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La pratique d’activité physique fait partie intégrante des recommandations médicales pour prévenir et traiter les maladies coronariennes. Suivant un programme d’entraînement structuré, serait-il possible d’améliorer la réponse à l’exercice tout en offrant une protection cardiaque au patient? C’est ce que semblent démontrer certaines études sur le préconditionnement ischémique (PCI) induit par un test d’effort maximal. Les mêmes mécanismes physiologiques induits par le PCI sont également observés lorsqu’un brassard est utilisé pour créer des cycles d’ischémie/reperfusion sur un muscle squelettique. Cette méthode est connue sous l’appellation : préconditionnement ischémique à distance (PCID). À l’autre extrémité du spectre de l’activité physique, des sportifs ont utilisé le PCDI durant leur échauffement afin d’améliorer leurs performances. C’est dans l’objectif d’étudier ces prémisses que se sont construits les projets de recherches suivants. La première étude porte sur les effets du PCID sur des efforts supra maximaux de courte durée. Les sujets (N=16) ont exécuté un test alactique (6 * 6 sec. supra maximales) suivi d’un test lactique (30 secondes supra maximales) sur ergocycle. Les sujets avaient été aléatoirement assignés à une intervention PCID ou à une intervention contrôle (CON) avant d’entreprendre les efforts. La procédure PCID consiste à effectuer quatre cycles d’ischémie de cinq minutes à l’aide d’un brassard insufflé à 50 mm Hg de plus que la pression artérielle systolique sur le bras. Les résultats de ce projet démontrent que l’intervention PCID n’a pas d’effets significatifs sur l’amélioration de performance provenant classiquement du « système anaérobie », malgré une légère hausse de la puissance maximal en faveur du PCID sur le test de Wingate de trente secondes (795 W vs 777 W) et sur le test de force-vitesse de six secondes (856 W vs 847 W). Le deuxième essai clinique avait pour objectif d’étudier les effets du PCID, selon la méthode élaborée dans le premier projet, lors d’un effort modéré de huit minutes (75 % du seuil ventilatoire) et un effort intense de huit minutes (115 % du seuil ventilatoire) sur les cinétiques de consommation d’oxygène. Nos résultats démontrent une accélération significative des cinétiques de consommation d’oxygène lors de l’intervention PCID par rapport au CON aux deux intensités d’effort (valeur de τ1 à effort modéré : 27,2 ± 4,6 secondes par rapport à 33,7 ± 6,2, p < 0,01 et intense : 29,9 ± 4,9 secondes par rapport à 33,5 ± 4,1, p < 0,001) chez les sportifs amateurs (N=15). Cela se traduit par une réduction du déficit d’oxygène en début d’effort et une atteinte plus rapide de l’état stable. Le troisième projet consistait à effectuer une revue systématique et une méta-analyse sur la thématique du préconditionnement ischémique (PCI) induit par un test d’effort chez les patients coronariens utilisant les variables provenant de l’électrocardiogramme et des paramètres d’un test d’effort. Notre recherche bibliographique a identifié 309 articles, dont 34 qui ont été inclus dans la méta-analyse, qui représente un lot de 1 053 patients. Nos analyses statistiques démontrent que dans un effort subséquent, les patients augmentent leur temps avant d’atteindre 1 mm de sous-décalage du segment ST de 91 secondes (p < 0,001); le sous-décalage maximal diminue de 0,38 mm (p < 0,01); le double produit à 1 mm de sous-décalage du segment ST augmente de 1,80 x 103 mm Hg (p < 0,001) et le temps total d’effort augmente de 50 secondes (p < 0,001). Nos projets de recherches ont favorisé l’avancement des connaissances en sciences de l’activité physique quant à l’utilisation d’un brassard comme stimulus au PCID avant un effort physique. Nous avons évalué l’effet du PCID sur différentes voies métaboliques à l’effort pour conclure que la méthode pourrait accélérer les cinétiques de consommation d’oxygène et ainsi réduire la plage du déficit d’oxygène. Nos découvertes apportent donc un éclaircissement quant à l’amélioration des performances de type contre-la-montre étudié par d’autres auteurs. De plus, nous avons établi des paramètres cliniques permettant d’évaluer le PCI induit par un test d’effort chez les patients coronariens. / Physical activity is an integral part of medical recommendations for preventing and treating coronary heart disease. By following a structured training program, is it possible to improve response to exercise and provide heart protection at the same time? This is suggested by certain studies on ischemic preconditioning (IPC) induced by a maximal exercise test. The same physiological mechanisms induced by IPC are also observed when a pressure cuff is used to create cycles of ischemia/reperfusion on skeletal muscle. This is known as remote ischemic preconditioning (RIPC). At the other end of the physical activity spectrum, athletes have used RIPC during warm-ups to improve performance. The following research projects were developed to study these premises. The first trial addressed the effects of RIPC on short supra-maximal exercise. The subjects (N = 16) performed an alactic test (six seconds of supra-maximal exercise) followed by a lactic test (30 seconds of supra-maximal exercise) on a cycle ergometer. The subjects were randomly assigned to an RIPC or CON intervention before the exercise. The RIPC procedure involved four cycles of ischemia using a pressure cuff inflated to 50 mmHg above systolic blood pressure at the