How to feel old, Part II

So, I think I'm finally over the trauma of nearly passing out at the gym in March (or was it February?). No, I haven't back. But after catching sight of The Couch-to-5K Running Plan on someone's blog, I decided to get back on the horse. Not yet fully recovered from the humiliation of nearly passing out at the gym, I hit my mom's treadmill. Whereupon, for the first time ever in my not-as-short-as-it-used-to-be life, I felt my ass bounce violently, the vertical manifestation of the tricep wobble. How did that happen?!