Basic Crunch on a Ball
Begin laying face up on ball. For greater intensity of movement, begin with your head and shoulders off the ball; for lower intensity, maintain your shoulders on top of the ball. Feet are flat on the ground, hip distance apart, hands gently supporting neck. Keep eyes fixed on the ceiling, gently lift upper body up toward the ceiling. Be careful not to pull on your neck. Hold at the top, then return back down. Repeat.