The connection between the heart and the brain was coined 150 years ago by Claude Bernard and has since then been an interesting topic of research. Scientists have for many years searched for biomarkers of stress and health to map the current status of the organism. Heart rate variability (HRV) has been presented as an emerging objective and promising marker to achieve just this. HRV refers to the beat-to-beat variations in heart rate (HR) and is thought to be a useful signal in understanding and providing valuable information of the autonomic nervous system (ANS). HRV has also been proposed as a marker of stress and health by sharing neural correlates and functions with several executive functions. This thesis identified several regions, including the ventromedial prefrontal cortex and the amygdala, in which significant associations across several studies were found between threat and safety perception, emotional regulation and HRV. This suggest that HRV may function as an index of the brain mechanism and structures that guide and govern adaptive functions and thus, provide researchers with valuable information regarding the stress and health of an organism. Two major theoretical frameworks, which articulate and explain the role of HRV as an indicator of individuals ability to adapt to environmental changes and cope under stress is presented. HRV can also be used in practice in several ways and a growing and promising field of application is HRV biofeedback.

Master of Science / Department of Human Nutrition / Mark Haub / The purpose of this review is to examine the role of heart rate variability (HRV) as a predictor of athletic readiness and performance and assess whether nutrition strategies can be implemented to create favorable HRV indices with the goal of improving athletic readiness and performance. The balance between training and recovery is crucial for reaching an optimal adaptation and avoiding overtraining, allowing for improved readiness to train and compete. The measurement of HRV is non-invasive and is used primarily to quantify physical and mental stress in athletes by monitoring the effects of the autonomic nervous system on the heart. Current data suggests a relationship between resting parasympathetic tone, via time and frequency domains, and athletic performance. Parasympathetic modulated HRV indices have been associated with performance metrics such as peripheral work capacity, aerobic power, running and sprint performance, swimming performance, weight lifting performance, anaerobic capacity, strength, and enhanced mental focus/skill execution. The use of nutrition to help enhance sports performance is becoming more common. Evidence-based sports nutrition provides fuel for training/competition, assists in maximizing training adaptations, enhances recovery, improves mental focus, and aids in injury prevention and recovery. The use of nutrition strategies to influence HRV is novel and current evidence is scarce in regards to nutritional effects on HRV, specifically in athletes. Current research suggests that achieving energy balance and decreasing body fat in overweight/obese individuals has positive effects on the vagal component of HRV indices. Proper hydration, fruit and vegetable intake, a moderate carbohydrate diet, omega-3 fatty acid supplementation/intake also seem to have positive effects on HRV indices. Certain individual supplements have been studied in regards to HRV including casein hydrolysate, amaranth oil, and bovine colostrum. Caffeine seems to have the opposite effect on HRV indices, increasing sympathetic modulation while decreasing parasympathetic modulation. Much more research needs to be done in regard to potential nutritional influences on HRV so that sport dietitians feel confident in the methods currently used to assess athlete readiness and determining what types of nutrition strategies may be used to further improve the performance of an athlete.

