Limited cardiopulmonary capacity in patients with liver cirrhosis when compared to healthy subjects.

OBJECTIVES: The present study compared cardiorespiratory capacity between cirrhotic patients and healthy subjects. METHODS: Nineteen cirrhotic patients and 19 healthy subjects, paired by age and gender, participated in the study. Volunteers performed an incremental cardiopulmonary test with a ramp protocol, a ventilatory and metabolic variables were obtained and analyzed. The recovery was analyzed by calculating the time needed for 50% of oxygen consumption (VO2) recovery to occur as the median between the peak of the exercise and the end of recovery on the VO2 curve (T1/2). The VE/VCO2 slope were performed by the linear regression of ventilation (VE) and carbon dioxide production (VCO2) data. RESULTS: During resting condition, cirrhotic patients presented significantly higher levels of VO2 compared to healthy subjects. The VE/ VO2 and VE/ VCO2 values were significantly higher in the control group at the anaerobic threshold and at the peak of the test compared to cirrhotic patients. Time under effort was significantly higher for healthy subjects. CONCLUSIONS: Based on these findings, it is possible to conclude that liver cirrhosis can compromise the patients' quality of life, mainly by inducing metabolic alterations which can impair functional capacity and lead to a sedentary lifestyle.

Limited cardiopulmonary capacity in patients with liver cirrhosis when compared to healthy subjects

SUMMARY OBJECTIVES: The present study compared cardiorespiratory capacity between cirrhotic patients and healthy subjects. METHODS: Nineteen cirrhotic patients and 19 healthy subjects, paired by age and gender, participated in the study. Volunteers performed an incremental cardiopulmonary test with a ramp protocol, a ventilatory and metabolic variables were obtained and analyzed. The recovery was analyzed by calculating the time needed for 50% of oxygen consumption (VO2) recovery to occur as the median between the peak of the exercise and the end of recovery on the VO2 curve (T1/2). The VE/VCO2 slope were performed by the linear regression of ventilation (VE) and carbon dioxide production (VCO2) data. RESULTS: During resting condition, cirrhotic patients presented significantly higher levels of VO2 compared to healthy subjects. The VE/ VO2 and VE/ VCO2 values were significantly higher in the control group at the anaerobic threshold and at the peak of the test compared to cirrhotic patients. Time under effort was significantly higher for healthy subjects. CONCLUSIONS: Based on these findings, it is possible to conclude that liver cirrhosis can compromise the patients' quality of life, mainly by inducing metabolic alterations which can impair functional capacity and lead to a sedentary lifestyle.

Acute effects of expiratory positive pressure on autonomic cardiac modulation during spontaneous and slow deep breathing in COPD patients.

AIM: to evaluate the acute effects of expiratory positive airway pressure on cardiac autonomic modulation in chronic obstructive pulmonary disease patients during spontaneous breathing and slow deep breathing. METHODS: 17 patients were evaluated. The R-R intervals were collected (Polar® S810i) during spontaneous breathing (10 minutes) and slow deep breathing (4 minutes), with and without 5 cmH2O expiratory positive airway pressure. Stable signals were analyzed by Kubios®. Heart rate variability indices were computed in time domain and in frequency domain. RESULTS: Expiratory positive airway pressure application affected low frequency (spontaneous breathing: 62.5±4.1 vs slow deep breathing: 28.2±4.2, p<0.001) and high frequency (spontaneous breathing: 37.4±17.3 vs slow deep breathing: 58.9±18.1, p<0.001). Interactions were observed between expiratory positive airway pressure effect and slow deep breathing effect for low frequency (p<0.001), high frequency (p<0.001) and low frequency/high frequency ratio (p<0.001). When patients were stratified by disease's severity, we identified a significant low frequency reduction (p<0.001) and high frequency increase (p<0.001) for all stages when slow deep breathing was associated with expiratory positive airway pressure. CONCLUSION: A 5 cmH2O expiratory positive airway pressure during spontaneous and slow deep breathing can elicit an acute response, resulting in a cardiac autonomic control improvement in moderate-to-very severe patients.

Functional and systemic effects of whole body electrical stimulation post bariatric surgery: study protocol for a randomized controlled trial.

