Ce projet de thèse avait pour objet d’étudier la régulation de la biodisponibilité du monoxyde d’azote (NO) à travers la supplémentation en nitrate (NO3-) chez l’homme, et la perfusion d’ADMA chez l’animal. Nous avons essayé de déterminer les répercussions de la modulation de la biodisponibilité du NO sur la perfusion musculaire à l’exercice, et l’effet de l’aptitude aérobie sur cette modulation. Dans notre méta-analyse, nous avons rapporté une diminution de la consommation d’oxygène (V̇O2) lors d’exercices d’intensité modérée à élevée, avec une amélioration de la tolérance à l’exercice sans réduction du V̇O2 chez les sujets présentant une pathologie. Dans une seconde étude, aucune amélioration de la tolérance à l’effort n’a été observée chez des athlètes [consommation maximale d’oxygène (V̇O2max) > 65 mL.min-1.kg-1] au cours d’un exercice intermittent d’intensité supramaximale après une supplémentation en NO3- et sans modification au niveau du V̇O2 et de la perfusion musculaire. Une troisième étude montre que l’aptitude aérobie et l’apport en O2 aux muscles, dépendante de la perfusion musculaire, ne sont pas associés à la concentration plasmatique d’ADMA chez des sujets jeunes et sains. Enfin, notre quatrième étude ne rapporte pas d’effet de la perfusion de l’ADMA sur la perfusion musculaire au cours d’un exercice de course chez des rats. En conclusion, la supplémentation en NO3- peut contribuer à une amélioration de la performance à travers une réduction du coût en O2 pour des exercices sous-maximaux. Cependant, les sujets entraînés en endurance avec une aptitude aérobie élevée ne présentent ni d’effet ergogénique, ni d’amélioration de la perfusion musculaire à la suite d’une supplémentation en NO3- lors d’exercices intermittents supramaximaux, contrairement aux sujets modérément entraînés. En outre, l’ADMA, en tant inhibiteur de la synthèse du NO, ne semble pas jouer un rôle dans la régulation du débit sanguin et de l’apport en O2 aux muscles actifs, en l’absence de conditions pathologiques. / We aimed to determine whether dietary nitrate (NO3-) supplementation and ADMA modulate NO bioavailability and muscle blood flow during exercise. The second purpose was to establish whether aerobic fitness alters the effects of dietary NO3- supplementation and ADMA on muscle blood flow during exercise. In our meta-analysis, we found that dietary NO3- supplementation decreases V̇O2 during exercise performed in the moderate and heavy intensity domains in healthy subjects, and enhances exercise tolerance in subjects with chronic diseases, but no change in V̇O2. Our second study showed that dietary NO3- supplementation did not increase the number of repetitions completed during supramaximal intensity intermittent exercise in endurance athletes with high aerobic fitness (V̇O2max > 65 mL.kg-1.min-1), and did not increase muscle blood volume. In the third study, aerobic fitness is not related to muscle O2 delivery and plasma ADMA concentrations in young male subjects with a wide range of aerobic fitness level. In the fourth study, increased plasma ADMA levels did not decrease muscle blood flow during low-treadmill running exercise in healthy rats. In conclusion, dietary NO3- supplementation could contribute to an improved tolerance to exercise by reducing O2 cost during exercises at submaximal intensities. However, endurance-trained athletes with high V̇O2max level do not benefit from the effects of dietary NO3- supplementation on exercise performance and muscle blood flow as reported in moderately trained subjects. Moreover, ADMA did not regulate muscle blood flow and O2 delivery during exercise in conditions free from cardiovascular and metabolic diseases in humans and in the rat with pharmacological-induced increase in plasma ADMA levels.

Title Regime intervention to influence aerobic fitness level of middle age women Objective The aim of the work is to evaluate the effect of two-month physical intervention on the aerobic fitness level of middle-aged women and the influence of this intervention on the change of the body composition of individual study participants. Methods The tested group consisted of 5 middle-aged women with a sedentary occupation and no regular physical activity. The evaluation of their aerobic fitness and body composition was performed before the start of the intervention. These values were compared to the results of the same tests after the intervention. The values of VO2max measured before and after the intervention were used for the evaluation of aerobic fitness. The regression equation, based on the results of 2 km walking test (part of the UNIFITTEST 6-60), was used for the calculation of VO2max. The methods of bioimpedance (using the portable device Body stat 1500) and anthropometric measurement (body high, weight, circuits) were used for determination of body composition - mainly % FFM and% BF. The physical intervention itself was focused on walking for two months period. The form was used for monitoring of intervention individual exercise units. The group of middle-aged women performed the prescribed...

