Дисертації з теми "High-Intensity stress"
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1
Chalari, Eleanna. "The effect of high-intensity intermittent exercise on biomarkers of oxidative stress." Thesis, University of Hull, 2017. http://hydra.hull.ac.uk/resources/hull:16424.
Анотація:
There are evidence that high-intensity acute exercise can promote oxidative stress. High-intensity intermittent exercise (HIIE) is a type of structured physical training characterised by repeated bouts of high-intensity exercise interspersed by recovery periods. As the impact of intermittency during acute HIIE has not been extensively studied, it is possible that the repeated intensive bouts within HIIE could induce oxidative stress levels. Plasma biomarkers, including lipid hydroperoxides and markers of DNA damage, have been increasingly applied within acute exercise physiology research to measure oxidative stress. This thesis presents the experimental outcomes of research into the effect of different forms of HIIE on established and novel biomarkers of oxidative stress. For the 1st study (chapter 3) a liquid chromatography-mass spectrometry (LCMS) method was developed and optimised to measure DNA oxidation in plasma samples. Implementing a range of progressive analytical techniques, the method developed had a sensitivity to detect 8-hydroxy-2'-deoxyguanosine (8-Oxo-dG) in human plasma samples in the range of 5 – 500 nM. The implementation of this LC-MS method along with other oxidative stress biomarkers was thereafter applied to a randomised investigation of different high-intensity intermittent exercise protocols. The 2nd (chapter 4) and 3rd (chapter 5) studies considered the effect of different forms of intermittent exercise undertaken by 9 healthy, regularly active male participants (aged 21.0 ± 3.0 years). Each intermittent exercise session was performed for a total duration of 45 minutes. Each 45 minute exercise protocol consisted of 4 minute stages of high-intensity intermittent running at a mean 75% v!O2max, followed by 1 minute of passive recovery (halt of running). The experimental protocol was specifically designed to match for average speed, duration and distance but varied in either the intermittency (chapter 4) or the acceleration/deceleration (chapter 5). The effects of different forms of intermittent exercise (high, moderate, low) or different acceleration/deceleration components (high, moderate, low) in relation to oxidative stress biomarkers were determined. Results showed the absence of significant increases in all the biomarkers examined. However, significant variation in individual oxidative stress responses was observed. Within a final study, the 8-Oxo-dG method developed was compared to a widely used ELISA method, as there are indications in the literature that ELISA may overestimate 8-Oxo-dG. Determination of 8-Oxo-dG was undertaken on blood plasma samples from 30 chronic heart failure patients (males = 23, females = 7) recruited from the Academic Cardiology department at Castle Hill hospital, Hull, UK, as previous studies have characterised the heart failure syndrome to be associated with higher levels of oxidative stress. Results showed that the LC-MS method developed found no detectable levels of 8-Oxo-dG in plasma samples whereas ELISA showed quantifiable amounts of 8-Oxo-dG. Thus, this thesis presented that the impact of intermittency or acceleration/deceleration following acute HIIE does not induce significant oxidative stress as determined by plasma and serum biomarkers, including plasma 8-Oxo-dG.
2
Fisher, Gordon Pascoe David D. "Oxidative stress and antioxidant defenses in lymphocytes following high intensity interval training." Auburn, Ala., 2009. http://hdl.handle.net/10415/2003.
3
Tofique, Muhammad Waqas. "Very high cycle fatigue of duplex stainless steels and stress intensity calculations." Licentiate thesis, Karlstads universitet, Institutionen för ingenjörsvetenskap och fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-34591.
Анотація:
Very high cycle fatigue (VHCF) is generally considered as the domain of fatigue lifetime beyond 10 million (107) load cycles. Few examples of structural components which are subjected to 107-109 load cycles during their service life are engine parts, turbine disks, railway axles and load-carrying parts of automobiles. Therefore, the safe and reliable operation of these components depends on the knowledge of their fatigue strength and the prevalent damage/failure mechanisms. Moreover, the fatigue life of materials in the VHCF regime is controlled by the fatigue crack initiation and early growth stage of short cracks. This study was focussed on the evaluation of fatigue properties of duplex stainless steels in the VHCF regime using the ultrasonic fatigue testing equipment. The ultrasonic fatigue tests were conducted on the cold rolled duplex stainless strip steel and hot rolled duplex stainless steel grades. Two different geometries of ultrasonic fatigue test specimens were tested. Considerable attention was devoted to the evaluation of fatigue crack initiation and growth mechanisms using the high resolution scanning electron microscopy. The fatigue crack initiation was found to be surface initiated phenomena in all the tested grades, albeit different in each case. The second part of this thesis work was the development of a distributed dislocation dipole technique for the analysis of multiple straight, kinked and branched cracks in an elastic half plane. Cracks with dimensions much smaller than the overall size of the domain were considered. The main goal of the development of this technique was the evaluation of stress intensity factor at each crack tip. The comparison of results from the stress intensity factor evaluation by the developed procedure and the well-established Finite Element Method software ABAQUS showed difference of less than 1% for Jacobi polynomial expansion of sixth order in the dipole density representation.Article III was still in manuscript form at the time of the defense.
Very high cycle fatigue of stainless steels
4
HASANI, NAJAFABADI SEYED HUSEIN. "Numerical-Experimental Assessment of Stress Intensity Factors in Ultrasonic Very-High-Cycle Fatigue." Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2712549.
Анотація:
The continuous enhancement of reliability and durability requirements for many machinery components is significantly pushing the experimental research on the Very-High-Cycle Fatigue (VHCF) response of metallic materials. In order to significantly reduce testing time, ultrasonic testing machines are widely adopted when carrying out VHCF tests.
In the VHCF literature, the critical Stress Intensity Factor (SIF) is estimated by applying analytical SIF formulations to the typical semi-circular surface crack geometry revealed by fracture surfaces at final failure. However, when subjected to ultrasonic VHCF tests, analytical SIF formulations valid for static loading conditions could eventually lead to significant estimation errors.