Objective: The purpose of this dissertation was to reproduce Thayer and Lane’s (2000) neurovisceral model by examining both tonic and phasic heart rate variability (HRV) and emotion regulation (ER), and explore the effects of brief evidence-based intervention techniques in a sample of adults with clinically elevated levels of anxiety. Methods: This was a comprehensive multi-methodological study of 34 adults (ages 19 to 63 years) with clinically elevated levels of anxiety. Study 1 examined subjective and physiological effects of implementing ER strategies in response to a well-validated emotion elicitation paradigm consisting of viewing emotion-eliciting aversive images and sentences. Study 2 employed a within-subject RCT design and compared the impact of cognitive restructuring (CR), a top-down ER technique, with open monitoring mindfulness (OM), a bottom-up ER technique. Effects of intervention on self-regulation were assessed at a physiological (i.e. HRV), behavioral (i.e. ER and executive function (EF) computerized task) and subjective (i.e. self-report questionnaires) level. Results: Study 1 revealed that tonic HRV significantly predicted perceived ER success for both top-down and bottom-up generated emotions, whereas phasic HRV only predicted perceived ER success under conditions of bottom-up emotion generation. Variability emerged in our findings depending on the unique ER strategy used. Study 2 indicated a significant time by intervention effect on phasic HRV on the ER task, where HRV decreased with CR and increased with OM. There was a main effect of age independent of intervention on the EF task, such that increased age was related to increased phasic reactivity. On the ER task, CR led to greater perceived success in cognitive reappraisal. On the EF task, CR became faster, whereas OM became slower but more accurate. Significant intervention effects were also found on self-reported anxiety and aspects of mindfulness, with greatest reductions in anxiety found in OM compared to CR. Conclusions: In keeping with the neurovisceral integration model, HRV was reduced in individuals’ with clinically elevated levels of anxiety. Moreover, our findings illustrate that the method of emotion generation and regulation matters and has a significant impact on the degree to which persons with clinical levels of anxiety are able to successfully self-regulate. Finally, our results demonstrate the utility of multi-modal assessment of cognitive and emotional dysregulation in anxiety disorders, as well as the different pathways through which different interventions can impact HRV and ameliorate symptoms of anxiety. / Graduate

abstract: Low-income Mexican American women face significant risk for poor health during the postpartum period. Chronic stressors are theorized to negatively impact mental and physical health outcomes. However, physiological factors associated with increased self-regulatory capacity, such as resting heart rate variability, may buffer the impact of stress. In a sample of 322 low-income Mexican American women (mother age 18-42; 84% Spanish-speaking; modal family income $10,000-$15,000), the interactive influence of resting heart rate variability and three chronic prenatal stressors (daily hassles, negative life events, economic stress) on maternal cortisol output, depressive symptoms, and self-rated health at 12 weeks postpartum was assessed. The hypothesized interactive effects between resting heart rate variability and the chronic prenatal stressors on the health outcomes were not supported by the data. However, results showed that a higher number of prenatal daily hassles was associated with increased postpartum depressive symptoms, and a higher number of prenatal negative life events was associated with lower postpartum cortisol output. These results suggest that elevated chronic stress during the prenatal period may increase risk for poor health during the postpartum period. / Dissertation/Thesis / Masters Thesis Psychology 2015

Wellbeing and subjective wellbeing (SWB) has become some the most important goals of our time, both individually and societally. Thus, there is a need for reliable ways to measure SWB, as concerns regarding many current measures have been raised. Due to the interwoven nature of physiology and psychology, heart rate variability (HRV) has the potential to assess psychological processes in a physiological manner. HRV is an attractive measure since it is inexpensive, easy and non-invasive. Hence, the aim is to, from a cognitive neuroscientific standpoint, investigate whether HRV could serve as an objective measure to assess SWB. Most studies demonstrate associations between HRV and SWB, in particular between high frequency (HF)-HRV and positive affect (PA). However, the one study fully matching the theoretical framework only showed an inverse correlation between HRV and negative affect (NA). Plausibly implying that HRV does not serve as a reliable measure of SWB, but may be able to indicate inverse associations with NA, and possibly index certain aspect of SWB such as deactivated PA. The study of the relationship between HRV and SWB is still in its infancy and results are inconsistent. The lack of common standards regarding measurements, implementation details, and variable values, make results difficult to compare and generalize. Further standardizations and research are much needed before accurate conclusions can be drawn.

