Vigorous running — faster than 11 km an hour, more than 2.4 hours a week, more than three times a week — could be almost as harmful as sitting around doing nothing, according to a new cardiology study that's likely to stoke the debate over how much exercise is too much.

The paper, published recently in the Journal of the American College of Cardiology, suggests there may be a point at which exertion becomes dangerous, outweighing the benefits of exercise. While the study didn't specify how strenuous running could hurt people, researchers noted the stress that intense exercise can put on the cardiovascular system.

Previous research has shown that taxing workouts may put excessive strain on the heart, though plenty of studies have also underscored the many health benefits of exercise.