The physiological responses to exercise depend on intensity, duration, and type of exercise. The muscles in the body have complex regulation responses in order to create a certain resistance and adaptation to the exercise demands without fatigue. In the following study, we used the model of Alaskan sled dogs in order to analyze changes in gene expression within muscle tissue. Gene expression allows us to look more in depth into temporal or long term biological changes that take place in order for the muscle to adapt and maintain homeostasis. Eight dogs were used for the study; four biopsies from the femoris biceps were taken from each at different time points. Time point 1 (Tp1) untrained dogs, time point 2 (Tp2) after mid training, time point 3 (Tp3) fully trained and time point 4 (Tp4) were taken after dogs had completed a 400 mile run in 4 consecutive days. Time point one was used as a control ratio for the other three time points for analysis one, for the second analysis Tp1 was eliminated as a control. Analysis, one compared Tp2-Tp3 and Tp3-Tp4; the subsequent analysis looked at Tp1-Tp3. For Mid trained animals compared to fully trained, we looked at a total of 25 differentially expressed genes, for fully trained compared against acute exercise performance, we looked at total of 52 differentially expressed genes (based on a ≤0.01 p-value and fold change of ≥3), and untrained was compared to fully trained where we looked at a total of 26 differentially expressed genes. Known transcriptional regulators were mapped from these differentially expressed genes, such as exocyst complex, lysyl oxidase, protein tyrosine phosphatase, protein kinase C, creatine kinase, HSP40, cytochrome P450, ACSL6 gene responsible for Acyl-CoA synthesis, myosin chain, ATP binding, and ubiquitin, among others. These transcripts were linked to important biological pathways, and functional analysis of these pathways demonstrated that changes found in gene expression are responsible for muscle tissue remodeling, energy storage and metabolism changes, cardiovascular enhancement, and activation of elements that regulate metabolism via the nervous system. The following study of transcriptional regulation mechanisms helped identify specific responses to exercise stimuli in the organism that allow the athletes to adapt to the demands of exercise.

A lipemia pós-prandial (LPP) se caracteriza pelo aumento das concentrações de lipídeos sanguíneos, provocado por meio de refeição ou jejum e está diretamente relacionada com o sedentarismo e a formação da placa aterosclerótica. A adolescência é um período crítico no controle do peso e a inatividade física está associada com desenvolvimento de doenças cardiovasculares (DCV) prematuras. O exercício atua como um importante agente protetor contra o desenvolvimento e progressão de diversas doenças crônicas. Apesar dos efeitos do exercício sobre a LPP serem relativamente bem descritos, os seus efeitos sobre crianças e adolescentes têm sido negligenciados. Além disso, um dos aspectos intervenientes sobre a LPP é a intensidade de exercício. Dessa forma, o objetivo do estudo foi verificar os efeitos do exercício de intensidade média e alta na lipemia e glicemia pós-prandiais em adolescentes eutróficos saudáveis após refeição hiperlipídica. Treze adolescentes do sexo masculino, com idade entre 12 e 16 anos, foram selecionados e realizaram três protocolos: exercício de média intensidade (MI), exercício de alta intensidade (AI) e repouso (REP). No MI, os participantes pedalaram durante 45 minutos a 10% abaixo do 2° limiar ventilatório, seguidos de 180 minutos de repouso. No AI, os