Shaking rush

Starting position: Partners lay on their backs with legs straight and perpendicular to the body, touching each other at they back sides. Hands are hold on the floor. 

Performance: B pushes his legs forward and A bends her legs to her head. The same is repeated changing roles.  
 
 
After several cycles A opens her legs and moves them to B’s head. B moves his legs together to A’s head. Roles change and the exercise is repeated.