Didelio meistriškumo golfo žaidėjų varžybinės veiklos ir fiziologinių poreikių ypatumai sąlygoja ne tik tokio meistriškumo golfo žaidėjų treniravimo modelius, bet ir sudaro galimybes modeliuoti jaunųjų golfo žaidėjų daugiametį rengimą. Nors rengiant jaunuosius golfo žaidėjus taikomos skirtingos žaidimo sąlygos (nešant, traukiant golfo krepšį ir važiuojant golfo mašinėle), tačiau jų poveikis žaidimo kokybei, judėjimo charakteriui ir funkciniam pajėgumui nėra apibrėžtas. Aktuali problema – kokie yra jaunųjų golfo žaidėjų varžybinės veiklos struktūros, lokomocinių ir fiziologinių poreikių ypatumai žaidžiant skirtingomis sąlygomis? Tyrimo objektas – jaunųjų golfo žaidėjų varžybinė veikla ir funkcinis pajėgumas. Tyrimo hipotezė – sunkėjant žaidimo sąlygoms didėja jaunųjų golfo žaidėjų fiziologiniai poreikiai ir kartu blogėja varžybinės veiklos rodikliai. Sunkėjančios žaidimo sąlygos sudaro galimybes gerinti jaunųjų golfo žaidėjų aerobines galias. Tyrimo tikslas – nustatyti ir įvertinti jaunųjų golfo žaidėjų varžybinės veiklos struktūros, lokomocinių ir fiziologinių poreikių ypatumus žaidžiant skirtingomis sąlygomis. Tyrimo uždaviniai: 1. Nustatyti jaunųjų golfo žaidėjų varžybinės veiklos struktūros, lokomocinių ir fiziologinių poreikių rodiklius žaidžiant skirtingomis sąlygomis. 2. Nustatyti ir įvertinti didesnio ir mažesnio meistriškumo jaunųjų golfo žaidėjų varžybinės veiklos struktūros, lokomocinių ir fiziologinių poreikių ypatumus. 3. Nustatyti ir įvertinti jaunųjų golfo... [toliau žr. visą tekstą] / Sport performance indicators and physiological demands of elite golfers are fundamental factors, when youth golfers and their trainers compose training programs (models). Youth golfers practise and play under three different conditions (carrying golf bag, pulling golf bag and using golf power cart), but it is not known what influence these different conditions have on youth golfers’ peculiarities of their sport performance and physiological demands. The problem of the research: what are the peculiarities of the profile (structure) of sport performance and physiological demands in youth golfers? The object of the research was sport performance and physiological demands in selected youth golfers. The hypothesis of the research: youth golfers’ physiological demands will be higher, but sport performance indicators will be worse under more strenuous conditions. Training effect on youth golfers’ aerobic fitness will be higher under more strenuous conditions. The aim of the research was to determine and assess the peculiarities of sport performance and physiological demands in selected youth golfers under three different conditions. Objectives of the research: 1. To determine the sport performance and physiologicl demands indicators in selected youth golfers under three different conditions. 2. To determine and assess the sport performance and physiological demands peculiarities of different skills in selected youth golfers under three different conditions. 3. To determine and... [to full text]

The overall aim of this thesis was to identify valid, simple, and inexpensive physical tests that can be used for evaluation of firefighters’ physical work capacity. Paper I included fulltime- and part-time firefighters (n = 193), aged 20-60 years. Perceived physical demands of firefighting work tasks were ranked, and comparisons between subject groups rating were done with the Mann Whitney U-test and Binominal test. Papers II and III included male firefighters and civilian men and women (n = 38), aged 24-57 years. Laboratory and field tests of aerobic fitness, muscle strength and endurance, balance, and simulated firefighting work tasks were performed. Physical capacity comparisons between subject groups were done and bivariate correlations between physical tests and work capacity in the simulated firefighting work tasks analyzed. Paper IV included the same subjects as in Paper II-III (training-set), and additional 90 subjects (prediction-set), aged 20-50 years. Laboratory and field tests of aerobic fitness, muscle strength and endurance and balance, and simulated firefighting work tasks were included. Data from the training-set was used to build models for prediction of firefighters’ physical work capacity, using multivariate statistic. The prediction-set was used to externally validate the selected models. Several work tasks were rated as physically demanding and significant differences (p < 0.05) in ratings were found between full-time and part-time firefighters (Paper I). Significant differences were found between subject groups in physical capacity, and work capacity (p < 0.01) (Paper II-IV). Both laboratory and field tests were significantly (p < 0.01) correlated with work capacity time (Paper II-III). The prediction (R2) and predictive power (Q2) of firefighters’ work capacity (Carrying hose baskets upstairs, Hose pulling, Demolition at or after a fire, Victim rescue, and Carrying hose baskets over terrain) was R2 = 0.74 to 0.91, and Q2 = 0.65 to 0.85, and the external validation ranged between R2: 0.38 to 0.80 (Paper IV). In conclusion, rowing 500 m (s), maximal handgrip strength (kg), endurance bench press (n), running 3000 m (s and s scaled to body weight) upright barbell row (n) and standing broad jump (m) together provides valid information about firefighters’ physical work capacity.

