When you were a child, your heart was smaller than it is as an adult. According to the National Council on Strength and Fitness, you also had lower blood volume and each beat of your heart moved less blood through the body. That is why children usually have higher heart rates than adults. When you grow older, your cardiovascular system continues to change and your working heart rate slows down.
One tool you can use to calculate the intensity of your workout is your heart rate. The 220 minus age formula began in the 1970s when physicians from the U.S. Public Health Service’s Program on Heart Disease needed to provide a guideline for seriously ill heart patients to monitor their exercise intensity. The formula was never meant to take the fitness world by storm. But it was a simple formula that people could easily work out in their heads. Over the past 40 years, the formula has been programmed into heart rate monitors, posted on gym walls, recorded into fitness DVDs and written in health textbooks.
For men, a simple formula for calculating your maximum heart rate is to subtract your age from 220. If you are 70 years old, this formula would tell you your MHR is 150 beats per minute. Women should use a slightly different calculation based on a 16-year study that tracked women working out on the treadmill. It was found that women were at higher risk for heart events by working out at the old MHR. Subtract 88 percent of your age from 206 and aim to stay within 65 to 85 percent of your MHR.
If you are looking for a slightly different formula to calculate your MHR, try multiplying your age times 0.7 and subtracting that number from 208. This formula was developed by Dr. Douglas Seals and published in 2001, and it provides a much higher MHR for seniors. If you prefer to avoid the math, you can also gauge your work level by your ability to talk: at a moderate intensity you should be able to talk easily but not sing. At a high intensity, you should be able to say a few words at a time, and not be gasping for breath.
As you age, the walls of the left ventricle grow thicker. According to the National Institute on Aging, this increase may help the heart cope with increased stress, like pumping blood through harder blood vessels. An older heart tends to pump more blood per stroke than a younger one to compensate for its slower rhythm, but even though its stroke volume is higher, it can’t circulate as much blood as it did when it was young.
Although maximum heart rate does tend decline with age, there is a large variability between people. A highly-trained athlete may have a low resting heart rate that immediately jumps over 200 when he starts exercising. Exercise physiologist Dr. Fritz Hagerman of Ohio University found that the maximum heart rates of Olympic rowers ranged from 220 to 160 bpm.