L’endurance aérobie est rarement mesurée à des intensités maximales, mais plutôt sous-maximales, principalement via des protocoles à puissance ou à durée constante. Or, les conditions réelles d’une épreuve sportive en compétition sont mieux représentées par le maintien de la plus haute puissance métabolique possible, et ce, le plus longtemps possible. Cela implique une autogestion de la puissance de travail de la part du participant – qui peut donc varier tout le long de l’épreuve – ainsi que l’atteinte des capacités aérobies maximales, dans certains cas. Dans cette étude, nous avons voulu comparer les variations de certains paramètres ventilatoires (ventilation, volume courant, fréquence respiratoire) et systémiques (rendement mécanique externe brut [RMEC], consommation d’oxygène [VO2]) entre deux protocoles d’effort maximal, l’un à puissance constante (100 % PAM), l’autre à puissance décrémentée (> 95 % VO2max). En effet, comparativement à un protocole d’effort classique à puissance constante, un protocole décrémenté implique l’utilisation de VO2 et non de la puissance mécanique comme critère de sélection de l’intensité d’effort, et augmente la durée de l’épreuve. En conséquence, le maintien de la consommation d’oxygène maximale (VO2max), et non de la puissance aérobie maximale (PAM), nous a permis d’observer des réponses physiologiques différentes de celles généralement décrites lors d’efforts incrémentés ou à puissance constante. Ces différences se sont traduites par une fréquence respiratoire plus élevée et un volume courant plus bas, indiquant l’existence d’une réponse tachypnéique plus prononcée lors d’un protocole décrémenté par rapport à un protocole à puissance constante, et reflétant ainsi une respiration plus superficielle, probablement due à une fatigue plus accrue des muscles ventilatoires. Cette fatigue serait caractérisée par un rendement mécanique plus bas et un VO2 plus élevé, et ce, malgré la diminution progressive de la puissance de travail lors de l’atteinte d’une consommation d’oxygène proche de VO2max. / Aerobic endurance is more commonly measured at submaximal rather than maximal work intensities, mainly through constant-power output trials, or time trials. However, real competition conditions are better represented through the ability to sustain the highest power output (PO) for the largest period of time. That implies the use of self-pacing strategies, which leads power output to vary throughout the exercise duration, and can also induce the attainment of maximal oxygen consumption (VO2max), in some cases. The aim of this study was thus to compare the variation of some ventilatory (tidal volume, breathing frequency) and systemic (gross mechanical efficiency, O2 cost) parameters, between two maximal endurance protocols, the first one consisting of a constant-load test (100% MAP) and the second one a decremental test at near-maximal aerobic capacity (> 95 % VO2max). Indeed, compared to a “classical” constant-power output test, a decremental test implies the use of VO2 rather than mechanical PO to control intensity throughout the task, and a higher effort duration. Consequently, we observed that the sustainment of maximal O2 consumption rather than maximal aerobic power (MAP) led to different physiological responses from those usually observed during constant-power output tests. These differences were caracterized by a higher breathing frequency as well as a lower tidal volume during the decremental test, which both reflect a more exagerated tachypneic response, and therefore indicate the existence of a shallower breathing pattern in this type of effort, probably due to a higher ventilatory muscle fatigue. This fatigue could also be expressed through a lower gross mechanical efficiency and a higher O2 cost, despite a progressive decrease of mechanical power as soon as oxygen consumption gets near VO2max.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-08-31T14:27:00Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Mestrado LUCYANA GALINDO ARCOVERDE VAZ.pdf: 1541733 bytes, checksum: 075c4e7b9b3f5f39a8de2b68a1df2f24 (MD5) / Made available in DSpace on 2016-08-31T14:27:00Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Mestrado LUCYANA GALINDO ARCOVERDE VAZ.pdf: 1541733 bytes, checksum: 075c4e7b9b3f5f39a8de2b68a1df2f24 (MD5) Previous issue date: 2016-03-29 / CAPEs / A ação ergogênica da cafeína sobre a capacidade anaeróbia (CAN) está relacionada à melhora do desempenho. Entretanto, os estudos que investigaram o efeito da cafeína sobre a capacidade anaeróbia utilizaram apenas o máximo déficit acumulado de oxigênio (MAOD) como método de estimativa. Avaliar o efeito do consumo agudo de cafeína sobre a CAN estimada através dos principais métodos de estimativa, MAOD, potência crítica (ponto de intercepção y da função trabalho/tempo), fase rápida de recuperação do consumo de oxigênio + concentração de lactato (3 compartimentos) e eficiência mecânica grossa (EF), que por apresentarem medidas representativas da CAN, detectam igualmente os possíveis efeitos do consumo agudo de cafeína sobre o metabolismo anaeróbio. Nove participantes realizaram um teste incremental no cicloergômetro para determinação do primeiro limiar ventilatório (LV1) e do consumo máximo de oxigênio (VO2máx). A partir da carga referente ao LV1 foram calculadas a carga de aquecimento (90% do LV1), e as cargas dos testes experimentais. Foram doze testes experimentais, sendo seis com cafeína e seis placebo, em um desenho duplo-cego, contrabalanceado e controlado por placebo. A contribuição anaeróbia foi calculada pelos principais métodos de estimativa. Os achados mostraram que os métodos não detectam a mesma medida de CAN, logo, eles não são equivalentes na estimativa. Em relação ao efeito da cafeína sobre a estimativa sim, não houve diferença entre cafeína e placebo, exceto MAOD, que teve uma medida mais alta na situação cafeína. Além disso, não houve diferença no tempo de exaustão entre cafeína e placebo na carga supramáxima. Os métodos de estimativa não são equivalentes, eles não apresentam a mesma medida da CAN. A cafeína influenciou um dos métodos, MAOD, e isso levou a uma superestimativa da medida, quando corrigido pela estimativa do placebo, não apresentou mais diferença. Além disso, a cafeína não promoveu melhora no desempenho na carga supramáxima. / The caffeine ergogenic action on anaerobic capacity (AC) is related to performance’s improvement. However, some studies used only the maximal accumulated oxygen deficit (MAOD) as estimative method to investigate the effect of caffeine on anaerobic capacity. Evaluate the effect of acute caffeine consumption over the estimated AC through the main estimative methods, MAOD, critical power (interception point y work function/time), fast recovery phase of oxygen consumption + lactate concentration (3 compartments) and gross mechanical efficiency (GME), which by presenting representative measures of AC also detect the possible effects of acute caffeine consumption on the anaerobic metabolism. Nine participants performed an incremental test on a cycle ergometer to determine the first ventilatory threshold (VT1) and the maximal oxygen uptake (VO2max). From VT1 power output were calculated warm up load (90% of VT1), and the loads of the experimental trials. Twelve experimental trails were performed, being six after caffeine and six after placebo in a double-blind, placebo-controlled and counterbalanced design. AC was calculated by main estimative methods. The findings of the present study showed that AC was not detected similarly by the estimative methods, which might assume that they are not equivalent in the estimative. However, MAOD was higher in after caffeine ingestion when compared to placebo. There were no differences between trials in the other estimative methods. In addition, the time to exhaustion was not different between caffeine and placebo in supramaximal exercise. The estimative methods are not equivalent to measure AC. However, caffeine influenced MAOD, which probably overestimate the measurement. However, when corrected by the placebo estimative, no differences between trials was observed. Furthermore, caffeine was not efficient to improve the performance at supramaximal exercise.