The correct computation of the SIF in ultrasonic VHCF loading conditions is a key issue when investigating the crack growth rate curve with pre-cracked specimens or when evaluating critical SIF values from fracture surfaces of failed specimens. Dynamic conditions related to the resonance of the vibrating specimen, contact nonlinearity between crack faces and stress singularity at the crack tip make the SIF computation difficult and cumbersome. Numerical computation through Finite Element Models under non-linear dynamic conditions makes use of direct integration methods (implicit or explicit). However, in the high-frequency regime of ultrasonic VHCF tests, the procedure may lead to unacceptable computational time.
The present thesis aims at finding a robust, accurate, and simple method to calculate the critical SIF at final failure fracture of VHCF samples. In order to cope with the inefficiency of the time domain direct integration method, frequency domain analysis, and Multi Harmonic Balance Method were employed in this thesis. Even though the frequency domain analysis significantly reduced the computational time the overall reduction was still considered insufficient. Hence, reduction techniques via Reduce Order Modeling were also applied to decrease the total number of degrees of freedom for the system.
The solution obtained with the ABAQUS implicit solver was employed to verify the proposed hybrid technique. Results showed that the present method can accurately predict the displacement field and the SIF together with a drastic decrease of the computational time.
The proposed method was then applied to two models based on real sample geometries (Hourglass and Gaussian samples failed under ultrasonic VHCF) in order to evaluate the effect of the geometry on the critical SIF value. Results calculated by classical solutions valid for static conditions were also compared with the results obtained with the proposed hybrid method.
The comparison showed that conventional static solutions for SIFs could not be used to compute SIF values in ultrasonic conditions since computational errors are significant.
Another important finding was that, for the Gaussian sample, the SIF in both loading conditions (static and dynamic) is smaller than that for the Hourglass sample. The difference in static conditions is considerable and larger than that in dynamic conditions.
Besides the efficient and accurate computation of the critical SIF values from samples failed under ultrasonic VHCF tests, the proposed method can also be used: i) to design fatigue crack growth samples for investigating the near-threshold region with ultrasonic testing machines; ii) to accurately evaluate the SIF at the border of the relevant crack growth zones in ultrasonic VHCF (e.g., at the border of the fisheye and of the Fine Granular Area).
5
Morris, John G. "Effects of hot environmental conditions on human responses to prolonged, intermittent, high-intensity shuttle running." Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/7171.
6
Long, Meghan. "Comparison of High Intensity Interval Training Versus Moderate Intensity Continuous Training in a Phase II Cardiac Rehabilitation Program." Bowling Green State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1498769361795025.
7
Dernbach, Arthur R. "Indices of oxidant stress in the blood and muscle of rowers during four weeks of high intensity twice-daily rowing training /." The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487682558445274.
8
Hooley, Christopher Gary. "Examination of the effects of dietary protein and lipid on growth and stress response of Nile tilapia cultured in high intensity systems." Thesis, Montana State University, 2012. http://etd.lib.montana.edu/etd/2012/hooley/HooleyC0512.pdf.
Анотація:
Tilapia is the second most consumed farmed fish, after carp, and the most widely grown of any farmed fish. Significant feed price increases in recent years threaten sustainability of the industry. In the US tilapia are often subjected to extended hauling to reach live-fish markets. Therefore, the objectives of the current study were to optimize dietary protein and lipid levels for juvenile tilapia cultured in high-intensity recirculating-water system and assess how dietary changes alter hauling stress-tolerance. To achieve these objectives, a 3 X 3 factorial design was used with practical-type diets formulated to contain three levels of dietary protein (28, 32 and 36%) and three levels of dietary lipid (3, 6, and 9%). Juvenile tilapia (34.5 ± 0 .4g initial weight) were fed one of the nine diets, three feedings/d to apparent satiation, six d/wk for 12wk. Fish were weighed and counted every three weeks and feed consumed recorded weekly. At the conclusion of the feeding trial, three fish per tank were sampled for proximate composition analyses. One week post-conclusion of the feeding trial, tilapia remaining in each tank were subjected to a simulated live haul in which fish were transferred to insulated container (2lbs/gallon) with supplemental oxygen for 24h, and then returned to their source tank and allowed to recover for an additional 48h. Hematocrit, glucose, lactate and cortisol measurements were collected at time 0, 24h, and 72h. Increasing dietary protein significantly improved tilapia weight gain (P=0.01), feed conversion (FCR, P=0.03), feed intake (P=0.02), protein retention (P=0.01) and filet ratio (P=0.01). Increasing dietary lipid also significantly improved weight gain (P=0.05) and FCR (P=0.01) but at 9% decreased feed intake (P=0.02). Blood chemistry values were also altered by dietary protein and lipid levels (Figure 1). No significant interactions between dietary protein and lipid levels on growth performance or blood chemistry values were measured. Results of this study suggest that while increasing protein and lipid levels in tilapia diet formulations improved production of tilapia cultured in high intensity systems and that, stress tolerance during live hauls appeared to be reduced.
9
Lindberg, Felicia, and Rytterborg Julia Fex. "Anti-stressträning : En kvantitativ tvärsnittsstudie." Thesis, Gymnastik- och idrottshögskolan, GIH, Institutionen för idrotts- och hälsovetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:gih:diva-5682.
Анотація:
Syfte och frågeställningar: Syftet är att studera om träning på olika intensitetsnivåer påverkar upplevd stress hos kvinnor i Sverige. Denna studie kommer svara på dessa frågeställningar: - Finns det någon skillnad i upplevd stress hos kvinnor som deltar på lågintensiv träning i form av promenader jämfört med kvinnor som deltar på högintensiv träning i form av löpning? Finns det någon skillnad i upplevd stress hos kvinnor som deltar på högintensiv träning i form av löpning jämfört med kvinnor som inte tränar alls? Finns det någon skillnad i upplevd stress hos kvinnor som deltar på lågintensiv träning i form av promenader jämfört med kvinnor som inte tränar alls? Metod: Studien är en tvärsnittsstudie, genom enkätundersökningar har skillnader i upplevd stress jämförts på kvinnor med medelålder 39,03 år ( ± 14,44), som antingen tränat högintensivt eller lågintensivt. Resultaten har jämförts med en referensgrupp bestående av kvinnor som inte tränar alls. Perceived Stress Scale-10 (PSS10) inklusive tio stycken intensitets-frågor för inklusion i studien skickades ut via sociala medier, Facebook. Resultat: En signifikant skillnad sågs vid jämförandet av kvinnor som tränar högintensivt och referensgrupp, (p=0,001), poängmässig skillnad i PSS10; 7,67 poäng. Ingen signifikant skillnad redovisades mellan högintensiv och lågintensiv grupp (p=0,737), detsamma gällde lågintensiv och referensgrupp (p=0,081). Slutsats: Högintensiva kvinnor hade reducerad upplevd stress jämfört med kvinnor som inte tränade alls. Ingen skillnad i upplevd stress kunde urskiljas mellan kvinnor som tränar lågintensivt och kvinnor som tränade högintensivt. Samma gällde kvinnor som tränade på låg intensitet jämfört med kvinnor som inte tränade alls, ingen skillnad i upplevd stress.
