ABSTRACT Background A joint symbolic analysis (JSA) is applied to assess the strength of the cardiovascular coupling from spontaneous beat-to-beat variability of the heart period (HP) and the systolic arterial pressure (SAP) during an experimental protocol inducing a gradual baroreflex unloading evoked by postural change (i.e. graded head-up tilt). Method: The adopted JSA can quantify the degree of association between the HP and SAP variabilities as a function of the time scale of the HP and SAP patterns. Traditional linear tools assessing the HP-SAP coupling strength, such as squared correlation coefficient, squared coherence function, and percentage of baroreflex sequences, were computed as well for comparison. Results: We found that: i) JSA indicated that the strength of the cardiovascular coupling at slow temporal scales gradually increased with the magnitude of the orthostatic challenge, while that at fast temporal scales gradually decreased; ii) the squared correlation coefficient and percentage of baroreflex sequences did not detect this behavior; iii) even though squared coherence function could measure the magnitude of the HP-SAP coupling as a function of the time scale, it was less powerful than JSA owing to the larger dispersion of the frequency domain indexes. Conclusion: Due to its peculiar features and high statistical power, JSA deserves applications to pathological groups in which the link between HP and SAP variabilities is lost or decreased due to the overall depression or impairment of the cardiovascular control.

Background: Portable respiratory inductive plethysmography (RIP) systems have been validated for ventilatory assessment during resting conditions and during incremental treadmill exercise. However, in clinical settings and during field-based exercise, intensity is usually constant and submaximal. A demonstration of the ability of RIP to detect respiratory measurements accurately during constant intensity conditions would promote and validate the routine use of portable RIP devices as an alternative to ergospirometry (ES), the current gold standard technique for ventilatory measures. Objective: To investigate the agreement between respiratory variables recorded by a portable RIP device and by ES during rest and constant intensity exercise. Method: Tidal volume (VT), respiratory rate (RR) and minute ventilation (VE) were concurrently acquired by portable RIP and ES in seven healthy male volunteers during standing rest position and constant intensity treadmill exercise. Results: Significant agreement was found between RIP and ES acquisitions during the standing rest position and constant intensity treadmill exercise for RR and during the standing rest position for VE. Conclusion: Our results suggest that portable RIP devices might represent a suitable alternative to ES during rest and during constant submaximal exercise.

Contextualização: A insuficiência cardíaca (IC) crônica cursa com intolerância ao exercício físico. A ventilação não invasiva (VNI) tem se mostrado benéfica para a melhora da performance desses pacientes. Objetivos: Avaliar a eficiência da pressão positiva contínua nas vias aéreas (CPAP) sobre a tolerância ao exercício físico e a variabilidade da frequência cardíaca (VFC) de pacientes com IC crônica. Método: Sete homens com IC crônica (62±8 anos) e fração de ejeção do ventrículo esquerdo de 41±8% foram submetidos ao teste incremental (TI) sintoma-limitado em cicloergômetro. Posteriormente, foram aleatorizados para a realização de exercícios físicos de carga constante até a tolerância máxima com e sem CPAP (5 cmH2O) nas condições: i) 50% da carga pico do TI e ii) 75% da carga pico do TI. Em repouso e durante os testes, a frequência cardíaca (FC) instantânea foi obtida pelo cardiofrequencímetro, e a VFC foi analisada no domínio do tempo. A análise estatística foi realizada pelos testes de Wilcoxon ou Kruskall-Wallis com post-hoc de Dunn e as variáveis categóricas, pelo teste de Fischer (p<0,05). Resultados: Durante a CPAP, houve aumento significativo no tempo de exercício físico (405±52 vs. 438±58 s) e da FC pico (97±3 vs. 105±2 bpm) somente na intensidade de 75%. Em relação à VFC, observou-se que o RMSSD foi significativamente menor em exercício físico quando comparado ao repouso com CPAP na intensidade 50%. Conclusão: Em conclusão, a CPAP com 5 cmH20 mostrou-se um útil na melhora da capacidade funcional dos pacientes estudados com pouco impacto sobre a VFC.

