In talking recently about exercise and the heart, a really weird question came up. Sometimes those are the best questions, aren’t they?
Exercise makes the heart beat faster; so why doesn’t exercise wear the heart out faster? Why don’t you run out of heartbeats sooner if you spend a lot of time exercising?
After all, the heart has a lot of moving parts – heart valves, blood vessels and muscle. These presumably wear out, like anything else, kind of like the 100,000-mile powertrain warranty on your car. After the warranty expires, you’re on your own.
So you exercisers watch out, you might just shake something loose! Actually the heart is an absolute wonder of durable construction and lasts an astounding number of beats.
Let’s play with some numbers. How many beats do we get in a lifetime? If an individual averages 80 beats per minute, that’s 4,800 beats per hour, 115,200 beats per day, and more than 42 million per year, which calculates to roughly 3 billion if you live to age 72.
When you think about them that way, heartbeats are the most precious commodity on the planet. Hate to waste ‘em.
Assume a really compulsive 40-year-old exerciser does something strenuous and aerobic five days a week for 30 minutes. He will drive his heart rate up to 160 beats per minute (220 – your age is maximum heart rate and we like to exercise at 65 to 85 percent of that).
The math works out to an extra 2,400 heartbeats on your exercise days. That is a 2 percent increase in heartbeats per day for those who are keeping count.
But exercisers have slow heart rates – not in the first week, but after a month or two. Let’s assume exercise brings your resting pulse down from 80 to 60 beats a minute, a pretty reasonable goal.
The 72-year-old at the 60-pulse rate uses only 2.2 billion heartbeats. To put it another way, to use up 3 billion heart beats, at a pulse rate of 60, you have to live to age 95. Startling, isn’t it?
But lower pulse rate isn’t the whole story because your heart is living tissue, not a car. That’s a subtle distinction I know, but one that comes up every day in medical practice.
A mechanic comes in with a cut hand that requires sutures. He thanks me for fixing it and I usually say, “you’re doing the hard part, I just got it pushed together. You are healing it.”
A mechanic has to fix your car engine 100 percent or it won’t run properly. Cars can’t heal themselves, but people can.
Using your heart’s muscle makes it strong. You don’t wear tissue out by using it; you wear it out by not using it. So invest as little as 15 minutes a day in exercise and you will extend your warranty for more trouble-free years of body ownership.
Get that pulse down to 50 and it takes 105 years to use up 3 billion heartbeats.
Donald Bucklin, MD (Dr. B) is a Regional Medical Director for U.S. HealthWorks and has been practicing clinical occupational medicine for more than 25 years. Dr. B. works in our Scottsdale, Arizona clinic
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