When hand quilting in the round hoop on its stand, I sit in an armchair, cushion supporting the lumbar and I tilt the frame towards me and rest the hoop edge on my tummy. Arm of the chair supports my right elbow I have had two frozen shoulders and despite surgery on both I get pain if I hand quilt without support.
When it isn't on the stand, the hoop is supported by tummy and the arm of the chair. I spoon quilt so I need a bit more clearance underneath the hoop.
But as I get older, I can't sit too long in one position. When I free motion on the HQ Sweet 16 for a long time I get pain in the hip flexors which trips off sciatica. I'll get grief for a week.
As the others have said - get up walk around, change position and stretch. I don't advocate doing laundry but making tea is a good distraction.
HettyB