What is resting heart rate?

Resting heart rate is defined as the number of heartbeats per minute while the body is at rest. This measurement is an important indicator of cardiovascular fitness and overall health. A lower resting heart rate generally suggests a higher level of cardiovascular fitness, as the heart does not have to work as hard to maintain adequate blood circulation when the body is not under stress or exertion.

When considering the other options, they pertain to different contexts of heart rate measurement. The measurement during intense exercise captures the body's response to physical exertion and is not reflective of resting conditions. Counting total heartbeats over a 24-hour period provides an aggregate of heart activity but does not focus specifically on the resting state. Lastly, averaging heart rates over several hours of activity emphasizes the influence of exercise and movement, rather than the pure rest state that the resting heart rate signifies. Thus, option A accurately describes the concept of resting heart rate.