When doing twists, you don't always have to keep your pelvis perfectly still. For some body types, allowing the hips to move slightly is easier and safer on the back. To assess your needs, do this simple test, sitting in a chair.

1 Sit sideways on an armless chair. Place your feet on the floor, hip-width apart, heels under your knees. Sit up tall and hold the back of the chair with both hands. Inhale.

2 On an exhalation, rotate your upper torso to the right as far as you can. Reach around with your right arm and grasp the bottom edge of the chair. Notice if your left knee moved forward. Now return to center and repeat the twist, but this time, don't allow your left knee to move forward as you twist as far to the right as you comfortably can. Can you rotate far enough to grasp the bottom of the chair again? If so, then you can safely twist without moving your pelvis. If not, then practice letting your hips move slightly whenever you do twists.

This article originally appeared in the Los Angeles Times in the "Good Form" feature of the Health Section. "Good Form" is updated with a new Karen Voight article each Monday.