Identification of anaerobic threshold using heart rate response during dynamic exercise

The objective of the present study was to characterize the heart rate (HR) patterns of healthy males using the autoregressive integrated moving average (ARIMA) model over a power range assumed to correspond to the anaerobic threshold (AT) during discontinuous dynamic exercise tests (DDET). Nine young (22.3 ± 1.57 years) and 9 middle-aged (MA) volunteers (43.2 ± 3.53 years) performed three DDET on a cycle ergometer. Protocol I: DDET in steps with progressive power increases of 10 W; protocol II: DDET using the same power values as protocol 1, but applied randomly; protocol III: continuous dynamic exercise protocol with ventilatory and metabolic measurements (10 W/min ramp power), for the measurement of ventilatory AT. HR was recorded and stored beat-to-beat during DDET, and analyzed using the ARIMA (protocols I and II). The DDET experiments showed that the median physical exercise workloads at which AT occurred were similar for protocols I and II, i.e., AT occurred between 75 W (116 bpm) and 85 W (116 bpm) for the young group and between 60 W (96 bpm) and 75 W (107 bpm) for group MA in protocols I and II, respectively; in two MA volunteers the ventilatory AT occurred at 90 W (108 bpm) and 95 W (111 bpm). This corresponded to the same power values of the positive trend in HR responses. The change in HR response using ARIMA models at submaximal dynamic exercise powers proved to be a promising approach for detecting AT in normal volunteers

Determination of anaerobic threshold through heart rate and near infrared spectroscopy in elderly healthy men

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.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Universidade Federal do Rio de Janeiro School of Medicine Physical Therapy DepartmentUniversidade Federal de São Paulo (UNIFESP) Department of MedicineUniversity of Illinois College of Applied Health Sciences Physical Therapy DepartmentUniversidade Federal de Sao Carlos Physical Therapy Department Nucleus of Research in Physical ExerciseUNIFESP, Department of MedicineSciEL

Acute Application of Bilevel Positive Airway Pressure Influences the Cardiac Autonomic Nervous System

INTRODUCTION: Noninvasive positive pressure has been used to treat several diseases. However, the physiological response of the cardiac autonomic system during bilevel positive airway pressure (Bilevel) remains unclear. OBJECTIVE: The aim of this study was to evaluate the heart rate variability (HRV) during Bilevel in young healthy subjects. METHODS: Twenty men underwent 10-minute R-R interval recordings during sham ventilation (SV), Bilevel of 8-15 cmH2O and Bilevel of 13-20 cmH2O. The HRV was analyzed by means of the parallel R-R interval (mean R-Ri), the standard deviation of all R-Ri (SDNN), the root mean square of the squares of the differences between successive R-Ri (rMSSD), the number of successive R-Ri pairs that differ by more than 50 milliseconds (NN50), the percentage of successive R-Ri that differ by more than 50 milliseconds (pNN50), the low frequency (LF), the high frequency (HF) and SD1 and SD2. Additionally, physiological variables, including blood pressure, breathing frequency and end tidal CO2, were collected. Repeated-measures ANOVA and Pearson correlation were used to assess the differences between the three studied conditions and the relationships between the delta of Bilevel at 13-20 cmH2O and sham ventilation of the HRV indexes and the physiological variables, respectively. RESULTS: The R-Ri mean, rMSSD, NN50, pNN50 and SD1 were reduced during Bilevel of 13-20 cmH2O as compared to SV. An R-Ri mean reduction was also observed in Bilevel of 13-20 cmH2O compared to 8-15 cmH2O. Both the R-Ri mean and HF were reduced during Bilevel of 8-15 cmH2O as compared to SV, while the LF increased during application of Bilevel of 8-15 cmH2O as compared to SV. The delta (between Bilevel at 13-20 cmH2O and sham ventilation) of ETCO2 correlated positively with LF, HF, the LF/HF ratio, SDNN, rMSSD and SD1. Acute application of Bilevel was able to alter the cardiac autonomic nervous system, resulting in a reduction in parasympathetic activity and an increase in sympathetic activity and higher level of positive pressure can cause a greater influence on the cardiovascular and respiratory system

AGE INFLUENCE ON THE HEART RATE BEHAVIOR ON THE REST-EXERCICIO TRANSITION: AN ANALYSIS BY DELTAS AND LINEAR REGRESSION

Background: Changes in heart rate during rest-exercise transition can be characterized by the application of mathematical calculations, such as deltas 0-10 and 0-30 seconds to infer on the parasympathetic nervous system and linear regression and delta applied to data range from 60 to 240 seconds to infer on the sympathetic nervous system. The objective of this study was to test the hypothesis that young and middle-aged subjects have different heart rate responses in exercise of moderate and intense intensity, with different mathematical calculations. Methods: Seven middle-aged men and ten young men apparently healthy were subject to constant load tests (intense and moderate) in cycle ergometer. The heart rate data were submitted to analysis of deltas (0-10, 0-30 and 60-240 seconds) and simple linear regression (60-240 seconds). The parameters obtained from simple linear regression analysis were: intercept and slope angle. We used the Shapiro-Wilk test to check the distribution of data and the "t" test for unpaired comparisons between groups. The level of statistical significance was 5%. Results: The value of the intercept and delta 0-10 seconds was lower in middle age in two loads tested and the inclination angle was lower in moderate exercise in middle age. Conclusion: The young subjects present greater magnitude of vagal withdrawal in the initial stage of the HR response during constant load exercise and higher speed of adjustment of sympathetic response in moderate exercise.18530030

