When you sleep, your heart rate works in a cyclical variation. This variation ranges from a minimal heart rate of 63 bps to a maximum of 67 bps, according to a study by researchers at the University of Cape Town in South Africa, and published in a 2003 issue of "Journal of Sports Medicine." Physical fitness and well-being have yet to be determined as variables that influence a significant change in heart rate cyclical variation.
Cyclical Variation of Heart Rate
Cyclical variation of heart rate describes an increase and decrease of your heart rate stages. Some factors include sudden arousal, also called apneas, or hypopneas -- the suspension of abnormal breathing and overly shallow breathing, respectively. It represents why you may have repeated autonomic arousals, even when you sleep. However, the clinical significance of these arousals in daytime sleepiness remains unknown.
Heart Rate Arousals
Heart rate arousals during sleep occur for several reasons; some cannot be explained. For example, a change in your EEG levels, electric activity present along the scalp, can represent one valid occurrence. There must be a specific amount of activity over a certain threshold for you to have an arousal for "no apparent reason," according to a study published in a 2007 issue of "Computers in Cardiology." When respiratory events leading to arousal occur, they cause a sharp rise in your heart rate when you awaken. When you fall asleep once more, your heart returns to normal, causing a new cycle to begin.
Training Status and Sleep
As you exercise regularly, you may notice a shift in your heart rate, which can lead to your heart performing at an optimal level. The "Journal of Sports Medicine" study found that subjects, which self-reported physical activity and average sleep time, ranging from four to 12 hours per week, and 5.5 to nine per night, respectively, had minimal heart rates ranging between 36 to 65 bpm, and maximum heart rates varying between 82 to 116 bpm.
Heart Rate Pattern Findings
The "Computers in Cardiology" study concluded that an adult's cyclical variation of heart rate is frequent and easily quantifiable. An average of 60 events occurred, with the average heart rate increasing by 7 to 8 bpm, and the cyclical variation averaging 16 bpm. This finding suggests there is periodic activity activating the autonomic nervous system during sleep.
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