Orientador: Simone Biagio Chiacchio / Resumo: Atualmente, observa-se uma maior necessidade de uma assistência adequada tanto no período pré-natal, quanto neonatal, com a finalidade de redução da mortalidade de recém-nascidos, principalmente de animais com elevado valor genético e zootécnico, como os jumentos da raça Pêga. Desta forma, o presente estudo teve por objetivo, descrever os parâmetros clínicos, eletrocardiográficos (ECG) e índices de variabilidade da frequência cardíaca (VFC) em jumentas (no período pré e pós-parto), fetos (35 dias antes do parto) e na fase neonatal, até os 35 dias de idade. Para tal, utilizou-se 10 jumentas clinicamente saudáveis, no terço final de gestação e pós parto, 10 fetos e 10 neonatos pertencentes à raça Pêga, cujo os exames foram realizados ao 35º, 28º, 21º, 14º, 7º e 1º dia antes do parto (jumentas prenhes e fetos) e ao 1º, 7º, 14º, 21º, 28º e 35º dia após o parto para jumentas no período pós-parto e neonatos. Os índices da VFC em jumentas no período pós parto, diferiram significativamente (p<0,05) dentre os momentos de análise, onde o SDNN (ms) variou no primeiro dia após o parto, a RMSSD (ms) no primeiro e 14º dia após o parto, e BF (nu) e a relação BF/AF (nu) no primeiro dia após o parto. As jumentas apresentaram FC constante nos momentos analisados, enquanto que no período pós-parto, apresentaram redução, ambos não significativos. No traçado eletrocardiográfico das jumentas, observou-se significância (p<0,05) na FC (bpm), PR (ms), QT (ms), QTc (ms), T (ms) e R (mV) na derivação b... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Currently, there is a greater need for adequate prenatal and neonatal care in order to reduce the mortality of newborns, especially animals with high genetic and zootechnical value, such as Pêga donkeys. The aim of the present study was to describe the clinical parameters, electrocardiographic (ECG) and heart rate variability (HRV) indices in donkeys (pre and postpartum), fetuses (35 days before delivery) and in the neonatal phase, up to 35 days of age. For this, 10 clinically healthy donkeys were used, in the final third of gestation and postpartum, 10 fetuses and 10 neonates belonging to the Pêga breed, whose examinations were performed at 35º, 28º, 21º, 14º, 7º and 1º day before (pregnant donkeys and fetuses) and at the 1st, 7th, 14th, 21st, 28th and 35th days after delivery for postpartum donkeys and neonates. The HRV indices in donkeys in the postpartum period differed significantly (p <0.05) between the moments of analysis, where the SDNN (ms) ranged on the first day after delivery, the SDSS (ms) on the first and 14th day after delivery, and BF (nude) and the BF / AF ratio (nude) on the first day postpartum. The asses presented constant HR at the analyzed moments, while in the postpartum period, they presented reduction, both of which were not significant. In the electrocardiographic tracing of donkeys, significance was found (p <0.05) for HR (bpm), PR (ms), QT (ms), QTc (ms), T (ms) and R (mV) apex. And in the frontal plane the variables FC (bpm), PR (ms), QT (ms) and ... (Complete abstract click electronic access below) / Doutor

Submitted by Amanda Sarita Cruz Aleixo null (amanda.cruz21@hotmail.com) on 2016-12-21T14:03:47Z No. of bitstreams: 1 Dissertação Mestrado Amanda 2016.pdf: 1470462 bytes, checksum: b63a97da00d57805ec17f0f5d0b74cd9 (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-12-22T11:54:17Z (GMT) No. of bitstreams: 1 aleixo_asc_me_bot.pdf: 1470462 bytes, checksum: b63a97da00d57805ec17f0f5d0b74cd9 (MD5) / Made available in DSpace on 2016-12-22T11:54:17Z (GMT). No. of bitstreams: 1 aleixo_asc_me_bot.pdf: 1470462 bytes, checksum: b63a97da00d57805ec17f0f5d0b74cd9 (MD5) Previous issue date: 2016-12-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A relação