When you relax, your heart beats about 60 to 80 times a minute. (On average, a man’s heart beats 70 times per minute and a woman’s beats 75 times per minute.) If you’re an athlete or a fitness geek, the training you do improves your heart’s efficiency and helps it pump more blood with each beat. As a result, your resting heart rate may drop as low as 40 to 60 beats per minute.
If you’re older and out of shape, your heart may be gradually weakening. To keep up with the demands of your body, it may beat faster, increasing your resting heart rate to closer to 100 beats per minute. A heart rate like this is a hallmark of poor fitness and a flashing danger sign of heart trouble ahead. Studies show that a high resting heart rate goes hand-in-hand with a higher risk of heart attack, especially later in life. That said, there’s a healthy amount of natural variation in each person’s heart rate. So even if yours clocks in at 60 beats per minute and your friend’s sets a quicker pace of 75 beats per minute, you can’t assume that your heart is the superior specimen.
Unless your heart rate seems unnaturally fast or unnaturally slow, you’re unlikely to give it much thought. Tracking your heart rate during exercise, however, is worthwhile, because it tells you how hard your heart is working. You can use this information to make sure you get the most out of your cardio workouts.
Source of Information : Oreilly - Your Body Missing Manual