Cardiorespiratory coupling is associated with exercise capacity in athletes: A cross-sectional study.

PURPOSE: To determine the association between exercise capacity based on peak oxygen uptake (VO2peak) and resting cardiorespiratory coupling (CRC) levels in athletes and non-athletes' subjects. METHODS: A cross-sectional study was carried out in 42 apparently healthy male subjects, aged between 20 and 40 years old. The participants were allocated into athletes (n = 21) and non-athletes (n = 21) groups. Resting electrocardiogram and respiratory movement (RESP) were simultaneously acquired during 15 min in supine position and quiet breathing. The beat-to-beat heart period (HP) and RESP series were determined from the recorded signals. Traditional analysis of HP based on frequency domain indexes was performed considering the high-frequency (0.15 - 0.45 Hz) components. To compute the CRC, the linear association between HP and RESP series was determined via squared coherence function and directionality of interaction was investigated through the causal extension of this approach. The exercise capacity was assessed through incremental cardiopulmonary exercise testing in order to determine the VO2peak. RESULTS: Traditional analysis of HP based on high-frequency index was not correlated with exercise capacity in the athletes (r = -0.1, p = 0.5) and non-athletes (r = -0.1, p = 0.3) cohorts. However, resting CRC values was associated with exercise capacity in athletes (r = 0.4, p = 0.03), but not in the non-athletes group (r = -0.2, p = 0.3). CONCLUSION: These results suggest that improved resting values of CRC is associated with higher exercise capacity (VO2peak) in endurance athletes. Moreover, frequency domain of HP was not sensitive to identifying this relationship, probably because effects of training on parasympathetic modulation might be affected by respiratory dynamics, and this influence has a directionality (i.e., from RESP to HP).

Applicability of heart rate variability for cardiac autonomic assessment in long-term COVID patients: A systematic review.

PURPOSE: To carry out a systematic review to determine the main methods used to study the heart rate variability (HRV) in individuals after the acute phase of COVID-19. METHODS: The study followed the Preferred Items for Reporting for Systematic Reviews and Meta-Analyses (PRISMA) statement. PubMed, Web of Science, Scopus and CINAHAL electronic databases were searched from the inception to November 2022. The studies were included if they used HRV assessment based on linear and non-linear methods in long-term COVID-19 patients. Review studies, theses and dissertations, conference abstracts, longitudinal studies, studies conducted on animals and studies that included individuals in the acute phase of the COVID-19 were excluded. The methodological quality of the studies was analyzed using the Joanna Briggs Institute's critical evaluation checklist for cross-sectional analytical studies. RESULTS: HRV was mainly assessed using 24-h Holter monitoring in 41.6% (5/12) of the studies, and 12­lead ECG was used in 33.3% (4/12). Regarding the type of assessment, 66.6% (8/12) of the studies only used linear analysis, where 25% (3/12) used analysis in the time domain, and 41.6% (5/12) used both types. Non-linear methods were combined with the previously cited linear method in 25% (3/12) of the studies. Moreover, 50% (6/12) of the studies demonstrated post-COVID-19 autonomic dysfunction, with an increase in the predominance of cardiac sympathetic modulation. The average score of the evaluation checklist was 6.6, characterized as having reasonable methodological quality. CONCLUSION: 24-h Holter and 12­lead ECG are considered effective tools to assess HRV in post-COVID-19 patients. Furthermore, the findings reveal diverse effects of COVID-19 on the autonomic nervous system's sympathovagal balance, which might be influenced by secondary factors such as disease severity, patients' overall health, evaluation timing, post-infection complications, ventilatory functions, and age.

Cardiorespiratory coupling as an early marker of cardiac autonomic dysfunction in type 2 diabetes mellitus patients.