alométrica entre frequência cardíaca (FC) e peso corporal, postulada há anos, vem sendo refutada. Estudos acerca da variação e influência de fatores sobre parâmetros hemodinâmicos e eletrocardiográficos em cães não são abundantes. O escopo deste estudo foi avaliar a relação entre FC e peso corporal em cães, bem como a influência do peso sobre os parâmetros eletrocardiográficos (ECG). Foi realizado um estudo retrospectivo (1) mediante a análise da relação entre FC, parâmetros eletrocardiográficos e peso corporal através de traçados de ECG armazenados pelo Serviço de Cardiologiadurante os anos de 2012-2013;já no estudoprospectivo (2) – utilizou-se a eletrocardiografia e o exame de Holter para análise da variabilidade da frequência cardíaca e determinação das variáveis clínicas: peso corporal, idade, raça, sexo, temperamento, frequência respiratória (FR), temperatura corporal, pressão arterial sistêmica e dosagem séricade adrenalina e noradrenalina, dividindo-se os cães em cinco grupos de peso: < 5 kg (8), 5-10 (10), 10-25 (10), 25-45 (10) e > 45 kg (10). As variáveis do ECG variaram conforme o peso. A amplitude da onda R foi maior em cães com idade acima de cinco anos. A concentração de adrenalina aumentou conforme aumento do peso corporal. A FC foi maior no grupo de animais nervosos e a FR foi maior no grupo de animais agitados. As correlações obtidas entre FC e peso e FC e ASC foram fracas. Não houve diferença entre os índices do Holter entre os grupos de pesos.Não existe relação alométrica entre FC e peso corporal em cães. Existe uma relação diretamente proporcional entre adrenalina e peso em cães. O temperamento altera os parâmetros clínicos FC e FR. O peso influencia as variáveis eletrocardiográficas. A análise da FC deve ser realizada considerando-se patamares (direcionada ao metabolismo energético, segundo a faixa etária, sexo e temperamento). / The allometric relationship between heart rate (HR) and body weight, posited for years, has been refuted. Studies on the variation and influence of several factors on the hemodynamic and electrocardiographic parameters in dogs are not plentiful. The scope of this study was to evaluate the relationship between HR and body weight in healthy dogs, as well as the influence of the weight on the electrocardiographic parameters (ECG). We conducted a retrospective study (1) by means of the analysis of the relationship between HR, electrocardiographic parameters and body weight in ECG tracings stored by cardiology department during the years 2012-2013; prospective study (2)analyzing the ambulatory electrocardiogram and by Holter method for analysis of heart rate variability and clinical variables measurement: body weight, age, breed, gender, temperament, breath rate (BR), body temperature and blood pressure, and dosage of serum catecholamines epinephrine and norepinephrine, into five groups of dogs divided according to different weight ranges: < 5 kg (8), 5-10 (10), 10-25 (10), 25-45 (10) e > 45 kg (10). The ECG variables varied according to weight. The amplitude of the R wave was higher in dogs above five years. The epinephrine concentration increased as body weight increased. HR was higher in the group of nervous animals and BR was higher in the group with agitated animals. The correlations between HR and weight and HR and body surface area were weak. There was no difference between the Holter indices among the weight groups. There is no allometric relationship between HR and body weight in dogs. There is a directly proportional relationship between epinephrine and weight in dogs. Temperament changes the clinical parameters HR and BR. The weight influences the electrocardiographic variables. The HR analysis should be performed considering levels (directed to energy metabolism, according to age, gender and temperament).