Background: Chronic heart failure (CHF) leads to exercise intolerance. However, non-invasive ventilation is able to improve functional capacity of patients with CHF. Objectives: The aim of this study was to evaluate the effectiveness of continuous positive airway pressure (CPAP) on physical exercise tolerance and heart rate variability (HRV) in patients with CHF. Method : Seven men with CHF (62±8 years) and left ventricle ejection fraction of 41±8% were submitted to an incremental symptom-limited exercise test (IT) on the cicloergometer. On separate days, patients were randomized to perform four constant work rate exercise tests to maximal tolerance with and without CPAP (5 cmH2O) in the following conditions: i) at 50% of peak work rate of IT; and ii) at 75% of peak work rate of IT. At rest and during these conditions, instantaneous heart rate (HR) was recorded using a cardiofrequencimeter and HRV was analyzed in time domain (SDNN and RMSSD indexes). For statistical procedures, Wilcoxon test or Kruskall-Wallis test with Dunn's post-hoc were used accordingly. In addition, categorical variables were analysed through Fischer's test (p<0.05). Results: There were significant improvements in exercise tolerance at 75% of peak work rate of IT with CPAP (405±52 vs. 438±58 s). RMSSD indexes were lower during exercise tests compared to CPAP at rest and with 50% of peak work rate of IT. Conclusion: These data suggest that CPAP appears to be a useful strategy to improve functional capacity in patients with CHF. However, the positive impact of CPAP did not generate significant changes in the HRV during physical exercises.

Background: Reduced respiratory muscle endurance (RME) contributes to increased dyspnea upon exertion in patients with cardiovascular disease. Objective: The objective was to characterize ventilatory and metabolic responses during RME tests in post-myocardial infarction patients without respiratory muscle weakness. Method: Twenty-nine subjects were allocated into three groups: recent myocardial infarction group (RG, n=9), less-recent myocardial infarction group (LRG, n=10), and control group (CG, n=10). They underwent two RME tests (incremental and constant pressure) with ventilatory and metabolic analyses. One-way ANOVA and repeated measures one-way ANOVA, both with Tukey post-hoc, were used between groups and within subjects, respectively. Results: Patients from the RG and LRG presented lower metabolic equivalent and ventilatory efficiency than the CG on the second (50± 06, 50± 5 vs. 42± 4) and third part (50± 11, 51± 10 vs. 43± 3) of the constant pressure RME test and lower metabolic equivalent during the incremental pressure RME test. Additionally, at the peak of the incremental RME test, RG patients had lower oxygen uptake than the CG. Conclusions : Post-myocardial infarction patients present lower ventilatory efficiency during respiratory muscle endurance tests, which appears to explain their inferior performance in these tests even in the presence of lower pressure overload and lower metabolic equivalent.

Objective: To investigate the cardiac autonomic responses during upper versus lower limb discontinuous resistance exercise (RE) at different loads in healthy older men. Method: Ten volunteers (65±1.2 years) underwent the one-repetition maximum (1RM) test to determine the maximum load for the bench press and the leg press. Discontinuous RE was initiated at a load of 10%1RM with subsequent increases of 10% until 30%1RM, followed by increases of 5%1RM until exhaustion. Heart rate (HR) and R-R interval were recorded at rest and for 4 minutes at each load applied. Heart rate variability (HRV) was analyzed in 5-min segments at rest and at each load in the most stable 2-min signal. Results: Parasympathetic indices decreased significantly in both exercises from 30%1RM compared to rest (rMSSD: 20±2 to 11±3 and 29±5 to 12±2 ms; SD1: 15±2 to 8±1 and 23±4 to 7±1 ms, for upper and lower limb exercise respectively) and HR increased (69±4 to 90±4 bpm for upper and 66±2 to 89±1 bpm for lower). RMSM increased for upper limb exercise, but decreased for lower limb exercise (28±3 to 45±9 and 34±5 to 14±3 ms, respectively). In the frequency domain, the sympathetic (LF) and sympathovagal balance (LF/HF) indices were higher and the parasympathetic index (HF) was lower for upper limb exercise than for lower limb exercise from 35% of 1RM. Conclusions: Cardiac autonomic change occurred from 30% of 1RM regardless of RE limb. However, there was more pronounced sympathetic increase and vagal decrease for upper limb exercise than for lower limb exercise. These results provide a basis for more effective prescription of RE to promote health in this population.

