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Karla A. Kubitz and Daniel M. Landers

This study examined the effects of an 8-week aerobic training program on cardiovascular responses to mental stress. Dependent variables included electrocardiographic activity, blood pressure, electroencephalographic (EEG) activity, state anxiety, and state anger. Quantification of indicators of sympathetic, parasympathetic, and central nervous system activity (i.e., respiratory sinus arrhythmia, T-wave amplitude, and EEG activity, respectively) allowed examination of possible underlying mechanisms. Subjects (n = 24) were randomly assigned to experimental (training) and control (no training) conditions. Pre- and posttesting examined cardiorespiratory fitness and responses to mental stress (i.e., Stroop and mental arithmetic tasks). MANOVAs identified a significant effect on cardiorespiratory fitness, heart rate, respiratory sinus arrhythmia, and EEG alpha laterality. The results appear consistent with the hypothesis that enhanced parasympathetic nervous system activity and decreased central nervous system laterality serve as mechanisms underlying certain aerobic training effects.

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Laurent Mourot, Nicolas Fabre, Aldo Savoldelli, and Federico Schena

To determine the most accurate method based on spectral analysis of heart-rate variability (SA-HRV) during an incremental and continuous maximal test involving the upper body, the authors tested 4 different methods to obtain the heart rate (HR) at the second ventilatory threshold (VT2). Sixteen ski mountaineers (mean ± SD; age 25 ± 3 y, height 177 ± 8 cm, mass 69 ± 10 kg) performed a roller-ski test on a treadmill. Respiratory variables and HR were continuously recorded, and the 4 SA-HRV methods were compared with the gas-exchange method through Bland and Altman analyses. The best method was the one based on a time-varying spectral analysis with high frequency ranging from 0.15 Hz to a cutoff point relative to the individual’s respiratory sinus arrhythmia. The HR values were significantly correlated (r 2 = .903), with a mean HR difference with the respiratory method of 0.1 ± 3.0 beats/min and low limits of agreements (around –6/+6 beats/min). The 3 other methods led to larger errors and lower agreements (up to 5 beats/min and around –23/+20 beats/min). It is possible to accurately determine VT2 with an HR monitor during an incremental test involving the upper body if the appropriate HRV method is used.

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David V.B. James, Linda J. Reynolds, and Sara Maldonado-Martin

Background:

Heart rate variability (HRV) has been promoted as a noninvasive method of evaluating autonomic influence on cardiac rhythm. Although female subjects predominate in the walking studies, no study to date has examined the influence of the duration of a moderate intensity walking physical activity bout on HRV in this population.

Methods:

Twelve healthy physically active middle-aged women undertook 2 conditions; 20min (W20) and 60min (W60) bouts of walking on a treadmill. Resting HRV measures were obtained before (−1 h), and 1 h and 24 h after the walking bouts.

Results:

Mean NN interval (ie, normal-to-normal intervals between adjacent QRS complexes) was significantly lower (P = .017) at +1 h in W60 (832, 686−979ms) compared with W20 (889, 732−1046ms). A borderline main effect for time was observed for both the SDNN intervals in W60 (P = .056), and for low frequency (LFabs) power in W60 (P = .047), with post hoc tests revealing a significant increase between −1 h (51, 33−69 ms and 847, 461−1556 ms2) and +1 h (65, 34−97ms and 1316, 569−3042 ms2) for SDNN and LFabs power, respectively, but no increase at +24h compared with −1 h.

Conclusions:

It appears that a walking bout of 60 min duration does alter cardiac autonomic influence in healthy active women, and this alteration is not evident after 20 min of walking. Given the rather subtle effect, further studies with larger sample sizes are required to explore the nature of the changes in cardiac autonomic influence following a prolonged bout of walking.

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Gonzalo Varas-Diaz, Savitha Subramaniam, Larissa Delgado, Shane A. Phillips, and Tanvi Bhatt

primarily reflects cardiac parasympathetic influence due to the respiratory sinus arrhythmia ( Berntson et al., 1997 ). Consistent with our hypothesis, we observed a significant effect of the exergaming-based dance training on HRV values for the experimental group compared with the control group, increasing

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Melissa G. Hunt, James Rushton, Elyse Shenberger, and Sarah Murayama

higher tidal volume ( Omoluabi, 1994 ), has benefits above and beyond simple paced breathing. It is known that both depth and frequency of respiration affect respiratory sinus arrhythmia (RSA), which in turn is a measure of parasympathetic activity. Moreover, there is a linear relationship between tidal

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Joanne Perry, Ashley Hansen, Michael Ross, Taylor Montgomery, and Jeremiah Weinstock

cardiac cycle naturally accelerates and decelerates as a result of these physiological systems ( Khazan, 2013 ). This process is referred to as respiratory sinus arrhythmia (RSA; Khazan, 2013 ). Overall, when these physiological systems (i.e., ANS, RSA, and the baroreflex) are in coherence or “in sync