Objetivos/Hipótese: A Piridostigmina bloqueia a acetilcolinesterase, promove estimulação colinérgica e aumenta a variabilidade da freqüência cardíaca (VFC) em indivíduos saudáveis e com insuficiência cardíaca. Os efeitos sobre a modulação autonômica no diabetes mellitus tipo 2 (DM2) são desconhecidos. Nós testamos a hipótese de que a administração de piridostigmina aumenta a VFC em pacientes com DM2 e neuropatia autonômica cardiovascular (NAC). Métodos: Estudamos 34 pacientes com DM2 e NAC com idade entre 30 e 70 anos. Dezessete receberam 30 mg de piridostigmina via oral, de 8/8h por 24h (PI) e 17 receberam placebo (PL). A VFC foi avaliada pela média (RRMed) e desvio padrão dos intervalos RR (SDNN), pela raiz quadrada da média das diferenças sucessivas entre intervalos RR (RMSSD) e pelos índices do Mapa de Retorno Tridimensional P1, P2, P3 e MN. Resultados: Não houve diferenças significativas entre os grupos PI e PL quanto às características clínicas basais e à VFC sob efeito de piridostigmina e PL (RRMed - 748 ± 99 vs 733 ± 111ms; SDNN - 107 ± 26 vs 108 ± 36ms; RRMSD - 20,7 ± 12,7 vs 20,3 ± 10ms; P1 - 63 ± 11 vs 69 ± 14; P2 - 66 ±13 vs 63 ± 15; P3 - 86 ± 34 vs 80 ± 24 e MN - 392 ± 241 vs 369 ± 185). Conclusão: A piridostigmina não modifica a VFC em pacientes com DM2 e NAC. / Aims/Hypothesis: Pyridostigmine blocks acetylcholinesterase, promotes cholinergic stimulation and increases heart rate variability (HRV) in healthy individuals and with cardiac heart failure. The effects on the autonomic modulation in diabetes mellitus type 2 (DM2) are unknown. We have tested the hypothesis that the administration of pyridostigmine increases HRV in DM2 and CAN patients (CAN). Methods: We have studied 34 DM2 and CAN patients aged between 30 and 70 years old. Seventeen received 30mg of pyridostigmine via oral administration, every 8 hours during 24 hours (PY) and 17 received placebo (PL). HRV was assessed by the mean of all normal R-R intervals RR (mean RR) and the standard deviation of all normal R-R intervals (SDNN), by the root-mean-square of successive differences (RMSSD) and by the three-dimensional return map indices P1, P2, P3 and MN. Results: There were no significant differences between the PY and PL groups as to the baseline clinical characteristics and to HRV under the effect of pyridostigmine and PL (mean RR - 748 ± 99 vs 733 ± 111ms; SDNN - 107 ± 26 vs 108 ± 36ms; RRMSD - 20,7 ± 12,7 vs 20,3 ± 10ms; P1 - 63 ± 11 vs 69 ± 14; P2 - 66 ±13 vs 63 ± 15; P3 - 86 ± 34 vs 80 ± 24 e MN - 392 ± 241 vs 369 ± 185). Conclusion: Pyridostigmine does not modify HRV in DM2 and CAN patients.

Orientador: Dora Maria Grassi Kassisse / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-25T14:24:15Z (GMT). No. of bitstreams: 1 Ferreira_HeloisaAparecida_D.pdf: 2097137 bytes, checksum: 1a224a2d7aabc78ef67e541d8ebb6446 (MD5) Previous issue date: 2014 / Resumo: O processo seletivo para ingresso nas universidades públicas brasileiras é competitivo e um agente estressor para adolescentes. Técnicas de relaxamento, propostas pela terapia manual (TM), são utilizadas em diferentes populações para redução de sintomas de estresse. Objetivamos, neste trabalho, avaliar os efeitos de um programa de terapia manual (PTM) sobre a variabilidade da frequência cardíaca (VFC) e indicadores de estresse em vestibulandos. O estudo seguiu o desenho experimental longitudinal com análises pré-pós-programa em população única. Sessões de TM foram aplicadas, 40-50 min, 2x/semana, ao longo de nove semanas. O estudo da variabilidade da frequência cardíaca foi utilizado para avaliar o efeito do PTM sobre o tônus do sistema nervoso autonômico sobre o coração. Para o estudo da VFC, registramos a frequência cardíaca (FC, bpm) durante 15 min em 16 voluntários em posição supina (18 a 20 anos; 8 mulheres e 8 homens) antes e após a primeira e última sessão de TM, S810i - Polar® -Finlândia. A VFC