Years of running too long and too far could be as bad for you as doing nothing at all, a study has suggested.
Scientists have claimed "light" joggers who run for just one to 2.4 hours a week – and no more than three times a week – have the highest life expectancy rates.
Researchers tracked the progress of 1,098 healthy joggers and 413 healthy but sedentary non-joggers for 12 years.
The findings of the study, published in the Journal of the American College of Cardiology, found the life expectancy of heavy-duty joggers was as low as those who did no jogging at all.
The study also found significantly lower mortality rates among those who adopted a slow, or moderate jogging pace, while those who ran at a fast pace again had a similar rate as sedentary non-joggers.
A total of 28 deaths were registered among joggers during the study, while 128 deaths were seen among inactive non-joggers.
In general, joggers in the study were younger, had a lower blood pressure and body mass index. They were also less likely to smoke or suffer from diabetes.
Lead scientist Dr Peter Schnohr, from Frederiksberg Hospital in Copenhagen, Denmark, said: "It is important to emphasise that the pace of the slow joggers corresponds to vigorous exercise and strenuous jogging corresponds to very vigorous exercise.
"When performed for decades, this activity level could pose health risks, especially to the cardiovascular system.
"The U-shaped association between jogging and mortality suggests there may be an upper limit for exercise dosing that is optimal for health benefits.
"If your goal is to decrease risk of death and improve life expectancy, jogging a few times a week at a moderate pace is a good strategy. Anything more is not just unnecessary, it may be harmful."
Additional reporting by PAReuse content