This thesis is comprised of two studies. The objective of the first study was to find the frequency response and stiffness of the biceps brachii muscle group during recovery from exercise induced damage and to determine whether these data could be used to track muscle recovery by correlating changes in the frequency response with changes in muscle stiffness. Stiffness moduli were collected using Shear Wave Elastography (SWE) which were then applied to a proportional first mode frequency analysis. Data were collected for the muscle stiffness and frequency response for fifteen subjects (25.6 +- 4.5). By comparing the proportion of the square root of the SWE results, the variation in stiffness showed a less than 2 Hz change in first mode resonance for the control group. Frequency response results for the control group agreed with the modified SWE results and the proportion analysis. SWE results for the damage protocol group showed an average increase of 4 Hz. Frequency response results for the damage protocol group were sorted into three categories: three subjects had a change in frequency of peaks of at least 4 Hz in the positive direction; four subjects had an increase in amplitude, but no change in frequency of peaks; three subjects showed mixed responses like fewer resonance peaks, variable amplitudes, changes in peak bandwidth. This research allowed for the documentation of the in-vivo frequency response of the biceps brachii muscle. We believe that the frequency response of a muscle group may be used in the future to evaluate recovery from exercise induced damage. Lessons learned were also recorded for helping future studies in their efforts using an SLDV with human body testing.The second study focused on finding the effects on the surface velocity of tissue above and below a region of the lower leg wrapped in an elastic band when excited by an external source. Ten male subjects between the ages of 18-25 were seated in a chair with one foot placed on a vibrating platform. Two excitation frequencies were separately applied while three points along the leg were measured. A repeatability analysis, using results without the leg wrap, showed a 6.5%, 2.5%, and 10.5% variance in the x-, y-, and z-directions respectively, applying a 20 Hz frequency. With a 40 Hz frequency, the variations were 24%, 23.8%, and 28.4% respectively. A change in displacement of +38% and +10% occurred above the knee in the x-direction with 40 Hz and in the y-direction with 20 Hz, respectively. A change in displacement of -20% occurred below the knee in the x-direction with 20 Hz. A change in displacement of -24% occurred below the wrap location in the y-direction with 40Hz. With a confidence interval of 93%, surface velocity of the tissue located above the wrap increased, while the surface velocity of the tissue below the wrap decreased.

L’objectif de ce travail de thèse a été d’analyser les stratégies de réduction de la fatigue musculaire en course de trail et potentiellement d’identifier certains paramètres d’influence de cette fatigue. La course de trail est un nouveau sport en essor qui induit une combinaison spécifique de fatigue et dommages musculaires des principaux muscles locomoteurs. Afin de pouvoir conduire des études interventionnelles, une étude descriptive préliminaire a été conduite pour caractériser la fatigue spécifique et les dommages musculaires induits par ce type d’épreuve de trail. Ensuite, la reproductibilité du trail comme modèle de fatigue a été vérifiée afin de pouvoir l’utiliser dans un contexte d’intervention. Enfin, deux études visant à réduire la fatigue induite par le trail ont été conduites. D’une part l’utilisation des vêtements de compression - très à la mode en trail a été analysée comme stratégie d’optimisation de la performance. D’autre part, a aussi été étudié l’effet d’un réchauffement préalable du muscle sur les dommages musculaires : Dans cette optique, une étude contrôlée en laboratoire a été menée, examinant les effets d’un réchauffement passif sur les conséquences fonctionnelles de course en descente chez une population non-entraînée. En résumé, les travaux conduits au sein de cette thèse fournissent une description de la fatigue en trail, et valident l’utilisation du trail comme modèle reproductible de terrain pour investiguer les stratégies de réduction de la fatigue. De plus, ils relativisent l’effet positif des vêtements de compression sur la performance et montrent le lien fonctionnel entre le réchauffement musculaire et la réduction des dommages musculaires induits par un travail excentrique. / The aim of this thesis was to analyse strategies to reduce muscular fatigue in trail running and potentially draw conclusions on the underlying mechanisms. Trail running is a new and upcoming sport that induces a combination of fatigue and muscle damage in the main locomotor muscles. To obtain conclusive evidence on the effect of intervention studies a preliminary descriptive study was undertaken to characterise typical fatigue and damage. Subsequently a model was developed and validated that would allow the investigation of interventions in an applied field setting. A popular current strategy in trail running is the use of compression garments; therefore the effect of these on performance was studied as an intervention. Furthermore, prior heating is anecdotally considered beneficial and recent research has suggested a potential mechanism to link this with reduced muscle damage. Therefore a controlled laboratory study was conducted, examining the effects of passive heating on functional consequences of downhill running in an untrained population. In synopsis, the research conducted for this thesis provides descriptive evidence and a validated terrain model to further investigate fatigue reduction strategies in trail running. Additionally it adds to the current literature in disproving a positive effect of compression garments on performance and demonstrating the functional link between heating and eccentric-induced muscle damage reduction.