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Submitted by Sara Ribeiro (sara.ribeiro@ucb.br) on 2018-08-08T14:11:40Z No. of bitstreams: 1 ArilsonFernandesMendoncadeSousaTese2018.pdf: 5768876 bytes, checksum: 66d7e7ce78b9d2a4b54e615ac9d3282d (MD5) / Approved for entry into archive by Sara Ribeiro (sara.ribeiro@ucb.br) on 2018-08-08T14:11:52Z (GMT) No. of bitstreams: 1 ArilsonFernandesMendoncadeSousaTese2018.pdf: 5768876 bytes, checksum: 66d7e7ce78b9d2a4b54e615ac9d3282d (MD5) / Made available in DSpace on 2018-08-08T14:11:52Z (GMT). No. of bitstreams: 1 ArilsonFernandesMendoncadeSousaTese2018.pdf: 5768876 bytes, checksum: 66d7e7ce78b9d2a4b54e615ac9d3282d (MD5) Previous issue date: 2018-05-25 / Only two weeks of sprint interval training (SIT) has been shown to be associated with positive changes in aerobic capacity and cardiac autonomic control. Both aerobic capacity and autonomic control have been shown to be positively associated with improved attention. However, to date, the relationship between this type of training and attention has not been investigated yet. The aim of the present study was to investigate the influence of two weeks of SIT on aerobic capacity, cardiac autonomic control and attention components in healthy university students; Also, to verify if the training fidelity would influence these adaptations. One hundred and nine participants were divided into experimental (EG) and control (CG) groups. EG performed a SIT program consisting of 6 sessions of maximal 4 × 30 s all-out efforts on a cycle ergometer, interspersed with active 4-minute rests. The criterion for fidelity was to reach> 90% of the estimated maximum heart rate (HR) during sprint sessions. After analysis, EG was divided into fidelity groups HIGH (n = 26) and LOW (n = 46), respectively. The attention components were evaluated through the Attention Network Test (ANT). The aerobic capacity (VO2max) was estimated according to Astrand's nomogram while the sum of the skinfolds: pectoral, triceps, subscapular, medial axillary, abdomen, suprailiac and thigh was verified. Autonomic HR control was assessed by HR variability (HRV) and HR complexity at rest and during ANT, before and after six sessions of SIT. Both HIGH and LOW significantly increased aerobic capacity, vagal modulation before and during ANT and executive control, and decreased body fat after SIT (p <0.05). However, only HIGH participants showed an increase in HR complexity and accuracy in ANT responses when compared to LOW (p <0.05). Two weeks of SIT improved executive control, body fat, aerobic capacity and autonomic control in university students, with better results reported for the HIGH group. / Apenas duas semanas de treinamento intervalado de esforços supra máximos (TIsm) tem mostrado estar associado com modificações positivas na capacidade aeróbia e controle autonômico cardíaco. Tanto a capacidade aeróbia, como o controlo autonômico demonstram estar associados positivamente com melhoria da atenção. Entretanto, até o presente momento a relação entre este tipo de treinamento e atenção não foi investigada. O objetivo do presente estudo foi investigar a influência de um programa de TIsm na capacidade aeróbia, controle autonômico cardíaco e componentes da atenção em jovens universitários saudáveis; ainda, verificar se a fidelidade do treinamento influenciaria essas adaptações. Cento e nove participantes foram divididos em grupo experimental (GE) e controle (GC). O GE realizou um programa TIsm que consistiu em 6 sessões de TIsm de 4 × 30 s em um cicloergômetro, intercaladas com descansos ativos de 4 min. O critério para fidelidade foi atingir> 90% da frequência cardíaca máxima estimada (FC) durante as sessões de TIsm. Após as