Many exercisers like to use a heart rate monitor to guide intensity of exercise because it gives them actual numbers that they can follow. Many exercise programs and tests to measure heart function are based on the formula MAXIMUM HEART RATE = 220 – age. This is supposed to predict the fastest your heart can beat and still pump blood through your body. Although this formula is the standard used today, it is not dependable for everyone and it does not apply to very fit people.
Why the Standard Maximum Heart Rate Formula is Wrong
As you age, your maximum heart rate slows down. The standard maximum heart rate formula is supposed to help you predict what your heart rate should be based on your age, but it should not be used by athletes and is not even accurate for people who are not fit.
The formula was first proposed by Dr. Sam Fox, one of the most respected heart specialists in the world. In the 1960s, he was very helpful to me when I was competing in, planning and setting up running programs. In 1970 he was the director of the United States Public Health Service Program to Prevent Heart Disease. He and a young researcher named William Haskell were flying to a meeting. They put together several studies comparing maximum heart rate and age.
Fox took out a pencil and plotted a graph of age versus maximum heart rate and noticed that maximum heart rate appeared to be equal to 220 minus a person’s age. They reported this observation, and ever since then, the formula has been taught in physical education courses and is used to test heart function and athletic fitness and to plan workouts.
The formula is wrong because your legs drive your heart rate; your heart does not drive your legs. Maximum heart rate depends on the strength of your legs, and to a lesser extent, on the strength of your heart. When you contract your leg muscles, they squeeze against the blood vessels near them to pump blood from your leg veins toward your heart. When your leg muscles relax, your leg veins fill with blood, so your leg muscles pump increased amounts of blood toward your heart.
This increased blood fills the heart and causes your heart to beat faster and with more force. This is called the Bainbridge reflex. The stronger your legs, the more blood they can pump. An athlete’s heart is stronger than that of a non-athlete, and a stronger heart can pump more blood with each beat, so the maximum heart rate is likely to be lower in an athlete than in a non-athlete.
The Search for a Better Formula
A study of 43 different formulae for maximum heart rate concluded that “No acceptable formula currently existed” (Journal of Exercise Physiology, 2002;5 (2): 1-10). The formula that fit age better than others is: HRmax = 205.8 – (0.685 x age). It has a standard deviation that is 6.4 beats per minute, which is very large.
Another study from Oakland University in Rochester, Michigan showed that the standard maximum heart rate formula overestimated the maximum heart rate for younger exercisers and underestimated the maximum rate for older ones (Medicine and Science in Sports and Exercise, May 2007).
Maximum Heart Rate is Lower in Athletes
A study from Liverpool, England showed that the maximum heart rate for athletes is usually lower than for aged-matched sedentary people. The maximum heart rate of male athletes was calculated to be 202 – (0.55 x age), and for female athletes, 216 – (1.09 x age). At first glance, this makes no sense because you would think that the faster your heart can beat, the more blood your heart could pump and the better an athlete you would be.
However, a stronger heart pumps more blood with each beat, so stronger hearts don’t have to beat as often. Both weight lifters and runners had similar maximum heart rates, which were significantly lower than those of the age-matched sedentary people. The athletes have hearts that can pump more blood with each beat than the hearts of sedentary people, so they do not have to beat as often (International Journal of Sports Medicine, January 2008).
This means that as you become more fit, your maximum heart rate may go lower, not higher. Virtually everyone agrees that heart rate depends primarily on the amount of blood pumped toward it by exercising muscles (Bainbridge reflex). We know this is true because we are able to transplant hearts. If nerves to the heart primarily regulated heart rate, the heart would not be able to control its rate of beating since the nerves are cut during the transplant.
Use Your Recovery Heart Rate to Measure Fitness
If you want to use numbers to chart your progress in your exercise program, use your recovery heart rate instead of your maximum heart rate. Maximum heart rate is never used to measure fitness. A person with a failing fluttering heart can have a heart rate of 300 beats a minute. Researchers measure fitness by how fast your heart rate recovers one minute after maximum exercise.
A healthy person’s heart rate drops about 20 beats in one minute after all-out exercise, while fit athletes’ heart rates can drop more than 50 beats in one minute. People whose one-minute recovery heart rate dropped less than 12 beats were four times as likely to die in the next six years, compared with those whose heart rates dropped by 13 or more beats (Circulation, 1996; 93: 1520-1526).
What Does This Mean For You?
If you are an athlete who trains for competition, you don’t need a heart rate monitor unless you are obsessed with numbers. All you have to do is a program of interval workouts: two or three times a week, do a series of hard intervals in which you get short of breath, rest to recover, and repeat these intervals until your muscles start to feel heavy. For the rest of your week, try to do a lot of mileage at less than maximum effort.
If you are a non-competitive exerciser, you don’t need a heart rate monitor, either. First, make sure that you have a healthy heart. Then try to do intervals two or three times week. Start out slowly and then pick up the pace until you feel burning in your muscles or you are breathing harder than usual. Then slow down until you have recovered completely. Alternate faster bursts and recoveries until your muscles start to feel heavy and then stop for the day. On the other days, go at a casual and easy pace.
Caution: Check with your doctor before starting a new exercise program or increasing the intensity of your existing program.
Gabe Mirkin, M.D., is a sports medicine doctor and fitness guru. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin has run more than 40 marathons and is now a serious tandem bike rider with his wife, Diana. His website is http://drmirkin.com/. Click to read Gabe’s full bio.