Why does pulse fluctuate during the day?

Answer 1

The heart beats at different rates depending on whether your body is at rest or at work. When resting, the heart rate beats an average of 72 times per minute for high school students and an average of 85 BPM for middle school students. During strenuous physical activity, your heart rate or pulse increases, sometimes to twice or more its resting rate. Your stroke volume, the amount of blood pumped for each heartbeat, also increases. This is because the muscles that are working demand more blood to supply them with oxygen and other nutrients.