“This is an upper body chop PNF pattern that helps develop trunk and lower body stability, upper body strength and rotary mobility executed from a half kneeling stance.” – http://www.functionalmovement.com/exercises/chop_from_half_kneeling_with_cable_bar
 
In volleyball rotational stability is critical for many of the volleyball skills like spiking yet too few athletes really put attention into this important element of volleyball training and the result is often volleyball injuries. By going into the half-kneeling position we’re taking the legs out of the equation and putting a lot more work into the hips and trunk (Core).