So....

I got a chin up bar for the abode, and I'm sore in some funky places. In addition to doing chin ups, I use it to do leg curls [?]. It's where you pull your legs up to your chest and try and hold as long as you can; or repeat the process in a series of reps.

So now when I get out of my chair to go somewhere, a new mysterious sore muscle makes its presence known. Who knew such a low tech apparatus could be so effective.