análises, o GE foi dividido em grupos de fidelidade alta, GEA (n = 26) e baixa, GEB (n = 46), respectivamente. Os componentes da atenção foram avaliados por meio do Teste de Rede de Atenção (ANT). A capacidade aeróbia (VO2max) foi estimada segundo o nomograma de Astrand enquanto o somatório de dobras cutâneas: peitoral, tríceps, subescapular, axilar média, abdômen, supra-ilíaca e coxa foi realizada. O controle autonômico da FC foi avaliado por meio da VFC e complexidade da FC em repouso e durante o ANT, antes e depois de seis sessões de TIsm. Ambos GEA e GEB aumentaram significativamente a capacidade aeróbia, modulação vagal antes e durante a realização do ANT e o controle executivo e diminuição da gordura corporal após o TIsm (p <0,05). No entanto, apenas os participantes do GEA apresentaram um aumento na complexidade da FC e acurácia nas respostas do ANT quando comparados ao GEB (p <0,05). Duas semanas de TIsm melhoraram o controle executivo, a gordura corporal, a capacidade aeróbia e o controle autonômico em estudantes universitários, com melhores resultados relatados para o grupo com GEA fidelidade.

Declining youth physical activity levels and lack of aerobic fitness have been well documented with a corresponding rise in obesity levels and health issues. Based on Bandura's social cognitive theory, healthy physical activity levels and aerobic fitness are strongly connected to positive physical activity self-efficacy beliefs. This study examined whether student physical activity self-efficacy, motivation, and effort were different for the FitnessGram-® (FG) 1-Mile Run when compared to the 15-minute Aerobic Assessment Based on Improvement (AABI). A concurrent mixed method quasi-experimental approach measured 5th grade students' physical activity self-efficacy beliefs through a pretest and posttest survey while aerobic assessment scores provided data that measured and compared student performance. Percent improvement and t-test analytic procedures found significant differences between groups and genders. The FG group (n = 131) improved 1.49% while the AABI group (n = 209) improved 22.53%; furthermore, FG girls' percent improvement decreased to -7.56% and the AABI girls' percent improvement was above the average score at 24.21%. Qualitative data collected and coded from teachers' (n = 6) found no noticeable differences in student behaviors or preparation between the FG or AABI groups. A 3-day workshop was created to initiate change in aerobic fitness assessment. Assessing student aerobic fitness based on improvement theoretically builds physical activity self-efficacy beliefs, especially for girls. Positive physical activity self-efficacy beliefs motivate greater student participation and engagement in physical education, which improves aerobic fitness. Social implications from these results indicate that students would increase their physical activity self-efficacy by assessing aerobic fitness based on individual improvement.

Made available in DSpace on 2016-12-06T17:06:47Z (GMT). No. of bitstreams: 1 Rogerio Bulhoes Corvino.pdf: 873037 bytes, checksum: 3dd80890c4711166c207e26044d827a4 (MD5) Previous issue date: 2012-02-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The aim of this research was analyze the effect of a training realized in cycle ergometer with leg blood flow occlusion on aerobic fitness, muscular strength and body composition parameters. Participate in this study 11 apparently healthy individuals of both genders, with ages between 18 and 30 years old. Subjects performed before and after four weeks of training these tests: 1) Progressive tests to the exhaustion to determine the anaerobic threshold (LAn), maximal oxygen uptake (VO2máx), and peak power (PMAX). 