Stairs make you work against gravity when carrying your body weight and this helps improving your strength and power. You'll need both, whether you're sprinting for the tape in a 5 km race or trying to hold your pace in the latter stages of a marathon.
stair-climbing. The plyometric motion strengthens the same muscles as lunges and squats, and taxes your lungs and heart as you power to the top.
Moore adds that stair-climbing “forces you to utilize muscle stabilizers, like the gluteus medius, that get neglected during regular runs,” because you’re balancing on and activating one leg, briefly, as the other moves to the next step. Strengthen these areas and you’ll reduce your risk of injury.
Finally, stairs are much steeper than most hills: Indoor stairs have a roughly 65 percent grade, while Boston’s Heartbreak Hill is just 4.5 percent. That’s why climbing them accelerates your heart rate so rapidly and makes you breathe faster to take in more oxygen. This, in turn, improves your VO2 max—the maximum amount of oxygen you can utilize during intense exercise.