participantes pedalaram a 10% acima do 2° limiar ventilatório até alcançarem o mesmo gasto energético do MI. No REP, os participantes permaneceram em repouso durante todo o período. Foi fornecida uma refeição rica em gordura após cada protocolo. Amostras de sangue foram coletadas nos tempos 0 (jejum), 45min (logo após exercício), 105min (1h após a refeição), 135min, 165min, 195min e 225min em cada protocolo. Os níveis de triglicerídeos (TG), colesterol total (CT), HDL, LDL e glicose foram mensurados. Não houve diferenças entre as condições em relação aos níveis de CT, HDL, LDL e glicose. Foi encontrada uma redução significativa (p<0,05) nos níveis de TG (mg/dl) na condição MI quando comparado ao REP e AI no minuto 105 (70,1 + 10,3 vs. 92,2 + 32,4 e 82,2 +10,4) e 135 (68,4 + 14,4 vs. 97,3 + 15,6 e 91,54 + 24,9), respectivamente, e no minuto 165 entre REP e MI (103,14 + 24,2 vs. 82,4 + 18,8). A área sob a curva de TG (mg/dl/min) no MI foi 17,19% significativamente inferior quando comparado ao REP (16.437 vs 19.848) e 12,82% inferior quando comparado ao AI (16.437 vs 18.856). Em conclusão, o exercício de MI mostrou-se eficaz na redução dos triglicerídeos pós-prandiais em adolescentes saudáveis, quando comparado ao repouso e ao exercício de AI. / Postprandial lipemia (PPL) is characterized by increased concentrations of blood lipids, caused by meal or fasting and is directly related to a sedentary lifestyle and the formation of atherosclerotic plaque. Adolescence is a critical period in weight and physical inactivity is associated with premature cardiovascular disease (CVD) development. Exercise acts as an important protective mediator against the development and progression of several chronic diseases. Despite the effects of exercise on LPP are relatively well described, its effects on children and adolescents have been neglected. Moreover, one of the factors on aspects LPP is the intensity of exercise. Thus, the aim of this study was to investigate the effects of exercise of medium and high intensity on postprandial lipemia and glycemia in healthy normal adolescents after a high fat meal. Thirteen male adolescents, aged between 12 and 16 years, were selected and performed three protocols: exercise of moderate intensity (MI), high-intensity exercise (HI) and rest (RES). In MI, participants cycled for 45 minutes at 10% below 2nd ventilatory threshold, followed by 180 minutes of rest. In HI, participants cycled at 10% above the 2nd ventilatory threshold in order to achieve the same energy expenditure MI. RES, the participants remain at rest during the entire period. A high fat meal was provided after each protocol. Blood samples were collected at 0 (fasting), 45min (after exercise), 105min (1h after the meal), 135min, 165min, 195min and 225min in each protocol. Triglycerides (TG), total cholesterol (TC), HDL, LDL and glucose were measured. There were no differences between conditions in relation to the levels of TC, HDL, LDL and glucose. A significant reduction (p <0.05) was found in the levels of TG (mg / dL) in the condition MI when compared to the REP and HI at 105 minutes (70.1 ± 10.3 vs. 92.2 + 32.4 and 82.2 +10.4) and 135 (14.4 vs. 68.4 +. 97.3 + 15.6 + 24.9 and 91.54), respectively, and at 165 minutes between REP and MI (24.2 vs 103.14 +. 82.4 + 18.8). The area under the curve of TG (mg / dl / min) in MI was 17.19% significantly lower when compared to REP (16,437 vs 19,848) and 12.82% lower when compared to HI (16,437 vs 18,856). In conclusion, the MI exercise was effective in reducing the postprandial triglyceride levels in healthy adolescents, when compared at rest and during HI exercise.