Purpose and aims: The aim is to study if different exercise-intensities affects perceived stress in Swedish women. This study will answer the following questions:
- Is there a difference in perceived stress in women who participate in low-intensity exercise in the form of walking compared to women who participate in high-intensity exercise in the form of running? Is there a difference in perceived stress in women who participate in high-intensity exercise in the form of running compared to women who do not exercise at all? Is there a difference in perceived stress in women who participate in low-intensity exercise in the form walking compared to women who do not exercise at all? Method: The study is a cross-sectional study, through questionnaires, differences in perceived stress have been compared in women with a mean age of 39,03 years (± 14,44), who either exercised with high intensity or with low intensity. The results have been compared to a reference group consisting of non-training women. Perceived Stress Scale-10 (PSS10) together with ten intensity-questions for inclusion in the study was sent out via social media, Facebook. Results: A significant difference was detected in the comparison of the high intensity group and the reference group, (p=0.001), score difference in PSS10; 7,67 points. No significant difference between the high-intensity group and the low-intensity group (p=0.737), the same applied to the low-intensity group and the reference group (p=0,081). Conclusions: Women who participated in high intensity exercise had reduced percieved stress compared to women who did not exercise at all. No difference in percieved stress was observed between women who participated in low intensity exercise and women who participated in high intensity exercise. Similarly, no difference in percieved stress in women who participated in low intensity exercise and women who did not exercise at all.
10
Pugliese, L. "EFFECTS OF TRAINING REGIMES AT DIFFERENT INTENSITIES ON PERFORMANCE AND OXIDATIVE STRESS IN MASTERS ATHLETES." Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/258143.
Анотація:
Over the last decade, the participation of middle-aged and older (‘masters’) involved in sport activities at different levels has significantly increased, particularly in long-distance events. Master athletes are typically characterized as people who continue physical training throughout life and in this population, the incidence and risk of chronic and age-related diseases are reportedly lower, and self-rated health is better than in apparently healthy controls. However, regardless of training a decline in peak athletic performance in both endurance and sprint events and for all competitions/disciplines usually occurs with aging. In particular, declines in endurance exercise performance and its physiological determinants with ageing appear to be mediated in large part by a reduction in the exercise training ‘stimulus’, mainly as a result of increased work and family commitments, few masters still follow structured training programs, and the increased prevalence of exercise training-associated injuries that probably contributes to their reduced training intensity and volume. Furthermore, aging is accompanied by a progressive increase in free radical production (i.e., synthesis of reactive oxygen species) with a concomitant decrease in the enzymatic defence mechanisms, promoting the development of oxidative stress. The chronic repetition of exercise, i.e. exercise training, may have the capability to develop a compensation to oxidative stress in skeletal muscle fibres by means of an adaptation of the antioxidant and repair systems. This might result in a decreased resting level of oxidative damage and an increased resistance to oxidative stress.
In general, the main types of training used to improve endurance exercise performance are: i) continuous training at moderate intensity (CON); and ii) discontinuous training at high intensity (DHIT). Different studies showed that even in sedentary or moderately trained individuals, DHIT might be an efficient strategy to induce adaptations in skeletal muscle and exercise performance that are comparable with conventional endurance training. The first part of the thesis is focus on master runners. First study aims to evaluate if an individualized training schedules characterized by an overall reduction of training volume is able to improve running performance. Moreover, the impact of CON and DHIT training programs on running performance and its main physiological factors in master runners has been evaluated. The second study aims to evaluate the effects of 8-week of DHIT and CON on resting level and time-course changes of several indexes of oxidative stress. The main findings of these studies show that despite a significant reduction of training volume, CON and DHIT, characterized by the same total volume, improve running economy and running performance. Furthermore, both CON and DHIT induced similar beneficial effects, reducing the resting levels of oxidative stress biomarkers in plasma and urine. The second part of the thesis is focused on master swimmers. The third study aims to compare the effects of two opposite training protocols (low-volume high-intensity vs high-volume low-intensity) in a group of trained master swimmers. The fourth study aims to examine the effects of low-volume high-intensity training on ROS production and on antioxidant capacity in master swimmers by applying electron paramagnetic resonance measurement. The results indicate that in master swimmers an increase of training volume may lead to an improvement of indexes of aerobic capacity and middle-long distance performance. A subsequent period of high-intensity low-volume training, besides maintaining previous improvements, may positively affect also short distance performance. Moreover, high intensity training improves antioxidant capacity and significantly decreases baseline ROS production.
11
Wardwell, Kyoko Konaka. "Effects of Self-Selected and Imposed Intensity of Acute Exercise on the HPA-axis Response and Psychological Well-Being in Inactive Women with High Levels of Stress." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1307122619.
12
Meleiro, Mônica Cristina Zandoná. "A influência do estresse experimentado por cavalos de corrida, em determinados momentos de sua rotina, sobre a função imune in vitro." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/10/10132/tde-15012007-123505/.