BACKGROUND: The second heart rate (HR) turn point has been extensively studied, however there are few studies determining the first HR turn point. Also, the use of mathematical and statistical models for determining changes in dynamic characteristics of physiological variables during an incremental cardiopulmonary test has been suggested. OBJECTIVES: To determine the first turn point by analysis of HR, surface electromyography (sEMG), and carbon dioxide output ( ) using two mathematical models and to compare the results to those of the visual method. METHOD: Ten sedentary middle-aged men (53.9±3.2 years old) were submitted to cardiopulmonary exercise testing on an electromagnetic cycle ergometer until exhaustion. Ventilatory variables, HR, and sEMG of the vastus lateralis were obtained in real time. Three methods were used to determine the first turn point: 1) visual analysis based on loss of parallelism between and oxygen uptake ( ); 2) the linear-linear model, based on fitting the curves to the set of data (Lin-Lin ); 3) a bi-segmental linear regression of Hinkley' s algorithm applied to HR (HMM-HR), (HMM- ), and sEMG data (HMM-RMS). RESULTS: There were no differences between workload, HR, and ventilatory variable values at the first ventilatory turn point as determined by the five studied parameters (p>0.05). The Bland-Altman plot showed an even distribution of the visual analysis method with Lin-Lin , HMM-HR, HMM-CO2, and HMM-RMS. CONCLUSION: The proposed mathematical models were effective in determining the first turn point since they detected the linear pattern change and the deflection point of , HR responses, and sEMG.

BACKGROUND: Aging leads to low functional capacity and this can be reversed by safe and adequate exercise prescription. OBJECTIVE: The aim of this study was to identify the anaerobic threshold (AT) obtained from the V-slope method as well as visual inspection of oxyhemoglobin ( O2Hb) and deoxyhemoglobin (HHb) curves and compare findings with the heteroscedastic (HS) method applied to carbon dioxide production ( CO2), heart rate (HR), and HHb data in healthy elderly men. A secondary aim was to assess the degree of agreement between methods for AT determination. METHOD: Fourteen healthy men (61.4±6.3 years) underwent cardiopulmonary exercise testing (CPX) on a cycle ergometer until physical exhaustion. Biological signals collected during CPX included: ventilatory and metabolic variables; spectroscopy quasi-infrared rays - NIRS; and HR through a cardio-frequency meter. RESULTS: We observed temporal equivalence and similar values of power (W), absolute oxygen consumption (O2 - mL/min), relative O2 ( mL.Kg - 1.min -1), and HR at AT by the detection methods performed. In addition, by the Bland-Altman plot, HR confirmed good agreement between the methods with biases between -1.3 and 3.5 beats per minute. CONCLUSIONS: (i) all detection methods were sensitive in identifying AT, including the HS applied to HR and (ii) the methods showed a good correlation in the identification of AT. Thus, these results support HR as valid and readily available parameter in determining AT in healthy elderly men.

BACKGROUND: The cardiovascular system is noticeably affected by respiration. However, whether different inspiratory resistive loading intensities can influence autonomic heart rate (HR) modulation remains unclear. OBJECTIVE: The objective was to investigate HR modulation at three different inspiratory resistive loading intensities in healthy elderly men. METHOD: This was a prospective, randomized, double-blind study that evaluated 25 healthy elderly men. Cardiac autonomic modulation was assessed using heart rate variability (HRV) indices. All of the volunteers underwent maximal inspiratory pressure (MIP) measurements according to standardized pulmonary function measurements. Three randomly-applied inspiratory resistive loading (30, 60 and 80% of MIP) intensities were then applied using an inspiratory resistance device (POWERbreathe, Southam, UK), during which the volunteers were asked to inhale for 2 seconds and exhale for 3 seconds and complete 12 breaths per minute. Each effort level was performed for 4 minutes, and HR and the distance between 2 subsequent R waves of electrocardiogram (R-R intervals) were collected at rest and at each intensity for further HRV analysis. RESULTS : The parasympathetic HRV (rMSSD, SD1 and HF) indices demonstrated lower values at 80% (rMSSD: 19±2 ms, SD1: 13±2 ms and HF: 228±61 ms2) than at 30% MIP (rMSSD: 25±3 ms, SD1: 18±2 ms and HF: 447±95 ms2; p<0.05). CONCLUSIONS: Lower inspiratory resistive loading intensities promoted a marked and positive improvement of parasympathetic sinus node modulation.

