Played game of rugby on Saturday (5 days ago). Someone stood on my abdomen - I have had pretty severe pain since then - also noticed that when I have a bowel movement (not as often as usual), it's a very dark color, but does seem to be getting a bit lighter... any ideas?

Better safe than sorry............go get it checked out just to be sure no damage has been done to your organs.

Its probably just bruising but if it is still bothering you then you should get it checked out.

Usually very dark, black stools indicate some bleeding in your GI, that was kind of foolish to have someone stand on your stomach with all their weight. If everything clears up and your Bm"S go back to light brown or the color that you know of your body then I wouldn't worry about it, but if your stools continue to be black, then a visit to the gastro doctor would be advisible.