When it comes to exercise there is a “Goldilocks Effect.” That’s the latest word from two new studies that suggest an ideal dose of exercise for a long life is more than most people get, but less than you might expect.

The studies — published in the journal JAMA Internal Medicine — also found that prolonged or intense exercise is not harmful and may in fact add years to people’s lives, The New York Times reports.

In one study, researchers with the National Cancer Institute, Harvard University, and other institutions tracked the exercise habits of more than 661,000 adults, most of them middle-aged and compared 4 years’ worth of death records for the group.

The results showed:

• Those who did not exercise at all were at the highest risk of early death.
• Those who worked out even a little bit without meeting federal recommendations — to get at least 150 minutes of vigorous exercise each week — still lowered their risk of premature death by 20 percent.
• Those who met the guidelines precisely greater longevity — having a 31 percent less risk of dying during the 14-year period compared with those who never exercised.
• Those who tripled the recommended level of exercise — working out moderately, mostly by walking, for 450 minutes per week, or a little more than an hour per day — were 39 percent less likely to die prematurely than people who never exercised.

The second study examined health records, exercise habits, and mortality rates for more than 200,000 Australian adults. As with the first study, researchers found that meeting the exercise guidelines substantially reduced the risk of early death, even if someone’s exercise was moderate, such as walking. But those who engaged in even occasional vigorous exercise gained a small but not unimportant additional reduction in mortality, while those who engaged in more intense workouts or longer workouts had the biggest benefits.

The take-home message: Most people should aim for “at least 150 minutes of physical activity per week and have around 20 to 30 minutes of that be vigorous activity,” says Klaus Gebel, a senior research fellow at James Cook University in Cairns, Australia, who led the second study.