I get asked frequently what abdominal and torso exercises I prefer with hockey players. People are always surprised by my answer: I want them off their back and either standing or in a braced position. Doing crunches lying on your back or performing back extensions with your legs fixed trains the torso musculature in ways it will not be used: in isolation. Although the torso can contribute to the development of power or reduction of power in deceleration, its primary role is as a strong, stable platform to transfer power generated by the legs to the body as a whole or the upper body.
A basic series of exercises that I want my athletes to demonstrate proficiency in are bridging movements that require the torso to remain rigid and stable against gravity. Lying facing down on the ground, the athlete will prop themselves up on their elbows and lift their entire torso and hold that position for a set period of time. The entire body must be rigid and straight as a board; I should be able to draw a straight line from shoulders through the hips and knees to the ankles. No sagging, no arching of the back.
A side bridge is performed by propping yourself up on one arm and facing sideways. Now, not only do you keep the torso flat as a board like the first motion, but you must keep your hips from protruding backwards or rotating your shoulder girdle forwards. Again, the goal of this exercise is time.
The back bridge is probably the least challenging of the exercises but just as important. The hips are lifted off the floor, creating a rigid, straight, flat torso through the knees, hips and shoulders. The hips must remain up throughout the prescribed time.
Be sure to check with a qualified trainer and your doctor before you integrate any exercises into your exercise program.