I have heard of studies that have shown that the prevalence of back pain in surfers is very low, but that it is one of the first things to surface when someone stops their surfing career. May give some cred to the strengthening in ext,rotation plus abdominal control during flexion as one stands onto the board. It would make a nice kinematic study from video analysis. You could then couple it to a survey on LBP, and then generate a group treatment program based on the fundementals movements involved in surfing. Hey you could even brand it and sell the concept globally. Why not??