Determining anaerobic threshold through heart rate variability in patients with COPD during cycloergometer exercise

INTRODUCTION: Chronic Obstructive Pulmonary Disease (COPD) is characterized by structural alterations of lung parenchyma resulting in systemic manifestations. These patients may have marked change in cardiac autonomic control. In this context, studies investigating heart rate variability (HRV) in patients with COPD during physical exercise cycloergometers have been little explored. OBJECTIVE: To determine the anaerobic threshold through HRV in order to establish parameters of evaluation and prescription of exercise intensity in these patients on a cycloergometer. MATERIALS AND METHODS: Eight male patients diagnosed with COPD, mean age 69.5 ± 7.6 years were studied. Heart rate was analyzed at rest and at different intensities of exercise. The test was performed on a cycloergometer and consisted of a warm-up period of four minutes at a minimum power. Steps were performed with initial power of 4W, with increments of 5 in 5W, until the patient reached the anaerobic threshold. RESULTS: Patients that presented higher values of FEV1 showed greater powers during the cycloergometer. Additionally, there was significant reduction in HRV during exercise compared to rest sitting p < 0.05. CONCLUSION: Patients had a severe physical deconditioning reaffirmed the impossibility determined by the anaerobic threshold of 50% of the sample.INTRODUÇÃO: A Doença Pulmonar Obstrutiva Crônica (DPOC) é caracterizada por alterações estruturais do parênquima pulmonar, acarretando manifestações sistêmicas. Além disso, esses pacientes podem apresentar marcada alteração do controle autonômico cardíaco. Nesse contexto, estudos investigando a variabilidade da frequência cardíaca (VFC) em pacientes com DPOC durante a realização de exercício físico em cicloergometro têm sido pouco explorados. OBJETIVO: Determinar o limiar anaeróbio por meio da VFC com o propósito de estabelecer parâmetros de avaliação e prescrição da intensidade de exercício desses pacientes em cicloergômetro. MATERIAIS E MÉTODOS: Foram avaliados oito pacientes do sexo masculino com diagnóstico de DPOC com idade média de 69,5 ± 7,6 anos. A frequência cardíaca foi analisada no repouso e em diferentes intensidades do exercício. O teste foi realizado em um cicloergômetro e consistiu em um período de aquecimento de quatro minutos em uma potência mínima. Foram, também, realizados degraus com potência inicial de 4W, com acréscimos de 5 em 5W, até que o paciente atingisse o limiar anaeróbio. RESULTADOS: Os pacientes que apresentaram maiores valores de VEF1 apresentaram maiores potências no cicloergômetro. Houve redução significativa da VFC durante o exercício físico se comparado ao repouso sentado p < 0,05. CONCLUSÃO: Os pacientes estudados apresentaram um severo descondicionamento físico reafirmado pela impossibilidade determinada pelo LA de 50% da amostra.Universidade Federal de São Carlos Departamento de Fisioterapia Núcleo de Pesquisa em Exercício FísicoUniversidade Federal de São Carlos Fisioterapia CardiovascularUniversidade Federal de São Paulo (UNIFESP) MedicinaUniversidade Federal de São Carlos GeriatriaUniversidade de Federal de São Carlos FisioterapiaUNIFESP, MedicinaSciEL

Cardiovascular control in women with fibromyalgia syndrome: Do causal methods provide nonredundant information compared with more traditional approaches?

The cardiovascular autonomic control and the baroreflex sensitivity (BRS) have been widely studied in FMS patients through the computation of linear indices of spontaneous heart period (HP) and systolic arterial pressure (SAP) variabilities. However, there are many methodological difficulties regarding the quantification of BRS by the traditional indices especially in relation to the issue of causality. This difficulty has been directly tackled via a model-based approach describing the closed loop HP-SAP interactions and the exogenous influences of respiration. Therefore, we aimed to assess if the BRS assessed by the model-based causal closed-loop approach during supine and active standing in patients with FMS could provide complementary information to those obtained by traditional indices based on time and frequency domains. The findings of this study revealed that, although the traditional methods to quantify BRS did not show any significant differences between groups, the causality analysis applied to the HP, SAP and respiratory series, through the model based closed loop approach, detected lower BRS in supine position as well as a blunted response to the orthostatic stimulus in patients with FMS compared to healthy control subjects. Also, the strength of the causal relation from SAP to HP (i.e., along the cardiac baroreflex) increased during the active standing only in the control subjects. The model-based closed-loop approach proved to provide important complementary information about the cardiovascular autonomic control in patients with FMS

