Heart rate variability and autonomic activity at rest and during exercise in various physiological conditions

Abstract

The rhythmic components of heart rate variability (HRV) can be separated and quantitatively assessed by means of power spectral analysis. The powers of high frequency (HF) and low frequency (LF) components of HRV have been shown to estimate cardiac vagal and sympathetic activities. The reliability of these spectral indices, as well as that of LF/HF ratio as a marker of autonomic interaction at rest and during exercise, is briefly reviewed. Modifications in autonomic activities induced by different physiological conditions, e.g. hypoxia exposure, training, and water immersion, have been found in HRV power spectra at rest. The changes in HF and LF powers and in LF/HF ratio observed during exercise have been shown not to reflect the decrease in vagal activity and the activation of sympathetic system occurring at increasing loads. HF peak was recognised in power spectra in the entire range of relative intensity, being responsible for the most part of HR variability at maximal load. LF power did not change during low intensity exercise and decreased to negligible values at medium-high intensity, where sympathetic activity was enhanced. There was no influence from factors such as fitness level, age, hypoxia, and blood distribution. In contrast, a dramatic effect of body position has been suggested by the observation that LF power increased at medium-high intensities when exercising in the supine position. The increased respiratory activity due to exercise would be responsible of HF modulation of HR via a direct mechanical effect. The changes in LF power observed at medium-high intensity might be the expression of the modifications in arterial pressure control mechanisms occurring with exercise. The finding of opposite trends for LF rhythm in supine and sitting exercises suggests that different readjustments might have occurred in relation to different muscular inputs in the two positions.

Autonomic modulation of heart rate of young and postmenopausal women undergoing estrogen therapy

“…Previous studies in young (32) and middle-aged subjects (32,33) have demonstrated alterations in HRV indices due to postural changes. Other investigators have reported that these changes lose their statistical significance with advancing age (34,35). The cross-sectional design of this study is a limitation, since the characteristics of the autonomic control of HR in postmenopausal women prior to the use of estrogen therapy were not known.…”

Correlation of retinal neurodegeneration with measures of peripheral autonomic neuropathy in type 1 diabetes

“…Assessment of HRV is a standardized, non‐invasive method for quantification of autonomic function and thus recommended for the evaluation of subclinical and manifest CAN in diabetes (Pumprla et al. 2002; Perini & Veicsteinas 2003; Spallone et al. 2011).…”

Parameters of Autonomic Nervous System Dysfunction in Acute and Chronic Forms of Ischemic Heart Disease

“…Therefore, the LF/HF ratio reflects the balance of the autonomic nervous system. Perine et al [9] examined these parameters in healthy people during exercise, at a controlled respiration, and changes of body position. The authors believe that spectral parameters do not reflect increase of sympathetic and decrease of parasympathetic contribution during exercise.…”

“…Different mechanisms of arterial pressure control are likely to be involved in these situations. LF are known to be partly caused by the activity of baroreflex when the rate of cardiac contraction is decelerated if pressure in the aorta increases [9]. Billman [12] shows in his work that it is impossible to physiologically interpret this common index.…”