I think stairs are a challenge for everyone, even those who are in “tip-top” shape. If you want to get better at climbing stairs, then make them part of your workout. The most effective way to adapt your body to a particular exercise… is to do that very exercise!
Being in good health isn’t an automatic pass for being good at everything you do. Stairs, just like running, jump roping, cycling, skiing or any other cardio, requires that you practice to get better!
So, run up and down stairs when you can. Use a stair climber if you have a gym membership. But add them into your routine to see improvement!