This exercise is great to strengthen the deep abdominal and spinal muscles simultaneously, providing support for your lower back, and increasing power for your surfing. (blog.errantsurf.com)
Adding the resistance band creates a super-gravity effect on the upper body, requiring a stronger response of spinal muscles to stretch out and lengthen through the arms. (onnit.com)
An impact will strain spinal muscles and ligaments while the facet joints absorb its force. (ccdlaw.com)