She didn’t have back pain - genuinely.
Her doctors gave her a back exercise regimen to give her musculature the strength needed, and she trained her back muscles intensively throughout her career. She was able to take the strain without pain or discomfort.
Although yeah, must still have been incredibly awkward and exhausting, they eventually grew to weigh 20kg EACH.
They’re just really big boobs.
You don’t need to like them of course, but it never hurt anyone else that she had them.