BACKGROUND: Obesity represents a major public health problem and is the fifth leading risk factor for mortality. Morbid obesity is associated with chronic systemic inflammation which increases the risk of comorbidities. Bariatric surgery (BS) is considered an effective intervention for obese patients. However, BS is associated with dietary restriction, potentially limiting physical activity. Whole-body neuromuscular electrical stimulation (WBS) could represent an innovative option for the rehabilitation of BS patients, especially during the early postoperative phase when other conventional techniques are contraindicated. WBS is a safe and effective tool to combat sarcopenia and metabolic risk as well as increasing muscle mass, producing greater glucose uptake, and reducing the proinflammatory state. Therefore, the objective of this study is to evaluate the effects of WBS on body composition, functional capacity, muscle strength and endurance, insulin resistance, and pro- and anti-inflammatory circulating markers in obese patients undergoing BS. METHODS/DESIGN: The present study is a randomized, double-blind, placebo-controlled, parallel groups clinical trial approved by the Ethics Committee of our Institution. Thirty-six volunteers (body mass index (BMI) > 35 kg/m2) between 18 and 45 years of age will be randomized to the WBS group (WBSG) or control (Sham) group (ShamG) after being submitted to BS. Preoperative assessments will include maximal and submaximal exercise testing, body composition, blood inflammatory markers, and quadriceps strength and endurance. The second day after discharge, body composition will be evaluated and a 6-min walk test (6MWT) will be performed. The WBS or Sham protocol will consist of 30 daily sessions for 6 consecutive weeks. Afterwards, the same assessments that were performed in the preoperative period will be repeated. DISCUSSION: Considering the important role of WBS in skeletal muscle conditioning and its value as an aid in exercise performance, the proposed study will investigate this technique as a tool to promote early rehabilitation in these patients, and as a strategy to enhance exercise capacity, weight loss, and peripheral muscle strength with positive systemic effects. The present study is still ongoing, and data will be published after its conclusion. TRIAL REGISTRATION: REBEC, RBR-99qw5h . Registered on 20 February 2015.

COPD assessment test and FEV1: do they predict oxygen uptake in COPD?

BACKGROUND: Chronic obstructive pulmonary disease (COPD) manifests itself in complex ways, with local and systemic effects; because of this, a multifactorial approach is needed for disease evaluation, in order to understand its severity and impact on each individual. Thus, our objective was to study the correlation between easily accessible variables, usually available in clinical practice, and maximum aerobic capacity, and to determine models for peak oxygen uptake (VO2peak) estimation in COPD patients. SUBJECTS AND METHODS: Individuals with COPD were selected for the study. At the first visit, clinical evaluation was performed. During the second visit, the volunteers were subjected to the cardiopulmonary exercise test. To determine the correlation coefficient of VO2peak with forced expiratory volume in 1 second (FEV1) (% pred.) and the COPD Assessment Test score (CATs), Pearson or Spearman tests were performed. VO2 at the peak of the exercise was estimated from the clinical variables by simple and multiple linear regression analyses. RESULTS: A total of 249 subjects were selected, 27 of whom were included after screening (gender: 21M/5F; age: 65.0±7.3 years; body mass index: 26.6±5.0 kg/m2; FEV1 (% pred.): 56.4±15.7, CAT: 12.4±7.4). Mean VO2 peak was 12.8±3.0 mL⋅kg-1⋅min-1 and VO2peak (% pred.) was 62.1%±14.9%. VO2peak presented a strong positive correlation with FEV1 (% pred.), r: 0.70, and a moderate negative correlation with the CATs, r: -0.54. In the VO2peak estimation model based on the CAT (estimated VO2peak =15.148- [0.185× CATs]), the index explained 20% of the variance, with estimated error of 2.826 mL⋅kg-1⋅min-1. In the VO2peak estimation model based on FEV1 (estimated VO2peak =6.490+ [0.113× FEV1]), the variable explained 50% of the variance, with an estimated error of 2.231 mL⋅kg-1⋅min-1. In the VO2peak estimation model based on CATs and FEV1 (estimated VO2peak =8.441- [0.0999× CAT] + [0.1000× FEV1]), the variables explained 55% of the variance, with an estimated error of 2.156 mL⋅kg-1⋅min-1. CONCLUSION: COPD patients' maximum aerobic capacity has a significant correlation with easily accessible and widely used clinical variables, such as the CATs and FEV1, which can be used to estimate peak VO2.

Effects of Coexistence Hypertension and Type II Diabetes on Heart Rate Variability and Cardiorespiratory Fitness.

