A 1993 study not of snow shovels but of shovels generally found a "significant reduction" in muscle stress when a different type of ergonomic design was used. With this shovel, a second, short shaft was added perpendicular to the main shaft about two-thirds of the way toward the scoop. I've never actually seen a snow shovel of this type in a hardware store, but they do exist. Probably there's something wrong with them, too; we just haven't yet figured out what it is.
Are you one of those compulsive people who starts shoveling snow before the snowstorm is over? Please don't. Since it's usually colder during the snowstorm than afterward, your shoveling will burn up extra energy and put additional strain on your heart. Compensate for the cold by bundling up more and you'll risk getting too hot, which is also dangerous.
One of the most distressing pieces of health-conscious advice is that you're not supposed to drink coffee before you head outside to shovel the walk. That makes perfect sense; coffee increases your heart rate. But how the hell do you face a job like this without first downing a cup of coffee or three? Hot cocoa is bad, too, for some reason.
The safest tool to clear your walk is a snowblower, which, "when used correctly," puts less strain on your back. But these are nasty, noisy machines that will make your neighbors hate you, and you probably won't think to get one until you're already snowed in.
Here, then, is what I recommend. Wait till someone younger or poorer than you knocks on your door and offers to shovel your walk for $20 or $30. This person probably needs the money—nobody would volunteer for such dreadful work if he didn't—and assuming he's no older than 40 and doesn't smoke, his constitution can probably handle the strain. Delegate. The economy will benefit and your cardiologist will thank you.