The movement for chest hooping is the same whether you're kneeling or standing. While you're standing you're assisted slightly by your legs but the majority of the movement is above the waist. When you're kneeling you've taken the legs out of it but it's the same movement above the waist.
The hard part is getting to your knees and back up again. That's all leg and core strength. It's mostly quads getting up and down and mostly QL (quadratus lumborum) and obliques stabilizing your core. QL is a deep back muscle.
If you're talking about leaning back where your butt drops to your heels that will take a lot of quad strength and stretch to get down and hamstrings and quads to get you back up. If these muscles aren't strong that move will work right into your lower back through your hip flexors which will grip on the way down and up.
Try the movement without the hoop and see how it feels. You'll have your hands free to help yourself get up if you get stuck. Hope this helps.