Heart rate variability in athletes and nonathletes at rest and during head-up tilt

Abstract

The purpose of the present study was to determine if autonomic heart rate modulation, indicated by heart rate variability (HRV), differs during supine rest and head-up tilt (HUT) when sedentary and endurance-trained cyclists are compared. Eleven sedentary young men (S) and 10 trained cyclists (C) were studied. The volunteers were submitted to a dynamic ECG Holter to calculate HRV at rest and during a 70º HUT. The major aerobic capacity of athletes was expressed by higher values of V. O 2 at anaerobic threshold and peak conditions (P < 0.05).At rest the athletes had lower heart rates (P < 0.05) and higher values in the time domain of HRV compared with controls (SD of normal RR interval, SDNN, medians): 59.1 ms (S) vs 89.9 ms (C), P < 0.05. During tilt athletes also had higher values in the time domain of HRV compared with controls (SDNN, medians): 55.7 ms (S) vs 69.7 ms (C), P < 0.05. No differences in power spectral components of HRV at rest or during HUT were detected between groups. Based on the analysis of data by the frequency domain method, we conclude that in athletes the resting bradycardia seems to be much more related to changes in intrinsic mechanisms than to modifications in autonomic control. Also, HUT caused comparable changes in sympathetic and parasympathetic modulation of the sinus node in both groups.

Indirect measures of human vagal withdrawal during head-up tilt with and without a respiratory acidosis

“…During HUT, the mean heart rate was 86 beats min -1 with HF and LF components of 28.6 NU and 63.4 NU respectively J Physiol Sci (2009) 59: 31-36 33 ventilation, as shown by others [23][24][25][26][27]. Also, in the current study, a decrease in HF cardiac variability was shown with HUT, again similar to the findings of others [14,[18][19][20]33]. However, in the present study, when using the HF component as an index of cardiac vagal tone, the expected vagal withdrawal during HUT was reduced when the HF component was already elevated by an increase in ventilation.…”

“…Pagani et al [5] observed significant increases in cardiac variability at low frequencies with HUT, but also reported no correlation between the increases in the LF component and the tilt-induced increase in heart rate. Similarly, higher LF NU during HUT was recorded in trained and untrained subjects [33] but no correlation between time and frequency domain measures were reported. In the current study, the lack of a clear directional change in the LF component of HRV may reflect the small number of subject tested.…”

Autonomic response to exercise as measured by cardiovascular variability

“…4,8,[10][11][12][13]15,17,18,[19][20][21]25,27,[30][31][32][34][35][36]38,39,45,47 The results of 10 articles on ANS response measured during exercise are shown in Table I. Some authors expressed concern about the measurement of spectral analysis of HRV during exercise, while others reported increases (↑), decreases (↓) and no changes in variability indicators (↔) of sympathetic (SNS) and parasympathetic (PNS) influence.…”

Stratification of the level of aerobic fitness based on heart rate variability parameters in adult males at rest

“…The result of the logistic regression model supported the hypothesis that CDR index adequately represents the parasympathetic control of the heart rate, and thus it could be applicable to estimate the positive adaptation to cardiorespiratory fitness (Buchheit et al, 2010;Bucheit & Ginder, 2006;De Meersman, 1996;Martinelli et al, 2005;Moreira et al, 2013;Plews et al, 2013;Yataco, Fleisher, & Katzel, 1997), or the autonomic control of post-exercise heart rate (Martinelli et al, 2005;Moreira et al, 2013;Plews et al, 2013) and the increasing vagal activity (Trevizani, Belchimol-Barbosa, & Nadal, 2012). Therefore, it is possible to speculate that regular aerobic exercise, with enough intensity to cause further increase in VO2max could be evaluated by the CDR index.…”