Анотація:
Embora os cavalos apresentem características excepcionais frente a situações de estresse na natureza, foi considerada a possibilidade do cavalo de corrida ser submetido, por vezes, a alguma situação de estresse, que afetasse sua saúde e bem estar. Foram verificadas alterações do número e da função de populações celulares implicadas com a defesa, principalmente neutrófilos e linfócitos. Trinta cavalos de corrida da raça puro-sangue inglês, locados no Jockey Club de São Paulo, na cidade de São Paulo, foram utilizados. Os animais foram divididos em dois grupos e as amostras de sangue foram coletadas em momentos diferentes da rotina dos animais. No grupo I, foram coletadas amostras onze dias antes da corrida (-11d), imediatamente após a corrida (0d), um dia após a corrida (+1d), dois dias após a corrida (+2d) e três dias após a corrida (+3d). Enquanto, no grupo II as amostras foram coletadas oito dias antes da corrida (-8d), imediatamente após a corrida (0d), um dia após a corrida (+1d) e cinco dias após a corrida (+5d). Foram realizados ensaios de fagocitose e burst oxidativo dos neutrófilos, determinação de cortisol sérico, ensaios de apoptose, linfoproliferação e hemograma. A função de fagocitose, tanto em porcentagem, quanto em intensidade, mostrou-se diminuída nas amostras coletadas imediatamente após a corrida, nos dois grupos de animais. Os valores médios de burst oxidativo das amostras coletadas imediatamente após a corrida, dos animais do grupo I apresentaram-se diminuídos. Não foram encontradas diferenças estatísticas significantes entre os resultados obtidos em relação às células apoptóticas, quando os diferentes momentos foram comparados; o mesmo ocorreu quando foi realizado o confronto dos valores do ensaio de linfoproliferação. Os valores médios dos níveis séricos de cortisol apresentaram-se aumentados no momento imediatamente após a corrida, em relação aos valores dos outros momentos, nos dois grupos de animais. Quanto aos dados de hemograma, houve aumento do número percentual de neutrófilos no momento imediatamente após a corrida quando foi realizada comparação com os demais momentos. Nos cavalos estudados, ainda que tenha sido encontrada uma diminuição transitória na função dos neutrófilos, a função adaptativa não chegou a ser acometida, que sugere que, embora se constitua em um exercício de alta intensidade, a fugacidade da corrida acabe por evitar danos maiores, em animais bem condicionados e adaptados a situações de estresseAlthough horses can present exceptional responses during stress situations in nature, it was raised the possibility that racehorses under certain stress conditions could develop changes that may affect their health and welfare. Alterations of the number and function of cells that are involved with the defense response, mainly neutrophils and lymphocytes populations were verified. Thirty Thoroughbred racehorses housed at the Jockey Club de São Paulo, in São Paulo, Brazil, were used in the present study. The animals were divided in two groups and blood samples were collected at different moments of their routine. In group I, the samples were collected eleven days before race (-11d), immediately after race (0d), one day (+1d), two days (+2d) and three days after race (+3d). In group II, the samples were collected eight days before race (-8d), immediately after race (0d), one day (+1d) and five days after race (+5d). Phagocytosis assay and oxidative burst activity of neutrophils, serum cortisol determination, apoptosis and lymphocyte proliferation assay and haematology tests were performed. The percentage and intensity of phagocytosis functions decreased in samples collected immediately after race, in both groups of animals. The mean values of oxidative burst activity of samples collected immediately after race, from animals of group I also decreased. Statistically significant differences between the results were obtained in relation to the apoptotic cells, when compared on different moments and the same occurred in Relation to the lymphocyte proliferation values. The mean values of serum cortisol levels increased at the moment immediately after race when compared with the values of the other moments, in both groups of animals. In relation to the haematologycal values, the percentage of neutrophils was increased at the moment immediately after race when compared with the other moments. Even though a transitory reduction in the neutrophils function has occurred, the adaptive function was not impaired, which suggest that, in spite of the high intensity of this exercise, the short-term race can prevent further damages in well-conditioned and stress-adapted animals
13
Lardant, Emma. "Hétérogénéité de la réponse à un stress de forte intensité : Évidences comportementale, neurobiologique et hypnique chez la souris." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASL003.
Анотація:
Le trouble de stress post- traumatique (TSPT) est un trouble mental qui affecte certaines personnes exposées à un stress de forte intensité. L’hétérogénéité d’expression des différents symptômes pourraient expliquer l’absence de traitement efficace et/ou la rechute des patients. Ces sous-types de symptômes sont associés à des activités cérébrales spécifiques, leur meilleure compréhension semble alors cruciale pour la recherche de traitement plus personnalisé et donc plus efficace. Dans ce contexte, le comportement de souris non consanguines a été évalué par plusieurs tests pendant 28 jours après avoir reçu deux chocs électriques de forte intensité. Une analyse des profils comportementaux en deux étapes a permis de révéler trois phénotypes chez les animaux exposés au stress de forte intensité. La première étape, basée sur un score composite des comportements de type anxiété généralisée, a permis de dissocier les animaux résilients et susceptibles et d’établir un score de sévérité des altérations comportementales. La seconde étape, axée sur les comportements de défense persistants lors de différentes réexpositions à des stimuli associés aux chocs électriques, a permis d’identifier deux phénotypes comportementaux chez les animaux susceptibles : Les immobiles et les fuyants. L’analyse de l’expression cellulaire de la protéine Fos a mis en évidence des activations cellulaires distinctes au niveau de l’amygdale (AMG) et de la substance grise périaqueducale (PAG). Plus précisément, la sévérité des altérations comportementales de type TSPT est corrélée positivement à l‘activation de l’AMG droite et les phénotypes susceptibles sont associés à des activations différentes le long de l’axe antéropostérieur de la PAG. Les analyses de sommeil mettent également en évidence des différences entre les trois phénotypes d’animaux. En particulier, le sommeil paradoxal semble être un marqueur de résilience post- exposition mais également un indicateur de susceptibilité au développement de la pathologie avant exposition. En conclusion, en montrant des activations cérébrales distinctes et des effets différentiels sur le sommeil dans les trois phénotypes d’animaux, cette étude montre l’importance d’analyser les profils comportementaux chez la souris. Le raffinement des méthodes d’analyses de ce type devrait renforcer la validité translationnelle du modèle de TSPT, ouvrant ainsi de nouvelles perspectives pour des traitements plus personnalisésPost-Traumatic Stress Disorder (PTSD) is a mental disorder that affects some individuals exposed to high-intensity stress. The heterogeneity in the expression of various symptoms could explain the lack of effective treatment and/or patient relapse. These subtypes of symptoms are associated with specific brain activities; their better understanding appears crucial for the pursuit of more personalized and thus more effective treatment. In this context, the behavior of outbred mice was evaluated through various tests for 28 days after receiving two high- intensity electric shocks. An analysis of behavioral profiles in two steps revealed three phenotypes in animals exposed to high-intensity stress. The first step, based on a composite score of generalized anxiety-like behaviors, allowed for the differentiation of resilient and susceptible animals and the establishment of a severity score for behavioral alterations. The second step, focused on persistent defensive behaviors during different re-exposures to stimuli associated with electric shocks, identified two behavioral phenotypes in susceptible animals: immobile and fleeing. Analysis of the cellular expression of the Fos protein highlighted distinct cellular activations in the amygdala (AMG) and the periaqueductal gray matter (PAG). Specifically, the severity of PTSD- like behavioral alterations is positively correlated with right AMG activation, and susceptible phenotypes are associated with different activations along the anteroposterior axis of the PAG. Sleep analysis also revealed differences among the three animal phenotypes. In particular, rapid eye movement (REM) sleep appears to be a marker of post-exposure resilience but also an indicator of susceptibility to pathology development before exposure. In conclusion, by demonstrating distinct brain activations and differential effects on sleep in the three animal phenotypes, this study highlights the importance of analyzing behavioral profiles in mice. Refinement of analysis methods of this kind should enhance the translational validity of the PTSD model, thus opening new perspectives for more personalized treatments
14
Souza, Lúcio Marques Vieira. "Efeitos do treinamento intervalado de alta intensidade de curto prazo sobre os biomarcadores de estresse oxidativo e danos musculares em ratos." Pós-Graduação em Educação Física, 2018. http://ri.ufs.br/jspui/handle/riufs/7837.