Adaptações do sistema respiratório referentes à função pulmonar em resposta a um programa de alongamento muscular pelo método de Reeducação Postural Global

A proposta deste estudo foi analisar as adaptações do sistema respiratório referentes à função pulmonar em resposta ao alongamento da cadeia muscular respiratória pelo método de Reeducação Postural Global (RPG). Foram estudados 20 homens, sedentários, de antropometria semelhante, sem antecedentes de doenças musculoesqueléticas ou cardiorrespiratórias. Os voluntários foram divididos aleatoriamente em dois grupos de dez, sendo um grupo controle (GC), que não participou do protocolo de alongamento, e o outro submetido à intervenção pelo método de RPG, denominado grupo tratado (GT). O alongamento foi realizado duas vezes por semana, durante oito semanas, totalizando 16 sessões. Os dois grupos foram submetidos à prova de função pulmonar, medindo-se a capacidade vital lenta, capacidade vital forçada e ventilação voluntária máxima, antes e após o período de intervenção. Os valores obtidos em todas as variáveis dos voluntários do GC na avaliação inicial não apresentaram diferença estatisticamente significante quando comparados aos obtidos na avaliação final (p>;0,05). No GT os valores finais apresentaram-se significativamente maiores que os iniciais (pThe aim of this study was to analyse the respiratory system adaptations concerning pulmonary function in response to stretching the respiratory muscle chain, by means of Global Posture Reeducation (GPR). Twenty sedentary young men with similar anthropometry and no history of musculoskeletal or cardiorespiratory disease were randomly divided into two groups of ten each: control group (CG), who did no stretching, and treated group (TG), submitted to GPR. Stretching was carried out twice a week for 8 weeks, in a total of 16 sessions. The two groups were submitted to pulmonary function tests to assess slow vital capacity, forced vital capacity and maximal voluntary ventilation, before and after the intervention period. The initial values of all spirometric variables measured in CG volunteers showed no statistically significant differences when compared to those of the final evaluation (p>;0.05), whereas in TG all values increased after intervention (

Pressão expiratória positiva nas vias aéreas não reproduz as respostas de frequência cardíaca à manobra de Valsalva em homens jovens saudáveis

The expiratory positive airway pressure (EPAP) is a therapeutic resource that comprises an inspiration followed by expiration against resistance. During its application there were adjustments in the cardiovascular system, similar to those observed during the Valsalva maneuver (VM). The aim of this study was to analyze the heart rate (HR) response to VM and to different ways of EPAP application to identify if and in which condition this technique reproduces the HR response observed in the VM, in apparently healthy young men. Ten subjects (24±3 years, 25±3 kg/m²) performed randomly the VM and EPAP procedures on different days. The expiratory effort in VM was sustained for 15 s (oral pressure of 40 mmHg [53.4cm H2O]). Two EPAP techniques were employed (alone and therapeutic) against three pressure levels (10, 15 and 20 cmH2O), randomly applied. The maneuvers were repeated three times with five minutes interval. It was considered the greatest value of HR variation (DHR) for each maneuver analysis. Were used the Shapiro-Wilk test to analyze the data distribution and the ANOVA for repeated measures, with Fisher's post-hoc, considering &#945;A pressão expiratória positiva nas vias aéreas (EPAP) é um recurso terapêutico que compreende uma inspiração seguida de expiração contra resistência. Sua aplicação promove ajustes no sistema cardiovascular, de maneira similar ao observado durante a manobra de Valsalva (MV). O objetivo deste estudo foi analisar a resposta da frequência cardíaca (FC) à MV e às diferentes formas de aplicação de EPAP a fim de identificar se e em qual condição esta técnica reproduz a resposta da FC observada na MV, em homens jovens aparentemente saudáveis. Foram estudados 10 sujeitos (24±3 anos; 25±3 kg/m²) que realizaram os procedimentos de MV e EPAP, aleatoriamente em dias diferentes. Na MV o esforço expiratório foi sustentado por 15 s (pressão oral de 40 mmHg [53,4 cmH2O]). Empregou-se duas técnicas de EPAP (isolada e terapêutica) contra 3 níveis de pressão (10, 15 e 20 cmH2O), aplicados aleatoriamente. As manobras foram repetidas três vezes com intervalo de cinco minutos. Considerou-se o maior valor de variação da FC (DFC) de cada manobra para análise. Empregou-se o teste Shapiro-Wilk para verificar a distribuição dos dados e ANOVA para medidas repetidas, com post-hoc de Fisher, considerando-se &#945