The defensive power forehand depends on executing the upper arm rotation in the right measure relative to advancing the shoulder. In general, the shoulder must dominate the stroke, and the upper arm rotation must support the stroke. When the upper arm rotation is dominant, the entire stroke breaks down. Below left is the start of the acceleration stage; on the right is an animation of the sequence to be discussed.

Because the upper arm rotation is dominant, the entire stroke begins to break across the body, as seen in the figure below left. Below right is the associated rollover sequence.

	Move your cursor over the image to see the transition

Once the breakover begins, it is impossible to stop, and thus the opportunity for a clean strike is lost. In fact, no straight-line interval is possible, and you will likely snag the ball. Also, it is likely that the ball will fall short or hit the net.

	Move your cursor over the image to see the transition

This error is most common during times of nervousness or stress—in short, the tight points. During stress, players are prone to reduce their stroke to the upper arm motion rather than maintain a good shoulder presence in the stroke. The shoulder is what drives the stroke forward and provides a straight-line interval. When the upper arm rotation dominates, the shoulder can drop out of the stroke completely. You will not be able to sense this during stress without a lot of study and practice because, when you are in a nervous state, your "feeling" is nearly nonexistent and cannot be used to guide you back to correct your motion.