Анотація:
High intensity interval training (HIIT) has become very popular due to the
dissemination of experimental results. HIIT promotes similar adaptations to longterm
and low-intensity exercises, such as improvement in cardiorespiratory
capacity, VO2max, respi- ratory metabolism, increased pulmonary ventilation,
among others. However, these adaptations are obtained with much lower duration
at maximum or submaximal intensities, with seconds or few minutes of interval.
However, frequent performance may increase susceptibility to injury, promote
chronic fatigue and overtraining, partly because of the high synthesis of reactive
oxygen species (ROS). Stress is a state of imbalance between oxidation and
oxidation reactions. However, the effects of HIIT on oxidative status and muscle
damage are still not well understood in the scientific literature. The objective of this
dissertation was to verify the effects of short-term HIIT on biomarkers of oxidative
stress and muscle damage in Wistar rats. Thus, three studies were elaborated: 1)
The effects of short-term HIIT on the markers of oxidative stress and muscle
damage were evaluated; 2) It was sought to characterize the responses of cardiac
oxidative stress markers to HIIT in rats. 3) The effects of twelve consecutive
sessions and on different days of HIIT on the markers of hepatic oxidative stress
were verified. In studies 1 and 2 significant changes were found in only one marker
of oxidative damage, a fact that did not happen in study 3. Still on study 1 there were
no changes in the markers of muscle damage, however there was a significant
reduction in a marker of defense antioxidant. In studies 2 and 3 there were no
significant changes in antioxidant capacity. It is concluded that HIIT is performed on
consecutive or distinct days, and depending on tissue it may or may not promote
liver, heart and muscle damage in rats.O treinamento intervalado de alta intensidade (HIIT) na comunidade científica tem se tornado muito notório em função da divulgação de estudos experimentais. O HIIT promove adaptações semelhantes aos exercícios de longa duração e baixa intensidade, tais como melhora da capacidade cardiorrespiratória, do metabolismo de respouso, aumento da ventilação pulmonar, entre outros. Porém, estas adaptações são obtidas com duração muito inferior em intensidades máximas ou submáximas, com segundos ou poucos minutos de intervalo. Contudo, a frequente realização pode aumentar a suscetibilidade a lesões, promover a fadiga crônica e overtraining, parcialmente em razão da elevada síntese de espécies reativas de oxigênio (EROs). Estresse oxidativo é um estado de desequilíbrio entre as reações de oxidação e de antioxidação. Entretanto, ainda existem lacunas a serem preenchidas acerca dos efeitos do HIIT sobre o estado oxidativo e danos musculares, sobretudo em modelo animal. O objetivo desta dissertação foi verificar os efeitos do HIIT de curto prazo sobre os biomarcadores de estresse oxidativo e danos musculares em ratos. Desta forma, foram elaborados três estudos: 1. Avaliou-se os efeitos do HIIT de curto prazo sobre os marcadores de estresse oxidativo e danos musculares; 2. Buscou-se caracterizar as respostas dos marcadores de estresse oxidativo cardíaco ao HIIT em ratos. 3. Verificou-se os efeitos de doze sessões consecutivas e em dias distintos de HIIT sobre os marcadores de estresse oxidativo hepático. Nos estudos 1 e 2 foram encontradas alterações significativas em apenas um marcador de dano oxidativo, fato este que não aconteceu no estudo 3. Ainda sobre o estudo 1 não houveram alterações nos marcadores de danos musculares, no entanto houve uma redução significativa num marcador de defesa antioxidante. Nos estudos 2 e 3 não houveram mudanças significativas na capacidade antioxidante. Conclui-se que o HIIT, seja realizado em dias consecutivos ou distinitos, e a depender do tecido pode ou não promover danos hepáticos, cardíacos e musculares em ratos.
São Cristóvão, SE
15
Sawyer, Mikel Louis. "High intensity heat transfer to a stream of monodispersed water droplets." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/17991.
16
Hangya, Josef. "Účinky elektrického namáhání na vlastnosti elektroizolačních materiálů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-220958.
Анотація:
Diploma thesis treat of effect of direct, alternate and pulse electrical stress on the properties surveyed electrical insulating material. Object of this experiment is crystalline high-density polystyrene QUINN PS. To monitor the stress is used the method of dielectric relaxation spectroscopy. Under examinations are the resultant dielectric spectra, which constitute the frequency dependencies of components of complex permitivity. Samples of the selected material are exposed to effects of alternate and pulse electrical stress on the different intensities of the electric field. In the direct field are then monitored absorption characteristics and specific volume resistance of the samples.
