You know that other feeling, after completing a challenging workout that was also the first workout you'd had in several days? Feeling like every muscle between your waist and knees is cursing your name? Feeling like you have to use the handicapped stall in the bathroom because you need the assist bars in order to find the least painful ways to maneuver into a sitting position?
Delayed-onset muscle soreness, you are literally a pain in my ass.
(Asses courtesy of Free Pictures.)