arm. The results of the project show that RIPC intervention does not significantly improve performance typical of the anaerobic system, despite a slight increase in maximal power output in favour of RIPC in the 30 second Wingate test (795 W vs. 777 W) and in the 6 seconds test (856 W vs. 847 W). The aim of the second clinical trial was to study the effects of RIPC during eight minutes of moderate exercise (75% of ventilatory threshold) and intense exercise (115% of ventilatory threshold) on the kinetics of O2 uptake. Our results showed a significant acceleration in the kinetics of O2 uptake during the RIPC intervention compared to the CON intervention for the two exercise intensities (value of 1 during moderate exercise: 27.2 ± 4.6 seconds compared with 33.7 ± 6.2, p < .01 and intense exercise: 299 ± 4.9 seconds compared with 33.5 ± 4.1, p < .001) in amateur athletes (N= 15). This means a reduction in the oxygen deficit at the onset of exercise and more rapid achievement of the steady state. The third project involved performing a systematic review and meta-analysis on ischemic preconditioning (IPC) induced by an exercise test in coronary patients. Our literature search identified 309 articles, 34 of which were included in the meta-analysis, which represents a batch of 1,053 patients. Our statistical analyses show that in subsequent exercise, patients' time to 1 mm ST segment depression is augmented by 91 seconds (p < .001); the maximum depression decreases by 0.38 mm (p < .01); the double product at 1 mm ST segment depression increases by 1.80 x 103 mmHg (p < .001) and the total time of exercise increases by 50 seconds (p < .001). Our research projects have promoted the advancement of knowledge in exercise science by the use of a cuff as a stimulus to the RIPC before sports performance. We evaluated the effect of the RIPC on different metabolic pathways and we concluded that the method could accelerate the kinetics of oxygen consumption and reduce the range of oxygen deficit. In addition, we have established clinical parameters for assessing the IPC induced by a stress test for coronary patients. / Il praticare attività fisica è parte integrante delle raccomandazioni mediche atte a prevenire e trattare le coronopatie. Seguendo un programma di allenamento strutturato, sarebbe possibile migliorare la risposta all’esercizio, pur offrendo una protezione cardiaca al paziente: è ciò che sembrano dimostrare alcuni studi sul precondizionamento ischemico (PCI) indotto mediante test da sforzo massimale. Gli stessi meccanismi fisiologici indotti dal PCI vengono inoltre osservanti utilizzando una fascia da braccio per creare dei cicli d’ischemia/riperfusione su un muscolo scheletrico. Tale metodo è conosciuto con il nome di “precondizionamento ischemico a distanza” (PCID). All’estremità opposta dello spettro dell’attività fisica, alcuni sportivi hanno impiegato il PCID durante il riscaldamento, al fine di migliorare le proprie prestazioni. I seguenti progetti di ricerca sono stati elaborati con l’obiettivo di studiare queste premesse. Il primo studio riguarda gli effetti del PCID sugli sforzi sovramassimali di breve durata. I soggetti (N = 16) hanno effettuato un test anaerobico alattacido (6 x 6 sec. sovramassimali), seguito da un test anaerobico lattacido (30 secondi sovramassimali) su ergociclo. I soggetti sono stati aleatoriamente assegnati a un intervento di PCID o a un intervento di controllo (CON) prima di effettuare gli sforzi. La procedura di PCID consiste nell’effettuare quattro cicli d’ischemie con l’ausilio di una fascia da braccio a 50 mm Hg in più rispetto alla pressione arteriosa sistolica. I risultati del progetto dimostrano che l’intervento di PCID non ha effetti significativi sul miglioramento della prestazione proveniente classicamente dal “sistema anaerobico”, nonostante un leggero aumento di potenza a favore del PCID sul test di Wingate (795 W vs 777 W) di sei secondi (856 W vs 847 W). La seconda sperimentazione clinica aveva come obiettivo lo studio degli effetti del PCID durante uno sforzo moderato di otto minuti (75% della soglia ventilatoria) e intenso (115% della soglia ventilatoria) sulle cinetiche di consumo d’ossigeno. I nostri risultati dimostrano un’accelerazione significativa delle cinetiche di consumo d’ossigeno durante l’intervento di PCID rispetto al CON alle due intensità di sforzo (valore da 1 a sforzo moderato: 27,2 ± 4,6 secondi rispetto a 33,7 ± 6,2, p < 0,01 e intenso: 29,9 ± 4,9 secondi rispetto a 33,5 ± 4,1, p < 0,001) negli sportivi dilettanti (N= 15). Ciò si traduce con una riduzione del deficit di ossigeno all’inizio dello sforzo e un raggiungimento più rapido dello stato stazionario. Il terzo progetto consisteva nell’effettuazione di una revisione sistematica e una meta-analisi sulla tematica del precondizionamento ischemico (PCI) indotto mediante test da sforzo nei pazienti coronopatici. La nostra ricerca bibliografica ha individuato 309 articoli, 34 dei quali sono stati inclusi nella meta-analisi, che rappresentano un gruppo di 1.053 pazienti. Le analisi statistiche da noi effettuate dimostrano che in uno sforzo susseguente, i pazienti aumenti i loro tempi prima di raggiungere 1 mm di sottoslivellamento del segmento ST di 91 secondi (p < 0,001); il sottoslivellamento massimo diminuisce di 0,38 mm (p < 0,01); il doppio prodotto a 1 mm di sottoslivellamento del segmento ST aumenta di 1,80 x 103 mm Hg (p < 0,001) e il tempo totale di sforzo aumenta di 50 secondi (p < 0,001).

