Implication de l’oxygénation cérébrale dans les limitations à l’exercice musculaire des personnes non-entraînées et sportifs d’endurance. L’objectif général de ce travail était de déterminer si l’oxygénation cérébrale était un facteur de la limitation à l’exercice de type aérobie. Dans un premier temps, nous nous sommes attachés à étudier le rôle de l’oxygénation cérébrale mesurée par la Spectroscopie dans le proche Infra-Rouge (NIRS) dans la limitation de l’exercice progressif maximal en rampe. Nous avons montré l’existence d’un seuil de déclin de l’oxygénation cérébrale associé au point de compensation respiratoire (RCP). L’amélioration de la performance avec une supplémentation d’O2 était liée au décalage de ce seuil à de plus hautes intensités d’exercice chez des sujets actifs (étude 1). Dans un second temps, nous avons montré que ce seuil de déclin de l’oxygénation, retrouvé aussi chez des sportifs entraînés en endurance apparaîssait à de plus hautes intensités d’exercice que chez des sujets non-entraînés (étude 2). Enfin, nous avons déterminé l’impact de l’hypoxémie artérielle induite par l’exercice (HIE) des sportifs d’endurance sur l’oxygénation cérébrale au cours d’un exercice maximal en rampe et d’un exercice de temps limite à charge constante. Nous avons ainsi montré que l’oxygénation cérébrale était augmentée avec la HIE suggérant un effet compensatoire à l’hypoxémie artérielle au cours de l’exercice progressif maximal en rampe. Ceci, n’existait pas au cours de l’exercice de temps limite ne supportant pas l’implication de l’oxygénation cérébrale dans ce type d’exercice (étude 3). Ces travaux ont donc mis en évidence l’implication de l’oxygénation cérébrale dans la limitation de l’exercice maximal en rampe chez des sujets actifs et des sportifs entraînés en endurance présentant ou pas une HIE. Toutefois, elle ne semble pas être un facteur majeur de limitation de l’exercice de temps limite. / Involvement of cerebral oxygenation in muscular exercice limitation in untrained and trained endurance men. A decrease in oxygen availability in the brain could be a physiological mechanism limiting aerobic fitness. We first studied the role of cerebral oxygenation measured by Near Infra-Red Spectroscopy (NIRS ) in maximal cycle ramp exercise limitation. We showed a cerebral oxygenation threshold decline associated with respiratory compensation point (RCP). This threshold appeared for higher exercise intensities -related to performance improvement with hyperoxia in untrained endurance men (study 1). Secondly , we showed that the cerebral oxygenation threshold in athletes occurred for higher sub-maximal exercise intensities than untrained (study 2). Finally , we determined the involvement of exercise-induced arterial hypoxemia (EIH) in endurance athletes on cerebral oxygenation during maximal cycle ramp exercice and exercice time to exhaustion. We showed that cerebral oxygenation was improved by EIH suggesting a compensatory effect of EIH during the maximal cycle ramp. This did not occur during exercise time to exhaustion, and does not support the involvment of cerebral oxygenation in this type of exercise (study 3). This work has therefore highlighted the involvement of cerebral oxygenation in maximal cycle ramp exercice limitation in untrained and trained endurance men with or without EIH. However, it was unlikely been the major factor limiting the exercise time to exhaustion.

The elevated CO2 levels, elevated temperature, and lower blood pH that may occur during exercise should enhance O2 delivery to the exercising muscles. It was hypothesized that performance of prior exercise (PE) would result in a faster VO2 response, as well as a reduced slow component contribution, in subsequent exercise bouts. Five women (21 ± 1 yr) and 10 men (23 ± 2 yr) performed nine 6-min bouts of heavy intensity cycle ergometer exercise (i.e., above the ventilatory threshold, individually determined by an incremental test). Three bouts were performed without prior heavy exercise (noPE), three were performed 6 min after a 6-min bout of heavy intensity arm cranking (PEA), and three were performed 6 min after a 6-min bout of heavy intensity cycle ergometer exercise (PEL). Breath-by-breath VO2 data from each of the three sets of three tests were combined and fitted to a two-component model, which ignores the cardiodynamic phase. The primary and slow component amplitudes were truncated to reflect actual increases in VO2 in each phase. The effects of PE on the time constant of the primary component were inconsistent. As hypothesized, the amplitude of the slow component was reduced by PE (noPE vs PEA vs. PEL: 25% > 16% < 14%; p < .05). It is concluded that heavy intensity PE affects characteristics of the VO2 profile in a subsequent bout of heavy intensity leg exercise.

