Congratulations, couch potatoes: A new study might give you ammunition to rationalize your lack of exercise. The review of six studies found that 10% of regular exercisers ended up with worse levels of blood pressure or insulin, two indicators of heart disease, reports the New York Times. On the other hand, about the same percentage ended up drastically improving on at least one measure, according to the study in Plos One.
Still, the finding that some people actually worsened is "bizarre," says the study's lead author. And a co-author—who happens to have contributed to the national guidelines on exercise—says people should continue to work out, but maybe get heart disease factors checked regularly. “I am an exercise guy," he says. "I believe in exercise for health. I would rather have everyone exercise. But you can’t ignore the data.” (Read more exercise stories.)