Principles of exercise testing and interpretation

Autonomic nervous system (ANS) plays an important role in the regulation of the physiological processes of the human organism during normal and pathological conditions. Among the techniques used in its evaluation, the heart rate variability (HRV) has arising as a simple and non-invasive measure of the autonomic impulses, representing one of the most promising quantitative markers of the autonomic balance. The HRV describes the oscillations in the interval between consecutive heart beats (RR interval), as well as the oscillations between consecutive instantaneous heart rates. It is a measure that can be used to assess the ANS modulation under physiological conditions, such as wakefulness and sleep conditions, different body positions, physical training and also pathological conditions. Changes in the HRV patterns provide a sensible and advanced indicator of health involvements. Higher HRV is a signal of good adaptation and characterizes a health person with efficient autonomic mechanisms, while lower HRV is frequently an indicator of abnormal and insufficient adaptation of the autonomic nervous system, provoking poor patient's physiological function. Because of its importance as a marker that reflects the ANS activity on the sinus node and as a clinical instrument to assess and identify health involvements, this study reviews conceptual aspects of the HRV, measurement devices, filtering methods, indexes used in the HRV analyses, limitations in the use and clinical applications of the HRV.

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Basic notions of heart rate variability and its clinical applicability

Muscles Alive: Their Functions Revealed by Electromyography

Background—Cardiac mortality and electrophysiological dysfunction both increase with age. Heart rate variability (HRV) provides indices of autonomic function and electrophysiology that are associated with cardiac risk. How habitual physical activity among older adults prospectively relates to HRV, including nonlinear indices of erratic sinus patterns, is not established. We hypothesized that increasing the levels of both total leisure-time activity and walking would be prospectively associated with more favorable time-domain, frequency-domain, and nonlinear HRV measures in older adults. Methods and Results—We evaluated serial longitudinal measures of both physical activity and 24-hour Holter HRV over 5 years among 985 older US adults in the community-based Cardiovascular Health Study. After multivariable adjustment, greater total leisure-time activity, walking distance, and walking pace were each prospectively associated with specific, more favorable HRV indices, including higher 24-hour standard deviatio...

Physical Activity and Heart Rate Variability in Older Adults The Cardiovascular Health Study

Summary Correspondence Marianne Penachini da Costa de Rezende Barbosa,Physiotherapy Program, Universidade EstadualPaulista – FCT/UNESP, A/C Luiz Carlos Mar-ques Vanderlei, Roberto Simonsen St, 305 – zipcode: 19060–900 Presidente Prudente, SP, BrazilE-mail: mapenachini@hotmail.com Accepted for publication Received 10 August 2014;accepted 24 September 2014 Key words autonomic nervous system; electrocardiography;heart rate; sympathetic nervous system; validationstudies The Polar RS800G3 TM rate monitor was released in the market to replace thePolar S810i TM , and few studies have assessed that the RR series obtained by thisequipment is reliable for analysis of heart rate variability (HRV). We comparedHRV indexes among the devices Polar RS800G3 TM , Polar S810i TM and eletrocar-diogram (ECG) to know whether the series of Polar RS800G3 TM are as reliable asthose devices already validated. We analysed data from 30 healthy young adults,male, with an average age of 20 66 1 40 years, which had captured the heartrate beat to beat in the three devices simultaneously with spontaneously breath-ing, ﬁrst in the supine position and subsequently sit both for 30 min. Theobtained series of RR intervals was used to calculate the indexes of HRV in thetime domain (SDNN and RMSSD) and in the frequency domain (LF, HF and LF/HF). There were no signiﬁcant differences in HRV indexes calculated from seriesobtained by the three devices, regardless of the position analysed, and a high cor-relation coefﬁcient was observed. The results suggest that the Polar RS800G3

Comparison of Polar® RS800G3™ heart rate monitor with Polar® S810i™ and electrocardiogram to obtain the series of RR intervals and analysis of heart rate variability at rest.

