News Review From Harvard Medical School — More Intense Exercise May Extend Life

July 7, 2015

Working up more of a sweat when you exercise may help you live longer, two new studies find. And for most people more vigorous exercise appears to be safe, a third study suggests. All of the studies focused on middle-aged or older adults. One included more than 204,000 people. Researchers kept track of them for more than 6 years. They were divided into groups based on how much of their exercise was vigorous, such as running, compared with moderate activity, such as brisk walking. Those who said up to 30% of their exercise was vigorous were 9% less likely to die during the study than those who did no vigorous activity. The death rate was 13% lower for those who did more than 30% vigorous exercise. A second study had similar results. The journal JAMA Internal Medicine published both of them. The journal Circulation published the third study, which looked at cardiac arrest risk. Researchers reviewed more than 1,200 cardiac arrests among adults age 35 to 65. Only 5% occurred during vigorous exercise. People who were exercising were more likely to get help quickly and to survive. The journal Circulation published the study. HealthDay News wrote about the first JAMA study and the Circulation study April 6.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor’s Reaction?
We know that some exercise is better than none. But how much more health benefit do we get if we exercise longer or harder or both? Is vigorous exercise better than moderate-intensity exercise? And what’s the risk of dropping dead from vigorous exercise in middle age and beyond?
Three articles published online yesterday provide data to help us answer these questions.
People who don’t exercise now get the greatest health benefits if they do the recommended minimum of:
• 150 minutes per week of moderate-intensity exercise OR
• 75 minutes per week of vigorous exercise
Regularly getting this much exercise can lower the risk of death by 20% over a period of 14 years. That is the conclusion of a study done by Hannah Arem, Ph.D., and her colleagues. JAMA Internal Medicine published the study.
Exercising for up to 3 times the minimum continues to lower your risk of dying. Increasing the amount or intensity of exercise even more may have other health benefits. But this study measured only the risk of dying. So you may not gain any further years of life if you go beyond 7½ hours of moderate-intensity exercise or 3 hours and 45 minutes of vigorous exercise each week.
The researchers also looked at whether too much exercise might be harmful. The answer appears to be no. At least, it appears that a lot of exercise does not increase the risk of dying.
People who exercised 10 times the minimum amount had similar death rates as those who did 3 to 5 times the minimum. Ten times the minimum means more than 3 hours per day of moderate-intensity exercise or more than 1½ hours per day of vigorous exercise.
JAMA Internal Medicine also published a second related article online. Researchers in Australia looked at the potential extra benefits of vigorous exercise in adults 45 to 75 years of age. This study also looked at death risk. Results of their study showed a reduced risk of death for people who did more vigorous exercise compared with those who did only moderate exercise.
The journal Circulation published the third article. It provides some reassurance about the very low risk of middle-aged adults suddenly dropping dead while exercising. The study also showed that the chance of surviving a cardiac arrest (when the heart stops beating) is much greater during exercise than at other times. The likely reasons:
• People tend to exercise with or around other people.
• If you exercise regularly, your body can survive longer without your heart beating than if you don’t exercise.
What Changes Can I Make Now?
If you don’t exercise now, the best thing you can do is to get started. Exercise improves multiple body functions:
• The heart becomes more efficient at pumping blood.
• The lungs move oxygen into the blood stream faster.
• Blood vessels deliver the oxygen to tissues throughout the body with ease.
• Muscles get stronger.
• The body’s cells respond better to insulin. This helps to keep blood sugar levels from rising.
Do you have any health factors that increase your risk of heart disease? If you do, take action to improve them. In the study in Circulation, most of the people who had a cardiac arrest during exercise had a higher than average risk of heart attack. They had one or more of these risk factors:
• A family history of heart disease at an early age, younger than 55 for men or younger than 65 for women
• Smoking
• High LDL cholesterol
• High blood pressure
• Diabetes
Once you start exercising, don’t ignore symptoms that might be caused by heart disease. Chest pain is just one of the symptoms. Sometimes you might have little or no chest pain. You might just:
• Feel faint
• Break out in a cold sweat
• Get unexpectedly short of breath
• Feel pain in the jaw or arm
If this happens, stop exercising right away. Call your doctor for advice. And don’t test yourself to see if it will happen again.
What Can I Expect Looking to the Future?
Recent studies suggest that vigorous exercise might offer the greatest health benefits. For most people, though, it’s difficult and exhausting to exercise at high intensity for more than a few minutes.
Instead, consider interval training. You can start with bursts of high-intensity exercise for 10 to 15 seconds only. Then go back to moderate intensity. For example, if you walk or jog, speed up for short bursts every few minutes. Then resume your prior pace.

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