Made available in DSpace on 2014-06-11T19:30:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-04-13Bitstream added on 2014-06-13T19:40:24Z : No. of bitstreams: 1 molina_r_dr_rcla.pdf: 1580344 bytes, checksum: 7e4493046f62a81aaae554c81ae0e39c (MD5) / Exercícios intensos e/ou não habituais, realizados através de contrações excêntricas, ocorrem constantemente em nossas vidas, os quais podem resultar em dores musculares imediatas ou tardias, com um marcado e prolongado efeito sobre nossa capacidade funcional. Desta forma, o presente trabalho teve como objetivo analisar o efeito do exercício excêntrico (EE), associado com dano muscular, sobre as propriedades mecânicas do músculo e índices de aptidão aeróbia. Metodologicamente o experimento foi dividido em 1 e 2. No primeiro experimento, doze homens (21,7±2,3 anos) saudáveis, não treinados, foram avaliados, através de três contrações voluntárias máximas (CVM), no pico de torque (PT) isocinético do quadríceps, e correspondente, pico da taxa de desenvolvimento de torque (pico TDT), pico da taxa de desenvolvimento de velocidade (pico TDV) e impulso contrátil (IC) a 60º.s-1 antes e após 24h e 48h de um protocolo de exercícios excêntricos de dez séries de dez repetições máximas. No segundo experimento, vinte homens (24,4±3,5 anos) saudáveis e não treinados foram divididos em dois grupos, de acordo com a cadência realizada no ciclismo (50 rpm e 100 rpm), e avaliados para a cinética de consumo de oxigênio ( O2) e eficiência mecânica bruta (EB) e de trabalho (ET), através de três transições de ciclismo com duração cada uma de 6min a 90% do limiar de lactato precedidas de 4min a 0W, antes e após 24h e 48h do protocolo de EE. Nos dois experimentos os indicadores indiretos de dano muscular de dor muscular tardia (DMT), atividade da creatina quinase (CK) plasmática e pico de torque isocinético concêntrico (PT) foram significantemente alterados 24h e 48h após o protocolo de exercícios excêntricos, em relação aos valores de base. No primeiro experimento o PT (-15,3%, p=0,002), pico TDT (-13,1%,. p=0,03) e IC (-29,3%,. p=0,01) diminuíram significantemente... / Intense and/or unusual exercises, related to eccentric contractions are constant in our lives, resulting in immediate or delayed onset muscle soreness (DOMS) and may have a marked and prolonged effect on our functional capacity. Thus, this study was to analyze the effect of eccentric exercise (EE), associated with muscle damage, on the mechanical properties of muscle and indices of aerobic fitness. Methodologically the experiment was divided into 1 and 2. In the first experiment, twelve (21.7 ± 2.3 years) healthy untrained men subjects were assessed at peak torque (PT) isokinetic quadriceps, and the corresponding peak rate of torque development (peak RTD), peak rate velocity development (peak RVD) and contractile impulse (CI) at 60o. s-1 before and after 24h and 48h isokinetic EE protocol of 10 sets of 10 repetitions. In the second experiment, twenty (24.4 ± 3.5 years) healthy and untrained men were divided into two cycling cadence groups (50 rpm and 100 rpm) and evaluated for the pulmonary oxygen uptake ( O2) kinetics and gross (GE) and work (WE) mechanical efficiency through 3 transitions cycling lasting each of 6 min at 90% lactate threshold preceded by 4min at 0W, before and after 24h and 48h protocol EE. In both experiments, DOMS (DMT), activity of creatine quinase (CK) in plasma and peak isokinetic concentric torque (PT) was significantly altered at 24h and 48h after the eccentric exercise protocol. In the first experiment, the PT (-15.3%, p = 0.002), peak RTD (-13.1%. p = 0.03) and CI (- 29.3%. p = 0.01) decreased significantly to 24h and peak RVD not changed. After 48h, PT (-7.9%, p = 0.002) and CI (-29.2%, p = 0.003) were maintained less values but RTD recovered to baseline values. RTD normalized to PT (% CVM.s-1) measured at 30 ms (24h = 580.5%, p = 0.01 and 48h = 681.3%, p = 0.006) and 100 ms (48h = 623.3 %, p = 0.009) the onset of contraction was higher than the previous... (Complete abstract click electronic access below)