Cinemática do nado "crawl" sob diferentes intensidades e condições de respiração de nadadores e triatletas

ABSTRACT Front crawl swimming kinematics parameters of 15 front-crawl competitive swimmers (nine sprint and six long distance athletes) and seven triathletes were compared. Mean stroke length (CB), mean stroke rate (FB), mean swimming velocity (VN) and mean stroke index (IN) were determined under six different swimming conditions: three specific intensities (slow, moderate and fast) with and without breathing. Six trials of 25 m under the intensities and breathing described conditions were recorded in the sagital plane with a motion analisys system (60 Hz). A reflective landmark was fixed on the swimmers' right wrist to determine the kinematics parameters. Stature, mass and upper limbs length were also measured in all participants. Statistical analyses (p < 0.05) indicated that sprinters were taller and had longer upper limbs than triathletes, but these results did not affect the groups. kinematics data comparisons. As intensity of swimming increased, CB decreased, FB increased, VN increased and IN did not show a consistent behavior for all groups. To increase VN, all groups enhanced FB as the adopted strategy. IN seems to be not an adequate index to assess swimming kinematics. Breathing motion modifies VN in sprinters and triathletes.Parâmetros cinemáticos do nado "crawl" de 15 nadadores competitivos (nove velocistas e seis fundistas) e sete triatletas foram comparados sob diferentes condições de nado (três intensidades - baixa, moderada e alta - com e sem respiração). Comprimento (CB) e freqüência média de braçada (FB), velocidade media (VN) e índice médio de nado (IN) foram determinados. Seis repetições de 25 m, em nado "crawl", nas condições de intensidade e respiração descritas foram gravadas no plano sagital com um sistema de vídeo operando a 60 Hz. Um marcador reflexivo foi fixado no punho direito de cada nadador, a fim de posterior digitalização das imagens e obtenção de CB, FB, VN e IN. Estatura, massa e envergadura foram mensuradas. Análise estatística (p < 0,05) indicou que velocistas apresentaram maior estatura e envergadura do que triatletas, mas estes resultados não afetaram os resultados das comparações das variáveis cinemáticas entre os grupos. Ao passo que a intensidade do nado aumentou, nos três grupos, CB diminuiu, FB e VN aumentaram e IN não mostrou um comportamento consistente. Nadadores e triatletas utilizaram-se do aumento da FB como estratégia para o incremento da VN. O IN não parece ser adequado para a avaliação de atletas de alto nível. Movimento para respiração altera o desempenho de velocistas e triatletas

Increasing extracellular H2O2 produces a bi-phasic response in intracellular H2O2, with peroxiredoxin hyperoxidation only triggered once the cellular H2O2-buffering capacity is overwhelmed

Reactive oxygen species, such as H2O2, can damage cells but also promote fundamental processes, including growth, differentiation and migration. The mechanisms allowing cells to differentially respond to toxic or signaling H2O2 levels are poorly defined. Here we reveal that increasing external H2O2 produces a bi-phasic response in intracellular H2O2. Peroxiredoxins (Prx) are abundant peroxidases which protect against genome instability, ageing and cancer. We have developed a dynamic model simulating in vivo changes in Prx oxidation. Remarkably, we show that the thioredoxin peroxidase activity of Prx does not provide any significant protection against external rises in H2O2. Instead, our model and experimental data are consistent with low levels of extracellular H2O2 being efficiently buffered by other thioredoxin-dependent activities, including H2O2-reactive cysteines in the thiol-proteome. We show that when extracellular H2O2 levels overwhelm this buffering capacity, the consequent rise in intracellular H2O2 triggers hyperoxidation of Prx to thioredoxin-resistant, peroxidase-inactive form/s. Accordingly, Prx hyperoxidation signals that H2O2 defenses are breached, diverting thioredoxin to repair damage

Protein folding: A missing redox link in the endoplasmic reticulum

Native disulphide-bond formation duping protein folding in the endoplasmic reticulum requires oxidative machinery, the components and mechanism of which are not yet fully understood. Two recent papers have identified a novel protein component that appears to play a key rose In this important redox pathway