OBJETIVOS: Verificar se há correlação entre a cinética-on do consumo de oxigênio (VO2) e da frequência cardíaca (FC) no teste de carga constante em cicloergômetro (TCC) com o índice BODE e suas variáveis isoladas em pacientes com doença pulmonar obstrutiva crônica (DPOC).MÉTODO: Foram avaliados 14 homens com DPOC de obstrução moderada a muito grave, entre 55 e 78 anos, submetidos em dias alternados à espirometria, teste de caminhada de seis minutos (TC6), teste incremental em cicloergômetro (TI) e TCC. Foram coletados os gases expirados, e a cinética-on do VO2 e da FC foi analisada. O índice BODE foi calculado.RESULTADOS: Observou-se que a tau(τ) e o tempo de resposta média (TRM) do VO2 foram significativamente maiores que a τ e o TRM da FC. Observou-se correlações moderadas e fortes entre a τ e o TRM do VO2 e da FC com o índice BODE (r=0,75 e r=0,78; r=0,62 e r=0,63, respectivamente) e correlações entre a τ e o TRM do VO2 com o volume expiratório forçado no primeiro segundo (VEF1) (r=-0,60; r=-0,53), a distância percorrida no TC6 (DP-TC6) (r=-0,61; r=-0,44) e a DP-TC6 %prevista (r=-0,62; r=-0,46). A τ e o TRM da FC correlacionaram-se com a DP-TC6 (r=-0,59; r=-0,58) e a DP-TC6 %prevista (r=-0,62; r=-0,62). CONCLUSÃO: A lentificação da cinética-on do VO2 e principalmente da FC em cicloergômetro pode ser um marcador importante de gravidade da doença. Adicionalmente, a limitação ao fluxo aéreo e a reduzida capacidade ao exercício estão associadas à lentificação da cinética-on do VO2 e da FC nesses pacientes.

OBJECTIVES: To assess whether there is a correlation between oxygen uptake (VO2) and heart rate (HR) on-kinetics in the constant-load cycle-ergometer test (CLT) and the BODE index and its isolated variables in patients with chronic obstructive pulmonary disease (COPD). METHOD: Fourteen male patients between 55 and 78 years of age with moderate to severe COPD were evaluated. Each patient underwent spirometry, the six-minute walk test (6MWT), the cycle-ergometer incremental test (IT) and CLT on alternate days. The exhaled gases were collected, and the VO2 and HR on-kinetics were analyzed. The BODE index was calculated. RESULTS: It was noted that the VO2tau(τ) and mean response time (MRT) were significantly higher than HR τ and MRT. Moderate and strong correlations between τ and MRT of the VO2 and HR and the BODE index was noted (r=0.75 and r=0.78; r=0.62 and r=0.63, respectively), and there were correlations between the VO2τ and MRT and the forced expiratory volume in one second (FEV1) (r=-0.60; r=-0.53) and the distance traveled at 6MWT (DT-6MWT) (r=-0.61; r=-0.44) and DT-6MWT % predicted (r=-0.62; r=-0.46). The HR τ and MRT were correlated with DT-6MWT (r=-0.59; r=-0.58) and DT-6MWT % predicted (r=-0.62; r=-0.62).CONCLUSION: The slowing of cycle-ergometer VO2, and especially of HR on-kinetics, may be key markers of disease severity. Furthermore, airflow obstruction and reduced exercise capacity are associated with the slowing of patients' VO2 and HR on-kinetics.