Performance of a series of eccentric contractions produces adverse effects including muscle weakness, delayed onset muscle soreness (DOMS), fluid accumulation and decreased muscle function. The repeated bout effect is a physiological adaptation observed when a single-bout of eccentric exercise protects against muscle damage from subsequent eccentric bouts. Similar to the repeated bout effect, increases in flexibility have been linked to attenuations in acute muscle damage, muscle fatigue and strength loss after eccentric exercise. Purpose: The purpose of this study was to examine the muscle physiological responses to eccentric strength training after first priming the muscles with either a period of static flexibility training or a single intense bout of eccentric exercise performed weeks earlier; and compare these to the responses from eccentric strength training when no prior intervention is administered. Methods: Twenty-five participants were randomly assigned to a flexibility (F) (n=8), a single-bout (SB) (n=9), or a control (C) (n=8) group. The design consisted of two 4-week phases; 1) priming intervention, 2) eccentric training. The priming intervention included static stretching (3x/week; 30mins/day) (F), a single-bout of eccentric exercise (SB) or no priming intervention (C). All groups proceeded to complete eccentric training of the knee flexors using isotonic contractions (%load progressively increased over training period) on a dynamometer following the priming intervention phase. Testing was completed at baseline, post-priming intervention and post-eccentric training, in conjunction with data being collected during the acute eccentric training phase (0hr, 24hr, 48hr; post-bout 1 and 4). Dependent measures included muscle thickness, isometric maximal voluntary contraction (MVC), eccentric and concentric MVC, optimal angle, active range of motion (ROM), passive ROM, maximal power, electromyography (EMG) and delayed onset muscle soreness (DOMS). Results: Acute data during the eccentric training phase revealed a significant reduction in DOMS for both the F and SB groups compared to the C following the first bout of eccentric exercise (p<0.05). The F also had reduced soreness in comparison to both the SB and C post fourth bout of eccentric exercise (p<0.05). The F group demonstrated attenuated loss in isometric strength (post fourth bout) and maximal power (post first bout) during eccentric training compared to the C group (p<0.05). However, there was no significant difference between groups across all dependent variables following the eccentric training phase. Conclusion: This is the first study to directly compare the protective effects observed with static flexibility training to that of a single-bout of eccentric exercise throughout a subsequent eccentric training regime. Although differences in muscle soreness, strength and maximal power occurred during the acute stages of eccentric training, there appeared to be no significant advantage of either protective priming method at the end of eccentric training.

Raumens adaptacija įgyta po pirmo krūvio, vadinama pakartoto krūvio efektu (PKE). PKE aiškiai reiškiasi po ekscentrinių pratimų ir yra siejamas su raumens pažeida. Raumens pažeidos dydis priklauso nuo pradinio intensyvumo, kartojimų kiekio bei raumens ištempimo amplitudės. Nėra aišku, kaip skiriasi pakartotas krūvio efektas, atliekant didėjantį ir vienodą fizinį krūvį. Tyrimo hipotezė: antro krūvio metu padidinus krūvio intensyvumą ir raumens ištempimo amplitudę sumažės pakartotas krūvio efektas. Tyrimo tikslas – nustatyti ir palyginti PKE po vienodo ir didėjančio fizinio krūvio. Uždaviniai: 1. Palyginti PKE po šuolių nuo skirtingo aukščio pakylos; 2. Palyginti PKE po šuolių su skirtinga raumens ištempimo amplitude. Praktinė darbo reikšmė: aiškesnis pakartoto krūvio efekto suvokimas gali padėti pasirinkti teisingą krūvio strategiją saugantis nuo raumenų pažeidos. Metodika: Pirmo tyrimo metu, pirma tiriamųjų grupė, šuolius atliko nuo didėjančio aukščio pakylos, pirmo krūvio metu buvo 30 cm, o antro - 60 cm