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The purpose of this study was to develop a regression equation to predict VO2max based on non-exercise (N-EX) data. All participants (N = 100), aged 18-65 years old, successfully completed a maximal graded exercise test (GXT) to assess VO2max (mean ± SD; 39.96 mL∙kg-¹∙min&sup-1; ± 9.54 mL∙kg-¹∙min-¹). The N-EX data collected just before the maximal GXT included the participant's age, gender, body mass index (BMI), perceived functional ability (PFA) to walk, jog, or run given distances, and current physical activity (PA-R) level. Multiple linear regression generated the following N-EX prediction equation (R = .93, SEE = 3.45 mL∙kg-¹∙min-¹, %SEE = 8.62): VO2max (mL∙kg-¹∙min-¹) = 48.0730 + (6.1779 x gender) - (0.2463 x age) - (0.6186 x BMI) + (0.7115 x PFA) + (0.6709 x PA-R). Cross validation using PRESS (predicted residual sum of squares) statistics revealed minimal shrinkage (Rp = .91 and SEEp = 3.63 mL∙kg-¹∙min-¹); thus, this model should yield acceptable accuracy when applied to an independent sample of adults (aged 18-65) with a similar cardiorespiratory fitness level. Based on standardized β-weights the PFA variable (0.41) was the most effective at predicting VO2max followed by age (-0.34), gender (0.33), BMI (-0.27), and PA-R (0.16). This study provides a N-EX regression model that yields relatively accurate results and is a convenient way to predict VO2max in adult men and women.

Objective: To determine if water treadmill running with (WTR-S) or without water shoes (WTR-NS) could produce similar cardiorespiratory responses as land treadmill running (LTR). Design and Setting: A repeated measures design was used to assess the differences between LTR and WTR-S and WTR-NS. All testing was done in either a research laboratory or an athletic training hydro-therapy room. Subjects: Eighteen trained runners (9 men and 9 women) volunteered for this study. All 18 subjects participated in three running conditions. Measurements: Treadmill speed, HR, and SF were assessed at four exercise intensities representing 50%, 60%, 70%, and 80% of land VO2max for all three running conditions. Results: WTR with and without water shoes produces similar cardiorespiratory responses to LTR. The VO2/HR relationship showed that at a HR of 150 bpm, VO2 was significantly less (p < 0.0001) when running on a land treadmill (34.66 ml/kg/min) compared to a water treadmill with shoes (37.51 ml/kg/min) and without shoes (37.21 ml/kg/min) were nearly identical. At a HR 150 of bpm, the VO2 in males (40.52 ml/kg/min) was 8.12 ml/kg/min higher than that of their female (32.40 ml/kg/min) counterparts. At a treadmill speed of 6 mph, stride frequency during LTR was 23.6 steps/min greater (p < 0.0001) than WTR-S and 21.8 strides/min greater than WTR-NS. VO2 was on the average 4.12 ml/kg/min higher (p < 0.0001) during WTR-S compared to WTR-NS running condition at the same treadmill speed. Conclusion: Statistical analysis indicated that 50%, 60%, 70%, and 80% of land VO2max was achieved in the water. Therefore, WTR can be used during rehabilitation of athletes unable to fully weight bear to prevent deconditioning. Wearing the AQinc water running shoe increases the metabolic demand by 4.12 ml/kg/min at any given water treadmill speed. Gender differences existed in the absolute HR/VO2 relationship but not in the relative HR/VO2 relationship among the three running conditions.

