Snow shoveling is serious business.
In addition to the obvious dangers such as broken butts and icicle caressed skin, is the hidden killer: your heart.
The following is based on my recollection of the reasons why. Which means you should take the specifics with a grain of salt, and just remember that shoveling snow is quite taxing on your heart, regardless of how faulty my memory is.
See when you shovel snow you're doing this static-dynamic contraction of your muscles: you're holding your arms in a fairly rigid fixed position while you're also moving your system as a whole. This causes your blood pressure to sky rocket. If you're a healthy individual, it probably won't matter, but if you've already got heart problems, it's a serious risk.
So this winter, give the kid down the street $5 to shovel your driveway. Their broken butt will heal in time.