Before kids, I was a hard-core athlete. I LOVED to run, to push myself, to get the adrenaline flowing. Running was my favorite activity; I’d lace on the sneakers, grab my Walkman (I told you, BEFORE kids. Like a long time ago, when cassettes were still a thing.), and hit the streets for a few miles. The Captain and I even joined a gym together shortly after we got married, because that’s what cute, childless, yuppie couples do. And I was introduced to… the treadmill. I still vividly remember walking confidently up to the bank of treadmills that faced the mirrored wall. Two older, heavier women were strolling side by…