foi avaliada nos 5 min centrais (Kubios HRV Analysis Software). Os indicadores de estresse escolhidos foram o instrumento psicológico ¿ questionário de estresse para adolescentes (QEA) e a concentração e ritmicidade de produção de cortisol (Alka, ng/mL). O estudo estatístico foi realizado utilizando o programa GraphPad Prism versão 5.00 para Windows. A normalidade dos resultados foi testada utilizando os testes de Kolmogorov Smirnov. Quando adequado, utilizamos os testes: ANOVA seguido de Tukey ou t Student pareado e não pareado ou Kruskal-Wallis seguido de Dunns. Os resultados foram considerados significativos quando os valores de p foram menores que 5%. PTM reduziu (p<0,05) os valores do QEA de 143,1±8,8 para 114±7,1 e da FC (bpm) de 80,68 (128,8-64,26) para 69,6 (93,44-56,86). A TM causou efeito agudo induzindo queda na concentração de cortisol após as sessões e crônico, pois a concentração de cortisol no momento antes da última sessão estava abaixo daquela antes do início do programa. A concentração de cortisol (ng/mL) foi de 15,9±0,9 para 12,0±0,9 após todo o PTM. A ritmicidade de produção de cortisol, desta população, apresentou-se normal e foi preservada ao longo das 9 semanas. A concentração de cortisol avaliada em AUC (ng/mL) foi mais elevada no dia da prova de vestibular e as amostras do meio-dia e das 20 h apresentaram os valores mais elevados neste dia. Efeitos agudos da TM foram identificados nas análises do domínio da frequência e do tempo nos registros da VFC. Os efeitos na VFC foram devido ao aumento na atividade do tônus parassimpático e atividade global do coração. Os resultados deste estudo permitem concluir que a TM é eficaz em sessão única e ao longo de um programa induzindo efeitos agudos e crônicos. O efeito crônico, possível plasticidade neural, foi observado na redução na concentração de cortisol antes da última sessão de TM e este pode ser o fator responsável pela predominância do tônus do sistema nervoso parassimpático sobre o coração registrado nestes voluntários / Abstract: The selective process for admission to the Brazilian public universities is competitive and one stressor for adolescents. Relaxation techniques, proposed by manual therapy (MT) are used in different populations to reduce stress symptoms. We aim in this study evaluate the effects of a manual therapy program (MTP) on heart rate variability (HRV) and on indicators of stress in school students. The study followed a longitudinal experimental design with pre- post- analysis program in a single population. MT sessions, 40-50 min, twice a week were applied over nine weeks. The study of heart rate variability was used to assess the effect of MTP on the heart autonomic nervous system tonus. For the study of HRV, we recorded heart rate (bpm) for 15 min in 16 volunteers in the supine position (18 to 20 years, 8 women and 8 men) before and after the first and last session of MT, S810i - Polar ® - Finland. HRV was evaluated in 5 min stations (Kubios HRV Analysis Software). The stress indicators chosen were the psychological instrument - the questionnaire of stress for adolescents (ASQ) and the concentration and rhythm of cortisol production (Alka , ng/mL) . Statistical analysis was performed using the program GraphPad Prism version 5.00 for Windows. The normality of the results was tested using the Kolmogorov-Smirnov test. Where appropriate, we use the following tests: ANOVA followed by Tukey or t Student paired or unpaired or Kruskal-Wallis followed by Dunns. Results were considered significant when P values were less than 5 %. MTP reduced (p < 0.05) values of the ASQ 143.1±8.8 to 114±7.1 and HR (bpm) to 80.68 (from 128.8 to 64.26) to 69.6 (93.44 to 56.86). The MT induced acute decrease in cortisol concentration after the sessions and chronic effects since the concentration of cortisol in the time before the last session was below that observed before