Make sure that the feet are not too far apart. A wide stance may feel more stable but creates a static position that makes it difficult to transfer weight from one foot to the other. With a narrower stance, it is easier to shift the center of weight of the body from one foot to the other as a stroke is done.
The authors concluded that little evidence was found supporting the hypothesis that extension McKenzie exercises affect disc fluid content.
Feelings of back stiffness may be a subjective protective construct of the mind, rather than reflecting objective biomechanical properties of the back.