With your mid-back across an elevated bench (or table or couch) and feet planted firmly on the ground, push through your heels and squeeze glutes to lift hips. Use the hiit bar or sandbag across your hips for extra resistance.
Stand with your feet about shoulder-width apart and slightly turned out with your weight in your heels. Hinge your hips to sit your butt back and bend your knees until your thighs are parallel to the ground. Drive through your heels to stand back up straight. Squeeze your butt and keep your core tight as you stand.