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Syfte och frågeställningar. Syftet med studien är att, hos äldre personer, över 65 år, samt hos yngre vuxna, mellan 20-30 år, jämföra syreupptagningsförmågan med två olika metoder, fem-minuterspyramidtest (5MPT) samt VO2max-test på löpband. Vid båda mätmetoderna används direkt syrgasmätning. Metod. Totalt deltog 36 personer i studien, varav 17 äldre personer 65 till 85 år (9 kvinnor och 8 män) samt 19 yngre med en ålder mellan 20 till 35 år (10 kvinnor och 9 män). Deltagarnas syreupptagningsförmåga mättes under 5MPT vid två tillfällen som sedan jämfördes med VO2max mätt via ett maximalt test på löpband vid ett tillfälle. Således utfördes sammanlagt tre mätningar med direkt syrgasmätning, via andningsmask, under ett maximalt löpbandstest samt under två separata tester av 5MPT med minst 48 timmar mellan varje testtillfälle. Utandningsluften analyserades sedan, vid 5MPT för alla, via det trådlösa portabla systemet Jaeger Oxycon Mobile och vid test på löpband för testgruppen med yngre deltagare. För den testgrupp med äldre deltagare användes, vid testet på löpband, den fasta on-line-utrustningen Jaeger Oxycon Pro som är en liknande mätmetod för syreupptag. 5MPT är ett fem minuter långt test där individen från golvnivå, med högsta möjliga tempo, förflyttar sig fram och tillbaka på en 5,50 meter lång sträcka med en centralt placerad trappramp som är pyramidformad och med en högsta central höjd på 0,62 meter. Resultat. Det primära fyndet i studien var att en stark signifikant korrelation (r = 0,99) visade sig mellan direkt uppmätt VO2max under maximalt test på löpband gentemot syreupptagningsförmågan vid 5MPT då båda åldersgrupperna var sammanslagna, uppmätt i l·min–1. Slutsats. Då det i undersökningen visades en stark signifikant korrelation mellan direkt uppmätt VO2max vid 5MPT och ett maximalt test på löpband i l·min–1 för äldre och yngre vuxna ger det indikationer på att 5MPT kan används som en tillförlitlig metod vid undersökning och uppföljning av en persons aeroba förmåga. Fyndet kan vara av värde då det genom mindre kostsamma och enklare metoder går att få ett mått på en persons hälsa i form av aerob kapacitet, vilket är betydelsefullt ur flera hälsoaspekter på individ- och samhällsnivå. / Aim. The purpose of the study was to investigate the results and correlation between oxygen uptake levels (VO2max) at five-minute pyramid test (5MPT) against maximal oxygen uptake test (VO2max) on a treadmill test, both measured by direct oxygen measurement, in elderly people over 65 years and younger adults aged 20-30 years. Method. A total of 36 people participated in the study, 17 elderly people aged between 65 to 85 years (9 women and 8 men) and 19 younger adults aged between 20 to 35 years (10 women and 9 men). The participants' oxygen uptake was measured twice during 5MPT and then compared with VO2max measured by a maximal treadmill test at one occasion. Thus a total of three measurements with direct oxygen measurement, via the breathing mask, during a maximum treadmill test and two separate tests of 5MPT with at least 48 hours between each test. The exhaled air was analyzed at 5MPT for all, through the wireless portable system Jaeger Oxycon Mobile and also during the test on treadmill for the test group with younger participants. The test group of older participants, got their exhaled air analyzed through a stationary on-line equipment Jaeger Oxycon Pro instead of the portable system which is a similar reliable method to measure VO2max. 5MPT is a five minute test where the subjects from floor level, with the highest possible speed, moves back and forth at a measured distance of 5.50 meter with a central staircase ramp, which is pyramid-shaped, with a maximum center height of 0.62 meters. Results. The main finding of the study was that there was a strong significant correlation (r = 0.99) between directly measured VO2max during a maximum treadmill test compared to oxygen uptake at 5MPT when both the elderly people and the younger adults were combined, measured in l·min–1. Conclusion. The study showed a strong significant correlation between directly measured VO2max at 5MPT and a maximal treadmill testing l·min–1 for older and younger adults. This indicates that 5MPT can be used as a reliable method for investigation and monitoring a person’s aerobic capacity. This finding may be of value because it shows that less expensive and easier methods can be used to measure a person's health in terms of aerobic capacity, which is important from several aspects of health at both the individual and society level.

Les oxydes doubles lamellaires de cobalt et les oxydes de vanadium ont récemment suscité un vifintérêt suite à la découverte de leurs propriétés thermoélectriques prometteuses. Nos efforts visentà synthétiser de nouveaux composés dérivés de ces systèmes en utilisant la synthèse à l'étatsolide, l'échange d'ions et/ou les techniques hydrothermales. Afin de moduler et d'optimiser leurscaractéristiques thermoélectriques, nous avons ajusté la composition des oxydes de cobalt grâce àdes substitutions appropriées. Au sein du dioxyde de vanadium quasi-1D, nous avons considérétrois différentes structures polymorphes : M1, A et B. Nous avons exploré les différents systèmesen construisant l’ensemble des diagrammes de phases. Nous avons également étudié l'effet de lasubstitution du vanadium par le molybdène et le chrome sur la stabilité de ces structurespolymorphes et caractérisé leurs propriétés électroniques en relation avec les mécanismes detransition de phase. / Lamellar cobalt double oxides and vanadium oxides have recently attracted tremendous interestafter the discovery of their interesting thermoelectric properties. Our efforts aimed at synthesizingnovel related compounds using standard solid state, ion exchange and/or hydrothermaltechniques. In order to modulate and optimize their thermoelectric characteristics, we have tunedthe composition of cobalt double oxides by appropriate substitutions. In quasi 1D vanadiumoxides, the interplay between spin, charge and orbital degrees of freedom often leads toremarkable properties. Here we dealt with three different polymorphs of vanadium dioxide,namely M1, A and B. We explored the several novel systems by constructing systematic phasediagrams. We also studied the effect of Mo and Cr:V substitution on the stability of thesepolymorphs and characterized their electronic properties in relation with the structural phasetransition mechanisms. Finally, we explored their potentiality for thermoelectric applications.