Growing up around racing kayaks in Nova Scotia and then when being trained as a young coach I was often told to imagine a steal rod from the top of the paddler's head and through the spine into the seat. This rod, was to be imagined as the axis of rotation. "Sit tall in the kayak and rotate around the axis", I still hear this instruction given to kids today. BUT... It is not quite right...
Lets take a closer look.
Imagine an old school house clock, now imagine it flopped down on its side and it resting on the kayak seat with 12:00 pointing forward. The centre of the clock is the steal rod. The outside of the clock represents the path of rotation around the centre of the clock (the rod).
Below is the clock image showing the path of the paddlers hips as they rotate on the clock. The first image has the paddler sitting in in neutral position, facing forward with both hips and knees even. The next at the exit on the right side and the third, at the exit on the left.
However, the goal is not just to rotate, we must do so in a way that delivers a powerful forward impulse to the boat. All methods of rotation are not equal in this regard. We want our rotation to maximize power, in the forward direction with as little effort as possible.
One way we save our energy is to use our body weight and let gravity add force to our motion. We use rotation in order to 'land on each stroke' with our body weight. Although, we will never get all our weight on the paddle, where possible we want to be supported more on the paddle rather than just on our bum and heals in the boat.
More specifically, we want to land on the paddle and simultaneously on the stroke side heal and the stroke side bum. Imagine a house of cards with the bottom of one card as the paddle on the water and the bottom of the other on the stroke side of the boat (not the middle of the boat and certainly not the opposite side). Below is a simple diagram showing the paddle-water and the stroke-side boat support.
At moment of the catch, the paddler should land on the stroke-side of the boat and near the paddle. The above image of the clock, with the axis of rotation as the paddlers spine, does not give us this result. On the contrary it has both hips moving closer to the centre-line of the boat.
With a small change to the model we can get a big impact.
Modify the image of the rod through the head and spine by moving the axis (the middle of the clock) from inside the body to now be in front of the body. Here is the updated version of the clock and the paddler moving in the boat. See now that the paddler moves to the position needed to land on the next stroke.
The result is a rhythmic and powerful 'u-shape' swing around the clock between 3:00 and 9:00. Notice that in the original model the paddler could imagine moving past 3:00 or 9:00 as they rotate further. The updated model has the padders direction and momentum thrust down the side of the boat and towards the finish-line. We can see this in action in the below video. Watch how Erik uses each stroke to swing around the axis slightly in front of his body and land in position above the catch on the next stroke. We clearly see the side to side element of the action with space seen opening up between his hips and the side of the boat.
Imagine an old school house clock, now imagine it flopped down on its side and it resting on the kayak seat with 12:00 pointing forward. The centre of the clock is the steal rod. The outside of the clock represents the path of rotation around the centre of the clock (the rod). 
