How many of us walk up in the stairs instead of taking lifts…probably 10 out of 100. But as a practice you should always walk up stairs. Because when you climb up stairs you need to use the muscles against the gravity so they are getting activated/strengthened as well. When you climb down stairs your muscles been taught how to control because you are going towards the gravity. And on top of it your Hip, Knee and Ankle joints being moved..as a result you would maintain the mobility too.You almost all the muscles of your Lower Body when you climb up and down stairs. The main muscles are your front and back thigh, buttock and calf muscles. So every time these are getting exercised and will become active as well. If this keeps happening your joints would stay healthy and you can delay arthritic changes that might appear in the joints.