2) Constant load tests until volitional exhaustion (Tlim) in the intensities of 95% and 110% of PMAX to determine the on-kinetics of VO2 (Tau) in moderate (30%PMAX) and severe (110%PMAX) domains, Critical Power (CP), 3) Tests to determine the maximum isometric force of the quadriceps muscle. 4) Measurement of anthropometric variables. During a period of 4 weeks, the experimental group (N=11) performed a total of 12 sessions of leg blood flow occlusion in cycle ergometer at a low intensity (30%PMAX) The parameters Lan (BEFORE 160±52; AFTER 177±57 W), PMAX (BEFORE 246 ±48; AFTER 269±57 W), Tau30% (BEFORE 22,9±8; AFTER 18,4±5 s), Tau110% (BEFORE 43,3±19; AFTER 31,9±12 s), PC (BEFORE 180±52; AFTER 199±46 W), and maximal isometric strength (BEFORE 289±62; AFTER 318±56 N.m-1) were significantly increased after training. For the VO2max (BEFORE 1296±187; AFTER 3329±732 ml/min), VO2 at 30%PMAX (BEFORE 1296±187; AFTER 1317±220 ml/min) and anthropometric variables did not show any significantly different after training. We conclude that four weeks of leg blood flow occlusion training in cycle ergometer was able to generate changes in aerobics and neuromuscular parameters in active subjects in the similar proportions to traditional training methods. Moreover, the no effect on VO2máx whit improvements seen on the aerobic capacity and VO2 kinetcs suggest that major adaptations caused by this type of training should have been more peripheral than central factors / O objetivo deste estudo foi analisar o efeito do treinamento realizado em cicloergômetro com oclusão parcial de fluxo sanguíneo das pernas sobre parâmetros relacionados à aptidão aeróbia, força muscular e composição corporal. Participaram deste estudo 11 indivíduos aparentemente saudáveis de ambos os gêneros, com idades entre 18 e 30 anos. Os indivíduos realizaram, antes e após um período de quatro semanas de treinamento: 1) testes progressivos até a exaustão para a determinação do limiar anaeróbio (LAn), consumo máximo de oxigênio (VO2max), e potência máxima (PMAX) em cicloergômetro. 2) testes de carga constante com 6 min de duração à 30% da PMAX e até a exaustão voluntária (Tlim) à 95 e 110% da PMAX para determinação da cinética do VO2 (Tau) em intensidade moderada (30%PMAX) e severa (110%PMAX), e Potência Crítica (PC) através da relação linear entre a potência e seu respectivo Tlim (95 e 110%PMAX). 3) testes para determinação da força máxima isométrica dos músculos extensores do joelho. 4) Mensuração das variáveis antropométricas. Durante o período de 4 semanas, o grupo experimental (n = 11) realizou um total de 12 sessões de treinamento aeróbio de baixa intensidade (30%PMAX) com oclusão de fluxo sanguíneo em ambas as pernas. Os parâmetros LAn (PRÉ 160±52; PÓS 177±57 W), PMAX (PRÉ 246 ±48; PÓS 269±57 W), Tau30% (PRÉ 22,9±8; PÓS 18,4±5 s), Tau110% (PRÉ 43,3±19; PÓS 31,9±12 s), PC (PRÉ 180±52; PÓS 199±46 W), e força máxima isométrica (PRÉ 289±62; PÓS 318±56 N.m-1) foram significativamente aumentados após o treinamento. Para os valores de VO2max (PRÉ 3242±707 ; PÓS 3329±732 ml/min), e VO2 à 30%PMAX (PRÉ 1296±187; PÓS 1317±220 ml/min) e variáveis antropométricas não foram observadas diferenças significativas após o treinamento. Podemos concluir que quatro semanas de treinamento em bicicleta ergométrica com oclusão de fluxo foi capaz de gerar adaptações em parâmetros aeróbios e neuromusculares em sujeitos ativos em proporções similares a outros métodos tradicionais de treinamento. Além disso, a ausência de efeito sobre o VO2max e as melhoras observadas sobre a capacidade aeróbia e cinética do VO2 sugerem que as principais adaptações causadas por esse tipo de treinamento devem ter sido mais periféricas do que centrais.

