Too much of a good thing -- even something considered as good for your health as jogging -- could be bad for you, researchers have found.
People who indulge in light jogging are less likely to die than sedentary non-joggers -- no surprise there -- but they're also less likely to die than those who engage in highly strenuous jogging, researchers at the Frederiksberg Hospital in Copenhagen, Denmark say.
Study researcher Jacob Marott and his colleagues analyzed data on almost 1,100 healthy joggers and 413 sedentary non-joggers gathered over 12 years, with the joggers recording their hours and frequency of jogging.
The study findings suggest strenuous jogging -- faster than 7 mph, for more than 2.4 hours a week, more than three sessions a week -- could be almost as risky in terms of health as sitting around doing nothing, the researchers report in the Journal of the American College of Cardiology.
Light or moderate jogging was found to be best for a person's health, they say.
"In this study, the dose of running that was most favorable for reducing mortality was jogging 1 to 2.4 hours per week, with no more than three running days per week," says researcher Jacob Marott, adding that the best jogging pace is about 5 miles per hour.
How could exercise, long thought to be part of a healthy lifestyle, be bad for you?
"We believe that long-term strenuous endurance exercise may induce pathological structural remodeling of the heart and large arteries," Marott said.
Not everyone agrees, and one U.S. researchers say the debate over how much exercise is too much is likely a long way from being settled.
D.C. Lee, a professor of kinesiology at Iowa State University who co-authored an editorial accompanying the Danish study, said the study has limitations.
In Marrot's study, a very small group logged the most jogging time, he say, with just 47 joggers putting in more than four hours a week, and just 80 running more than three times a week.
These small numbers could have affected the comparisons and results, Lee says.
His own study involving some 13,000 runners found a lower risk of death over a follow-up period in joggers logging the highest running time and frequency -- around 3 hours a week and with at least six sessions a week -- compared to non-runners, he said.
Lee's study was also published in the Journal of the American College of Cardiology in 2014.