BACKGROUND: Type 2 diabetes Mellitus (T2DM) is associated with cardiac autonomic dysfunction, which is an independent predictor of mortality in chronic diseases. However, whether the coexistence of systemic arterial hypertension (HTN) with DMT2 alters cardiac autonomic modulation remains unknown. OBJECTIVE: To evaluate the influence of HTN on cardiac autonomic modulation and cardiorespiratory fitness in subjects with DMT2. METHODS: 60 patients of both genders were evaluated and allocated to two groups: DMT2 patients (n = 32; 51 ± 7.5 years old) and DMT2 + HTN patients (n = 28; 51 ± 6.9 years old). RR intervals were obtained during rest in supine position. Linear and nonlinear indices of heart rate variability (HRV) were computed using Kubios HRV software. Pulmonary gas exchange was measured breath-by-breath, using a portable telemetric system during maximal incremental exercise testing on a cycle ergometer. Statistical analysis included Shapiro-Wilk test followed by Student's t Test, Pearson correlation and linear regression. RESULTS: We found that patients in the DMT2+HTN group showed lower values of mean RR intervals (801.1 vs 871.5 ms), Shannon entropy (3 vs 3.2) and fractal dimension SD 1 (9.5 vs 14.5), when contrasted with patients in the DMT2 group. Negative correlations were found between some HRV nonlinear indices and exercise capacity indices. CONCLUSION: HTN negatively affects the cardiac autonomic function in diabetic patients, who are already prone to develop autonomic dysfunction. Strategies are need to improve cardiac autonomic functionality in this population.

Metabolic syndrome impact on cardiac autonomic modulation and exercise capacity in obese adults.

Obesity is often associated with increased risk of cardiometabolic morbidities and mortality. However, evidence shows that some obese individuals are more likely to develop such risk factors early in life, including those with Metabolic Syndrome (MetS). Whether the presence of MetS in obese people impairs cardiac autonomic modulation (CAM) remains to be investigated. METHODS: Cross-sectional study. Sixty-six subjects were classified as normal-weight (NW, n = 24) or obese (BMI ≥ 30 kg·m-2): metabolically healthy (MHO, n = 19) vs unhealthy (MUHO, n = 23: NCEP/ATPIII-MetS criteria). Body composition (bioimpedance), metabolic (glucose-insulin/lipid) and inflammatory profiles were determined. Linear and nonlinear heart rate variability (HRV) indices were computed at rest and during the submaximal six-minute step test (6MST). Blood pressure (BP) and metabolic and ventilatory variables were assessed (oxygen uptake, VO2; carbon dioxide production, VCO2; minute ventilation, VE) during the 6MST and the maximal cardiopulmonary exercise testing (CPX). RESULTS: All groups reached the same 6MST intensity (VO2 ~ 80% and HR ~ 87% of CPX peak values). Both obese groups, independently of MetS, presented higher BP and lower maximal VO2 than NW. However, HRV differed between groups according to MetS at rest and during exercise: MUHO had lower meanRRi and SD1 than NW and lower RMSSD and pNN50 than MHO at rest; during exercise, the lowest SDNN, TINN, SD1 and Shannon entropy were observed for MUHO. Significant correlations were found between MetS, insulin resistance and HRV indices; and between insulin resistance and aerobic capacity (VO2peak). CONCLUSION: Obesity per se impairs aerobic-hemodynamic responses to exercise. However, MetS in obese young adults negatively impacts overall HRV, parasympathetic activity and HRV complexity.

Effects of Coexistence Hypertension and Type II Diabetes on Heart Rate Variability and Cardiorespiratory Fitness / Efeitos da Coexistência de Diabetes Tipo 2 e Hipertensão sobre a Variabilidade da Frequência Cardíaca e Capacidade Cardiorrespiratória

