Oh, to be young and jump with such reckless abandon.
I remember those days well. I wouldn't want to re-live them, but I remember them, and it warms my heart to see my children run, jump and explore and learn that they might hurt themselves jumping from high spots by actually hurting themselves instead of me telling them that they might. Parents are fallible beings; our children will not always believe us, even when what we tell them is true, unless they figure it out for themselves.
My children climb trees. They jump off ledges at the beach. They are given age-appropriate responsibility and freedom.
I am, I have discovered, a Free Ranger. Go ahead; check out the website. You may not agree with much (or anything) she writes, but she is interesting and, I guarantee, some of the statistics she talks about will astound you (for instance, your child is at no more risk of being kidnapped on a solo walk home from school than you were when you did it).