The aim of this study was to assess cardiorespiratory coupling (CRC) in type 2 diabetes mellitus patients (T2DM) and apparently healthy individuals, in order to test the hypothesis that this method can provide additional knowledge to the information obtained through the heart rate variability (HRV). A cross-sectional study was conducted in T2DM patients(T2DMG=32) and health controls (CON=32). For CRC analysis, the electrocardiogram, arterial pressure, and thoracic respiratory movement were recorded at rest in supine position and during active standing. Beat-to-beat series of heart period and systolic arterial pressure were analyzed with the respiratory movement signal via a traditional non-causal approach, such as squared coherence function. In this sample of T2DM, no differences in HRV were observed when compared to the CON, but the T2DMG showed a reduction in resting CRC. We conclude that in CRC in T2DM, reflected by the squared coherence may already be compromised even before HRV changes.

Cardiorespiratory coupling strength in athletes and non-athletes.

PURPOSE: Despite the relevant presence of nonlinear components on heart period (HP) likely due to cardiorespiratory coupling (CRC), the HP is frequently analyzed in absence of concomitant recordings of respiratory movements (RESP). This study aims to assess the cardiovascular dynamics and CRC during postural challenge in athletes and non-athletes via joint symbolic analysis (JSA). METHODS: A cross-sectional study was conducted in 50 men, aged between 20 and 40 yrs, divided into athletes (n = 25) and non-athletes (n = 25) groups. The electrocardiogram, blood pressure and RESP signals were recorded during 15 min in both supine position (REST) and after active postural maneuver (STAND). From the beat-to-beat series of HP, systolic arterial pressure (SAP) and RESP, we computed the time and frequency domain indexes and baroreflex sensitivity. The JSA was based on the definition of symbolic HP and RESP patterns and on the evaluation of the rate of their simultaneous occurrence in both HP and RESP series. RESULTS: The JSA analysis was able to identify higher CRC strength at REST in athletes. Moreover, the response of CRC to STAND depended on the time scales of the analysis and was much more evident in athletes than in non-athletes, thus indicating a more reactive autonomic control in athletes. CONCLUSION: Assessing CRC in athletes via JSA provides additional information compared to standard linear time and frequency domain tools likely due to the more relevant presence of nonlinearities in HP-RESP variability relationship.

Can high-intensity interval training change cardiac autonomic control? A systematic review.

BACKGROUND: High intensity interval training (HIIT) has been used as a cardiovascular exercise strategy to promote greater adherence in cardiovascular rehabilitation. However, little is known about the effect of this training modality on cardiac autonomic control. OBJECTIVE: To perform a systematic review to evaluate the effects of HIIT on cardiac autonomic responses in humans. METHODS: PEDro, SCOPUS and PubMed were searched from the inception to March 29th, 2018. Moreover, the methodological quality and statistical reporting from all eligible clinical trials were assessed by the PEDro scale. The articles were eligible if: The primary objective was related to the effects of HIIT on the cardiac autonomic nervous system. Outcomes evaluated were indirect measures of cardiac autonomic control, represented by HRV indexes. RESULTS: The search strategies resulted in 339 citations and 2 additional citations were identified through other sources. After deleting the duplicate articles and revising the full text, 6 articles were included. Overall, the results showed an improvement in parasympathetic and/or sympathetic modulation after HIIT, when evaluated by linear and non-linear indexes of HRV. CONCLUSIONS: HIIT is a promising tool to improve the cardiac autonomic control, with more recommendation in healthy individuals and patients with metabolic syndrome.

Effects of heated water-based exercise on blood pressure: a systematic review / Efeito do exercício em piscina aquecida sobre a pressão arterial: uma revisão sistemática / Efecto del ejercicio en piscina climatizada sobre la presión arterial: una revisión sistemática

Abstract Introduction: Systemic arterial hypertension is one of the main cardiovascular risk factors affecting several population. In this context, heated water-based exercise has emerged as a potential alternative to land- based physical exercise to reduce blood pressure (BP) in hypertensive patients. Objective: To systematically synthesize evidence for the lowering effects of heated water-based exercise on BP in a non-specific population. Methods: Scielo, Pubmed and Scopus electronic databases were searched for studies from 2005 to 2016, with the following descriptors in English: "blood pressure, exercise, immersion, blood pressure and hydrotherapy". A total of 10,461 articles were found and, after applying the inclusion and exclusion criteria, 13 articles were selected and included in the final analysis. All included articles evaluated individuals from different populations and age groups, submitted to a heated water-based exercise session and/or program. Results: The results suggest that both an acute single session and chronic training period (12 to 24 weeks) of heated water-based exercise may reduce BP in different populations (normotensive, hypertensive, postmenopausal women, and heart transplant populations). The magnitude and duration of acute and chronic hypotensive effect of exercise ranged substantially, which was probably due to the variety of exercise frequency, duration and intensity, as well as due to the studied population. Conclusion: These results suggest that heated water-based exercise may promote acute and chronic hypotensive effects in different populations. However, there is no homogeneity in the protocols used, which may have led to the heterogeneity in magnitude and duration of BP reductions.

