Surely you brush your teeth in the morning and at night, while brushing can use that time to do knee bends.
Whenever you are in a house or building using the stairs and avoid the elevator.
Try to walk as much as you can and if you are short distances not use the car, use your feet.
Remember that if you walk briskly and keep constant.
As you turn on your computer you can use the time waiting for stretching, over time you’ll see results.
One of the most recommended exercises for when you’re sitting in your office, is the contracting and relaxing the buttocks, or abdomen, keeping contracted for five to six seconds and then relax.
Repeat these exercises consistently and gradually you will go further strengthening.