Analysis of Heart Rate Variability between Rest and Exercise States in Hypoxic Environment Using Fuzzy Measure Entropy

This study aimed to employ the recently developed fuzzy measure entropy (FuzzyMEn) method to compare the difference in heart rate variability (HRV) between rest and exercise states in hypoxic environment. Four healthy male volunteers were enrolled in this study. For each subject, electrocardiography (ECG) and finger pulse were recorded in ten days to obtain the heart rate (HR) time series. For each day, the measurement lasted 150 min and was divided into six consecutive experimental sections: 3 repeat rest sections (each 30 min) and 3 repeat exercise sections (each 20 min). The repeat rest and repeat exercise sections were in turn. In each rest or exercise section, the segment of HR time series from the second 5 min episode (from the 6th min to the 10th min) was selected for the FuzzyMEn calculation. The effects of subject, day, repeat measurement and state (rest or exercise) on the FuzzyMEn were investigated. The mean FuzzyMEn differences among ten days and between rest and exercise states were also analyzed. Results showed that day and state factors have significant effects on FuzzyMEn (both P