During rapid, high-intensity exercise, your muscles use large amounts of energy in the form of a compound called adenosine triphosphate, or ATP. To allow you to keep working out, ATP stores must be replenished quickly.
Most adults have a resting heart rate of 60-100 beats per minute (bpm). The fitter you are, the lower your resting heart rate is likely to be. For example, athletes may have a resting heart rate of 40-60 bpm or lower. You should contact your GP if you think your heart rate is continuously above 120 bpm or below 40 bpm, although this could just be normal for you.
1 The resting adult heart rate is normally 60 to 100 beats per minute. 2  Athletes or people on certain medications may have a lower resting normal rate. 3  The normal heart rate for children aged 1 to 8 years is 80 to 100 beats per minute. 4  The normal heart rate for infants age 1 to 12 months is 100 to 120 beats per minute. The normal heart rate for children aged 1 to 8 years is 80 to 100 beats per minute. 2  The normal heart rate for infants age 1 to 12 months is 100 to 120 beats per minute.