About 7 percent of patients treated at hospital emergency rooms for shoveling-related incidents had cardiac problems, according to a 2011 study. Some of these were deadly.

“While the overwhelming majority of people do not have heart problems while shoveling, for the few who do get into difficulties, there is a confluence of things happening,” said Gordon Tomaselli, president of the American Heart Association and director of the Division of Cardiology at the Johns Hopkins University School of Medicine.

For one, Tomaselli said, snow shoveling is more grunt work than such exercises as running and swimming. “It’s not aerobic,” he said. “There is a lot of tension in the body with all that lifting.” The cold air also can cause problems by making it more difficult for your body to react to the stress of heavy lifting and slowing the flow of oxygen into your bloodstream as frigid air narrows breathing passages.

Signs of a heart attack may include chest pain, discomfort in an arm, back, neck or jaw, shortness of breath or dizziness. Sometimes, a person can feel nauseated and clammy.

“If you have any symptoms at all, for anyone over the age of 40 or 50, stop immediately; get into the warm,” Tomaselli said. “If you have chest pain or dizziness, call 911.”

The American Heart Association offers these tips to protect your heart while shoveling:

●Take breaks so as not to overstress your heart.

●Eat lightly before and after shoveling. A large meal may strain your heart.

●Shovel small loads of snow. Lifting heavy snow can raise your blood pressure.

●Refrain from alcohol before and after shoveling. Alcohol may make you feel warm when you are not, and it may dull your attention to how your body feels.

●If you have a medical condition or don’t exercise regularly, ask your doctor beforehand if it’s okay to shovel this winter.

●Don’t underestimate the chance of getting hypothermia. Heart failure causes most deaths in hypothermia. When the body loses heat more quickly than it can generate it, your circulation, respiratory and nervous sytems become sluggish, and that can cause irregular heartbeats, which can be fatal in these circumstances. According to the University of Maryland Medical Center, more than 700 Americans die each year from hypothermia.

Laura Hambleton