When a doctor prescribes medicine, he gives a precise dose calculated to maximize the health benefits while minimizing any side effects. Similar to medicine, we know that exercise is good for our health; it reduces the risk of developing chronic disease and prolongs our life. In fact, the U.S. Centers for Disease Control estimates that more than 8 percent of people in the U.S. over age 40 die as a result of too little exercise.
But exactly how much exercise is enough to maintain our health? And is there such a thing as too much exercise?
Two new studies published in recent months shed light on these questions. It’s important to note that both studies show correlations between exercise and life expectancy, not causation. This means the studies have found a link between activity levels and longevity, but do not demonstrate a direct cause-and-effect relationship.
The first study, published in August in the Mayo Clinic Proceedings, used data from the Copenhagen City Heart Study, which has been collecting data on health and exercise from Danish adults since the 1970s. For this particular analysis, researchers chose more than 8,500 participants who had enrolled in the study in the 1990s and checked to see how many of them had since died. (About half had passed away.)
Researchers found that participants who had reported exercising between 2.6 and 4.5 hours a week were 40 percent less likely to have died than those who exercised less than 2.6 hours a week, or about 30 minutes a day.
Surprisingly, participants who exercised more than 4.5 hours a week were no more likely to live longer; and those who exercised for more than 10 hours a week, or about 90 minutes most days, were more likely to have died than those who exercised more moderately.
The second study, published this month in the Journal of the American Medical Association Network Open, used data from the Coronary Artery Risk Development in Young Adults study. Researchers followed more than 2,000 American participants in their 40s, who completed medical tests and wore an activity tracker for a week. More than 10 years later, the researchers returned to these participants to find out how many had died.
A total of 72 participants from the original group had died, at relatively young ages compared to the national average. Not surprisingly, participants who took fewer steps were more likely to die early. But researchers were surprised by exactly how many steps were required to boost longevity.
The U.S. Centers for Disease Control recommends healthy adults walk 10,000 steps a day, which is about five miles for most people. But in this study, 7,000 steps seem to be the magic number. (Those who walked at least 7,000 steps each day lowered their risk of dying.) And taking more than 10,000 steps a day did not improve participants’ chances of living longer.
The take-home message: These two studies seem to identify an ideal amount of daily exercise for prolonging your life: about 30 minutes or 7,000 steps a day. Exercising less than that amount may be correlated with a shorter lifespan. But exercising more than that may not provide any additional benefits.
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