This is is an example of the kinetic art of Volkert van der Wijk. He has designed the linkage so that it is statically balanced, which allows the observer to position the acrobat in a wide range of positions.
This is an installation of one of Volkert’s pieces which is a linkage balanced so that when the observer provides a small upward push the sculpture lifts and extends, and then slowly collapses when the force is removed.
I was pleased to meet Volkert at the 2012 Advances in Robot Kinematics conference in Innsbruck, where he presented the mathematical theory for static balancing the Acrobat. His other work can be seen at his web page: Kinetic Art