ive been bocking for about 12 months now got exos and am slowly getting better height now but certainly not to the max yet ive found over the last few days and after watching some of the other bockers at walk for life in london that as you heading towards the ground you need to almost snap your legs (really crap way to describe it sorry lol) so as you come into contact with the ground you flex your legs quickly so that you have the upward motion to get higher (reading back this makes no sense does it lol but its really hard to explain) watch some videos of the better bockers and you'll see what i mean, its a very swift movement and dont actualy spend alot of time in contact with the ground