CONTEXTUALIZAÇÃO: A reduzida tolerância ao exercício está relacionada à diminuída capacidade funcional consequente da obesidade. Objetivos: Analisar e comparar respostas cardiopulmonares, metabólicas e subjetivas durante um teste de esforço cardiopulmonar e um teste de caminhada de seis minutos na esteira em mulheres obesas e eutróficas. MÉTODO: Foram incluídas 29 mulheres com idades entre 20 e 45 anos. Catorze voluntárias foram alocadas no grupo de obesas e 15, no grupo de eutróficas. Foram realizadas medidas antropométricas e de composição corporal. RESULTADOS: Em ambos os testes, as obesas apresentaram maiores valores de consumo absoluto de oxigênio, ventilação-minuto e pressão arterial sistólica e diastólica; ainda apresentaram menor velocidade de caminhada, distância percorrida e consumo de oxigênio relativo, quando comparadas com as eutróficas. Durante o teste máximo de exercício, a dispneia percebida foi maior e o quociente respiratório menor nas obesas em relação às eutróficas. Durante o teste submáximo, produção de dióxido de carbono, volume corrente e frequência cardíaca foram maiores nas obesas, comparadas às eutróficas. Houve forte correlação entre a frequência cardíaca e moderada correlação entre o consumo de oxigênio no pico dos testes. A frequência cardíaca obtida no teste submáximo aplicado foi capaz de predizer a frequência cardíaca obtida no teste máximo. Os gráficos de Bland-Altman demonstraram concordância entre os testes para identificar parâmetros metabólicos e fisiológicos no pico do exercício. CONCLUSÃO: O teste de caminhada de seis minutos induziu respostas ventilatórias, metabólicas e cardiovasculares concordantes com as do teste máximo, provando ser importante na rotina de avaliação funcional fisioterápica de mulheres obesas.

BACKGROUND: Impaired exercise tolerance is directly linked to decreased functional capacity as a consequence of obesity. OBJECTIVES: To analyze and compare the cardiopulmonary, metabolic, and perceptual responses during a cardiopulmonary exercise test (CPX) and a treadmill six-minute walking test (tread6MWT) in obese and eutrophic women. METHOD: Twenty-nine female participants, aged 20-45 years were included. Fourteen were allocated to the obese group and 15 to the eutrophic group. Anthropometric measurements and body composition assessment were performed. RESULTS: In both tests, obese women presented with significantly higher absolute oxygen uptake, minute ventilation, and systolic and diastolic blood pressure; they also presented with lower speed, distance walked, and oxygen uptake corrected by the weight compared to eutrophics. During the maximal exercise test, perceived dyspnea was greater and the respiratory exchange ratio was lower in obese subjects compared to eutrophics. During the submaximal test, carbon dioxide production, tidal volume, and heart rate were higher in obese subjects compared to eutrophic women. When analyzing possible correlations between the CPX and the tread6MWT at peak, there was a strong correlation for the variable heart rate and a moderate correlation for the variable oxygen uptake. The heart rate obtained in the submaximal test was able to predict the one obtained in the maximal test. Bland-Altman plots demonstrated the agreement between both tests to identify metabolic and physiological parameters at peak exercise. CONCLUSIONS: The six-minute walking test induced ventilatory, metabolic, and cardiovascular responses in agreement with the maximal testing. Thus, the six-minute walking test proves to be important for functional evaluation in the physical therapy routine.

CONTEXTUALIZAÇÃO: A medida de pressão expiratória máxima (PEmáx) possui algumas contraindicações, pois acredita-se que as respostas obtidas nessa medida são similares às respostas encontradas na manobra de Valsalva (MV). OBJETIVOS: O objetivo principal é avaliar a resposta da frequência cardíaca (FC) durante a medida da PEmáx e da MV em jovens saudáveis, em diferentes posturas, para identificar se e em qual condição a PEmáx reproduz as respostas obtidas na MV e, adicionalmente, estimar o trabalho realizado nas manobras. MÉTODO: Doze jovens saudáveis foram avaliados, orientados e familiarizados com as manobras. A MV foi composta por um esforço expiratório (40 mmHg) durante 15 segundos contra um manômetro. A PEmáx foi executada segundo a American Thoracic Society. Ambas as medidas foram realizadas nas posturas supino e sentado. Para a análise da variação da frequência cardíaca (∆FC), índice de Valsalva (IV), índice da PEmáx (IPEmáx) e o trabalho estimado das manobras (Wtotal, Wisotime, Wtotal/∆FCtotal e Wisotime/∆FCisotime ), utilizou-se ANOVA two-way com post-hoc de Holm-Sidak (p<0,05). RESULTADOS: A ∆FC durante as manobras não foi influenciada pelas posturas; entretanto, durante a MV, a ∆FC e os valores do IV foram maiores (supino: 47±9 bpm, 2,3±0,2; sentado: 41±10 bpm, 2,0±0,2, respectivamente) do que a ∆FC e os valores de IPEmáx observados durante a PEmáx (supino: 23±8 bpm, 1,5±0,2; sentado 24±8 bpm, 1,6±0,3, respectivamente) (p<0,001). Os trabalhos estimados das manobras foram estatisticamente diferentes (p<0,001) entre elas, exceto para o Wtotal/∆FC. CONCLUSÕES: Nas condições estudadas, a PEmáx não reproduz as respostas da FC observadas durante a MV em jovens saudáveis.

