372 research outputs found
Cycling in the Heat
No full textThe sport of cycling involves many sub-disciplines (e.g. road and mountain) incorporating different events (e.g. road racing, time trialling, cross-country). When undertaken in the heat, performance in endurance events is progressively impaired relative to temperate conditions, whereas sprint performance may be improved in the absence of marked hyperthermia. Several pathways mediate these adjustments in performance and will be discussed in this chapter. The role of thermal strain will also be discussed as it pertains to exertional heat illness, along with countermeasures to minimise its risk and optimise performance. Differences between cycling in a laboratory and in the field will also be addressed and contextualised.<br/
Neural and Muscular Function in the Heat
No full textThe development of hyperthermia impacts on several aspects of neural and muscular function. Hyperthermia has been shown to impair cognitive performances during complex planning or working memory tasks. This is likely due to the cognitive load imposed by heat stress limiting the available resources available to perform such tasks. However, cognitive function in the heat may be protected or preserved when chronically exposed to heat stress. During acute exercise in the heat, cerebral blood flow may become compromised when intensity is elevated, leading to a suppression of arousal and disengagement to a task. The development of hyperthermia also induces a supraspinal failure in sustaining neural drive during prolonged muscle contractions. As with some aspects of cognitive function, part of this supraspinal failure may be recovered following heat acclimation. Hyperthermia also induces peripheral alterations in neural drive transmission. These peripheral alterations are likely due to a faster nerve conduction velocity when temperature increases and are not affected by heat acclimation. There are also changes occurring at the level of the skeletal muscle when temperature increases, with an increase in contraction and relaxation velocity. Although a rise in muscle temperature can increase muscle power production, whole-body hyperthermia reduces performance and may affect motor control. Finally, an increase in muscle temperature has also been shown to trigger signalling cascades regulating myofibrillar and mitochondrial mass
Julien Benda’s political Europe and the treason of intellectuals
Full text linkWhenever the problem of the relationship between culture and politics is
addressed, Julien Benda undoubtedly remains the most frequently
mentioned author at the international level. His indictment of the
intellectuals’ betrayal is as famous as his speeches to the European
nation, published in 1933, about !ve years later than his widely difused
La Trahison des clercs. Throughout the Discours à la nation européenne,
the author explicitly addresses the intellectuals already mentioned in
his previous essay and asks them to assume responsibility – becoming
protagonists of a new moral revolution. His intention was to reply to
Fichte’s well-known Reden an die deutsche Nation. The idea of Europe
could be built to transcend nations, manifesting itself as the individual’s
renunciation of himself. In this way, the idea of Europe might appear as
a ‘moral act’: renouncing the distinct and the finite and turning to unity
and infnity. Benda was aware of the possible rise of a type of ‘Europhile
nationalism’. To prevent this, he saw it necessary to avoid the closure of
the nation and prolong this movement of association so that it might
increase its tendency to be inclusive. The political vision of Europe that
Julien Benda hoped for should not generate European sovereignty. But,
by prompting intellectuals to follow practical and political methods, he
consciously exploits their role – stated in La Trahison des clercs – with
the hope of building the moral and political framework of a united
Europe
Influence of heat stress and exercise intensity on vastus lateralis muscle and prefrontal cortex oxygenation
No full textThis study examined whether a rise in thermal and cardiovascular strain during exercise to exhaustion in the heat at different intensities is associated with compromised muscle and cerebral oxygenation. Using near-infrared spectroscopy, oxygenation changes in the vastus lateralis and prefrontal cortex of ten subjects cycling to exhaustion in 40 °C conditions at 60 % (H60%) and 75 % (H75%) maximal oxygen uptake (VO₂(max)) and for 60 min in 18 °C conditions at 60 % VO₂(max) (C60%) were examined. Thermoregulatory and cardiovascular responses were also monitored. Rectal temperature reached 38.1 °C in the C60% trial, 39.7 °C (~60 min) and 39.0 °C (~27 min) in the H60% and H75% trials, respectively (P < 0.001). The core-to-skin temperature gradient was similarly narrow (~0.9 °C) at exhaustion in the heat, occurring >97 % of maximum heart rate and accompanied by significant declines in stroke volume, cardiac output and mean arterial pressure (P < 0.01). Vastus lateralis oxygen saturation (SmO(2)) declined at the onset of exercise in all conditions, remaining similarly depressed at exhaustion in the heat. Prefrontal cortex oxygen saturation (ScO(2)) was ~10 % lower at exhaustion in the H60% and H75% trials compared with C60% (P < 0.01), which remained above baseline from 15 min onward. These findings indicate that changes in SmO(2) and ScO(2) are associated with the development of thermal and cardiovascular strain during exercise to exhaustion in the heat, which is accelerated by exercise intensity. In locomotor muscles, a potential reduction in oxygen delivery may develop, whereas in the brain, the progressive reduction in ScO(2) may induce mental fatigue.</p
Julien Green et la hantise de l’imposture