17
Martin, Damian. "Effects of high intensity, large-scale free-stream turbulence on combustor effusion cooling." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/14725.
Анотація:
Full-coverage or effusion cooling is commonly used in the thermal management of gas turbine combustion systems. The combustor environment is characterised by highly turbulent free-stream conditions and relatively large turbulent length scales. This turbulent flow field is predominantly created by the upstream fuel injector for lean burn systems. In rich burn systems the turbulent flow field is augmented further by the addition of dilution ports. The available evidence suggests that large energetic eddies interact strongly with the injected coolant fluid and may have a significant impact on the film-cooling performance. The desire to create compact low-emission combustion systems with improved specific fuel consumption, has given rise to a desire to reduce the quantity of air used in wall cooling, and has led to the need for improved cooling correlations and validated computational methods. In order to establish a greater understanding of effusion cooling under conditions of very high free-stream turbulence, a new laboratory test facility has been created that is capable of simulating representative combustor flow conditions, and that allows for a systematic investigation of cooling performance over a range of free-stream turbulence conditions (up to 25% intensity, integral length scale-to-coolant hole diameter ratios of 26) and coolant to mainstream density ratios (??_c/??_??? ???2). This thesis describes this new test facility, including the method for generating combustor relevant flow conditions. The hot side film cooling performance of cylindrical and fanned hole effusion has been evaluated in terms of adiabatic film-cooling effectiveness and normalised heat transfer coefficient (HTC) and heat flux reduction (HFR). Infrared thermography was employed to produce spatial resolved surface temperature distributions of the effusion surface. The analysis of this data is supported by fluid temperature field measurements. The interpretation of the data has established the impact of turbulence intensity, integral length scale and density ratio on the mixing processes between free-stream and coolant flows. Elevated levels of free-stream turbulence increase the rate of mixing and degrade the cooling effectiveness at low blowing ratios whereas at high blowing ratios, where the coolant detaches from the surface, a modest increase has been observed under certain conditions; this is due to the turbulent transport of the detached coolant fluid back towards the wall. For angled cylindrical hole injection the impact of density ratio as an independent parameter was found to be relatively weak. Adiabatic effectiveness data gathered at DR's of 1 - 1.4 scaled reasonable well when plotted against momentum flux ratio. This suggests data collected at low DR's can be scaled to engine representative DR's. The investigation of shaped cooling holes found fanned effusion has the potential to dramatically improve film effectiveness. The diffusion of the flow through a fanned exit prevented jet detachment at blowing ratios up to 5, increasing spatially averaged effectiveness by 89%.
18
Yi-Han, Chiu, and 邱亦涵. "Effect of High Intensity Exercise-Induced Oxidative Stress on Leukocytes Apoptosis." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/30007344058951343830.
Анотація:
碩士臺北巿立體育學院
運動科學研究所
91
The intensity and duration of exercise will strongly influence the physical responses. After high intensity exercise (85% VO2max), the reactive oxygen species (ROS) are numerously generated, which makes an imbalance between the oxidatants and antioxidatants of organism to result in oxidative stress. Oxidative stress can potentially induce immune cell programmed cell death, or called apoptosis after high intensity exercise. However, the possible mechanisms have not been investigated. The purpose of this study was to investigate the effect of consecutive high intensity exercise induced-oxidative stress on leukocytes apoptosis. Twelve volunteers (22.8 ± 2.39 yrs) were recruited into this study. All subjects performed the session of aerobic exercise at an intensity of 85% VO2max for 30 min daily for 3 consecutive days. 20 mL of venous blood samples were collected before first day (D1) of exercise, immediately postexercise on the first day (D1’), preexercise on the third day (D3), immediately postexercise on the third day, the fifth day (D5) and the seventh day (D7). The oxidative stress and apoptosis in leukocytes were measured by flow cytometry, and the transcription and translation of the apoptosis associated genes also were determined by RT-PCR and western blotting. The results showed that exercise at 85% VO2max intensity leaded to a depletion of intracellular glutathione (GSH) (p＜.001) and quite often accompanied by a concomitant increase in ROS (p＜.001). This phenomenon could contribute to oxidative stress and apoptosis. In PBMC, it is extremely critical steps that both the loss of the mitochondrial transmembrane potential (MTP) (p＜.001) and the release of cytochrome c from the inner membrane of mitochondria can potentially trigger caspase cascade activation, then results in apoptosis. As for PMN, not only collapse of MTP and cytochrome c released to cytosol from mitochondria but also CD95 receptor activated particularly (p＜.001) could produced caspase cascade. In conclusion, it is proposed that the consecutive high intensity exercise will increase oxidative stress and induce PBMC apoptosis via mitochondria apoptotic pathway, whereas consecutive high intensity exercise induced PMN apoptosis were mediated via both mitochondria and Fas / FasL activated pathways.
19
Dalton, Douglas Allen. "Fast rate fracture of aluminum using high intensity lasers." 2009. http://hdl.handle.net/2152/6861.
Анотація:
Laser induced shock experiments were performed to study the dynamics of various solid state material processes, including shock-induced melt, fast rate fracture, and elastic to plastic response. Fast rate fracture and dynamic yielding are greatly influenced by microstructural features such as grain boundaries, impurity particles and alloying atoms. Fast fracture experiments using lasers are aimed at studying how material microstructure affects the tensile fracture characteristics at strain rates above 106 s-1. We used the Z-Beamlet Laser at Sandia National Laboratories to drive shocks via ablation and we measured the maximum tensile stress of aluminum targets with various microstructures. Using a velocity interferometer and sample recovery, we are able to measure the maximum tensile stress and determine the source of fracture initiation in these targets. We have explored the role that grain size, impurity particles and alloying in aluminum play in dynamic yielding and spall fracture at tensile strain rates of ~3x106 s-1. Preliminary results and analysis indicated that material grain size plays a vital role in the fracture morphology and spall strength results. In a study with single crystal aluminum specimens, velocity measurements and fracture analysis revealed that a smaller amplitude tensile stress was initiated by impurity particles; however, these particles served no purpose in dynamic yielding. An aluminum-magnesium alloy with various grain sizes presented the lowest spall strength, but the greatest dynamic yield strength. Fracture mode in this alloy was initiated by both grain boundaries and impurity particles. With respect to dynamic yielding, alloying elements such as magnesium serve to decrease the onset of plastic response. The fracture stress and yield stress showed no evidence of grain size dependence. Hydrodynamic simulations with material strength models are used to compare with our experiments. In order to study the strain rate dependence of spall in aluminum we used a shorter pulsed laser and thinner targets. From these experiments we do not observe an increase in spall strength for aluminum up to strain rates of ~2x107 s-1.text
20
"Fatigue during high intensity exercise: the interaction between pH and thermal stress." Texas Christian University, 2007. http://etd.tcu.edu/etdfiles/available/etd-06222007-150406/.