Resumo Introdução: A hipertensão arterial sistêmica (HAS) é um dos principais fatores de risco cardiovasculares que afeta diferentes populações. Sendo assim, o exercício físico em piscina aquecida tem surgido como uma potencial alternativa ao exercício físico em solo para a redução da pressão arterial (PA) de indivíduos hipertensos. Objetivo: Revisar a evidência dos efeitos do exercício físico em piscina aquecida na redução da PA em populações não especificas. Métodos: Foram pesquisadas as bases de dados eletrônicas Scielo, Pubmed e Scopus, de 2005 a 2016, com os seguintes descritores em inglês: "pressão arterial, exercício, imersão, pressão arterial e hidroterapia". Foram encontrados 10.461 artigos e, após a aplicação dos critérios de inclusão e exclusão, foram selecionados 13 artigos que fizeram parte da análise final. Todos os artigos incluídos avaliaram indivíduos de diferentes populações, em diferentes faixas etárias, submetidos a uma sessão e/ou programa de exercícios físicos em piscina aquecida. Resultados: Os resultados sugerem que uma sessão aguda de exercício físico em piscina aquecida, bem como um programa de treinamento de 12 a 24 semanas, pode reduzir a pressão arterial em diferentes populações (normotensos, hipertensos, mulheres na pós-menopausa e transplantados cardíacos). Houve uma grande variação na magnitude e duração do efeito hipotensivo do exercício, o que pode ter sido devido à grande variação de frequência, duração e intensidade das sessões, bem como de populações estudadas. Conclusão: Estes resultados sugerem que o exercício físico em piscina aquecida pode ter efeito hipotensivo agudo e crônico em diferentes populações. No entanto, não há homogeneidade nos protocolos utilizados, o que pode ter levado à heterogeneidade na magnitude e duração das reduções de PA.

Resumen Introducción: La hipertensión arterial sistémica es uno de los principales factores de riesgo cardiovascular que afecta diferentes poblaciones. Siendo así, el ejercicio físico en piscina calentada ha surgido como una alternativa potencial al ejercicio físico en suelo para la reducción de la presión arterial (PA) de pacientes hipertensos. Objetivo: Revisar la evidencia de los efectos del ejercicio físico en la piscina calentada en la reducción de la PA en poblaciones no específicas. Métodos: Buscamos las bases de datos electrónicas Scielo, Pubmed y Scopus, de 2005 a 2016, con los siguientes descriptores en inglés: "presión arterial, ejercicio, inmersión, presión arterial e hidroterapia". Se encontraron 10461 artículos y, después de la aplicación de los criterios de inclusión y exclusión, fueron seleccionados 13 artículos que fueron parte del análisis final. Todos los artículos incluidos evaluaron individuos de diferentes poblaciones en diferentes grupos de edad sometidos a programas de ejercicios físicos acuáticos. Resultados: Los resultados sugieren que el ejercicio físico realizado en una piscina calentada puede llevar a diferentes respuestas en la presión arterial, dependiendo de la frecuencia, la duración y la intensidad de las sesiones. Conclusión: Estos resultados sugieren que el ejercicio realizado en una piscina calentada durante 12 a 24 semanas de entrenamiento puede promover efectos benéficos sobre la reducción de la PA. Por otra parte, la sesión aguda no es suficiente para causar un efecto hipotensor. Sin embargo, no hay homogeneidad en los protocolos utilizados, lo que puede haber llevado la divergencia en los resultados.