I'm not going to type much today. Today's post is a video Zen "first time" moment. P.S. She's 3 weeks shy of her 1st birthday and been working up to this since she was about 4 weeks old.
I will stress that what you are witnessing is not an increase in strength here. Her strength (in the classic sense) has not changed much in 47 seconds. What you are witnessing is an organization of muscular recruitment.
Also, check out the load to her hand-skin. She's not gripping to do the hanging. Her hands are almost entirely vertical. The load of her body is held primarily by her hand-skin's traction with the bar. MARK MY WORDS: The failure to address the foot and hand skin's contribution to the kinetic chain will come up in future human-motion science.
I might be dead by then, so hopefully one of you young whippersnappers can mark my words for me.
For more information on kids and upper body strength, you can read this article I was interviewed for: http://breakingmuscle.com/family-kids/katy-bowman-and-biomechanics-human-growth-necessity-monkey-business
If you're interested in increasing your own hanging and swinging skills, read Hanging and Swinging 101.