A Harvard Medical School professor was giving a lecture on involuntary muscular contraction late one afternoon. Realizing his lecture was boring the class he decided to spice things up a bit. Suddenly he pointed to a female student in the front row and asked, "Do you know what your asshole is doing while you're having an orgasm?"
The student looked away for a moment, and then said, "Hunting buffalo in Tanzania."

You obviously shoveled too much snow today!