Heart Rate Variability, Standard of Measurement, Physiological Interpretation and Clinical Use in Mountain Marathon Runners during Sleep and after Acclimatization at 3480 m

Abstract

Fluctuations in autonomic cardiovascular regulation during exposure to high altitude may increase the risk of heart attack during waking and sleep. This study compared heart rate variability (HVR) and its components during sleep at low altitude and after 30-41 hours of acclimatization at high altitude (3480 m) in five mountain marathon runners controlled for diet, drugs, light-dark cycle and jet lag. In comparison to sea level, RR-intervals during sleep at high altitude decreased significantly (P < 0.001). The significant increase in sympathetic autonomic cardiovascular modulation at high altitude protects against excessive oxygen deprivation during sleep. Increases in R-R intervals can require longer periods of acclimatization at 3480 m to mitigate the effects of altitude/hypoxia on sympathetic tone, thus reducing cardiovascular distress at rest during waking and sleep and probably before during and after athletic performance at altitude.

Assessment of Heart Rate Variability during an Endurance Mountain Trail Race by Multi-Scale Entropy Analysis

“…HR varies according to individuals based on several factors, heredity, fitness level, exercise mode (e.g., endurance or resistance training), skill (economy of exercise), environmental (temperature [18], humidity, altitude [19]), state of mood [20] and diet, among others. Nevertheless, while HRV analysis is mainly associated with the prediction of sudden cardiac death [21,22] and with assessing cardiovascular [23] and metabolic illness [24] progression, recent observations have suggested it is also applicable to exercise and training [25].…”

Lucky Rhythms in Orbitofrontal Cortex Bias Gambling Decisions in Humans

“…Specifically, it measures the effects of both parasympathetic and sympathetic systems on the subject32. HRV for each trial was calculated from the variance of the interbeat intervals preceding that trial and was measured through concurrently recorded ElectroCardioGrams (ECG)3334. HRV was found to be significantly correlated with luck ( ρ  = −0.09, p  = 0.039).…”

“…The HRV for each trial was taken over a 5-minute window preceding the show card epoch. This window length is the established standard for HRV recording34. The HRV was normalized within each subject by dividing by the mean HRV across all trials and then by taking the logarithm as HRV distributions are often skewed right.…”

Effect of Cigarette Smoking on Heart Rate Variability in Health Adult Smokers in The Age of 20-60 Years

“…Normalization of LF and HF power tends to minimize the effect of the changes in the total power on the values of these two components. [14] According to research conducted by the Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology, in a time-domain analysis, higher values of the standard deviation of the normal to normal intervals (SDNN), root mean square successive difference (RMSSD), and percentage of adjacent normal R-R intervals 50 ms (pNN50) indicate stronger parasympathetic dominance. Among the frequency-domain measurement indicators, a high frequency (HF) denotes parasympathetic activity, and a low frequency (LF) is related to the activity of both the sympathetic nervous system and the parasympathetic nervous system.…”

“…[13] The parasympathetic influence on heart rate is modulated by acetylcholine released by the vagus nerve on the sinoatrial node and the sympathetic influence by the release of epinephrine and norepinephrine. [14] The HRV is evaluated by two ways: time domain analysis and frequency domain analysis. [15] VLF, LF, HF power are usually measured in absolute values of power (milliseconds squared [ms 2 ]).…”