Submitted by ISABELA MAIA DA CRUZ FERNANDES null (isabelamaia.cf@gmail.com) on 2017-09-06T19:07:55Z No. of bitstreams: 1 Defesa_Isabela_final_com certificado.pdf: 1267984 bytes, checksum: ad309a61c522002d4498d84f2bb8f0fc (MD5) / Approved for entry into archive by Monique Sasaki (sayumi_sasaki@hotmail.com) on 2017-09-11T19:23:50Z (GMT) No. of bitstreams: 1 fernandes_imc_me_prud.pdf: 1267984 bytes, checksum: ad309a61c522002d4498d84f2bb8f0fc (MD5) / Made available in DSpace on 2017-09-11T19:23:50Z (GMT). No. of bitstreams: 1 fernandes_imc_me_prud.pdf: 1267984 bytes, checksum: ad309a61c522002d4498d84f2bb8f0fc (MD5) Previous issue date: 2017-07-24 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Introduction: The non-specific chronic low back pain (NSCLBP) is the most commonly found in clinical practice as well as being one of the most discussed problems in the world. Individuals with non-specific chronic low back pain (NSCLBP) have a lower level of physical activity when compared with individuals without NSCLBP, and therefore a decrease in aerobic power (V̇O2max). The guidelines of NSCLBP recommend as treatment the practice of physical exercise, as they claim to be effective in reducing the intensity of pain and functional disability. However, studies that use exercise as a treatment for LBP fail to prescribe exercise in a specific way. Objective: Evaluate and compare the effectiveness of different treadmill protocols for aerobic fitness determination in individuals with and without NSCLBP. Materials and Methods: Twenty individuals (10 with NSCLBP and 10 without NSCLBP) underwent two tests (modified Bruce and incremental) on treadmill. The following were collected during the tests: oxygen consumption (V̇O2), heart rate (HR), rate perceived exertion (RPE 6-20), blood lactate concentration ([Lac]), respiratory quotient (RQ) and pain intensity. Independent t-test was used to evaluate the difference between groups. Differences in physiological responses within groups (with and without NSCLBP) and between groups (Group vs. Test Interaction) were analyzed using two-way ANOVA. Statistical significance was set at p < 0.05. Results: When the groups were compared, no differences were observed on age (p-value = 0.839) or HRrest (p-value = 0.730), however the group with NSCLBP was overweight (p-value = 0.031). Only for the respiratory quotient (RQ) variable was observed a main effect of the test (p-value = 0.015) with higher RQ values in the modified Bruce test than in the incremental test. Conclusion: Both tests are good methods for assessing aerobic fitness. However, it can be speculated that using incremental test is a better method for prescribing treatment for this population.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-06T11:46:44Z No. of bitstreams: 1 deboradonascimentomoreira.pdf: 1954485 bytes, checksum: 0fa18e724e230d4f5f2d2e111e4c4fca (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-04-06T12:17:00Z (GMT) No. of bitstreams: 1 deboradonascimentomoreira.pdf: 1954485 bytes, checksum: 0fa18e724e230d4f5f2d2e111e4c4fca (MD5) / Made available in DSpace on 2017-04-06T12:17:00Z (GMT). No. of bitstreams: 1 deboradonascimentomoreira.pdf: 1954485 bytes, checksum: 0fa18e724e230d4f5f2d2e111e4c4fca (MD5) Previous issue date: 2009-03-13 / FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais / A variabilidade da freqüência cardíaca (VFC) é uma ferramenta não invasiva de estudo da regulação neurocardíaca em várias condições fisiológicas, como no repouso e durante manobras posturais. Pesquisas têm sugerido que a modulação autonômica cardíaca é influenciada tanto pelo nível de atividade física quanto pelo nível de aptidão aeróbia (VO2 pico), sendo caracterizada por aumento da atividade vagal e redução da atividade simpática em repouso. A maioria dos estudos analisa o efeito do nível de atividade física na VFC em condições de repouso e a influência da aptidão aeróbia inicial dos indivíduos não é analisada isoladamente, sendo esse um fator citado como determinante da VFC em alguns estudos com indivíduos ativos. O objetivo geral desse trabalho foi determinar as respectivas associações do nível de atividade física e aptidão aeróbia com a modulação autonômica cardíaca, por meio da análise da FC e VFC na posição supina (PS) e na postura ortostática (PO) em indivíduos jovens, saudáveis e com aptidão aeróbia próxima à média populacional. Foram delimitados dois modelos de estudo. No primeiro estudo, o objetivo foi verificar a influência do nível de aptidão aeróbia na modulação autonômica cardíaca em indivíduos jovens e sedentários por meio da análise da FC e VFC, na PS e PO. Participaram do estudo 24 indivíduos saudáveis, não obesos, do gênero masculino, com idade de 18 a 29 anos que foram alocados em dois grupos de acordo com o VO2 pico mensurado através do teste cardiopulmonar: VO2 pico alto com valores médios de 44,2 ± 4,8 ml/Kg/min (n=11) e VO2 pico baixo com valores de 33,8 ± 4,2 ml/Kg/min (n=13). Houve diferença significativa entre os grupos apenas nos índices da VFC no domínio da freqüência na PS, sendo que os indivíduos com VO2 pico alto