A lipemia pós-prandial (LPP) se caracteriza pelo aumento das concentrações de lipídeos sanguíneos, provocado por meio de refeição ou jejum e está diretamente relacionada com o sedentarismo e a formação da placa aterosclerótica. A adolescência é um período crítico no controle do peso e a inatividade física está associada com desenvolvimento de doenças cardiovasculares (DCV) prematuras. O exercício atua como um importante agente protetor contra o desenvolvimento e progressão de diversas doenças crônicas. Apesar dos efeitos do exercício sobre a LPP serem relativamente bem descritos, os seus efeitos sobre crianças e adolescentes têm sido negligenciados. Além disso, um dos aspectos intervenientes sobre a LPP é a intensidade de exercício. Dessa forma, o objetivo do estudo foi verificar os efeitos do exercício de intensidade média e alta na lipemia e glicemia pós-prandiais em adolescentes eutróficos saudáveis após refeição hiperlipídica. Treze adolescentes do sexo masculino, com idade entre 12 e 16 anos, foram selecionados e realizaram três protocolos: exercício de média intensidade (MI), exercício de alta intensidade (AI) e repouso (REP). No MI, os participantes pedalaram durante 45 minutos a 10% abaixo do 2° limiar ventilatório, seguidos de 180 minutos de repouso. No AI, os participantes pedalaram a 10% acima do 2° limiar ventilatório até alcançarem o mesmo gasto energético do MI. No REP, os participantes permaneceram em repouso durante todo o período. Foi fornecida uma refeição rica em gordura após cada protocolo. Amostras de sangue foram coletadas nos tempos 0 (jejum), 45min (logo após exercício), 105min (1h após a refeição), 135min, 165min, 195min e 225min em cada protocolo. Os níveis de triglicerídeos (TG), colesterol total (CT), HDL, LDL e glicose foram mensurados. Não houve diferenças entre as condições em relação aos níveis de CT, HDL, LDL e glicose. Foi encontrada uma redução significativa (p<0,05) nos níveis de TG (mg/dl) na condição MI quando comparado ao REP e AI no minuto 105 (70,1 + 10,3 vs. 92,2 + 32,4 e 82,2 +10,4) e 135 (68,4 + 14,4 vs. 97,3 + 15,6 e 91,54 + 24,9), respectivamente, e no minuto 165 entre REP e MI (103,14 + 24,2 vs. 82,4 + 18,8). A área sob a curva de TG (mg/dl/min) no MI foi 17,19% significativamente inferior quando comparado ao REP (16.437 vs 19.848) e 12,82% inferior quando comparado ao AI (16.437 vs 18.856). Em conclusão, o exercício de MI mostrou-se eficaz na redução dos triglicerídeos pós-prandiais em adolescentes saudáveis, quando comparado ao repouso e ao exercício de AI. / Postprandial lipemia (PPL) is characterized by increased concentrations of blood lipids, caused by meal or fasting and is directly related to a sedentary lifestyle and the formation of atherosclerotic plaque. Adolescence is a critical period in weight and physical inactivity is associated with premature cardiovascular disease (CVD) development. Exercise acts as an important protective mediator against the development and progression of several chronic diseases. Despite the effects of exercise on LPP are relatively well described, its effects on children and adolescents have been neglected. Moreover, one of the factors on aspects LPP is the intensity of exercise. Thus, the aim of this study was to investigate the effects of exercise of medium and high intensity on postprandial lipemia and glycemia in healthy normal adolescents after a high fat meal. Thirteen male adolescents, aged between 12 and 16 years, were selected and performed three protocols: exercise of moderate intensity (MI), high-intensity exercise (HI) and rest (RES). In MI, participants cycled for 45 minutes at 10% below 2nd ventilatory threshold, followed by 180 minutes of rest. In HI, participants cycled at 10% above the 2nd ventilatory threshold in order to achieve the same energy expenditure MI. RES, the participants remain at rest during the entire period. A high fat meal was provided after each protocol. Blood samples were collected at 0 (fasting), 45min (after exercise), 105min (1h after the meal), 135min, 165min, 195min and 225min in each protocol. Triglycerides (TG), total cholesterol (TC), HDL, LDL and glucose were measured. There were no differences between conditions in relation to the levels of TC, HDL, LDL and glucose. A significant reduction (p <0.05) was found in the levels of TG (mg / dL) in the condition MI when compared to the REP and HI at 105 minutes (70.1 ± 10.3 vs. 92.2 + 32.4 and 82.2 +10.4) and 135 (14.4 vs. 68.4 +. 97.3 + 15.6 + 24.9 and 91.54), respectively, and at 165 minutes between REP and MI (24.2 vs 103.14 +. 82.4 + 18.8). The area under the curve of TG (mg / dl / min) in MI was 17.19% significantly lower when compared to REP (16,437 vs 19,848) and 12.82% lower when compared to HI (16,437 vs 18,856). In conclusion, the MI exercise was effective in reducing the postprandial triglyceride levels in healthy adolescents, when compared at rest and during HI exercise.

