfit (2) test the hypothesis that VO 2max plateau duration is not correlated with VO2max and (3) verify that limiting factors of VO2max plateau duration are different from those of VO2max amplitude. Therefore, 14 subjects performed two incremental cycling tests (1) a classical incremental test (CIT) to determine VO2max, the power at VO2max (PVO 2max) and at the lactate threshold (PLT) (2) a new incremental test (NIT) in which the power was decreased just after the subject reached VO 2max. During both protocols, heart rate, stroke volume, cardiac output, the arterio-venous difference and the oxygen blood saturation were recorded. The results showed that, with the NIT, subject could maintain along VO2max plateau (6 ± 3 min), even those who could not reach VO2max plateau at the end of CIT (n = 5). The VO2max plateau duration was not correlated with VO2max amplitude which was correlated with the power at SVmax (r = 0.888, pandlt;0.001). The VO2max plateau duration was correlated with the power decrease (W/s) during the VO2max plateau (r = -0.72, p = 0.003) but not with cardiac-related factors nor with PVO2max. In conclusion, these experiments showed that it was possible to get a long VO2max plateau at the end of NIT whatever the individual VO2max amplitude was. The limiting factor of VO2max duration was the power output. © 2011 Springer-Verlag

The sustainability of VO2max Effect of decreasing the workload

International audienceThe study examined the maintenance of VO2max using VO 2max as the controlling variable instead of power. Therefore, ten subjects performed three exhaustive cycling exercise bouts (1) an incremental test to determine VO2max and the minimal power at VO2max (PVOmax), (2) a constant-power test at PVOmax and (3) a variable-power test (VPT) during which power was varied to control VO 2 at VO2max. Stroke volume (SV) was measured by impedance in each test and the stroke volume reserve was calculated as the difference between the maximal and the average 5-s SV. Average power during VPT was significantly lower than PVOmax (238 ± 79 vs. 305 ± 86 W; p andlt; 0.0001). All subjects, regardless of their VO2max values and/or their ability to achieve a VO2max plateau during incremental test, were able to sustain VO2max for a significantly longer time during VPT compared to constant-power test (CPT) (958 ± 368 s vs. 136 ± 81 s; p andlt; 0.0001). Time to exhaustion at VO2max during VPT was correlated with the power drop in the first quarter of the time to exhaustion at VO2max (r = 0.71; p andlt; 0.02) and with the stroke volume reserve (r = 0.70, p = 0.02) but was not correlated with VO 2max. This protocol, using VO2max rather than power as the controlling variable, demonstrates that the maintenance of exercise at VO 2max can exceed 15 min independent of the VO2max value, suggesting that the ability to sustain exercise at VO2max has different limiting factors than those related to the VO2max value. © 2012 Springer-Verlag