Full text linkYoung author of a religious pamphlet, Julien Green suspected an ethical and aesthetic imposture in this literary positioning. The desire for truth allows him to profess his faith, but the autobiographical confidences are subjected to complex requirements. For his novels, gushing out from the depths of the psyche, he rejects the catholic label: the spiritual sense of a writing that explores the darkness of the human condition paradoxically depends on the renunciation of any apologetic purpose
Integrative Human Cardiovascular Responses to Hyperthermia
Full text linkProgressive whole-body hyperthermia with passive heat stress is associated with a host of physiological adjustments. These include large increases in peripheral blood flow and cardiac output and a smaller selective redistribution of blood flow from the cerebral and visceral tissues to the limbs, head, and torso, with perfusion pressure being only slightly reduced. Aerobic metabolism also increases in these conditions, but the magnitude is small in absolute terms, suggesting a predominant role of thermosensitive mechanisms in passive hyperthermia-induced cardiovascular adjustments. Although exercise heat stress requires substantially greater blood flow requirements compared to passive heat stress alone, the magnitude of this hyperemic response is less than would be expected given the extent to which both conditions independently increase blood flow in isolation. As a result, submaximal exercise limb blood flow is only slightly higher during small muscle-mass exercise in the heat, and is similar to control conditions during whole-body exercise. When exercise intensity is increased further towards maximal levels, the superimposition of heat stress leads to earlier reductions in regional and systemic blood perfusion, compromised locomotor limb aerobic metabolism, and ultimately results in impaired endurance capacity. This chapter provides an integrative overview of the human cardiovascular response to passive heat stress and exercise heat stress, with emphasis on its consequences on exercise performance in the heat
Heat Acclimation
Full text linkPhysical exercise under heat stress can impair performance through multiple physiological mechanisms including cardiovascular, central nervous system, and skeletal muscle metabolism factors. However, repeated heat exposure that increases whole-body temperature, stimulates profuse sweating, and stresses the cardiovascular system, leads to increases in blood volume, decreases in core and skin temperatures, and induces important molecular adaptations that stimulate physiological heat acclimation. These integrated physiological adaptations act to improve exercise capacity in the heat, as well as minimise the risk of exertional heat illness. Most physiological benefits are noticeable within a few days of daily heat exposure, but the full benefits take about 2 weeks or longer to improve exercise capacity in the heat
`ANTAR ET LES POETES DES MUʿ ALLAQĀT L`EPOP É E DANS SON ROLE D`HISTORIOGRAPHIE POPULAIRE
Full text linkOne of the main episodes of the Sīrat ʿAntar is the one where ʿAntar decides to hang his muʿallaqa on the Kaaba of Mecca. In this passage the storyteller use these very famous poems as literary devices to satisfy the audience. The sīra doesn‟t use to incorporate this kind of fixed texts in its narration, so it is interesting to analyse the way the author puts these od es on. However it appears that this episode also assumes a historiographical role which is essential in order to be fully understood. We aim to shed light on both the literary and the historiographical aspects of this excerpt
Muscular Responses During and Following Acute Physical Activity Under Heat Stress
No full textAcute exercise provides a unique challenge to several regulatory systems. From a circulatory and metabolic perspective, exercise is associated with a rise in systemic blood flow, which allows for the adequate delivery of oxygen to the working musculature, as well as the dissipation of metabolically generated heat to the environment. Prolonged exercise or repeated contractions also lead to the development of fatigue, characterized by a reduction in the ability to generate force or power. This loss of strength has both peripheral and central mechanistic causes, which are influenced by increases in whole-body temperature. Hence, when exercise is performed in hot environmental conditions, the development of hyperthermia contributes to alter skeletal muscle performance. The aim of this chapter is to provide a brief overview of the circulatory and thermoregulatory responses associated with acute dynamic exercise, as well as the influence of heat stress on the development of skeletal muscle fatigue. Skeletal muscle damage will also be addressed to provide a wider perspective on what occurs within active muscles during and following acute exercise
Perspiration:Training in a hot and humid environment
No full textPerforming an "aerobic" exercise of submaximal or maximum intensity in a constraining climatic environment (ie, high heat) is usually accompanied by a decrease in locomotor performance [1]. Some of the world's biggest sporting events take place regularly in hot and / or humid environments like the 1996 Olympic Games (Atlanta), 2008 (Beijing) or 2016 (Rio), or the 2014 FIFA World Cups (Brazil). ) and 2022 (Qatar). With a view to protecting the health of elite athletes, the International Olympic Committee (IOC) [2] and the International Amateur Football Federation (FIFA) [3] have recently organized expert meetings on the theme of risk Heat-related medical conditions induce significant changes in thermoregulation, including sustained cutaneous blood flow rates that allow thermal exchanges to be adjusted to the environment. The purpose of this article is to recall some elements on evaporative thermolysis that will influence responses to training in hot and humid environments and to describe the beneficial effects of acclimation
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