| Author: | Kan, Wai-yee |
| Title: | The relationship of heart rate variability and physical stress in healthy adults |
| Degree: | M.Sc. |
| Year: | 2009 |
| Subject: | Hong Kong Polytechnic University -- Dissertations. Heart beat -- Measurement. Physical fitness. Exercise -- Physiological aspects -- Research. |
| Department: | School of Nursing |
| Pages: | xxi, 143 p. : ill. ; 30 cm. |
| Language: | English |
| Abstract: | Aim: The aim of the present investigation is to examine cardiac autonomic modulation, as measured by heart rate variability (HRV), after stress exercise of two different intensities and recovery of two different postures in order to provide a clearer picture of HRV changes after exercise and prescribe a safe and effective exercise programme for enhancement of cardiovascular health. Design: The study used a cross-sectional, two-way factorial design in which 48 Chinese healthy university students were recruited. The study was composed of three sessions: pre-exercise, exercise and post-exercise. HRV recordings were obtained during a supine 5-min period before exercise and during one hour of post-exercise recovery. Participants were assigned into four groups: low intensity exercise with recovery in a supine resting posture, low intensity exercise with recovery in a sitting upright posture, high intensity exercise with recovery in a supine resting posture, high intensity exercise with recovery in a sitting upright posture and engaged in a 15 minutes symptom-limited graded exercise test on the treadmill. Results: The results were quite provocative and suggested the possible cardioprotective effects of cardiac vagal regulation were diminished for a high intensity exercise of 400kcal of short duration and the vagal outflow was increased for a low intensity exercise of 240kcal, especially when recovering with in a supine resting posture. The results showed that post-exercise cardiac autonomic kinetics is intensity dependent. The overall variability represented by the standard deviation of all NN intervals (SDNN) and total power (TP), which were increased in low intensity exercise compared to high intensity exercise. Moreover, the markers of vagal modulation, Square root of the mean of the sum of squares of difference between adjacent filtered NN intervals (RMSSD) and normalized high frequency (HFnu) presented in the high intensity exercise group suggested a reduced vagal outflow to the heart while highly increased within the low intensity exercise group especially in supine resting recovery posture. The sympathetic systems represented by normailized low frequency (LFnu) was persistently increased in post-exercise 60min after high intensity exercise. Conclusion: HRV profiles were associated with low intensity exercise of 240kcal, with a supine resting posture, showing a better cardioprotective effect. |
| Rights: | All rights reserved |
| Access: | restricted access |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| b23018823.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 2.45 MB | Adobe PDF | View/Open |
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