back_circle has definitions from the field of sport
1
[ noun ] (sport) a feat in which an acrobat arches the back from a prone position and bends the knees until the toes touch the head

Used in print

(Bonnie Prudden, "The Dancer and the Gymnast"...)

To further increase back flexibility , work_on the back_circle .

Related terms

acrobatic_stunt

*