the beginning of the program. The concentration of cortisol (ng/mL) was 15.9±0.9 to 12.0±0.9 after the end of MTP. The rhythm of cortisol production of this population was normal and was preserved over 9 weeks. Cortisol levels measured in AUC (ng/mL) was higher on race day and vestibular samples noon and 20 h showed the highest values for this day. Acute effects of MT have been identified in the analysis of frequency and time domain of HRV. These alterations were due to an increase in parasympathetic tone and overall activity of the heart activity. The results of this study allow us to conclude that MT is effective in one session and throughout a program inducing acute and chronic effects. The chronic effect, possible neural plasticity was observed as a reduction in the concentration of cortisol before the last session of MT and this may be the cause for the predominance of the tone of the parasympathetic nervous system on the heart recorded in these volunteers / Doutorado / Fisiologia / Doutora em Biologia Funcional e Molecular

Orientador: Mara Patrícia Traina Chacon Mikahil / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Educação Física / Made available in DSpace on 2018-08-23T03:14:09Z (GMT). No. of bitstreams: 1 Souza_LucianaCristinade_M.pdf: 3136861 bytes, checksum: 3f028a579a4869dd47ab258e4144ea85 (MD5) Previous issue date: 2013 / Resumo: A redução da Variabilidade da Frequência Cardíaca (VFC) está associada com o alto risco de eventos cardiovasculares, e também ao processo de envelhecimento e ao grau de sedentarismo. A prática regular de exercícios físicos, destacadamente os aeróbios, reflete em um aumento da VFC, decorrente da reduzida atividade simpática quase sempre acompanhada do aumento da atividade parassimpática sobre o coração, tanto em condições de repouso, como após sessão de treinamento. A prescrição do treinamento de força no envelhecimento tem sido prescrito por gerar ganhos de força e hipertrofia diminuindo o risco de lesões e quedas. Nesse sentido, o exercício resistido (RE) associado com uma restrição do fluxo sanguíneo (RE-BFR) tem sido utilizado por proporcionar ganhos de força ou hipertrofia muscular similar ao treinamento tradicional, fazendo uso de intensidades reduzidas de treinamento. Entretanto, pouco se sabe sobre as respostas autonômicas cardiovasculares agudas associadas a este tipo de treinamento. Objetivo: Desta forma, o presente estudo se propôs a comparar as respostas agudas da VFC após sessões de RE tradicional e RE-BFR, utilizando um ou dois exercícios em membros inferiores. Métodos: Quinze homens (47,6±5,28 anos, 76,81±10,95 kg, 1,74±0,08m), saudáveis e não ativos participaram desse estudo. Os voluntários foram submetidos a quatro sessões randomizadas de treinamento, compostas pelos seguintes exercícios: Leg Press de alta intensidade (Leg-HI) (80% 1RM), Leg Press de baixa intensidade com restrição parcial do fluxo sanguíneo (Leg-BFR) (20% 1RM), Extensão do joelho e Flexão de joelho de alta intensidade (EF-HI) (80% 1RM) e Extensão do joelho e Flexão de joelhos de baixa intensidade com restrição parcial do fluxo sanguíneo (EF-BFR) (20% 1RM). Os dados de VFC foram coletados nos momentos pré durante 20min, e imediatamente após a sessão de treinamento durante 60min, na posição supina. A coleta foi feita utilizando monitor Polar® s810 e os dados foram analisados a partir do software Kubios HVR Analysis 1.1. Foi utilizada uma análise da curva de crescimento para expressar o comportamento das variáveis ao longo do período de recuperação, bem como a comparação entre as diferentes sessões de exercício. Foi utilizado o software SAS 9.2. Resultados: A análise da curva de crescimento identificou aumento no índice LFnu para o grupo Leg-HI comparado ao Leg-BFR(P = 0,0033) e EF-BFR(P = 0,0062). O grupo Leg-HI também mostrou maior redução de HFnu comparado ao Leg-BFR (P = 0,0033) e EF-BFR(P = 0,0062). Além