Circular Press Up Exercise
A difficult one to explain, start off in the standard position shown (feet wide apart for balance and so your body can move back and forwards easily) then bend your arms and lower yourself, towards the bottom of the motion push your body forward then up to the top anf back again, imagine your are trying to move your body in a circular motion. This exercises you in a way you cannot get with a regular pressup, try doing then slowly as you get better at them.