A kayaker uses a double-bladed paddle for steering and propulsion. With the correct technique, the torso and lower extremity are used for much of the force applied to the paddle. If the technique is not correct, however, a sudden unexpected force against the paddle can often result in stress in the upper extremity, particularly the shoulders. This can happen when a kayaker flips over and attempts to “roll” back up. If the technique being used to roll is not correct, it can create a great deal of stress on the shoulder, resulting in pain.
A couple of years ago I ruptured my left bicep doing swift water rescue exercises. I had a lot of pain doing simple things, mainly, I think, because my shoulder was compensating more for the lack of bicep strength. My wife showed me this exercise and bought the pully system.
My shoulder pain is now gone, but I continue to do the exercise. The cost of the equipment is minimal, so you should give the exercise a try.