disso, houve uma tendência para maior LF/HF para EF-HI comparado ao Leg-BFR(P = 0,0758). Houve efeito de tempo (P=0,0001; P=0,0001; P=0,0067) e efeito de grupo (P=0,001; P=0,0169; P=0,0001) para os índices iRR, SDNN e RMSSD, respectivamente. Entretanto, não houve efeito grupo x tempo para essas variáveis. Conclusões: Os resultados mostraram aumento da modulação simpática e diminuição na modulação parassimpática para Leg-HI quando comparado com ambos os protocolos de RE-BFR após a sessão de exercício. Esses resultados podem ser importantes especialmente para pessoas envelhecendo, visto que o RE-BFR pode ser um método interessante, pois somados aos benefícios neuromusculares já reportados, apresenta menor stress autonômico comparado ao RE de alta intensidade / Abstract: Reduced Heart Rate Variability (HRV) is associated with high risk of cardiovascular events, and also to the aging process and the degree of inactivity. The regular practice of physical exercise, the aerobic prominently, reflects an increase in HRV, due to reduced sympathetic activity almost always accompanied by an increase in parasympathetic activity on the heart, both at rest, and after the exercise session. The prescription of strength training in aging has been prescribed for generating gains in strength and hypertrophy decreasing the risk of injury and falls. Accordingly, the resistance exercise (RE) associated with a restriction of blood flow (RE-BFR) has been used for providing strength gains and muscle hypertrophy similar to traditional training with lower intensity training. However, studies about the acute cardiovascular autonomic responses associated with this type of training are scarce. Objective: Thus, the present study purposed to compare the acute responses of HRV after sessions of traditional RE and RE-BFR, using one or two exercises for lower limbs. Methods: Fifteen men (47.6 ± 5.28 years, 76.81 ± 10.95 kg, 1.74 ± 0.08m), healthy and non-active participated in this study. The volunteers were randomly assigned to four sessions of training, consist of the following exercises: Leg Press high intensity (Leg-HI) (80% 1RM), Leg Press low intensity with partial blood flow restriction (Leg-BFR) (20% 1RM), knee extension and knee flexion high intensity (EF-HI) (80% 1RM) and knee extension and knee flexion low intensity with partial restriction of blood flow (EF-BFR) (20% 1RM). HRV data were collected in pre session during 20min and immediately after session during 60min in the supine position. The collection was made using Polar ® S810 monitor and data were analyzed using the software Kubios HVR Analysis 1.1. Random coefficient growth curve analysis allowed comparison between slopes to express the behavior of variables over the period of recovery, as well as the comparison between different exercise sessions. We used SAS 9.2 software. Results: The analysis of the growth curve identified an increase in LFnu index to Leg-HI compared to Leg-BFR (P = 0.0033) and EF-BFR (P = 0.0062). The Leg-HI group also showed greater reduction in HFnu compared to Leg-BFR (P = 0.0033) and EF-BFR (P = 0.0062). In addition there was a tendency for higher LF/HF compared to EF-HI-Leg BFR (P = 0.0758). There was a time effect (P = 0.0001, P = 0.0001, P = 0.0067) and group effect (P = 0.001, P = 0.0169, P = 0.0001) to iRR, SDNN and RMSSD indices, respectively. However, no significant group vs time effect for these variables. Conclusions: The results showed increased sympathetic modulation and reduced parasympathetic modulation for Leg-HI when compared with both protocols RE-BFR after the exercise session. These results are especially important for aging people, since RE-BFR may be an interesting method because in addition to neuromuscular benefits reported, presented lower autonomic stress compared to RE high intensity / Mestrado / Atividade Fisica Adaptada / Mestra em Educação Física