BACKGROUND: The measure of the maximal expiratory pressure (MEP) has some contraindications, as it is believed that the responses obtained in this measure are similar to the Valsalva maneuver (VM). OBJECTIVE: The main purpose of this study was to evaluate the heart rate responses (HR) during the MEP and the VM measures in healthy young men into different postures aiming to identify whether and in which situation the MEP reproduces the responses obtained in the VM. Additionally we aim to estimate the workload realized during the maneuvers. METHOD: Twelve healthy young men were evaluated, instructed and familiarized with the maneuvers. The VM was characterized by an expiratory effort (40 mmHg) against a manometer for 15 seconds. The MEP measure has been performed according to the American Thoracic Society. Both measures were performed at sitting and supine positions. ANOVA two-way with Holm-Sidak post-hoc test (p<0.05) was used to analyse the heart rate variation (∆HR); Valsalva index (VI); MEP index (MEPI), and the estimated workload of the maneuvers (Wtotal, Wisotime, Wtotal/∆HRtotal and Wisotime/∆HRisotime ). RESULTS: The ∆HR during the maneuvers was not influenced by the supine and sitting positions. However, the ∆HR during the VM and VI were higher (supine: 47±9 bpm, 2.3±0.2; sitting: 41±10 bpm, 2.0±0.2, respectively) than ∆HR during the MEP and MEPI values (supine: 23±8 bpm, 1.5±0.2; sitting 24±8 bpm, 1.6±0.3, respectively) (p<0.001). The estimated workload of the maneuvers was statistically different (p<0.001) between the maneuvers, except to Wtotal/∆HR. Conclusions: In the studied conditions the MEP does not reproduces the HR response observed in the VM in healthy young men.

CONTEXTUALIZAÇÃO: A redução da variabilidade da frequência cardíaca (VFC) é considerada como um importante marcador de disfunção autonômica. OBJETIVOS: Avaliar a VFC em pacientes com doença arterial coronariana (DAC) e compará-los com sujeitos saudáveis. MÉTODOS: Cinquenta e dois homens (53±7,2 anos), divididos em três grupos, sendo dois grupos com obstrução coronariana (DAC+ com obstrução ≥50%, n=17 e DAC+ com obstrução ≥50%, n=18) e um grupo controle (GC, n=17). A frequência cardíaca (FC) foi captada batimento a batimento, a partir do Polar®S810i, em repouso supino, durante 15 minutos. A análise da VFC foi feita pelos cálculos da entropia de Shannon (ES) e pelos padrões da análise simbólica (0V e 2ULV%), relacionados à predominância simpática e vagal, respectivamente. A análise estatística incluiu o teste de Kruskal-Wallis e a análise multivariada (p<0,05) RESULTADOS:O grupo DAC+ apresentou menores valores de ES e 2ULV% e maior 0V quando comparado aos grupos DAC- e CG. Na análise multivariada, observou-se menor ES e maior 0V na presença das características clínicas prévias, como infarto e revascularização do miocárdio no grupo DAC+ comparado ao grupo DAC-. O uso de inibidores da enzima conversora de angiotensina contribuiu para maior ES do grupo DAC- comparado ao DAC+. CONCLUSÃO: Na DAC+ não complicada, os padrões da VFC apresentam menor complexidade, maior modulação autonômica simpática e menor modulação parassimpática comparativamente ao DAC- e ao GC em repouso supino. Esses resultados indicam que a disfunção autonômica cardíaca está relacionada ao grau de oclusão coronariana e ao comprometimento cardíaco.

