The resting heart rate of the body (commonly called RHR) is the number of contractions of the heart that occur in a single minute while the body is at complete rest. This number will vary depending upon the age, gender, and general health of a person. There will also be a large different in the resting heart rate of athletes when compared to non-athletes. In general terms the resting heart rate of a person is a strong indicator of that person's basic level of fitness. The strength of the heart can be measured simply by taking the resting heart rate into account.