"Physically, what happens when you get really cold is you have constriction of the blood vessels," says Lawrence Phillips, a cardiologist at NYU Langone Medical Center. "It decreases the blood supply you're getting to your vital organs."
That's bad news for people with heart problems, diabetes or high blood pressure. But just as big a problem is that many people dig in despite not having exercised in weeks or months or years. "If you haven't been exercising and you haven't been exerting yourself, this is not the time to start," Phillips said. "The amount of work that goes into shoveling snow is tremendous. ... People will underestimate the amount of work they are doing."
At the gym, he noted, it's easy to hop off a treadmill when you start feeling winded or to slip out of that spin class early. But shoveling snow tends to be a "goal-oriented" activity. Call it pride, stubbornness or maybe naivete, but men especially tend to keep at it until the job is finished -- or, too often, until disaster strikes.
"They are pushing to clear a driveway or a sidewalk," Phillips said, "and they aren't thinking about how their bodies are responding to that."
William Suddath, an interventional cardiologist at MedStar Washington Hospital Center, likens it to "beginning a weightlifting program in freezing temperatures without any preparation."
Suddath has witnessed the consequences firsthand. During the epic "Snowmaggedon" that hit the Washington region in 2010, his hospital saw a wave of emergencies involving people who'd suffered heart attacks while shoveling the mountains of snow.
"Heart attack rates go up, sudden deaths go up," he said, with the weather often preventing paramedics from reaching people as quickly as they otherwise might. "Some heart attacks likely will not be reversed as they could have been in another situation. It's a major problem during a snowstorm when you just can't get to patients."
Even just walking through heavy snow, particularly if a person is older or out of shape, can pose health risks. "That's a tremendous blast of exercise," Suddath said.
But the link between blizzards and increased heart-attack deaths is more than anecdotal. It's supported by a growing body of research.
In a study several years ago, for example, researchers at Nationwide Children's Hospital in Ohio found that an average of 11,500 snow-shoveling-related injuries and medical emergencies occur annually in the United States. More than half involve soft-tissue injuries, as well as lacerations, bone fractures and harm from slips and falls. Cardiac-related injuries account for fewer than 10 percent of the total cases, but between 1990 and 2006, they comprised more than half of the hospitalizations and all of the more than 1,600 deaths.
The researchers also found that people over 55 were more than four times as likely as younger patients to experience heart-related problems while shoveling snow. Men were twice as likely as women to experience symptoms.
So as another blizzard bears down on the Washington region, here are some safety tips from the experts. While shoveling:
- Dress warmly, making sure to cover your mouth, ears and extremities to maintain body heat.
- Warm up with light exercise before beginning.
- Pace yourself. Take frequent breaks.
- Try to push snow out of the way rather than lifting heavy loads.
- When possible, shovel several times throughout the storm to make the task more manageable.
- Stay well hydrated.
A bit of positive news for those who do plan to clear the white stuff in the days ahead: If done properly, it can provide a good workout. According to a 1999 Surgeon General's report, 15 minutes of shoveling snow qualifies as a moderate amount of physical activity, on par with bicycling five miles, raking leaves for half an hour or swimming laps for 20 minutes.
Or, you could just splurge on a snow blower.