The surfski paddle stroke is essentially the same as the sprint kayak stroke (let's ignore variations you may make in technique on rough water). Two of the most common health issues that sprint kayaking programs report relate to shoulders and lower backs. Issues with other joints probably tend to become more common as paddlers age.

A good, powerful stroke includes significant torso rotation. Torso rotation needs to be accompanied by hip rotation. If the hips do not rotate in concert with the torso then significant stress can be concentrated in the lower back and likely contribute to lower back strain or injury. Emphasis on leg drive should also include parallel hip rotation. Avoiding inadequate hip rotation can sometimes be as simple as making sure your hips and seat are as friction free as possilble (though maybe not so far as to make you slide out of your seat too easily)

Seat Friction Reduction

• good paddle shorts - designed to slide easily with seams that minimize rubbing or discomfort during rotation
• use teflon tape and/or teflon-like treatment on you seat surface or seat padding
  • Marine Polish
  • …

Core Strengthening

• exercises to assist rotation and syncing hips with torso rotation
  • such exercises will likewise assist in core stability and reduction of excess movement that may be likely to lead to back strain
• See
  • On Water Rotation Drill
  • Hip Flexibility Exercises
  • …

Discussion

• Lumbar Spine and Surfski Paddling
• Rude Vertebrae