apresentaram maiores valores de HFnu, e menores valores de LFnu e relação LF/HF, o que sugere maior atividade vagal e menor atuação simpática em repouso. Não houve diferenças nas variáveis quanto ao VO2 pico na PO. O estudo sugere que o nível de aptidão aeróbia é determinante da VFC em indivíduos sedentários na PS, mas não na PO. O segundo estudo possibilitou a comparação de indivíduos com níveis de aptidão aeróbia semelhantes, o que permitiu a determinação da capacidade da atividade física em modificar a regulação autonômica cardíaca, minimizando a influência do fator aptidão aeróbia. O objetivo deste estudo foi verificar a influência do nível de atividade física na FC e VFC na PS e durante a PO em indivíduos jovens e saudáveis com aptidão aeróbia semelhante. A amostra foi constituída de 34 indivíduos, limitados pelo VO2 pico, para que fosse possível formar um grupo homogêneo quanto ao nível de aptidão aeróbia. Os sujeitos foram divididos de acordo com o nível de atividade física habitual em três grupos: sedentário, nível de atividade física baixa e moderada de acordo com os valores brutos do domínio exercício físico/esporte do questionário de Baecke. Os resultados sugerem que nível de atividade física de intensidade baixa a moderada não altera a VFC na PS e PO em indivíduos jovens saudáveis com valores médios de VO2 pico similares e próximos à média populacional. Sendo assim, é importante isolar o efeito do nível de aptidão aeróbia e da atividade física nos estudos envolvendo a VFC em jovens saudáveis, pois esses fatores podem modificá-la de diferentes maneiras em condições fisiológicas estáticas e dinâmicas. / The heart rate variability (HRV) is a non-invasive tool to study the neurocardiac regulation in various physiological conditions, such as the ones when at rest and postural maneuvers. Research has suggested that the cardiac autonomic modulation is influenced both by the level of physical activity and by the level of aerobic fitness (VO2 peak), being characterized by the increase of the vagal activity and the reduction of the sympathetic nerve activity when at rest. Most studies analyze the effect of the level of physical activity on the HRV in rest conditions, and the influence of the initial aerobic fitness of the individuals is not analyzed separately, being the latter mentioned as a determining factor of the HRV in some studies with active individuals. The general purpose of this study was to determine the respective associations of the level of physical activity and aerobic fitness with the cardiac autonomic modulation by means of the analysis of the HR and HRV in conditions of rest and in the orthostatic posture (OP) in young, healthy individuals and with aerobic fitness close to that of the population average. Two study models were defined. In the first study, the purpose was to verify the influence of the level of aerobic fitness in the cardiac autonomic modulation of young sedentary individuals by means of the analysis of the HR and HRV in rest conditions and the OP. 24 healthy, non-obese male individuals aged from 18 to 29 years old took part in this study. They were allocated in two groups, according to the VO2 peak, measured by means of the cardiopulmonary test: high peak VO2 with mean values of 44.2 ± 4.8 ml/kg/min (n=11) and low peak VO2 values of 33.8 ± 4.2 ml/kg/min (n=13). There was significant difference between the groups only in the HRV indexes in the domain of the frequency at rest. The individuals with high peak VO2 presented higher HFnu values and lower LFnu values and LF/HF ratio, which suggests greater vagal activity and lesser sympathetic activity at rest. There were no differences in the variables regarding the peak VO2 in the OP. The study suggests that the level of aerobic fitness influences the HRV in sedentary individuals in rest condition, but not in OP. The second study made it possible to compare individuals with similar levels of aerobic fitness, which allowed to determine the capacity of the physical activity to modify the cardiac autonomic modulation, minimizing the influence of the aerobic fitness factor. The purpose of this study was to verify the influence of the level of physical activity in the HR and HRV at rest and during the OP in young, healthy individuals with similar aerobic fitness. The sample was composed of 34 individuals, limited by peak VO2. The subjects were divided - according to the level of usual physical activity - into three groups: sedentary, low physical activity levels and moderate, according to the gross values of the physical activity/sport domain of the Baecke Questionnaire. The results suggest that low and moderate intensity level of physical activity do not influence the HRV in the rest condition and in OP in young, healthy individuals with similar mean values of peak VO2 which are close to the population average. Thus, it is important to isolate the effect of the level of aerobic fitness and of the physical activity in the studies involving HRV in healthy youngsters, as such factors can modify it in different ways in static and dynamic physiological conditions.