1. Start on the floor, on your hands and knees.
2. Tighten your belly muscles by pulling your belly button in toward your spine. Be sure you continue to breathe normally and do not hold your breath.
3. Keeping your back and neck straight, raise one arm off the floor and hold it straight out in front of you. Be careful not to let your shoulder drop down, because that will twist your trunk.
4. Hold for about 6 seconds, then lower your arm and switch to your other arm. Over time, work up to holding for 10 to 30 seconds each time.
5. Repeat 8 to 12 times with each arm.

When you feel steady and strong doing this exercise with your arms, try doing the exercise with your legs instead. Raise one leg and hold it straight out behind you. Be careful not to let your hip drop down, because that will twist your trunk.

When holding your leg straight out becomes easier, try raising your opposite arm at the same time.