aukščio pakylos. Kita tiriamųjų grupė šuolius atliko nuo vienodo 60 cm aukščio pakylos. Antro tyrimo metu, pirma tiriamųjų grupė šuolius atliko su didėjančia raumens ištempimo amplitude, pirmo krūvio metu 120º, antro - 90º kampu per kelio sąnarį. Kita grupė pirmo ir antro krūvių metu šuolius atliko su vienoda ištempimo amplitude - 90º per kelio sąnarį. Tyrimuose dalyvavo sveiki, aktyviai nesportuojantys vyrai (n=11) (amžius 19,5±1,7; ūgis 185,2±5,1 cm.; kūno masė 77,3±7... [toliau žr. visą tekstą] / Muscle’s adaptation gained after first workload is called repeated bout effect (RBF). RBF is clearly noticed after eccentric exercise and is associated with muscle damage. Muscle damage’s severity depends on the primary intensity and the extension of muscle’s amplitude. It is not clear how repeated bout effect changes performing enhanced and stable physical workload. Hypothesis. The repeated bout effect will reduce after enhancing the level of workload and the extension of muscle’s amplitude. Aim. To investigate and compare repeated bout effect after stable and enhanced physical workload. Objectives: 1. To compare RWE after jumps from different hight platforms. 2. To collate RWE with different muscles’ extension amplitude. Work significance to practice. The research results may help in choosing the right workload strategy in order to avoid muscles damage. Methods. During the first research, the first participants performed jumps from ascending height platform. During the first exercise platform was 30 cm, during the second – 60 cm height platform. Other participant group was performing jumps from stable, 60 cm height platform. During the second research, the first participant group performed jumps with enhanced muscle extension, first workload with 120°, second – 90° degrees in knee joint extension. Other group during first and second workload were performing jumps with equal – 90° degrees extension amplitude in knee joint. Healthy and not actively sporting men (n=11... [to full text]

We assessed potential mechanisms that may jeopardize skeletal muscle perfusion during surgery leading to adverse outcomes including muscle injury and flap hypoxia. In craniotomy patients, we observed an increase in serum lactate and creatine kinase and urine myoglobin; indicative of muscle damage. The early rise in lactate correlated with elevated BMI, suggesting that obesity caused tissue compression and muscle ischemia. In our rodent model, we investigated the effects of flap preparation and phenylephrine on muscle perfusion by assessing microvascular blood flow and tissue PO2. Phenylephrine reduced muscle blood flow by ~20%, yet increased PO2 by ~10% suggestive of decreased O2 metabolism. At baseline, muscle flap blood flow was reduced by ~50% while PO2 was severely reduced ~80% (~5 torr) suggesting that flap perfusion was attenuated and O2 metabolism was increased. Phenylephrine infusion further reduced muscle flap perfusion. These data demonstrate multiple mechanisms by which muscle perfusion is jeopardized during surgery.

We assessed potential mechanisms that may jeopardize skeletal muscle perfusion during surgery leading to adverse outcomes including muscle injury and flap hypoxia. In craniotomy patients, we observed an increase in serum lactate and creatine kinase and urine myoglobin; indicative of muscle damage. The early rise in lactate correlated with elevated BMI, suggesting that obesity caused tissue compression and muscle ischemia. In our rodent model, we investigated the effects of flap preparation and phenylephrine on muscle perfusion by assessing microvascular blood flow and tissue PO2. Phenylephrine reduced muscle blood flow by ~20%, yet increased PO2 by ~10% suggestive of decreased O2 metabolism. At baseline, muscle flap blood flow was reduced by ~50% while PO2 was severely reduced ~80% (~5 torr) suggesting that flap perfusion was attenuated and O2 metabolism was increased. Phenylephrine infusion further reduced muscle flap perfusion. These data demonstrate multiple mechanisms by which muscle perfusion is jeopardized during surgery.

