I am learning to walk on my hands. I started about two weeks ago, and my record is ten seconds. I have started doing the 7-minute workout. See the official 7 Minute workout here. I have been doing push-ups and pull-ups for over two years now.
I also run some, and that combined with cycling caused a stress fracture in my shinbone, simply because my calf was too tight, and my shin-muscle was too weak. The remedy to this is to lift a weight with your toe. In my case, I use the couch.
Update on cycling; I rode almost to "Farellones" a town of about 100 people up in the Andes a while outside of Santiago to the east. I gained 3,900 feet in elevation. The whole ride was 45 miles and took me a little over 4 hours. From my looking around on google maps in street view, the switchbacks up there seem to be some of the world's best.