Digging out from the weekend’s massive snow and ice storm could be hazardous to your heart.

Pennsylvania health officials announced three snow-removal related deaths Sunday. All were between the ages of 60 to 84. The Lehigh County coroner’s office cautioned people to take breaks and avoid over-exerting themselves.

Shoveling snow is heavy, hard work — research has shown that doing it for even a short time can make the heart work as hard as it does during a major workout. Adding to that stress, the cold temperatures cause blood vessels, including those feeding the heart, to constrict. That raises blood pressure which in turn increases the risk of a heart attack, stroke or cardiac arrest, according to the American Heart Association.

Snow shoveling is especially risky for anyone with known heart disease or who’s already survived a heart attack, as well as older adults and people with risk factors including high blood pressure or cholesterol. People who think they’re healthy can get in trouble, too, with that combination of heavy exertion in cold weather – especially if they’re generally sedentary until a snowstorm comes along.

The heart association advises that if you have to shovel, go slow and try to push the snow instead of lifting and throwing it. It also urges people to learn common warning signs of a heart attack and to call 911 if they experience them.