Prolonged and intense exercise is known to modulate and suppress certain aspects of the immunoendocrine system. Such effects are thought to be largely mediated by the release of stress hormones and regulatory cytokines which originate from a variety of stress related paradigms in sport. These include acute physical exertion, chronic and repetitive exercise as well as other psychological and psychosocial aspects of training and competing in an elite environment. It may be of particular interest to study the effects of regular competition and training on immunoendocrine markers in rugby union players. At the professional level, rugby is an intense and physically demanding game where a significant amount of tissue trauma occurs as a result of the many game collisions. The aims of the studies outlined in this thesis were to determine the effects of acute, repeated and chronic exercise exposure on immunoendocrine markers and illness incidence in professional rugby union. Additional case studies were also undertaken to supplement main study findings. The first part of the thesis documented the effects of acute and repeated exercise on immunoendocrine markers in a cohort of international rugby union players. Data in study 1 showed that large disturbances in immunoendocine and hormone levels occur in players (n = 10) following game play. The magnitude of this response appeared dependent on game physicality (number of rucks/mauls, tackles) and the number of collisions players received during match play. Findings also showed suppression in host immunity, and in particular, innate immune function (neutrophil degranulation) which was not resolved 38 h (-29%) into the recovery period. In study 2, bloods were taken from players (n = 8) across a 21-day international rugby series. Data revealed that players entered the international camp with residual muscle damage (creatine kinase; CK) and inflammation (hs-CRP) following previous club involvement in European cup rugby. Further increases in stress related markers (cortisol, IL-6, CK, CRP) were not evident throughout the players time at the international training base. Conversely, a progressive increase in anabolic-catabolic balance (T/C ratio) was observed across time. In comparison to values on camp-entry (day 1), increases in T/C ratio were evident on day-5 (9.8%), day-7 (13%), day-19 (35%) and day-21 (45%) (P < 0.05). This data is suggestive of improved physiological recovery and was commensurate with team fitness goals (reduced volume + maintenance of training intensity) for that time. Findings suggest that monitoring of player club activities and training load preceding international duty is pertinent if they are required to represent their country inside 7 days. The second part of the thesis evaluated the stress induced effects of chronic rugby exposure in professional club players. Questionnaire data analysed from study 3 showed that players (n = 65) perceived current season length as being ‘too long’ (55%), ‘poorly structured’ (56%) and that game demands are increasing with time (52%). Furthermore, the majority of players (80%) felt that time ‘away’ from rugby was not sufficiently long enough and were in favour of a mid-season break (2 wks in duration). Investigation into the effects of chronic exercise on illness incidence, immunological and psychological state was carried out in a squad of club players (n = 30) over a competitive season (n = 48 wks) in studies 4-6. Findings revealed that specific periods in a rugby season resulted in disturbances to hormonal and immune status. These periods occurred following breaks in club game fixtures [November international and Six-nations period: February/early March], times of increased training intensity and increased ratio of conditioning/rugby activity. Peaks in number of upper respiratory illnesses (URIs) and disturbances in psychometric variables also occurred during these time periods. In 23% of all URIs, players reported that the presence of the illness either reduced activity (14.4%) or felt the need to go to bed (8.6%). Positional differences in variables were also observed. A higher incidence of URIs (3.4 vs 4.3) and lower concentrations of resting immune markers [salivary lysozyme: s-Lys (-31%); immunoglobulin A: s-IgA (-27%)] was observed in ‘backs’ (vs forwards) over the season. Higher mid-season cortisol levels was also observed in backs (P < 0.05) while conversely, greater concentrations of plasma CK and CRP were found in forwards throughout the season. These findings indicate positional specific differences in response to exercise load and point to the role of group specific recovery at certain times during the season. Data from study 6 showed that the number of training related complaints decreased across the season, findings which closely resembled corresponding decreases in plasma CRP values. This data is suggestive of a ‘repeated-bout’ effect or ‘contact adaptation’ in rugby union. Finally, comparison of methods used in the recording of illness data revealed that players were more honest when disclosing the existence of banal infections to a web-based training diary and under-reported infections to medical staff.

We investigated biomarkers of injury, inflammation and oxidative stress in the blood after high intensity training. Nineteen male athletes performed a combination of high-intensity aerobic and anaerobic training. Samples were acquired immediately before and from 3 h to 72 h after the exercise. CK was elevated 200% at 3 h post-exercise, reaching a 300% peak increase at 12 h and returning to pre-exercise levels within 48 h. LDH activity was 25% higher 3 h after exercise, increasing to 56% higher 6 h after exercise and returning to pre-exercise levels within 12 h. Leukocyte levels were 50% higher and neutrophil levels were 70% higher 3 h after exercise than at baseline, while lymphocyte levels increased by up to 55% after 12 h. MCP-1 was elevated by 40% after 6 h and decreased by 37% 72 h after exercise. TNF-alpha levels were lower in all post-exercise samples. IL-6 and CRP levels remained stable throughout the entire recovery period. The levels of oxidative stress