BACKGROUND: A reduction in heart rate variability (HRV) is considered an important indicator of autonomic dysfunction. OBJECTIVES: The aims of this study were to evaluate the presence of autonomic dysfunction measured by HRV in patients with coronary artery disease (CAD) and to compare them with normal subjects. METHODS: A sample of 52 men (mean age 54±5.39 years) was allocated into three groups: obstructive CAD ≥50% (CAD+ n=18), obstructive CAD <50%, (CAD- n=17) and apparently healthy controls (CG n=17). Heart rate (HR) was measured at rest using a Polar®S810i for 15 min. HRV was analyzed via Shannon entropy (SE) and symbolic analysis (0V and 2ULV), which relate to sympathetic and vagal predominance, respectively. Statistical analysis included the Kruskal-Wallis test and multivariate analysis (p<0.05). RESULTS: The CAD+ group presented lower SE and 2ULV% values and higher 0V% compared to CAD- and control groups (p<0.05). In the multivariate analysis, the presence of the clinical characteristics such as myocardial infarction and revascularization in the CAD+ group lead to a lower SE and higher 0V compared to the CAD- group. The use of angiotensin converting enzymes led to a higher SE in the CAD- group compared to the CAD+ (p<0.05). CONCLUSION: In uncomplicated CAD+ patients the patterns of HRV have a lower complexity, a greater sympathetic modulation and a lower parasympathetic modulation compared to CAD- and control groups in supine resting conditions. These results indicate that autonomic heart dysfunction is related to the degree of coronary occlusion and cardiac compromise.

CONTEXTUALIZAÇÃO: A literatura refere que a ação muscular excêntrica produz maior força e menor atividade mioelétrica que a concêntrica, enquanto a resposta da frequência cardíaca (FC) é maior durante a contração concêntrica que durante a excêntrica. OBJETIVOS: Investigar as respostas de torque médio máximo (TMM), eletromiografia de superfície (EMGs) e FC durante diferentes tipos de contração muscular e velocidades angulares em homens idosos. MATERIAIS E MÉTODOS: Doze homens saudáveis (61,7±1,6 anos) realizaram flexões e extensões do joelho concêntrica (C) e excêntrica (E) em 60º/s e 120º/s. Registrou-se a atividade EMGs do músculo vasto lateral e normalizou-se pela RMS (µV) da extensão isométrica máxima do joelho em 60º. A FC (bpm) foi registrada em repouso e durante cada contração. Os dados foram analisados utilizando-se o teste de Friedman para medidas repetidas com post hoc de Dunn (p<0,05). RESULTADOS: Os valores médios de TMM (N.m/kg) foram menores e os de RMS (µV) foram maiores (p<0,05) nas contrações concêntricas (C60º/s=2,80 e 0,99; C120º/s=2,46 e 1,0) comparativamente com as excêntricas (E60º/s=3,94 e 0,85; E120º/s=4,08 e 0,89), respectivamente. Já a variação da FC foi semelhante nas quatro condições estudadas. CONCLUSÃO: A magnitude das respostas de TMM e RMS em homens idosos foi dependente da natureza da ação muscular e independente da velocidade angular, enquanto as respostas da FC não foram influenciadas por esses fatores.

BACKGROUND: The literature reports that the eccentric muscular action produces greater force and lower myoelectric activity than the concentric muscular action, while the heart rate (HR) responses are bigger during concentric contraction. OBJECTIVES: To investigate the maximum average torque (MAT), surface electromyographic (SEMG) and the heart rate (HR) responses during different types of muscular contraction and angular velocities in older men. METHODS: Twelve healthy men (61.7±1.6years) performed concentric (C) and eccentric (E) isokinetic knee extension-flexion at 60º/s and 120º/s. SEMG activity was recorded from vastus lateralis muscle and normalized by Root Mean Square - RMS (µV) of maximal isometric knee extension at 60º. HR (beats/min) and was recorded at rest and throughout each contraction. The data were analyzed by the Friedman test for repeated measures with post hoc Dunn's test (p<0.05). RESULTS: The median values of MAT (N.m/kg) was smaller and the RMS (µV) was larger during concentric contraction (C60º/s=2.80 and 0.99; C120º/s=2.46 and 1.0) than eccentric (E60º/s=3.94 and 0.85; E120º/s=4.08 and 0.89), respectively. The HR variation was similar in the four conditions studied. CONCLUSION: The magnitude of MAT and RMS responses in older men were dependent of the nature of the muscular action and independent of the angular velocity, whereas HR response was not influenced by these factors.