Americans as a whole don’t exercise enough—at least that’s what the latest studies show—and so the message is clear: get more active, take walks, Let’s Move! Basically anything is better than sitting on the couch. But how much exercise is enough? That’s a hotly debated question for which experts still don’t have a satisfactory answer. But given that most of us are starting from a sedentary position, the assumption has long been the more the better. 
 
 But in a report published Monday in the Journal of the American College of Cardiology researchers from Denmark say that people who push their bodies too hard may essentially undo the benefit of exercise. Those who ran at a fast pace more than four hours a week for more than three days a week had about the same risk of dying during the study’s 12-year follow up as those who were sedentary and hardly exercised at all. The link held even after the researchers accounted for potentially confounding factors such as age, sex, whether the participants had a history of heart disease or diabetes, or whether they smoked and drank alcohol. 
 
 MORE This Is How Much Exercise Experts Really Think You Need 
 
 In fact, those with the lowest risk of dying during the study period were people who ran less than three times a week for one to 2.4 hours, at a slow to moderate pace. Even people who ran slightly more, for 2.5 hours to four hours a week at an average pace less than three times a week, showed slightly higher mortality risk, at 66%, something that came as a surprise to the authors. 
 
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 “I would expect the light joggers to have really low risk,” says Jacob Marott, a researcher at the Copenhagen City Heart Study at Frederiksberg Hospital and one of the study’s co-authors. “But regarding the moderate joggers, I was a little surprised they didn’t have a bigger benefit from jogging than the light joggers. It made me think that if it’s really true, then exercise recommendations should take that into account.” 
 
 MORE It Doesn’t Matter How Much You Exercise If You Also Do This 
 
 What Marott and his team found was that both too little running and too much running are linked to higher rates of death. The most intense runners ended up with a risk of dying that was similar to that of those who opted to stay on the couch. Somewhere in between is the Goldilocks amount that’s just right to maintain heart health, burn off excess calories and keep blood sugar levels under control. And according to his results, that sweet spot is closer to the ‘less’ side of the curve than the ‘more’ side. 
 
 That dovetails with the mounting research that so-called micro-workouts—high intensity but brief workouts that could be as short at 1 minute, according to another recent paper—may be better for the body than long and continuous workouts. 
 
 That still means that some exercise is better than no exercise, but scientists may be getting more sophisticated about understanding that more isn’t always better, and that there may be a tipping point at which the harms of running start to outweighed its benefits. 
 
 Those negative effects might include things like changes in the structure and function of the heart and its vessels; previous studies showed that marathoners and long distance cyclists, for example, tend to be at higher risk of developing abnormal heart rhythms, and may be more vulnerable to enlarged hearts, which are less efficient at pumping blood and delivering oxygen and removing waste than normal-sized organs. 
 
 MORE Short Bursts of Exercise Are Better Than Exercising Nonstop 
 
 Marott acknowledges that it’s also possible that some other behaviors or factors common to avid runners, such as their exposure to the sun, which can increase their risk of skin cancer, might be explaining their higher risk of dying during the study. Other studies will have to investigate whether that’s the case, but in the meantime, Marott says “if you want to do something good for yourself, you don’t have to be extreme. Jogging one to four hours a week for no more than three days a week at a slow to moderate pace is actually achievable. And that’s a positive take-home message.” 
 
 Read next: 7 Reasons Why You’re Working Out and Still Not Losing Weight 
 
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 Contact us at editors@time.com. ||||| Running for only a few minutes a day or at slow speeds may significantly reduce a person's risk of death from cardiovascular disease compared to someone who does not run, according to a study published today in the Journal of the American College of Cardiology. 
 
 Exercise is well-established as way to prevent heart disease and it is component of an overall healthy life, but it is unclear whether there are health benefits below the level of 75 minutes per week of vigorous-intensity activity, such as running, recommended by the U.S. government and World Health Organization. 
 
 Researchers studied 55,137 adults between the ages of 18 and 100 over a 15-year period to determine whether there is a relationship between running and longevity. Data was drawn from the Aerobics Center Longitudinal Study, where participants were asked to complete a questionnaire about their running habits. In the study period, 3,413 participants died, including 1,217 whose deaths were related to cardiovascular disease. In this population, 24 percent of the participants reported running as part of their leisure-time exercise. 
 
 Compared with non-runners, the runners had a 30 percent lower risk of death from all causes and a 45 percent lower risk of death from heart disease or stroke. Runners on average lived three years longer compared to non-runners. Also, to reduce mortality risk at a population level from a public health perspective, the authors concluded that promoting running is as important as preventing smoking, obesity or hypertension. The benefits were the same no matter how long, far, frequently or fast participants reported running. Benefits were also the same regardless of sex, age, body mass index, health conditions, smoking status or alcohol use. 
 
 The study showed that participants who ran less than 51 minutes, fewer than 6 miles, slower than 6 miles per hour, or only one to two times per week had a lower risk of dying compared to those who did not run. DC (Duck-chul) Lee, Ph.D., lead author of the study and an assistant professor in the Iowa State University Kinesiology Department in Ames, Iowa, said they found that runners who ran less than an hour per week have the same mortality benefits compared to runners who ran more than three hours per week. Thus, it is possible that the more may not be the better in relation to running and longevity. 
 
 Researchers also looked at running behavior patterns and found that those who persistently ran over a period of six years on average had the most significant benefits, with a 29 percent lower risk of death for any reason and 50 percent lower risk of death from heart disease or stroke. 
 
 "Since time is one of the strongest barriers to participate in physical activity, the study may motivate more people to start running and continue to run as an attainable health goal for mortality benefits," Lee said. "Running may be a better exercise option than more moderate intensity exercises for healthy but sedentary people since it produces similar, if not greater, mortality benefits in five to 10 minutes compared to the 15 to 20 minutes per day of moderate intensity activity that many find too time consuming." 
 
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 The American College of Cardiology is a 47,000-member medical society that is the professional home for the entire cardiovascular care team. The mission of the College is to transform cardiovascular care and to improve heart health. The ACC leads in the formation of health policy, standards and guidelines. The College operates national registries to measure and improve care, provides professional medical education, disseminates cardiovascular research and bestows credentials upon cardiovascular specialists who meet stringent qualifications. For more information, visit Cardiosource.org/ACC
– It's common knowledge that a healthy person shouldn't sit around all day, but new research on running is emphasizing the opposite danger. Running too much can be just as bad for you as being sedentary, the study suggests. Researchers tracked some 1,100 healthy runners and 413 sedentary folks over a period of more than 12 years, HealthDay reports via Medical Xpress. People ranged in age from 20 to 95. The risk of dying during the study turned out to be approximately the same among heavy runners—those who ran quickly more than three days a week for a total of more than four hours—and sedentary people who rarely exercised, Time reports. The best plan, according to the study, was to run lightly: The group that had the best results ran at a slow-ish pace (about 5mph) less than three times each week, going for an hour to 2.4 hours total. Even a group that ran a bit more often and longer saw a slight increase in death risk, Time notes. The findings could perhaps relate to cardiovascular problems previously observed in the most die-hard runners and cyclists. "If you want to do something good for yourself, you don’t have to be extreme," says a study author. But another researcher points to a number of possible flaws in the findings, including the fact that the hardest-running group was quite small. (Another recent study has a warning on exercise: It could hurt your teeth.)