Over-engagement of Abs & Hip Flexors when sitting


Whenever I sit in burmese posture or quarter lotus, after a certain period of time it becomes clear that my abdominals and hip flexors are over-engaging in order to keep me upright. This is not sustainable for sitting long periods and can become fairly uncomfortable.

This is probably a somewhat complicated query, with many possible answers, but I was curious if anyone had any tips.

I am also trying to not over flex my lower back, and instead relax the pelvis from a position of excessive lordosis/ anterior tilt, but this can cause my abs and hip flexors to engage even more. Relaxing my pelvic floor and abdominals also causes my hip flexors to start engaging. I find that half lotus resolves some of this, but my hips do not seem flexible enough for this to be my main position.

Thank you