21
Liu, Chin-Chu, and 劉金矗. "Effect of Curcumin Supplement on Oxidative Stress Induced by High-Intensity-Interval Training." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/38839940038705104380.
Анотація:
碩士國立東華大學
體育學系
98
Exercises produce free radicals, especially high intensity exercises. Athletes constantly sustain free radical damage due the physical training they must endure over the long run. Under such conditions, health supplements are essential and daily health care products for athletes. Curcumin has superb anti-oxidative effects. The study was designed to investigate the effect of Curcumin supplements on post-exercise oxidative stress. Twelve outstanding basketball players from junior high schools (aged at 16 ± 0.5; height of 173.2 ± 5.2 cm; weight of 68.4 ± 13.6 kg) were randomized into two groups. Each subject had to undergo a two-stage experiment. Before each experiment, subjects were given, in a double-blind design a placebo or Curcumin supplements before performing 6 repetitions of 150-meter, high intensity interval training. Blood samples were collected before, immediately after and 24 hours after the training to analyze the changes in the level of superoxide disimutase, lipid peroxides, creatinine phosphokinase and lactic acid. The exercise intensity was monitored by heart rates and rating of perceived exertion. Data collected was analyzed by two-way ANOVA to test the difference between each variable including superoxide dismutase, lipid peroxides, creatinine phosphokinase and lactic acid. The result showed that: (1) The level of superoxide dismutase in the Curcumin group increased significantly immediate after and 24 hours after exercise; (2) The level of lipid peroxides in the Curcumin group reduced before and after exercise; (3) Curcumin was highly effective in inhibiting the inflammation of muscle fibers. Results from this study indicate that Curcumin had a significant effect on SOD, MDA and CK without directly affecting athletic performance. It could, however, be used as a reference for health care for athletes. Further studies should be conducted for prolonged exercise times and different supplement strategies.
22
Yau, Chen-Yu, and 姚承義. "The Effects of Antioxidant Supplementation on High-Intensity Exercise and Fish Oil-Induced Oxidative Stress." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/6d739s.
Анотація:
博士國立臺灣師範大學
體育研究所
90
Exercise can improve performance, fitness, and metabolism, as well as modify body-fat ratio. But high-intensity exercise may also induce active oxygen species (AOS). Fish oil, which is one of the ω-3 PUFA series that can decrease TG and influence other plasma lipids, appears to prevent arteriosclerosis and CHD, but some evidence suggests it increases the lipid peroxidation in the cell membrane. Fish oil would then seem to influence the antioxidant defense system that causes injury or disease. This study investigates the effects on the antioxidant defence system of combining high-intensity exercise with fish oil supplementation. Thirty-three healthy males were randomly assigned into eight groups (20.3±1.4 yrs; 64.3±7.9 kg), which were given set combinations of dietary fish oil (9 g per day), exercise (intensity 85-90 % HRmax reserve), anti-oxident supplementation (500 mg Vitamin C and 400 IU Vitamin E per day), and placebos. The experiment lasted 4 weeks in total. Venous samples were obtained prior to exercise and within 5 min after. 4 venous samples were also taken from fish oil groups during the four-week period. Blood from all groups was analyzed for sesuperoxide dismutase (SOD), glutathione peroxidase (GSH-Px), total glutathione (T-GSH), total antioxidant ability (TAA), malodialdehyde (MDA), vitamin C & E, TG, HDL-C, LDL-C from forearm vein. A Generalized Estimating Equations (GEE) method was used for data analysis. Result: in no group was there a significant change in the body weight and body composition of the subjects. In the fish oil groups SOD activity significantly increased 11.27 kU/g-HB（P<.05）. Fish oil and vitamin C & E groups saw a decrease in GSH-Px levels, which did not appear in the exercise groups. However, statistical evidence is not sufficient to draw solid conclusions in this area. MDA change increased significantly after exercise in both exercise and dietary fish oil groups (values: 0.12 and 0.27 mmole/ml [P<.05] respectively). The evidence shows that the dosage of fish oil decreased the values of LDL-C and TG (-4.61 mg/dl and -8.85 mg/dl [P <.05] respectively). Exercise increased LDL-C levels (+2.27 mg/dl). Following exercise in the fish oil group, t-GSH increased significantly (36.61Ug/ml [34.2%] [P<.05]). MDA increased significantly after exercise in both exercise-alone and exercise/fish oil groups (+0.12 and +0.27 mmole/ml [P<.05] respectively). Height intensity exercise and fish oil is a real factor that induced more oxidative stress in this study. There is not sufficient evidence to support the claim that oxidative stress decreases after antioxidant supplementation, although there is some indication that this may be true. More research is required. The study concludes that exercise and fish oil separately causes an increase in oxidative stress, and this increase is greater when they are combined. It is also conclude that antioxidant supplementation has no effect on oxidative stress, although it is possible that a larger dosage may produce such an effect.
23
Hu, Shao-Tseng, and 胡紹曾. "Effects of Carnitine Supplementation and High-intensity Interval Training on Endurance Performance and Oxidative Stress." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/31988538926304037718.