A lipemia pós-prandial (LPP) se caracteriza pelo aumento das concentrações de lipídeos sanguíneos, provocado por meio de refeição ou jejum e está diretamente relacionada com o sedentarismo e a formação da placa aterosclerótica. A adolescência é um período crítico no controle do peso e a inatividade física está associada com desenvolvimento de doenças cardiovasculares (DCV) prematuras. O exercício atua como um importante agente protetor contra o desenvolvimento e progressão de diversas doenças crônicas. Apesar dos efeitos do exercício sobre a LPP serem relativamente bem descritos, os seus efeitos sobre crianças e adolescentes têm sido negligenciados. Além disso, um dos aspectos intervenientes sobre a LPP é a intensidade de exercício. Dessa forma, o objetivo do estudo foi verificar os efeitos do exercício de intensidade média e alta na lipemia e glicemia pós-prandiais em adolescentes eutróficos saudáveis após refeição hiperlipídica. Treze adolescentes do sexo masculino, com idade entre 12 e 16 anos, foram selecionados e realizaram três protocolos: exercício de média intensidade (MI), exercício de alta intensidade (AI) e repouso (REP). No MI, os participantes pedalaram durante 45 minutos a 10% abaixo do 2° limiar ventilatório, seguidos de 180 minutos de repouso. No AI, os participantes pedalaram a 10% acima do 2° limiar ventilatório até alcançarem o mesmo gasto energético do MI. No REP, os participantes permaneceram em repouso durante todo o período. Foi fornecida uma refeição rica em gordura após cada protocolo. Amostras de sangue foram coletadas nos tempos 0 (jejum), 45min (logo após exercício), 105min (1h após a refeição), 135min, 165min, 195min e 225min em cada protocolo. Os níveis de triglicerídeos (TG), colesterol total (CT), HDL, LDL e glicose foram mensurados. Não houve diferenças entre as condições em relação aos níveis de CT, HDL, LDL e glicose. Foi encontrada uma redução significativa (p<0,05) nos níveis de TG (mg/dl) na condição MI quando comparado ao REP e AI no minuto 105 (70,1 + 10,3 vs. 92,2 + 32,4 e 82,2 +10,4) e 135 (68,4 + 14,4 vs. 97,3 + 15,6 e 91,54 + 24,9), respectivamente, e no minuto 165 entre REP e MI (103,14 + 24,2 vs. 82,4 + 18,8). A área sob a curva de TG (mg/dl/min) no MI foi 17,19% significativamente inferior quando comparado ao REP (16.437 vs 19.848) e 12,82% inferior quando comparado ao AI (16.437 vs 18.856). Em conclusão, o exercício de MI mostrou-se eficaz na redução dos triglicerídeos pós-prandiais em adolescentes saudáveis, quando comparado ao repouso e ao exercício de AI. / Postprandial lipemia (PPL) is characterized by increased concentrations of blood lipids, caused by meal or fasting and is directly related to a sedentary lifestyle and the formation of atherosclerotic plaque. Adolescence is a critical period in weight and physical inactivity is associated with premature cardiovascular disease (CVD) development. Exercise acts as an important protective mediator against the development and progression of several chronic diseases. Despite the effects of exercise on LPP are relatively well described, its effects on children and adolescents have been neglected. Moreover, one of the factors on aspects LPP is the intensity of exercise. Thus, the aim of this study was to investigate the effects of exercise of medium and high intensity on postprandial lipemia and glycemia in healthy normal adolescents after a high fat meal. Thirteen male adolescents, aged between 12 and 16 years, were selected and performed three protocols: exercise of moderate intensity (MI), high-intensity exercise (HI) and rest (RES). In MI, participants cycled for 45 minutes at 10% below 2nd ventilatory threshold, followed by 180 minutes of rest. In HI, participants cycled at 10% above the 2nd ventilatory threshold in order to achieve the same energy expenditure MI. RES, the participants remain at rest during the entire period. A high fat meal was provided after each protocol. Blood samples were collected at 0 (fasting), 45min (after exercise), 105min (1h after the meal), 135min, 165min, 195min and 225min in each protocol. Triglycerides (TG), total cholesterol (TC), HDL, LDL and glucose were measured. There were no differences between conditions in relation to the levels of TC, HDL, LDL and glucose. A significant reduction (p <0.05) was found in the levels of TG (mg / dL) in the condition MI when compared to the REP and HI at 105 minutes (70.1 ± 10.3 vs. 92.2 + 32.4 and 82.2 +10.4) and 135 (14.4 vs. 68.4 +. 97.3 + 15.6 + 24.9 and 91.54), respectively, and at 165 minutes between REP and MI (24.2 vs 103.14 +. 82.4 + 18.8). The area under the curve of TG (mg / dl / min) in MI was 17.19% significantly lower when compared to REP (16,437 vs 19,848) and 12.82% lower when compared to HI (16,437 vs 18,856). In conclusion, the MI exercise was effective in reducing the postprandial triglyceride levels in healthy adolescents, when compared at rest and during HI exercise.