Abstract Background: Type 2 diabetes Mellitus (T2DM) is associated with cardiac autonomic dysfunction, which is an independent predictor of mortality in chronic diseases. However, whether the coexistence of systemic arterial hypertension (HTN) with DMT2 alters cardiac autonomic modulation remains unknown. Objective: To evaluate the influence of HTN on cardiac autonomic modulation and cardiorespiratory fitness in subjects with DMT2. Methods: 60 patients of both genders were evaluated and allocated to two groups: DMT2 patients (n = 32; 51 ± 7.5 years old) and DMT2 + HTN patients (n = 28; 51 ± 6.9 years old). RR intervals were obtained during rest in supine position. Linear and nonlinear indices of heart rate variability (HRV) were computed using Kubios HRV software. Pulmonary gas exchange was measured breath-by-breath, using a portable telemetric system during maximal incremental exercise testing on a cycle ergometer. Statistical analysis included Shapiro-Wilk test followed by Student's t Test, Pearson correlation and linear regression. Results: We found that patients in the DMT2+HTN group showed lower values of mean RR intervals (801.1 vs 871.5 ms), Shannon entropy (3 vs 3.2) and fractal dimension SD 1 (9.5 vs 14.5), when contrasted with patients in the DMT2 group. Negative correlations were found between some HRV nonlinear indices and exercise capacity indices. Conclusion: HTN negatively affects the cardiac autonomic function in diabetic patients, who are already prone to develop autonomic dysfunction. Strategies are need to improve cardiac autonomic functionality in this population.

Resumo Fundamento: A diabetes mellitus tipo 2 (DM2) está associada com disfunção autonômica cardíaca, que é um preditor independente de mortalidade em doenças crônicas. No entanto, ainda não se sabe se a coexistência de hipertensão arterial sistêmica (HAS) e DM2 altera a modulação cardíaca autonômica. Objetivos: O objetivo deste estudo foi avaliar a influência de HAS sobre a modulação da função autonômica cardíaca e capacidade cardiopulmonar em indivíduos com DM2. Métodos: 60 pacientes de ambos os sexos foram avaliados e alocados em dois grupos; pacientes DM2 (n = 32; 51 ± 7,5 anos) e pacientes DM2 + HAS (n = 28; 51 ± 6,9 anos). Intervalos RR foram obtidos durante repouso e em posição supina. Índices lineares e não lineares da variabilidade da frequência cardíaca (VFC) foram registrados utilizando-se o programa Kubios HRV software. A troca gasosa pulmonar foi medida a cada inspiração, utilizando-se um sistema telemétrico portátil durante o teste incremental máximo de exercício em cicloergômetro. A análise estatística incluiu o teste Shapiro-Wilk seguido do teste t de Student, a correlação de Pearson e a regressão linear. Resultados: Encontramos que pacientes do grupo DM2+HAS apresentaram valores mais baixos de intervalos RR (801,1 vs 871,5 ms), entropia de Shannon (3,0 vs 3,2) e DP1 da dimensão fractal em comparação aos pacientes do grupo DM2. Foram encontradas correlações negativas entre alguns índices não lineares da VFC e índices da capacidade do exercício. Conclusão: A HAS afeta negativamente a função autonômica cardíaca em pacientes diabéticos, os quais já são propensos a desenvolverem disfunção autonômica. Estratégias são necessárias para melhorar a função autonômica cardíaca nessa população.

Noninvasive Ventilation as an Important Adjunct to an Exercise Training Program in Subjects With Moderate to Severe COPD.

BACKGROUND: The primary objective of this study was to investigate whether noninvasive ventilation (NIV) can positively affect exercise capacity, maximum oxygen uptake (V̇O2 ), and symptoms after a 6-week physical training program for subjects with moderate to very severe COPD. METHODS: 47 subjects with COPD who were enrolled in a physical training program were randomized to either physical training alone or NIV + physical training (NIV-Physical training). Physical training consisted of dynamic aerobic exercises on a treadmill 3 times/week for 6 weeks, for a total of 18 sessions. NIV was titrated according to the subject's tolerance at rest and during exercise. Assessments included physiological responses and symptoms at the incremental cardiopulmonary exercise test peak and during submaximal exercise on a treadmill, 6-min walk distance, maximum inspiratory (PImax) and expiratory pressure (PEmax), BODE index, and health-related quality of life. RESULTS: 43 subjects completed the 6-week physical training program. Both groups improved 6-min walk distance, PImax, BODE index, and quality of life, and no differences were found between groups. However, significant improvements were observed for subjects in the NIV-Physical training group with regard to PEmax, maximum V̇O2 , maximum metabolic equivalents, circulatory power, and maximum SpO2 . CONCLUSIONS: A 6-week physical training program alone can improve tolerance for exercise and quality of life, in addition to reducing the risk of mortality. However, NIV associated with a physical training program was shown to have an additive beneficial effect on powerful prognostic markers (maximum V̇O2 and circulatory power) and to reduce symptoms and improve oxygen saturation in subjects with moderate to very severe COPD.