Анотація:
碩士國立體育大學
競技與教練科學研究所
102
The purpose of this study was to investigate the effects of three weeks of carnitine supplementation and HIT combination on aerobic capacity and oxidative stress. Ten untrained healthy males were recruited and randomly assigned into carnitine group (25.0±4.4 yr, 80.3±8.5 kg, 170.2±4.3 cm) or placebo group (22.4±3.3 yr, 69.1±11.2 kg, 172.2±6.3 cm). Subjects received carnitine or placebo supplementation 2 g per day for 3 weeks. All subjects also performed the HIT three day per week. The HIT protocol contains 10 bouts of cycling trail at 90%VO2max, with each bout lasting 2 min and separated by 1 min of rest. The increment cycling tests were conducted before and after supplementation. The VO2max and time to fatigue were measured by the increment cycling test. High-intensity interval exercise tests were also performed 48 hours after the increment cycling test. Blood samples were drawn before the test, immediately after test, 1 h and 3 h after test to determine the activities or concentrations of creatine kinase (CK) and uric acid, TBARS,F2-isoprostanes. The result showed that after 3 week of supplementation, VO2max (43.0±2.4 vs. 37.6±5.0 mL/min/kg) and time to fatigue (1563.0±221.0 vs. 1496.0±207.6 sec) significantly increased (p < .05) in carnitine group. However, there were no differences in placebo group. In carnitine group, the values of blood uric acid in high-intensity interval exercise test before supplementation still elevated at 3 h after test (7.8±2.0 vs. 8.8±2.1 mg/dL, p < .05). However, the values returned to baseline after 3 weeks of supplementation (7.8±1.9 vs. 7.7±1.9 mg/dL, p >.05) and uric acid at 1 and 3 hr after test were significantly lower than pre- supplementation (p <.05). In carnitine group, the values of blood TBARS after high-intensity interval exercise test before supplementation significantly elevated as compared to baseline (5.7±0.8 vs. 4.2±0.7 µmol/L，p < .05). However, there were no significant differences after 3 weeks of supplementation (4.6±1.7 vs. 4.3±0.9 mg/dL，p > .05) and TBARS concentrations at post 3 hr after exercise were significantly lower than pre- supplementation (p <.05). In carnitine group, the values of blood F2-isoprostanes in high-intensity interval exercise test before supplementation significantly increased immediately after test, (1328.4±67.5 vs. 1135.5±156.4 pg/ml，p < .05). However, the values returned to baseline after 3 weeks of supplementation (1217.5±235.0 vs. 1179.4±174.2 pg/mL，p > .05) and F2-isoprostanes concentrations immediately after test, at 1 and 3 hr after test were significantly lower than pre- supplementation (p <.05). It is concluded that carnitine supplementation during HIT is benefit to aerobic capacity and reduce the oxidative stress after high-intensity interval exercise.
24
Wang, Ting-Yao, and 王錠堯. "Effects of Different Oxygen Concentrations during High-Intensity Interval Training Recovery Periods on Exercise-induced Stress Markers and Endurance Parameters." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/50012172846683431968.
Анотація:
博士國立體育大學
教練研究所
100
Purpose: To investigate the effects of recovery with normoxia (20.9%), hypoxia (16%) or hyperoxia (60%) during high-intensity interval training (HIT) on: 1. The training intensity markers (heart rate, blood lactate acid and glucose), as well as biomarkers of oxidative stress [thiobarbituric acid reactive substances (TBARS), lymphocyte mitochondrial transmembrane potential decline (MTP decline), apoptosis and necrosis], metabolic stress (cortisol) and mechanical stress (creatine kinase, CK) after one single bout of HIT. 2. The adaption of training intensity, oxidative stress, metabolic stress and mechanical stress markers after 5 times HIT. 3. The effects of endurance determinants (VO2max, VT, RE, vVO2max and time to fatigue) after 6 times HIT in two weeks. Methods: Twenty four healthy males (age: 22.1±2.5 yrs, height: 173.5±6.5 cm, weight: 73.9±9.6 kg) randomly assigned to hypoxia (16%, Hypo), normoxia (20.9%, Nor) or hyperoxia (60%, Hyper) groups. Participants were asked to perform an incremental running test to fatigue before and after the experiment intervention to measure VO2max, VT, RE and time to fatigue and calculate vVO2max. After the pre-test, participant performed 6 times HIT (7 reptitions, 4-min interval at 90% VO2max, 2-min rest between intervals) with different oxygen concentration provided in rest intervals. In the 1st and 6th HIT, the heart rate, La and Glu were measured before and after the 1st, 4th and 7th reptition during HIT. Blood sample were also collected to measure cortisol, TBARS, CK, lymphocyte MTP decline, apoptosis and necrosis before and immediately, 1 h, 2 h and 48 h after HIT. Training intensity and exercise induced stress biomarkers in single bout of HIT within group were compared by one way ANOVA with repeated measurment. Training intensity, exercise induced stress biomarkers in single bout HIT and endurance determinants after 2 weeks training between groups were compared by one way ANCOVA. Paired t-test was used to compare training intensity and exercise induced stress biomarkers between 1st and 6th HIT. The significant level was set as α = .05. Results: 1. The training intensity markers during HIT were not affected by different oxygen concentration recovery. The CK activity of 2 h and TBARS concentration of 1 h after HIT were no significant difference to before training in Hypo group. The apoptosis of 1 h after HIT in Hypo group was significantly lower than in Hyper group (15.16%±5.22% vs. 22.70%±8.18%, p < .05). In Hyper group, the cortisol concentration did not elevate after HIT. The cortisol of 1 h after HIT in Hyper group significantly lower than in Hypo group (249.8±107.0 nmol/L vs. 362.7±158.2 nmol/L, p < .05). 2. After 5 times adaption of HIT, the heart rate during training in three groups were significantly decreased. The TBARS concentrations of before and immediately, 1 h after HIT in Hypo group were significantly decreased (p < .05). 3. The VO2max、VT and time to fatigue in Hypo group were significantly improved after traing (p < .05), but there was no change in Hyper group. Conclusion: Recovery by 16% hypoxia during HIT could decrease oxidative and mechanical stress as well as decrease the oxidative stress from HIT after adaption. It can also improve endurance determinants. Using hypoxia recovery during HIT may reduce exercise induced damage and increase aerobic capacity.