The effects of the aging process and an active life-style on the autonomic control of heart rate (HR) were investigated in nine young sedentary (YS, 23 +/- 24 years), 16 young active (YA, 22 +/- 21 years), 8 older sedentary (OS, 63 +/- 24 years) and 8 older active (OA, 61 +/- 11 years) healthy men Electrocardiogram was continuously recorded for 15 min at rest and for 4 min in the deep breathing test, with a breath rate of 5 to 6 cycles/min in the supine position Resting HR and RR intervals were analyzed by time (RMSSD index) and frequency domain methods The power spectral components are reported in normalized units (nu) at low (LF) and high (HF) frequency, and as the LF/HF ratio The deep breathing test was analyzed by the respiratory sinus arrhythmia indices: expiration/inspiration ratio (E/I) and inspiration-expiration difference (deltaIE) The active groups had lower HR and higher RMSSD index than the sedentary groups (life-style condition: sedentary vs active, P < 005) The older groups showed lower HFnu, higher LFnu and higher LF/HF ratio than the young groups (aging effect: young vs older, P < 005) The OS group had a lower E/I ratio (116) and deltaIE (97 bpm) than the other groups studied (YS: 138, 224 bpm; YA: 140, 213 bpm; OA: 138, 185 bpm) The interaction between aging and life-style effects had a P < 005 These results suggest that aging reduces HR variability However, regular physical activity positively affects vagal activity on the heart and consequently attenuates the effects of aging in the autonomic control of HR

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Effects of age and physical activity on the autonomic control of heart rate in healthy men.

The aim of the present study was to compare the modulation of heart rate in a group of postmenopausal women to that of a group of young women under resting conditions on the basis of R-R interval variability. Ten healthy postmenopausal women (mean +/- SD, 58.3 +/- 6.8 years) and 10 healthy young women (mean +/- SD, 21.6 +/- 0.82 years) were submitted to a control resting electrocardiogram (ECG) in the supine and sitting positions over a period of 6 min. The ECG was obtained from a one-channel heart monitor at the CM5 lead and processed and stored using an analog to digital converter connected to a microcomputer. R-R intervals were calculated on a beat-to-beat basis from the ECG recording in real time using a signal-processing software. Heart rate variability (HRV) was expressed as standard deviation (RMSM) and mean square root (RMSSD). In the supine position, the postmenopausal group showed significantly lower (P<0.05) median values of RMSM (34.9) and RMSSD (22.32) than the young group (RMSM: 62.11 and RMSSD: 49.1). The same occurred in the sitting position (RMSM: 33.0 and RMSSD: 18.9 compared to RMSM: 57.6 and RMSSD: 42.8 for the young group). These results indicate a decrease in parasympathetic modulation in postmenopausal women compared to young women which was possibly due both to the influence of age and hormonal factors. Thus, time domain HRV proved to be a noninvasive and sensitive method for the identification of changes in autonomic modulation of the sinus node in postmenopausal women.

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Heart rate variability under resting conditions in postmenopausal and young women

Design of a computerized system to evaluate the cardiac function during dynamic exercise

The aim of this study was to assess and compare the heart rate variability (HRV) during resting conditions in supine and sitting positions of 10 middle-aged healthy men (HM), 9 hypertensive men (HYM) and 9 men with coronary heart disease (CHDM), mean ages of 52, 62 and 56 years, respectively. The HM volunteers were not engaged in regular physical exercise activities, while the HYM and CHDM volunteers had been engaged in aerobic physical training (APT) for approximately 3 years. Heart rate (HR) and R-R intervals (R-Ri-ms) were collected during 900s in supine and sitting positions. RMSSD index of R-Ri (ms) was used for time domain data analysis; for frequency domain analysis, an auto-regressive model was applied to HR data, which gives very low, low (LF) and high frequency (HF) bands. The LF and HF bands were expressed as normalized units and LF/HF ratio. Non-parametric tests (Kruskall-Wallis, Dunn post-hoc and Wilcoxon tests) were used. Level of significance a = 5%. No significant differences were found in intergroup and intragroup comparisons for HRV indexes in supine and sitting positions for both time and frequency domains. Our findings showing an absence of statistically significant differences amongst the three groups studied could be related to the effects of APT on HYM and CHDM compared to HM.

Avaliação da variabilidade da freqüência cardíaca em repouso de homens saudáveis sedentários e de hipertensos e coronariopatas em treinamento físico

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.

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L. Oliveira

Papers

Effects of age and physical activity on the autonomic control of heart rate in healthy men.

Heart rate variability under resting conditions in postmenopausal and young women

Design of a computerized system to evaluate the cardiac function during dynamic exercise

Avaliação da variabilidade da freqüência cardíaca em repouso de homens saudáveis sedentários e de hipertensos e coronariopatas em treinamento físico

Identification of anaerobic threshold using heart rate response during dynamic exercise