The glute-ham developer (GHD) is used primarily to build the strength and awareness necessary for midline stabilization. The hip and back extension is an advanced combination movement that should only be practiced after one develops proficiency with the individual movements. Both the hip and trunk are dynamic at different points in the hip and back extension. The benefits of practicing this movement are postural strength and awareness throughout the posterior chain. Demo: @KathrinElias , CF-L3 #