Gluteus Maximus
Muscles help the movement of your legs, while the bones are attached to your muscles to provide support and structure. Furthermore, the bone joins in your hip and knee have the necessary mobility used to climb stairs.
Arm muscles, leg muscles, grip in your palms and fingers, to a certain extent your ankles, and sometimes your abs, it depends on how your climbing it.
When a person is climbing a ladder, the primary form of energy being used is potential energy from the person's muscles. As the person lifts themselves up, they are converting chemical energy stored in their muscles into mechanical energy to move upwards.
Your leg muscles work together to help you walk up stairs.
There's no limit to the height of the stairs, but because power is the rate of doing work, different people would run up several flights of stairs at different rates, since each person has a "limit" on the amount of power she/she can produce.
Upward force, used to counter the downward force of gravity acting on the climber. Precisely the same force used when walking up a flight of stairs. Provided in both cases by the climber's muscles.
I believe that the amount of power/energy you exert on yourself climbing up the stairs is wasted, and the faster you go, the faster the power is used up. It takes a lot of energy to go up one flight of stairs than it does going down five or so, depending on the body type of the person and maybe even the amount of gravity in that specific area.
Two muscles are needed, one to extend the other to close
There are several muscles involved in bending the arm, and several others used to extend the arm. Muscles can only PULL; they cannot push or twist.
To safely use ladders on stairs, make sure the ladder is the right size and type for the job. Place the ladder on a level surface at the base of the stairs and secure it to prevent slipping. Use ladder stabilizers or leg levelers if needed. Always face the ladder and maintain three points of contact while climbing. Avoid overreaching and never lean the ladder against the stairs.
The rock climbing hooks used for securing ropes and gear while climbing are called carabiners.
Mount Everest is used for its resources such as water from its lakes and climbing for tourists