Abstract
Variability of minimum heart rates per minute in high school students were studied. There were 50 subjects selected from the ECG screening tests, and all of these tracings were within normal limits. In these subjects ECGs of 24 hours from 9 to next 8 o'clock were recorded and minimum heart rates per minute were calculated. Minimum heart rates per minute ranged from 45 to 80. The heart rate was lowest in the midnight, especially from 2 to 5 o'clock. These results suggest that, minimum heart rates per minute were affected by the circadian rhythm.
