Wikipedia
Stair climbing is the climbing of a flight of stairs. It is often described as a "low-impact" exercise, often for people who have recently started trying to get in shape. A common exhortation in health pop culture is "Take the stairs, not the elevator". Robotic stairclimbers assist with transporting objects and packages up and down a flight of stairs. Stair descent is a motor-task that overcomes the obstacle of a multi-layered surface (stairs) beginning at a certain height and ending at a lower landing. Mastering stair descent involves motor-skill, perceptual understanding of height, and proper strategy involved in descending. Descent requires walkers to maintain support on one leg, while swinging the other leg and bending the support leg to compensate for the level change.(Andriacchi et al., 1980; McFadyen & Winter, 1988)