I've done this before, about 11 years ago. I actually cracked 2 ribs on the back side of my ribcage, and 2 in the front, both on the left side, just from throwing a football! My right foot slipped in a hole just as I was throwing, I heard/felt this "pop," and later that night, the whole left front and back side of my ribcage turned black and blue. So, I went to the emergency room (I'm not one to go to the doctor, but this kinda freaked me out, as I didn't have any clue what I might have injured), and after taking x-rays (along with all the obligatory money-making tests), the doctor told me I had basically cracked 4 ribs, two in front, two in back. Hurt like hell, but there really wasn't anything they could do about it, so they just taped me up and sent me home. This time, the pain isn't quite as intense, and I haven't turned black and blue, so I'm thinking I'll just give it a few days, and see what happens. If it's what I think it is, there's not a whole lot doctors can do about it anyway. I'll just have to put up with it for several weeks, so no tennis for me for a while!! That sucks! Oh well, maybe I need to get in better shape...