maybe it's the altitudeI'll make it there some day. Just gotta strengthen my heart. It's strange though because I run up my stairs as a workout routine but walking back up that trail killed me. I can run up 20 flights of stairs with no problem but a 3000 ft decent was much worse.
ride a mule to the bottom of the canyon and you will have no problem with the first part of the ascent
the Colorado River is the same elevation as Phoenix, the canyon rim is a mile higher