I'm currently studying Psychological well-being in partipants of extreme sports as part of my thesis/dissertation in psychology. If I come accross any research I will let you know.
So far the only the thing I have found relates to heart rates in novice and expert parachutists, from a study done in 1997. The paper is: Breivik, G., Roth, W. T., & Jorgensen, P. E. (1998). Personality, psychological states and heart rate in novice and expert parachutists. Personality and Individual Differences , 25, 365-380.
If anyone has the time to complete a questionnaire as part of my study, I have posted a message on this board with a link to an online questionnaire, see "Psychological well-being and extreme sports" in this forum.
http://www.dropzone.com/cgi-bin/forum/gforum.cgi?post=3058230;sb=post_latest_reply;so=ASC;forum_view=forum_view_collapsed;;page=unread#unread
Cheers.