Heart rate recovery fast-to-slow phase transition: Influence of physical fitness and exercise intensity.

BACKGROUND: Postexercise heart rate (HR) recovery presents an exponential decay, with two distinct phases: a fast phase, characterized by abrupt decay of HR, and determined by parasympathetic reactivation; and a slow phase, characterized by gradual decay of HR, and predominantly determined by sympathetic withdrawal. Although several methods have been proposed to assess postexercise HR recovery, none of those methods selectively assesses the time of transition from the fast to the slow phase of the HR recovery curve (HRRPT ), and the magnitude of decay prior to (HRRFP ) and after this point (HRRSP ). Therefore, the aim of the present study was to propose a method to identify HRRPT , HRRFP , and HRRSP and to verify the effects of exercise intensity and physical fitness on such parameters. METHODS: Ten healthy young participants (24 ± 3 years; 23.6 ± 1.7 kg/m2 ) randomly underwent two exercise sessions (30 min of cycling), at moderate (MI) and high intensity (HI); followed by 5 min of inactive recovery. HR was continuously recorded during the sessions. The algorithm for HRRPT analysis was written in Python and is freely available online. RESULTS: HRRPT and HRRSP were increased in HI session compared with MI (81 ± 24 vs. 60 ± 20 s; 8 ± 10 vs. 1 ± 5 bpm; p = .04), and there was no difference in HRRFP between sessions (49 ± 15 vs. 46 ± 10 bpm; p = .17). In addition, HRRPT for MI exercise session was significantly and negatively associated with VO2max (r = -0.85, p < .05). CONCLUSION: The method herein presented was sensitive to exercise intensity, and partially responsive to aerobic fitness. Next studies should perform the pharmacological and clinical validations of the method.

SinusCor: an advanced tool for heart rate variability analysis.

BACKGROUND: Heart rate variability (HRV) is a widespread non-invasive technique to assess cardiac autonomic function. Time and frequency domain analyses have been used in HRV studies, and their interpretations are linked with both clinical prognostic and diagnostic information. Statistical and geometrical parameters, Fast Fourier Transform and Autoregressive based periodograms are commonly used approaches for the assessment of stationary RR intervals (RRi) signals. However, some conditions result in non-stationary HRV behavior such as the "tilt test" and exercise. This study presents the SinusCor, a new free software for HRV analysis that includes the classical time and frequency domain indices and also techniques for non-stationary data analyses in both time (i.e. root mean squared of successive differences; RMSSD calculated with moving segments) and frequency domains (i.e. time-frequency analysis). RESULTS: An example of RRi was acquired from a young male subject and its time and frequency domain indices were calculated. Time-varying and time-frequency analyses were also presented using the RMSSD and total power, respectively. Validation of the present software against a standard software for HRV analysis (Kubios v 3.0.1) was also performed [SinusCor vs. Kubios: RMSSD-93.96 (41.55) vs. 93.96 (41.55) ms; SDNN-101.29 (29.03) vs. 101.29 (29.03) ms; LF-50.42 (19.76) vs. 50.56 (19.56) n.u.; HF-49.57 (19.76) vs. 49.38 (19.56) n.u.; LF/HF-1.38 (1.08) vs. 1.38 (1.07)]. CONCLUSIONS: SinusCor might be a useful tool for classical stationary and non-stationary HRV analysis.

Methods of assessment of the post-exercise cardiac autonomic recovery: A methodological review.

The analysis of post-exercise cardiac autonomic recovery is a practical clinical tool for the assessment of cardiovascular health. A reduced heart rate recovery - an indicator of autonomic dysfunction - has been found in a broad range of cardiovascular diseases and has been associated with increased risks of both cardiac and all-cause mortality. For this reason, over the last several years, non-invasive methods for the assessment of cardiac autonomic recovery after exercise - either based on heart rate recovery or heart rate variability indices - have been proposed. However, for the proper implementation of such methods in daily clinical practice, the discussion of their clinical validity, physiologic meaning, mathematical formulation and reproducibility should be better addressed. Therefore, the aim of this methodological review is to present some of the most employed methods of post-exercise cardiac autonomic recovery in the literature and comprehensively discuss their strengths and weaknesses.

Water intake accelerates parasympathetic reactivation after high-intensity exercise.

UNLABELLED: It has been shown that water intake (WI) improves postexercise parasympathetic recovery after moderate-intensity exercise session. However, the potential cardiovascular benefit promoted by WI has not been investigated after high-intensity exercise. PURPOSE: To assess the effects of WI on post high-intensity parasympathetic recovery. METHODS: Twelve recreationally active young men participated in the study (22 ± 1.4 years, 24.1 ± 1.6 kg.m(-2)). The experimental protocol consisted of two visits to the laboratory. Each visit consisted in the completion of a 30-min high-intensity [~80% of maximal heart rate (HR)] cycle ergometer aerobic session performing randomly the WI or control (CON, no water consumption) intervention at the end of the exercise. HR and RR intervals (RRi) were continuously recorded by a heart rate monitor before, during and after the exercise. Differences in HR recovery [e.g., absolute heart rate decrement after 1 min of recovery (HRR60s) and time-constant of the first order exponential fitting curve of the HRR (HRRτ)] and in postexercise vagal-related heart rate variability (HRV) indexes (rMSSD30s, rMSSD, pNN50, SD1 and HF) were calculated and compared for WI and CON. RESULTS: A similar HR recovery and an increased postexercise HRV [SD1 = 9.4 ± 5.9 vs. 6.0 ± 3.9 millisecond, HF(ln) = 3.6 ± 1.4 vs. 2.4 ± 1.3 millisecond(2), for WI and CON, respectively; p < .05] was observed in WI compared with CON. CONCLUSION: The results suggest that WI accelerates the postexercise parasympathetic reactivation after high-intensity exercise. Such outcome reveals an important cardioprotective effect of WI.