Please Help: How come this doesnt hurt?

Question:

Please Help: How come this doesnt hurt?

http://www.youtube.com/watch?v=c_1rdll3-...

In this martial art demonstration 2 girls (about 110-130 pounds) jump on a guys stomach from a chair.

How can he take that?

Thanks

Best Answer - Chosen by Asker:

I think it has to do with how the guy being jumped on is able to tense up his abdominal muscles, creating a hard surface that protects his insides.