Getting Active Again

When I go to the fitness center and see the people on the rock climbing wall, maybe wearing their La Sportiva shoes or other rock climbing paraphernalia, I have to shake my head, That is something I could never do. Don't even have much interest. But seeing people active like that makes me wish for the days when I was more active and did some hardcore hiking. Like up to Mt. LeConte in the Smokys twice. That was my crowning achievement, hiking wise. I am getting in better shape, little by little, but am not sure I could do something strenuous like that no matter how much in shape I am. Now I am concerned about my knees--torn ACL in one knee, and cracked kneecap in the other. Just not sure the knees would hold up in such a hike. So my sights are set on less strenuous forms of exercise.