Why does James smack himself when singing the verses?

[The Gutless Wonder]

At Portugal during Tolerate (in amongst all the head whacking!) he did a movement with his hand against his arm that appeared to me to be insinuating what someone does when they inject a drug into their arm. (Sorry, I'm not very articulate! ) As someone said, whether it's because he has a little less to do on stage these days so wants to try and put some kind of expression into the song. Other than singing obviously!