Chronic obstructive pulmonary disease severity and its association with obstructive sleep apnea syndrome: impact on cardiac autonomic modulation and functional capacity.

BACKGROUND: The study was conducted to determine the impact of chronic obstructive pulmonary disease (COPD) in association with obstructive sleep apnea syndrome (OSAS) on cardiac autonomic control and functional capacity. SUBJECTS AND METHODS: The study was a cross-sectional prospective controlled clinical study. Heart rate variability indices of 24 COPD (n = 12) and COPD+OSAS (n = 12) patients were evaluated and compared by electrocardiographic recordings acquired during rest, active postural maneuver (APM), respiratory sinus arrhythmia maneuver (RSA-m), and the 6-minute walk test (6MWT). RESULTS: The COPD group presented higher parasympathetic modulation during APM when compared to the COPD+OSAS group (P = 0.02). The COPD+OSAS group presented higher sympathetic modulation during RSA-m when compared to the COPD group (P = 0.00). The performance during 6MWT was similarly impaired in both groups, despite the greater severity of the COPD group. CONCLUSION: Subjects with COPD+OSAS present marked sympathetic modulation, and the presence of OSAS in COPD subjects has a negative impact on functional capacity regardless of the severity of lung disease.

Increased parasympathetic cardiac modulation in patients with acute exacerbation of COPD: how should we interpret it?

BACKGROUND: Cardiac autonomic modulation (CAM) is impaired in patients with stable COPD. Exacerbation aggravates the patients' health status and functional capacity. While the clinical and functional effects of exacerbation are known, no studies investigated CAM during exacerbation and whether there is a relationship between CAM and functional capacity and dyspnea. METHODS: Thirty-two patients with moderate to severe COPD were enrolled into two groups: stable COPD (GSta, n=16) and acute exacerbation of COPD (GAE, n=16). The GAE patients were evaluated 24-48 hours after starting standard therapy for COPD exacerbation during hospitalization; the GSta patients were evaluated in an outpatient clinic and included in the study if no decompensation episodes had occurred during the previous month. The heart rate (HR) and R-wave peak detection intervals in ms (RRi) were registered using a heart rate monitor (Polar® system) at rest in seated position during 10 minutes. CAM was assessed by heart rate variability (HRV) linear and non-linear analysis. Functional capacity was evaluated by handgrip strength test, performed by Jamar® dynamometer, and dyspnea was scored using the modified scale of the Medical Research Council. RESULTS: GAE presented higher parasympathetic CAM values compared with GSta for square root of the mean squared differences of successive RRi (RMSSD; 17.8±5.6 ms vs 11.7±9.5 ms); high frequency (HF; 111.3±74.9 ms2 vs 45.6±80.7 ms2) and standard deviation measuring the dispersion of points in the plot perpendicular to the line of identity (SD1; 12.7±3.9 ms vs 8.3±6.7 ms) and higher CAM values for standard deviation of the mean of all of RRi (STD RRi; 19.3±6.5 ms vs 14.3±12.5 ms); RRi tri (5.2±1.7 ms vs 4.0±3.0 ms); triangular interpolation of NN interval histogram (TINN; 88.7±26.9 ms vs 70.6±62.2 ms); low frequency (LF; 203±210.7 ms2 vs 101.8±169.7 ms2) and standard deviation measuring the dispersion of points along the line of identity (SD2; 30.4±14.8 ms vs 16.2±12.54 ms). Lower values were observed for the complexity indices: approximate entropy (ApEn; 0.9±0.07 vs 1.06±0.06) and sample entropy (SampEn; 1.4±0.3 vs 1.7±0.3). Significant and moderate associations were observed between HF (nu) and handgrip strength (r=-0.58; P=0.01) and between LF (ms2) and subjective perception of dyspnea (r=-0.53; P=0.03). CONCLUSION: COPD exacerbated patients have higher parasympathetic CAM than stable patients. This should be interpreted with caution since vagal influence on the airways determines a narrowing and not a better clinical condition. Additionally, functional capacity was negatively associated with parasympathetic CAM in COPD exacerbation.

Exploring Vascular Function Biomarkers: Implications for Rehabilitation.