Given the proliferating aging population, increasing moderate-to-vigorous physical activity (MVPA) and exercise is critical because it enhances overall well-being and reduces the rates of many adverse age-related health conditions. However, intervention efforts to establish sustained changes in MVPA have yielded limited success due their sole focus on conscious factors (e.g., changing goals and intentions). Thus, older adults continue to represent the highest proportion of sedentary adults, despite their knowledge of the widespread health benefits associated with PA and exercise or even their intentions to engage in such behaviors. Consequently, the benefits of PA and exercise are not being fully realized and health problems perpetuate. Developing evidence-based interventions that establish sustained changes in MVPA and exercise behaviors in older adults is a major public health priority, but this requires going beyond social-cognitive constructs. The broad goal of my dissertation is to advance scientific understanding about the neural systems associated with changes in MVPA behaviors among sedentary older adults. Emerging evidence indicates that nonconscious processes also regulate exercise behaviors, stemming from accumulated affective responses from past exercise experiences (e.g., pleasant vs unpleasant). Grounded by current understanding about affect's role on decision-making, the present study hypothesized that physiological changes induced by single bouts of PA serve as somatic markers in the brain that guide future PA-related behaviors. Specifically, my dissertation extended previous research by testing whether acute exercise responses in affect-related brain systems predict PA behavior change following a 3-month exercise intervention. This hypothesis is supported by prior research indicating that self-reported changes in affect (i.e., pleasant/unpleasant feelings) during moderate-intensity exercise reliably predicts future MVPA behavior. The results of my dissertation advances previous findings by investigating how these affective responses to exercise are represented in the brain and how they relate to PA behavior change. I tested my central hypothesis through the following two specific aims: In Specific Aim 1, I investigated whether the acute physiological and neural responses to exercise were related to the subjective experience of exercise in older adults. Healthy, low-active, older participants (N = 34, Age = 67.2 years, 21 females) completed an acute exercise procedure consisting of two within-subjects exercise conditions occurring on separate counter-balanced sessions. During the active condition, participants cycled at a moderate intensity (65% of maximum heart rate), and during the passive condition, their legs were moved by motorized pedals on the same machine and at the same pedal rate as in the active condition. To investigate exercise-related changes in brain function, functional MRI scans were acquired before and after the acute exercise. Additionally, salivary samples were collected throughout the experiment to provide objective biomarkers that have been linked with psychological changes. Finally, participants provided self-reported changes in affect. I found that acute exercise was associated with increases in salivary markers of sympathetic activity and decreases in salivary cortisol levels with no significant differences between conditions. Acute exercise also resulted in observable increases in positive affect with no differences between conditions. Finally, no observable acute exercise-related changes in functional connectivity occurred. In Specific Aim 2, I identified predictors of exercise behavior change from objectively-measured biomarkers and neural systems that are acutely responsive to exercise. After completing the acute exercise sessions, participants began a 3-month supervised exercise intervention. To assess intervention-related changes in unsupervised PA behavior, participants wore a PA monitoring device for 7 days before and immediately after the intervention. Individuals who exhibited a stronger acute functional connectivity response between nucleus accumbens (NAcc) and medial prefrontal cortex (mPFC) before the intervention were more likely to increase their unsupervised levels of MVPA after the intervention. Given the role of NAcc-mPFC circuitry in affect-based decision making and self-referential processing, the present findings suggest that enhanced cognitive appraisal and awareness of affective changes are related to more sustained changes in long term behavior. This study is the first to demonstrate neurobiological evidence supporting the relationship between positive affective responses to acute exercise and long-term changes in exercise behavior. This research advocates the utility of affect-based measures in tailoring exercise interventions for sedentary older adults.

