Step 1: Sit in your chair and hold a bottle of water with both hands.
Step 2: Lift the bottle up over your head, keeping your arms straight.
Step 3: Gently bend toward the left as far as you can, contracting your abs.
Step 4: Come back to center and repeat to the right.
Step 5: Do 10 reps (bending to the right and left is 1 rep).
Put together your own office fitness routine by reviewing the exercises in our Workplace Fitness Library.
Source: About.com Exercise