The endothelium plays an important role in maintaining vascular homeostasis and regulating blood vessel function. Endothelial function is considered an independent predictor for risk of future cardiovascular events in cardiovascular and non-cardiovascular patients, as well as a predictor for postoperative complications in cardiovascular surgery patients. Brachial artery flow-mediated dilation by high-resolution ultrasound is widely used to evaluate endothelium-dependent vasodilation, which is mainly mediated by nitric oxide release. Physical exercise exerts beneficial effects on endothelial function and can be used in both primary and secondary prevention of cardiac and peripheral artery diseases, even in the postoperative period of cardiovascular surgery.

Exploring vascular function biomarkers: implications for rehabilitation

Abstract The endothelium plays an important role in maintaining vascular homeostasis and regulating blood vessel function. Endothelial function is considered an independent predictor for risk of future cardiovascular events in cardiovascular and non-cardiovascular patients, as well as a predictor for postoperative complications in cardiovascular surgery patients. Brachial artery flow-mediated dilation by high-resolution ultrasound is widely used to evaluate endothelium-dependent vasodilation, which is mainly mediated by nitric oxide release. Physical exercise exerts beneficial effects on endothelial function and can be used in both primary and secondary prevention of cardiac and peripheral artery diseases, even in the postoperative period of cardiovascular surgery.

Is cardiac autonomic modulation during upper limb isometric contraction and Valsalva maneuver impaired in COPD patients?

PURPOSE: To evaluate the heart rate variability (HRV) indices and heart rate (HR) responses during isometric contraction (IC) and Valsalva maneuver (VM) in COPD patients. METHODS: Twenty-two stable moderate to severe COPD patients were evaluated. R-R intervals were recorded (monitor Polar® S810i) during dominant upper limb IC (2 minutes). Stable signals were analyzed by Kubios HRV® software. Indices of HRV were computed in the time domain (mean HR; square root of the mean squared differences of successive RR intervals [RMSSD] and HRV triangular index [RR tri index]) and in the frequency domain (high frequency [HF]; low frequency [LF] and LF/HF ratio). The HR responses were evaluated at rest, at the peak and at the nadir of the VM (15 seconds). The Valsalva index was also calculated. RESULTS: During IC: time domain indices (mean HR increased [P=0.001], RMSSD, and RR tri index decreased [P=0.005 and P=0.005, respectively]); frequency domain indices (LF increased [P=0.033] and HF decreased [P=0.002]); associations were found between forced expiratory volume in 1 second (FEV1) vs RMSSD (P=0.04; r=-0.55), FEV1 vs HR (P=0.04; r=-0.48), forced vital capacity (FVC) vs RMSSD (P=0.05; r=-0.62), maximum inspiratory pressure (MIP) vs HF (P=0.02; r=0.68). FEV1 and FVC justified 30% of mean HR. During VM: HR increased (P=0.01); the nadir showed normal bradycardic response; the Valsalva index was =0.7. CONCLUSION: COPD patients responded properly to the upper limb IC and to the VM; however, HR recovery during VM was impaired in these patients. The severity of the disease and MIP were associated with increased parasympathetic modulation and higher chronotropic response.

Hemodynamic, Autonomic, Ventilatory, and Metabolic Alterations After Resistance Training in Patients With Coronary Artery Disease: A Randomized Controlled Trial.

OBJECTIVE: The aim of this work was to evaluate the hemodynamic, autonomic, and metabolic responses during resistance and dynamic exercise before and after an 8-week resistance training program using a low-intensity (30% of 1 repetitium maximum), high-repetition (3 sets of 20 repetitions) model, added to an aerobic training program, in a coronary artery disease cohort. DESIGN: Twenty male subjects with coronary artery disease (61.1 ± 4.7 years) were randomly assigned to a combined training group (resistance + aerobic) or aerobic training group (AG). Heart rate, stroke volume, cardiac output, minute ventilation, blood lactate, and parasympathetic modulation indices of heart rate (square root of the mean squared differences of successive RR intervals [RMSSD] and dispersion of points perpendicular to the line of identity that provides information about the instantaneous beat-to-beat variability [SD1]) were obtained before and after an 8-week RT program while performing exercise on a cycle ergometer and a 45-degree leg press. RESULTS: Resistance training resulted in an increase in maximal and submaximal load tolerance (P < 0.01), a decreased hemodynamic response (P < 0.01), and a reduction in blood lactate in the combined training group compared to the aerobic training group during the 45-degree leg press. During exercise on a cycle ergometer, there was a decreased hemodynamic response and increased minute ventilation (P < 0.01). The 8-week RT program resulted in greater parasympathetic tone (RMSSD and SD1) and an increase in the SDNN index during exercise on a cycle ergometer and 45-degree leg press (P < 0.05). CONCLUSIONS: An 8-week resistance training program associated with aerobic training may attenuate hemodynamic stress, and modify metabolic and autonomic responses during resistance exercise. The training program also appeared to elicit beneficial cardiovascular and autonomic effects during exercise.