The purpose of the study was to identify the effect of a single bout of moderately intense aerobic exercise on measures of executive function in young adults with ADHD. Thirty-two young adults between the ages of 18 and 25 years old were randomly assigned to either an acute exercise group or a control group. The exercise protocol was designed to address the methodological shortcomings in the exercise and executive function literature, and involved cycling on a stationary bike at moderate intensity for 30 minutes. Participants completed executive function tasks related to set shifting, working memory, and inhibition prior to and immediately following the treatment session. Results of the study reveal that acute exercise facilitated performance on the Stroop Color-Word task when compared to sedentary controls. However, unlike previous research on healthy adults, no improvements on the other measures of executive function were observed. These findings suggest that young adults with ADHD may specifically benefit from acute exercise on aspects of executive function related to the Stroop Color-Word measure. In conclusion, further research on this topic should continue to investigate this population, as well as consider the relationship between acute exercise and additional neuropsychological measures of inhibition, set shifting, and working memory in order to better determine the effects on each construct.

This thesis investigates the developmental trajectory of visuo-spatial working memory as well as the potential influence of acute exercise on working memory performance. Individuals between the ages of 6 and 25 years were randomly assigned to a 30-minute bout of exercise on an elliptical trainer or to a no-exercise control condition. Participants then performed a computerized N-back task to assess working memory. Developmental results suggest that working memory ability continues to develop into early adulthood with the exact trajectory depending on the cognitive demand of the task being assessed. No difference in working memory performance was found between the exercise and control conditions. Thus, acute exercise did not influence performance on the present working memory task, suggesting a need for more research in this area.

Recent findings suggest that leptin may be regulated in response to abrupt changes in energy homeostasis. Therefore, it is conceivable that transient changes in energy balance induced by exercise may also regulate leptin synthesis and secretion. As such, we hypothesized that acute increases energy expenditure (i.e. exercise), may regulate leptin concentrations in obese individuals. Fifteen healthy obese males underwent either a single exercise session of moderate intensity (58.4 % ± 4.0 of VO2max) for 60 min (n=8), or served as controls (n=7). The exercise session elicited an energy expenditure of 567±80 Kcal. No significant changes in plasma leptin (pre 23.5± 30.2; post 24.3± 34.3; 24h-post 34.9± 66.6; 48h-post 33.8±64.0 ng/ml), or insulin levels (pre 16.1± 9.2 vs. post 8.1± 9.1; 24h-post 14.3± 9.9; 48h-post 13.8± 10.2 ?U/ml) were detected immediately after the intervention. Baseline plasma leptin levels were positively correlated with BMI (r=0.65; p<0.01), body weight (r=0.64; p<0.01), % body fat (r=0.90; p<0.01) and were negatively correlated with VO2max (r=-0.82; p<0.01). The results of the present study suggest that acute exercise of moderate intensity and duration may not affect leptin concentration.

No description available.

