This is one of the areas I'm trying to improve one of my pitchers, disassociating the hips from the shoulder for a better whip. The hips should fire at plant with the shoulders twisted out of alignment to the hips. This creates core torque for better snap through the backside of the circle before release. I've trimmed up a Blaire Luna and Cat Osterman video. Focus on the hips firing with the shoulder and arm coming in right behind them.