Respiratory muscle strength effect on linear and nonlinear heart rate variability parameters in COPD patients.

INTRODUCTION: Chronic obstructive pulmonary disease (COPD) is recognized as a multisystemic inflammatory disease associated with extrapulmonary comorbidities, including respiratory muscle weakness and cardiovascular and cardiac autonomic regulation disorders. We investigated whether alterations in respiratory muscle strength (RMS) would affect cardiac autonomic modulation in COPD patients. METHODS: This study was a cross-sectional study done in ten COPD patients affected by moderate to very severe disease. The heart rate variability (HRV) signal was recorded using a Polar cardiofrequencimeter at rest in the sitting position (10 minutes) and during a respiratory sinus arrhythmia maneuver (RSA-M; 4 minutes). Linear analysis in the time and frequency domains and nonlinear analysis were performed on the recorded signals. RMS was assessed using a digital manometer, which provided the maximum inspiratory pressure (PImax) and the maximum expiratory pressure (PEmax). RESULTS: During the RSA-M, patients presented an HRV power increase in the low-frequency band (LFnu) (46.9±23.7 vs 75.8±27.2; P=0.01) and a decrease in the high-frequency band (HFnu) (52.8±23.5 vs 24.0±27.0; P=0.01) when compared to the resting condition. Significant associations were found between RMS and HRV spectral indices: PImax and LFnu (r=-0.74; P=0.01); PImax and HFnu (r=0.74; P=0.01); PEmax and LFnu (r=-0.66; P=0.01); PEmax and HFnu (r=0.66; P=0.03); between PEmax and sample entropy (r=0.83; P<0.01) and between PEmax and approximate entropy (r=0.74; P=0.01). Using a linear regression model, we found that PImax explained 44% of LFnu behavior during the RSA-M. CONCLUSION: COPD patients with impaired RMS presented altered cardiac autonomic control, characterized by marked sympathetic modulation and a reduced parasympathetic response; reduced HRV complexity was observed during the RSA-M.

Inductive plethysmography potential as a surrogate for ventilatory measurements during rest and moderate physical exercise

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.

Hippotherapy acute impact on heart rate variability non-linear dynamics in neurological disorders.

Neurological disorders are associated with autonomic dysfunction. Hippotherapy (HT) is a therapy treatment strategy that utilizes a horse in an interdisciplinary approach for the physical and mental rehabilitation of people with physical, mental and/or psychological disabilities. However, no studies have been carried out which evaluated the effects of HT on the autonomic control in these patients. Therefore, the objective of the present study was to investigate the effects of a single HT session on cardiovascular autonomic control by time domain and non-linear analysis of heart rate variability (HRV). The HRV signal was recorded continuously in twelve children affected by neurological disorders during a HT session, consisting in a 10-minute sitting position rest (P1), a 15-minute preparatory phase sitting on the horse (P2), a 15-minute HT session (P3) and a final 10-minute sitting position recovery (P4). Time domain and non-linear HRV indices, including Sample Entropy (SampEn), Lempel-Ziv Complexity (LZC) and Detrended Fluctuation Analysis (DFA), were calculated for each treatment phase. We observed that SampEn increased during P3 (SampEn=0.56±0.10) with respect to P1 (SampEn=0.40±0.14, p<0.05), while DFA decreased during P3 (DFA=1.10±0.10) with respect to P1 (DFA=1.26±0.14, p<0.05). A significant SDRR increase (p<0.05) was observed during the recovery period P4 (SDRR=50±30ms) with respect to the HT session period P3 (SDRR=30±10ms). Our results suggest that HT might benefit children with disabilities attributable to neurological disorders by eliciting an acute autonomic response during the therapy and during the recovery period.