After a two year break from snow, my wife and I spent most of the last day digging out from our snowstorm. My left arm is sore along the entire length now - but not my right arm. I also noticed that both my forearm and bicep measurements are almost half an inch bigger on my right arm than on my left arm.
This didn't used to be the case, and I'm pretty sure it happened because when I carry a kid, I do it with my right arm. My wife, however, often carries two kids at once - and her arms aren't sore at all.
I guess I should spend more time carrying two kids instead of just one - or at least switch the one kid back and forth betwen the two sides.