So after running a group through a workout today, I did a little training of my own with my little brother.  We started out with a number of weighted pullups on branches and various climbing techniques.  Then we did four laps around the playground on the 8" wide bordering cement "wall".  The lap is just under 300 meters, and so far my little brother holds the top time with 44.5 seconds (mine is 47.8).  Here's a video of it.