Autonomic response to exercise as measured by cardiovascular variability

Abstract

Heart rate variability (HRV), blood pressure variability (BPV) and baroreceptor sensitivity (BRS) are often used as measures of autonomic activity, even though reported results are not always comparable or as expected. It is known that endurance athletes have lower average resting heart rates than non-exercising individuals. 33,50 However, other exercise-induced autonomic influences on cardiac control are far more controversial.Autonomic control via sympathetic and parasympathetic modulation of the heart has been assessed by power spectral analysis of HRV 1,7,33,41,46,48,50 and BPV. 44,52 Different frequency peaks reflect specific physiological stimuli and it is possible to estimate the involvement of the autonomic nervous system (ANS) influence and balance in heart rate (HR) regulation. Method. An Ovid MEDLINE Database search for the period 1950 -March 2008 produced 46 articles for review. The published articles that evaluate the effect of exercise on the autonomic nervous system (ANS) are summarised in three categories: the response of the ANS during a bout of exercise, directly after exercise (recovery measurements), and after a long-term exercise programme. Results.Articles on the effect of training on the ANS as measured by cardiovascular variability indicators show increased variability, decreased variability, and no change in variability. Conclusion.Findings in this review emphasise that standardisation and refinement of these measuring tools are essential to produce results that can be repeated and used as reference. Standardisation is essential as these measurements are increasingly employed in studies regarding investigations of central autonomic regulation, those exploring the link between psychological pro cesses and physiological functioning, and those indicating ANS activity in response to exercise, training and overtraining. This review shows that important aspects are inter-individual differences, duration and intensity of the exercise programme, and choice and specific implementation of variability analysis techniques. CoRREspondEnCE:Mrs C C Grant Section Sports Medicine University of Pretoria Tel: 27 12 3624496 Fax: 27 12 3623369 E-mail: Rina.Grant@up.ac.za and also gives an indication of respiratory sinus arrhythmia (RSA). 1,48During measurement of systolic BPV the LF peak corresponds with sympathetic activity while the HF peak is determined by mechanical effects of respiration on intrathoracic pressure and cardiac filling. 44,52 The variability in blood pressure and identification of the corresponding physiological stimuli are difficult to identify. Indications are that the very low frequencies (≤0.04 Hz) are influenced by vascular tone, endothelium factors and thermoregulation, and the LF peak (0.07 -0.15 Hz) relates to sympathetic activity and represents vasomotor tone.2 BRS reflects mainly vagal modulation of the HR by the arterial baroreceptors and the magnitude of response in heart beat interval to a change in blood pressure (ms/mmHg). 6Physical exercise requires rapid and complex physio...

The contribution of preintervention blood pressure, VO2max, BMI, autonomic function and gender to exercise-induced changes in heart rate variability

“…Heart rate variability (HRV) as an indicator of exercise-induced changes in autonomic cardiac regulation shows wide interperson SDs, as well as inconsistent study results 1 2. Vesterinen et al 3 recently reported unexplained individual adjustments in performance ability as measured by VO 2 max after exercise training.…”

“…In the case of HRV quantification, technical aspects such as length and period of sampling times, choice of analytical techniques and non-standardisation of the populations investigated may play a role 1 4. However, little is known about the influence of preintervention physiology and genetic influence on autonomic cardiac changes, as measured by HRV, in response to exercise adaptation 4…”

The effect of exercise and lifestyle interventions on heart rate variability in students at risk of cardiovascular disease –A pilot study

“…Differing methodology and confounding factors in the studies make comparison difficult (Grant et al, 2008). The one common factor in studies showing improved HRV (increased vagal dominance) was exercise of moderate intensity (Buchheit et al, 2004;Iwasaki, Zhang, Zuckerman & Levine, 2003;Tulppo et al, 2003).…”

“…Abbreviations are commonly used to denote these calculations: SDNN -standard deviation of all N-N intervals, RMSSD -the square root of the mean of the sum of the squares of differences between adjacent N-N intervals and pNN50 -the number of interval differences of successive N-N intervals greater than 50ms divided by the total number of N-N intervals. The pNN50 and RMSSD represent parasympathetic modulation of the sino-atrial node (Grant & Ker, 2008;Stein et al, 1999). Frequency domain analysis quantifies the variance (power) in the rhythm of the heart rates periodic oscillations, by grouping them into frequency bands viz.…”

“…Normalized LF power (LF nu) is calculated LF/LF+HF and reflects primarily sympathetic modulation of the heart rate, normalized HF power (HF nu) equals HF/LF+HF and represents vagal control. The LF/HF ratio reflects sympathovagal balance; an increase in the ratio suggests an increase in sympathetic modulation and a decrease, parasympathetic or both (Grant & Ker, 2008;Stein et al, 1999).…”