This is a difficult but highly effective movement for hitting the entire core, hips, shoulder stabilizers, triceps, chest, lats, and more. Not only are you resisting lumbar and hip extension, which taxes the anterior core and transverse abs, but you're also resisting rotational forces that are more challenging due to the instability of the suspension system.
This move recruits all available stabilizers around the core, hips, and groin, making it one of the most effective core movements for bulletproofing your spine and reducing injury risks to the lumbo-pelvic hip complex.
Adding extra weight directly to the lumbar region (through plates or chains) targets anti-extension muscles around the abdominal region. And if you really want to hurt, elevate your feet.