markers remained stable during the experiment. CK and LDH blood appearance and clearance are faster than classic described, coaches and physicians must respect these windows to accurately estimate muscle damage. The neutrophil/lymphocyte ratio summarizes the mobilization of two leukocyte subpopulations in a single marker and may be used to predict the end of the post-exercise recovery period. Further analysis of the immune response using serum cytokines indicated that the high-intensity exercise performed by highly trained athletes only generates inflammation localized to the skeletal muscle. / Foram investigados biomarcadores séricos de lesão muscular, inflamação e estresse oxidativo após exercício combinado de alta intensidade. Dezenove atletas do sexo masculino executaram uma combinação de exercício aeróbico e anaeróbico de alta intensidade. Amostras foram coletadas imediatamente antes e entre 3h e 72 após o exercício. CK estava elavada 3h após o exercício, atingindo seu pico de 300% de incremento 12h após o exercício. A atividade de LDH estava 25% elevata 3h após o exercício, aumentando até 56% em 6h após e retornando aos níveis pré exercicio em até 12h. Os nívies dos marcadores de estresse oxidativo não se alteraram durante o experimento. A janela de aparacimento dos marcadores de lesão muscular foi mais rápido do que o classicamente descrito. Os treinadores devem respeitar essa janela para estimar a extensão muscular de forma precisa. A razão neutrófilo/linfócito resume a mobilização de duas populações de células brancas em um único marcador e pode ser usada para predizer o término da recuperação pós exercício. Uma análise mais profunda da resposta imune analisando citocínas séricas indicou que o exercício de alta intensidade proposto por nós e realizado por atletas de alto desempenho apenas gerou inflamação localizada no músculo esquelético. / Doutor em Genética e Bioquímica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Introduction: Strength training has been gaining more and more followers due to the benefits it has brought to health in both prevention and treatment of various pathologies. Among the different types of strength training, the following stand out: Kaatsu and traditional training. Both have gains in terms of strength gain and hypertrophy. Aims: Analyze muscle damage, peak torque, fatigue and asymmetry in different strength training methods. Methods: The study sample consisted of 10 males aged between 18 and 25 years old who had been practicing strength training for at least 12 months. All were subjected to two types of strength training, performed in Leg Press 45 ° apparatus. Venous blood was collected to analyze muscle damage indicators, before, immediately after, 24 and 48 hours after the training, as well as thermographic images collection to analyze the thermal asymmetry of the exercised limbs. Results: The results showed that the use of the Kaatsu method promoted greater muscle damage, higher fatigue index and lower torque peak immediately after training, compared to the same time in the traditional method. CK concentrations were 1093U/l in the Kaatsu method and 447,80U / l in the traditional method. As for the peak torque, it decreased after exercise to 755.38N /m in the Kaatsu method and 936, 28N /m in the traditional method. The fatigue index presented an increase of 58.28% and 37.30% in relation to the pre training in the Kaatsu and traditional methods, respectively. Regarding thermography, asymmetry found bilaterally can be considered normal, although isolated cases should be observed with more attention, considering parameters described in the literature. Conclusion: Kaatsu method promoted greater muscle damage, higher fatigue index and lower peak torque when compared to the traditional method, although it presented a faster recovery. Further research on these methods is needed to make these trainings safer and more effective for practitioners. / Introdução: O treinamento de força vem ganhando cada vez mais adeptos, devido aos benefícios que tem trazido para a saúde tanto na prevenção quanto no tratamento de diversas patologias. Dentre os diferentes tipos de treinamento de força, destacamse: o Kaatsu e o treinamento tradicional. Ambos apresentam ganhos no que diz respeito a força e hipertrofia. Objetivo: analisar o dano muscular, pico de torque, fadiga e assimetria em diferentes métodos de treino de força. Métodos: A amostra do estudo foi composta por 10 indivíduos do sexo masculino, com idade entre 18 e 25 anos, praticantes de treinamento de força há pelo menos 12 meses. Todos foram submetidos a dois tipos de treinamento de força, realizados no aparelho de Leg Press 45°. Foi realizada coleta de sangue venoso para análise dos indicadores de dano muscular, antes, imediatamente após, 24 e 48 horas após a realização do treino, bem como coleta de imagens termográficas para análise de assimetria térmica dos membros exercitados. Resultados: Os resultados encontrados mostraram que a utilização do método Kaatsu promoveu maior dano muscular, maior índice de fadiga e menor pico de torque imediatamente após o treinamento, em relação ao mesmo momento no método tradicional. As concentrações de CK elevaram-se a 1093U/l no método Kaatsu e a 447,80U/l no método tradicional. Quanto ao pico de torque, este diminuiu após o exercício para 755,38N/m no método Kaatsu e 936, 28N/m no método tradicional. Já o índice de fadiga apresentou elevação de 58,28% e 37,30% em relação ao pré treino nos métodos Kaatsu e tradicional, respectivamente. No que diz respeito a termografia, a assimetria encontrada bilateralmente pode ser considerada normal, embora casos isolados devam ser observados com mais atenção, considerando parâmetros descritos na literatura. Conclusão: O treinamento com o método Kaatsu promoveu maior dano muscular, maior índice de fadiga e menor pico de torque quando comparado ao método tradicional, embora, tenha apresentado uma recuperação mais rápida. É necessário novas investigações a respeito desses métodos no intuito de tornar a realização desses treinamentos mais segura e eficaz aos praticantes.

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