Estudos recentes têm associado à prática de exercício físico de alta intensidade e de forma inabitual a alterações musculares que incluem lesões estruturais das miofibras. Nessa perspectiva, a suplementação de aminoácidos de cadeia ramificada (BCAA) destaca-se como uma estratégia eficaz no controle do dano celular e na promoção da recuperação muscular. Uma vez que, dentre os BCAA, a leucina é o que apresenta maior influência sobre a regulação de mecanismos anabólicos que incluem o estímulo ao aumento da taxa de tradução de RNAm mediado pela proteína quinase mTOR, se especula quais os possíveis efeitos da sua suplementação isolada em um modelo de exercício físico extenuante e inabitual. Buscamos então, com o presente estudo, avaliar o efeito da suplementação com leucina sobre as concentrações séricas de creatina quinase - marcadores de lesão muscular - e sobre a expressão e fosforilação das proteínas mTOR, 4E-BP1, S6K1, IKK, IkB-&#945;, NF-&#954;B - componentes de vias envolvidas na síntese de proteínas e da inflamação - no músculo esquelético de ratos adultos não treinados, submetidos a uma sessão de exercício até a exaustão. Para tanto, 48 ratos machos adultos da linhagem Sprague-Dawley foram distribuídos em 10 grupos, sendo que T3L, T48L E T72L receberam suplementação com leucina [leucina (135 mg/100 g) e T3A, T48A e T72A receberam uma mistura de aminoácidos não essenciais (135 mg/100 g)] ao final de uma sessão de exercício físico agudo até a exaustão; T3E, T48E e T72E - não receberam suplementação e foram submetidos ao protocolo de exercício; o grupo controle não recebeu suplementação e não foi submetido ao protocolo de exercício. Em seguida os animais foram eutanasiados 3, 48 e 72 horas após o termino do exercício para análise dos marcadores investigados. Entre os parâmetros avaliados houve diferença significativa na atividade da creatina quinase entre os grupos TL3 e TL4. No entanto os marcadores biomoleculares não apontaram diferenças entre os grupos. No entanto a fosforilação do NF- Kb da fração nuclear demonstrou uma tendência a ser menor nos grupos suplementados com leucina e o mesmo acontece com a MCP-1 (proteína quimioatraente de monócitos). Visto isso, podemos concluir que, em nossas condições experimentais, as vias de sinalização estudadas estavam envolvidas na diminuição da atividade da creatina quinase, porém, nossos resultados apontam que a suplementação com leucina pode estar envolvida em mecanismos que atenuem o dano celular após o exercício agudo em ratos não treinados. / Recent studies have associated infrequent exercise of high intensity to muscle changes that include structural lesions in myofibres. The supplementation of branched chain aminoacids (BCAA) stands out as an effective strategy in controlling the cell damage and promoting muscle recovery. As leucine is the BCAA exerting more influence on the regulation of anabolic mechanisms that include stimulating the increase of mRNA translation rate mediated by the protein kinase mTOR, it is speculated the potencial effects of leucine supplementation alone in a model of strenuous and infrequent exercise. In the present study, we evaluate the effect of leucine supplementation on serum levels of creatine kinase - marker of muscle damage - and on the expression and phosphorylation of proteins mTOR, 4E-BP1, S6K1, IKK, IkB-&#945;, NF-&#954;B - components of pathways involved in protein synthesis and inflammation - in the skeletal muscle of untrained adult rats, after a single acute bout of exercise to exhaustion. Forty eight adult male Sprague-Dawley rats were divided into 10 groups: T3L, T48L and T72L groups were given leucine supplementation [leucine (135 mg/100 g), and T3A, T48A and T72A groups were given a mix of non-essential aminoacids (135 mg/100 g)] at the end of the acute bout of exercise to exhaustion; T3E, T48E and T72E groups did not receive supplementation and underwent the exercise protocol; control group was not given supplementation nor exercise protocol. The animals were killed 3, 48 and 72 hours after the end of exercise to analyze the markers under study. Among the parameters assessed, there was a significant difference in the activity of creatine kinase between groups TL3 and TL4. However, no differences were seen in the biomolecular markers between groups. Nevertheless, the nuclear fraction of NF- Kb phosphorylation tended to be lower in the groups supplemented with leucine and the same was seen with MCP-1 (monocyte chemoattractant protein). Taken together, we conclude that the signalling pathways studied, in our experimental condition, do not seem to be involved in the reduced activity of creatine kinase; conversely, our results indicate that leucine supplementation may be involved in mechanisms attenuating cellular damage after a single acute bout of exercise in untrained rats.