Sitting quietly for extended periods of time could be hurting your heart, according to a surprising new study. It finds that the more people sit, the greater the likelihood that they will show signs of injury to their heart muscles.

We all have heard by now that sitting for hours on end is unhealthy, even if we also occasionally exercise. People who sit for more than about nine or 10 hours each day — a group that includes many of us who work in offices — are prone to developing diabetes, heart disease and other problems, and most of these risks remain relatively high, even if we exercise.

Excessive sitting also has been associated with heart failure, a condition in which the heart becomes progressively weaker and unable to pump enough blood to keep the rest of the body oxygenated and well. But how sitting, which seems to demand so little from the heart, could be linked to heart failure, a condition in which the heart cannot respond adequately to exertion, has been unclear.

So recently a group of cardiologists from around the world began to wonder about troponins.

Troponins are proteins produced by cardiac-muscle cells when they are hurt or dying. A heart attack releases a sudden tsunami of troponins into the bloodstream.