Habitual physical activity and heart rate variability in 12-year old children
ABSTRACT Wennman, Heini 2012. Habitual physical activity and heart rate variability in 12-year old children. Department of Biology of Physical Activity, University of Jyväskylä, 92p. The study of heart rate variability (HRV) provides useful information about the function of the cardiac autonomic nervous system. The effects of many environmental factors on HRV are well known, but the associations between physical activity (PA) and HRV, especially in children, are less investigated. Higher HRV is related to health and many pathologic conditions are associated with reduced HRV. Exercise causes HRV to diminish, but improves HRV in long term. PA promotes many health related changes in energy metabolism, aerobic fitness and body composition in children and adults. The recommended minimum level of PA in children is 60 minutes of moderate- to vigorous intensity activity per day. There have been promising results that a high level of daily PA has beneficial effects on resting HRV but also many controversial findings exist. The aim of this study was to measure habitual PA and HRV in 12-year old children (n=28), and to investigate the relationship between the amount and intensity of PA, and, cardiac autonomic functions. Study population consisted of normal weight, Finnish boys and girls. PA and HRV were measured for three consecutive days. It was hypothesized that high PA level during the day would cause higher heart rate (HR) and less HRV the following night. The result of the study was that there was no consistent, clear relationship between habitual PA and nocturnal HRV. However, a dose-response kind of relationship was observed between habitual PA and daytime HRV. There was a significant variation in HRV between the three days, but no significant differences between the nights. The associations between PA and HRV observed might be sporadic but give a hint about a possibly existing relationship. Future studies with more subjects and longer periods of measurements can perhaps clarify the association between PA and HRV in children. Key words: Heart rate variability, habitual physical activity, heart rate, children, health. ...
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